kammerer (engels)

®Precision Screw Technology

– Ball Screws– Trapezoidal Screws

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®Issue 3/2003

More than50 years of Kammerer

Kammerer Gewindetechnik GmbHIn der Hausmatte 3D-78132 Hornberg-NiederwasserTelephone (0 78 33) 96 03-0Telefax (0 78 33) 96 03-80Internet: http://www.kammerer-gewinde.come-mail: [email protected]

All data, dimensions and particulars given in this catalogue are non-binding. We reserve theright to make changes and improvements. This catalogue is protected by copyright. Copyingand other forms of reproduction are not permitted without our prior agreement.

http://www.kammerer-gewinde.com

mailto:[email protected]

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ContentsPage

Product overview 4

Quality Assurance – General 6What is checked? – Reports 9DIN 69051 – Extracts 10Quality Assurance in the manufacturing process 16

Ball screws Application examples 17

Technology, Efficiency 21Wipers, Ball screw assembly 22Track profile, Axial play with a single nut, Ball feedback systems 23Pre-loading the nut 24Pre-loading the spindle, Rigidity 25Rigidity diagram 27Average load and speed, Drive torque and Drive power 28Efficiency, Lifetime 29Lifetime diagram 30Speed limits 32Critical bending speed 33Critical bending speed diagram 34Buckling 35Buckling diagram 36Leads – Overview 37Nut systems 37Nut data and dimensions 38Spindle ends with bearings 52Shaft nuts KMT 60Spiral spring covers 62Lubrication 64

Trapezoidal screw Application examples 66

Trapezoidal screw spindles (dimensions) 68Trapezoidal screw nuts (dimensions) 71Technical data 74Thread diameters and leads 75Maximum loading 76Efficiency 77Critical bending speed/Buckling calculation 78/79Mathematical calculations 80

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90

– rolled– turned– ground

About usA look at the factoryQuestionnaire

What we make

Quality Assurance

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What we make

Ball screws

rolled – Diameter 8 to 25 mm– Lead accuracy of 50 or 200 µ/300 mm– Spindle lengths up to 3,000 mm as standard, greater lengths

on request

turned – Diameter 8 to 160 mm– Lead accuracy 10, 25, 50, 100 µ/300 mm– Spindle lengths up to 6,000 mm as standard, greater lengths

on request– Right-hand and left-hand threads on one spindle– Any special lead can be supplied at customer’s request

ground – Diameter 8 to 50 mm– Lead accuracy 10, 25, 50 µ/300 mm– Spindle lengths up to 1,400 mm as standard, greater lengths

on request– Right-hand and left-hand threads on one spindle

– Own, optimised ball return system in the ball screw nut guaranteesimproved quiet running even at high speeds and resulting longerlifetime

– Dimensions to DIN 69051 allow replacement even after severalyears

– Cylindrical and flanged single nuts as well as zero-play nut combi-nations (pre-loading to customer’s requirements) can be supplied

– Even special designs can be supplied at relatively short notice

consistent quality A modern test machine, especially developed for measuring ball and trapezium screw spindles, ensures that the quality of every balland trapezoidal screw that leaves the factory is consistent

spindle end machining on the most up-to-date CNC machines in accordance with thecustomer’s drawing

test reports On request, we can supply test reports with particulars of the leadaccuracy and the tolerances of all important dimensions of the ballscrew

technical advice All calculations associated with our products will be provided by ourexperienced engineers to support you with your specific applicationto help you choose the optimum screw drive.

optimised ballreturn system

We also provide customer-specific assemblies and complete solutions.

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What we make

Threaded spindles and nutsWe manufacture spindles and nuts with trapezoidal, metric, saw-tooth,ACME and special threads from 8–160 mm Ø and up to a length of 6 metres (longer on request) in single and multi-start designs, ready toinstall to drawing.

We also carry out all follow up operations in our factory such as CNCturning, CNC milling, CNC grinding, etc. as well as the straightening ofspindles for maximum concentricity using modern straightening presses.

When choosing the material for the turning and spinning of spindleswith accurate leads it must be ensured that a homogeneous, consis-tently low stressed spindle material is used. We would ask you to con-sider our suggested materials where possible.

Rolled threads are manufactured in diameters of up to 60 mm and a lead of up to 9 mm.

When machining parts supplied by others on a piecework basis, the preparation carried out by you should be agreed with us in each case. The same applies to the choice of material for spindles and nuts.

Worms and worm shaftsWorms and worm shafts (single and multiple start) are manufacturedfrom module 2–12 and up to an outside diameter of 160 mm.

Worms are manufactured by turning or spinning; in this way we canachieve flank shapes approximating to DIN 3975 K.

Worms and worm shafts are manufactured exclusively to customer drawings.

Lead screwsKammerer also manufactures lead screws in the trapezoidal and ball screw range.

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Quality Assurance

Quality Assurance starts right at goods inwards. This forms the first stage of our manufacturing process.

Items checked are: – material designation– material quality– material dimensions– material treatment– delivery condition– material identification– packing– works test certificates– etc.

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Quality Assurance

We use the most up-to-date methods of measurement. The laser test equipment shown here is for the non-contactmeasurement of the lead accuracy, wobble error and shape of profile. All data can be stored for many years ondiskette. The resolution accuracy is 0.001 mm and the measuring length is 3000 mm without having to readjustthe spindle.

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Quality Assurance

In our tool making section, wemanufacture our own threadcutting and spinning tools inorder that we can supply ourcustomers with any type ofthread quickly and independ-ently. Here, our spinning toolsare checked. The angularaccuracies of the cutting toolsare ± 10 min. Profiles are alsomeasured here.

Our own test stand has beenbuilt to our specification tosatisfy particular customerrequirements. On this it is pos-sible to simulate different ballscrew applications. Amongstother things, we measure therigidity of the nut system, theno-load torques and the pre-loading. Furthermore, we canobserve the way in which thetemperature develops in the nutunder different loading condi-tions. The test stand can alsobe used for endurance test runsunder load.

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What is checked?Measurement of the lead accuracy every 300 mm of the ball screw

(to DIN 69051)the individual pitch of each thread or, for example, every 100 mmthe wobble errorthe radial runout error at the spindle endsthe length of the spindlethe flank diameter (accuracy and radial runout)

Ball screws are drive units that make it possible to position machine components highly accurately, e.g. in machine tools and measuring equipment. To achieve the required accuracy, extensive measurements are also essential between the individual processing phasesto check the manufacture.

Check measurements and tests are carried out for the following criteria, whereby some are of course only performed at the customer’s request:

Radial and axial runoutParallelismAxial playTooth bearingPre-loadingNo-load and load torquesRigidityLead variationMaterialThread profile

HardnessHardening cracksStraightnessDimensionsFit

Reports

We can make all the necessary measurements onball screw spindles and nuts on our test machine

with its computer analysed lead and measurementreports. Test reports can be supplied on request.

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Quality Assurance in the manufacturing process

A multi-position measuring machine with the latest measuring computer for largeproduction runs (e.g. automobile industry).

The measured values are displayed on the screen or printed out (static processcontrol).

Safeguarding check during batch production for Quality Assurance purposes(individual spindle check).

Production of 8/R cards, histograms, quality standard cards and CP/CPK values.

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Application examplesBall screw

Main areas of application:

Due to its high precision, the ball screw brings outstanding performance to measurement and control technology, which is a deciding factor in the following areas of application.

Textile processing

� Machine tool manufacture� Conveyor technology� Aviation industry� Reactor technology� Handling technology� Medicine technology� Military technology� Measurement and testing technology� Traffic engineering� Radar and antenna technology

Problem: Adjustment of textile rollers

Solution: The heavy rollers are adjusted by two ball scr-ews installed vertically. The high efficiency of the KGTspindle enables a small drive to be used.

Axial support

The diagram shows a part section of the axial sup-port of a numerically controlled lathe. The fast feedspeed is 1200 rpm. Pre-loaded and rigid bearingsare required for the ball screw spindle in this appli-cation.

Design solution

This type of ball screw spindle bearing is a typical standardsolution for precision ball screws. The drive side of the ballscrew spindle is mounted in a needle axial cylindrical rollerbearing from the ZARF..LTN range. This has a long life dueto the high dynamic rating. The positioning accuracy andrepeatability of the ball screw is guaranteed by the consi-derable rigidity of the bearing.

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Positioning technology

Steel sheet processing machine

Problem: Exact adjustment of a stop.

Solution: A fast and accurate positioning of the stop canbe achieved by using a ball screw.

Problem: Rapid movement of sheets for laser cutting.

Solution: The coordinate table is moved using a ball screw inthe X and Y axis. Long life and positional accuracy areachieved here without any problem.

The drawing shows the feed spindleof a CNC controlled laser cuttingmachine. The ball screw spindle hasa nominal diameter of 63 mm and alength of 3000 mm. Low friction andhigh precision determine the choice ofbearing.The operating conditions of the lasercutting machine are characterised bylow feed forces and a maximumspindle speed of 500 rpm.

Design solutionThe ball screw spindle is mounted atboth ends in angular-contact ball bearings from the ZKLF… 2RS range.The long spindle is stretched bymeans of an adjusting nut. A second,inner, slotted nut pre-loads the bear-ing. The O-arrangement in the axialangular-contact ball bearings with acontact angle of 60° works againstthe deflection of the spindle. The axialangular-contact ball bearings are bolt-

ed directly to the bearing blocks bytheir thick-walled, rigid outer rings.They absorb the axial forces thatoccur without any difficulty and gua-rantee low friction in operation. Theyare sealed on both sides with sealingrings from the RS range. Additionalseals in the surrounding constructionare unnecessary. The bearings aregreased for life with a synthetic lubri-cating grease with high ageing resi-stance.

Bearing arrangement for ball screw spindle

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ApplicationsBall screw3-co-ordinate manipulator

Problem: Magazining of production parts.

Solution: A gripper and four ball screws in the X, Y and Zaxes are moved by motors via a CNC control. Rapid move-ments are made possible by the low inherent weight of thedesign and the high efficiency of the ball screw.

Bearing arrangementfor the ball screw nutThe primary products manufacturedon this flat grinding machine are pro-filed workpieces. The vertical move-ment of the grinding head is to takeplace by means of an electro-mecha-nical drive with a ball screw spindle.

Design solutionVery small, continually varying adjust-ments to the grinding wheel are oftennecessary when grinding profiles.

The sealed and greased for life angular contact ball bearing, typeZKLN…2RS, prevents the stick-slipeffect with these adjustments. By thismeans, it is possible to achieve grind-ing results of the highest precision. Inorder to keep the oscillations fromthe ball screw as small as possible,in this case the rotating ball screwnut is mounted in bearings while theball screw spindle is stationary. Thetwo ball races in the anti-friction bear-ing are arranged in O-formation at60° contact angle to one anotherand are pre-loaded.

In order that the pullout torque of themotor is not absorbed solely by thefixed bearing, a needle bearing fromthe NA…2RS VGS range is providedas an additional supporting bearing.The needle bearing is fitted with apre-ground inner ring. This designallows the inner ring to be finish-ground in the assembled state inorder to achieve the smallest possi-ble radial play.

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Future-orientated manufacturing processes safeguard the technological advantage

Manufacturing process on a Waldrich machine during the production of a ball screw spindle.

Under these conditions, we can achieve a lead accuracy of 0.03 mm per 1000 mm. With the help of our electronic leadcorrection unit it is possible to optimise the accuracy of the machine guide spindle so that its individual and total errors donot exceed +/- 0.002 mm.

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Ball screw technologyThe ball screw is a working unit for converting a rotary to a linear movement and vice-versa.

It consists of the spindle, the nut system with ballfeedback elements and the balls as anti-friction ele-ments. The balls form the connection between thespindle and the nut by rolling in the appropriatetracks in the spindle and the nut. The forces to betransmitted are distributed over a number of balls sothat the result is a relatively small specific loading. On account of its rolling friction, the ball screw hasan extremely low coefficient of friction.

EfficiencyThe efficiency of ball screws is considerably higherthan that of conventional trapezoidal screws due tothe rolling friction that occurs in this case.Furthermore, there is no slip-stick effect, whichmakes it possible to traverse even the smallestdistances accurately. With ball screws it is fundament-ally possible to reverse the motion due to the lowfrictional losses even at relatively small lead angles,i.e. to convert a linear movement into a rotary one.Therefore, in installations where self-retardation isrequired, the appropriate safeguards such as brakes,for example, must be provided.

Advantages:Long life, which is many times that of the slide screw.The heat developed is considerably less, which meansthat higher traverse speeds are possible.The higher cost of the ball screw can be compensatedfor to a great extent by these factors. At the sametime, the fact that it is not self-retarding may need tobe taken into account.When sliding friction is combined with low relativespeeds (creep), intermittent sliding always occurs, theso-called slip-stick effect, even though a proportion-ately sized drive and a constant speed are used. Thisundesirable slip-stick effect does not occur with rollingfriction enabling the same position to be achievedrepeatedly.

Installation:Before installation, the ball screw must be cleaned witha cleaning fluid such as benzene, if necessary. Cleaningfluids must not act aggressively on the wiper materialssuch as nylon or felt. It is not usually necessary toremove the preservative. Ball screws are protectedagainst corrosion in the factory and must be lubricated(oil and grease) before putting to use.

Materials for ball screws

SpindlesSteel for surface hardening Cf53Material No. 1.1213Surface hardness 60 + 2 HRCTensile strength Rm 600 N/mm2

Elastic limit Rp 400 N/mm2

Material No. 1.7225 42 CrMo 4Surface hardness 60 + 2 HRCTensile strength Rm 900 N/mm2


Balls100 Cr 6. Accuracy quality class I – III (highest quality class) to DIN 5401,Hardness 63 ± 3 HRC.

NutsMaterial No. 1.2067 100 Cr 6Hardness 61 + 2 HRCTensile strength Rm 980 N/mm2


Hard up to Rm 2100 N/mm2

Material No. 1.3536Hardness 61 + 2 HRCTensile strength Rm 690 N/mm2


Hard up to Rm 1800 N/mm2

Material specification for 100Cr6: Material No. 1.3505,designation to DIN 17 006Special materials on request.

ball screw nut

ball screw spindle

ball screws

conventional trapezoidal spindles

Lead angle in degrees

Effi

cien

cy in

%

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Ball screws must be fundamentally protected againstdirt and contamination. With KAMMERER ball screwsthis is achieved as standard by means of plasticwipers, which can however slightly protrude beyondthe nut housing. At the customer’s request, we canalso supply ball screws with brush or felt wipers. Werecommend that the wipers be changed after the ballscrew has been running for an appropriate time inorder to improve the life.

The best solution however is to completely cover theball screw using a spiral spring cover, for example.

Wipers

Brush wiper

Dismantling the nut:If possible, the nut and the spindle should not be dismantled. However, if this should be necessary, anassembly sleeve must be used (see sketch).

Felt wiper

Plastic wiper

Outside ø of sleeve = core ø of spindle mm.

Slide the sleeve over the end of the spindle as far asthe start of the thread and then screw the nut careful-ly from the thread onto the sleeve. Dismantling mustbe carried out without the use of force. Make surethat the nut cannot slip off the sleeve (O-ring or simi-lar). When screwing the nut on to the spindle, thestart of the thread must be screwed in carefully.Note: The balls must not be allowed to getbehind the return sections. Cleanliness must beensured !!!

–0.1–0.3

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Track profileKammerer ball screws are basically equipped with Gothictrack profiles and offer the following advantages:Good running characteristics, high rigidity and a goodcontact angle � of around 45° are aimed for.

� = contact angleδa = axial playr1 = ball radiusr2 = track radius

This profile with the largest possible load angle �, goodlubrication conditions and a ball diameter calculated for theappropriate application brings the following advantages:

– highest ratings and thus long lifetime– best running characteristics– efficiency up to 98 %– maximum rigidity– almost constant drive torque

Axial play with a single nutLike the anti-friction bearing, due to its design, the ballscrew with a single nut has an axial play of 0.02 to 0.05 mmdepending upon its dimensions, which is constant regard-less of loading.

Loading causes an elastic deformation of the materialswith a hysteresis-like character, which in addition gives riseto an axial displacement (see Page 26, Rigidity).

Ball feedback systemsInternal axial ball feedback with single or multiple returnsdepending upon the number of turns of the thread, whichbear the load. The three-dimensional space curve causesthe balls to run softly and with little noise, as these aretaken off tangentially to the ball reference circle. The returnsystem is independent of the lead. Leads of 1 x D or amaximum of 2 x D of the spindle are also possible.

This return system is used by Kammerer.

External ball feedback systems (tube returns). Here, theballs are fed back through a return tube fixed to the outsi-de of the ball screw nut.

Full-hardened nut Full-hardened nut

Spindle, deep drynitride hardened

Spindle, inductivehardened

Internal axial return system

Internal return system

Tube return system

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Pre-loadingIn order to achieve the smallest possible relative movementbetween the nut and the spindle, certain single nuts are ten-sioned against one another.

Fb = operating load [N]Fv = pre-loading force [N]δv = deformation due to Fvδa = axial playδb = deformation due to Fb2 · δb = return distance

– the pre-loading force amounts to of the average opera-ting load.

Loads over and above this cause the balls of the unloadednut to lose contact and the return distance to increase.

– The average operating load is defined as the load consistentwith a life of 20 · 106 revolutions.

– The following relationship can be derived from the above:

Pre-loading nut systemsIn order to eliminate the axial play and to keep the axial dis-placement due to the material deformation as small as pos-sible, nuts are pre-loaded.

Three types of pre-loading are distinguished:

X-pre-loading:The forces are directed inwards. The spindle is under com-pression in the pre-loading range. The pre-loading is increasedby forcing the nuts together.

O-pre-loading:The forces are directed outwards. The spindle is under tensionin the pre-loading range. The pre-loading is increased by forcing the nuts apart.

Pre-loading using oversized balls:The most cost-effective solution, as only half the nut length hasto be manufactured, creates the pre-loading by the oversize ofthe balls (= four point contact) and which is thus finding morefrequent usage.The pre-loading is adjusted by varying the diameter of the balls.

12,83

Nut 1

F v(p

re-lo

adin

g fo

rce)

Axial play

Nut 2

O-pre-loading

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Pre-loading – KammererPre-loading No. 1 is the preferred method used by

Kammerer.

Pre-loading No. 2 is possible at special request.

Pre-loading 1 Pre-loading 2

Nut 2 Nut 1 Nut 2

KeyGrub screw withcentring point

Pre-loading of spindlesSpindles are pre-loaded to increase the positioning accuracy. Changes in length due to foreseeable temperaturedifferences are avoided.For this purpose, spindles must be ground with a lead going into the minus range. The necessary variation in thelead (∆ P) over the whole length is given by the following equation:

RigidityThe total rigidity (Ctot) of a system is made up ofthe individual rigidities (ball screw, bearings …).The effect of all the factors should therefore betaken into account.For the ball screw

coefficient of expansion (steel = 0.011 mm/m · degree)total length of spindle (m)

temperature difference (°C)

necessary lead variation from equationmodulus of elasticity (21 x 104 N/mm2 for steel)spindle cross section (mm2), see equationtotal length of spindle (mm)

average spindle diameter

A temperature difference of ca. 5° can be expected here. The nominal lead is achieved by stretching the spindle duringassembly. The axial force necessary for stretching the spindle (F2) must be produced by the bearings and is calculatedfrom:

The speeds can also be increased when a spindle has been put under tension.

A = nut cross sectional area [mm2]

E = modulus of elasticity 21 · 104 [N/mm2]

Use L1 or L2 according to the direction of the operatingload Fb

L1 ≈ 0.5 · nut length

L2 ≈ 0.75 · nut length

Rigidity of the nut unit (cme)

For an approximate calculation it is sufficient to say:

cme = fcm · ck [N/µm]

fcm = 0.55 (internal pre-loading for single nuts)fcm = 0.70 (pre-loaded double nut)

Rigidity of the body of the nut (cm)

Rigidity in the ball area (Ck)The axial rigidity in the ball area is derived from:

The rigidity values for the ball area can be read offfrom the table on Page 26.The rigidities for designs not given in the table canbe calculated from the following overview and for-mulae. For double nuts, assuming the same num-ber of revolutions for each nut and a ratio of

operating load [N]pre-loading force [N]rigidity factor [N/µm2/3]number of revolutions 3/2

[N/µm]

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Rigidity of the spindle between bearings (cs)

The rigidity of the spindle is dependent upon the type of bearings.

Single-sided fixed bearing, case 1

Double-sided fixed bearing, case 2

Example –Calculation of rigidity

Nut system DIN 69051 according to dimension sheet

Nominal diameter d0 = 50 mmLead P = 10 mmNumber of revolutions i = 4Dynamic rating C = 63200 NOperating load max. Fb = 25000 NSpindle length between bearings l = 1000 mmRigidity factor k = 54.6 N/µm3/2

Connection diameter dk = 43.8 mmSpindle cross sectional area A1 = 1654 mm2

Nut cross sectional area A2 = 2076 mm2

E = modulus of elasticity 21 · 104 [N/mm2]l = length between bearings or between

bearing and nut [mm]A = spindle cross sectional area [mm2]dm = average spindle diameter [mm]

(see table on Page 32 (“critical bendingspeed”)

Calculation of the total rigidity

1. Rigidity of the ball area

3. Rigidity of the spindle

3.1 Single-sided fixed bearing

3.2 Double-sided fixed bearing

4. Total rigidity





2. Rigidity of the nut area

2.1 Rigidity of the nut body

For further rigidity values (bearing rigidity values) see Pages 52 – 58 “Spindle end machining with bearings”.

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Rigidity

DK = ball diameter

d = ball reference circle

i = number of threads bearing the load

K = rigidity factor per thread

ck = rigidity of the double nut

Calculation of the axial resilience of a ball screw in theball area with a rigidity factor K (see adjacent table).

ball re-volution

RigidityDpM/ck

Nut rigidity Cme = fcm · ck

fcm = 0.55 for internally pre-loaded single nuts

fcm = 0.70 for pre-loaded double nuts

Here, the elastic deflection of thenut system can be read off fromthe rigidity factor and the opera-tional loading in N; e.g. KGT 50 x 10:

Example 1:K = 54.6F = 10,000 N→δ ≈ 30 µm

Example 2:K = 54.6F = 25,000 N→δ ≈ 57 µm

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Average loading

Constant speed / varying load

etc.

etc.

etc. [rpm]

Constant speed / linearly varying load

Speed and load varying

Fbm = average axial load [N]nm =average speed [rpm]q1 = proportion of time used referred to 100 %n1 = speed values

Average speed

Drive torque and drive power

If a torque is to be converted to a longitudinal force, then:

When a longitudinal force is converted to a torque (lead angle � ≥ 5°):

The drive power is calculated from:

F = Force [N]Ma = Drive torque [Nm]Me = Output torque [Nm]n = Speed [rpm]P = Lead [mm]Pa = Power [kW]� = Efficiency [0.9 – 0.95]

Load

FS

peed

n

Proportionof time

Proportionof time

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Efficiency � or �’

The lead angle is calculated from:

� = lead angle [°]P = lead [mm]d0 = ball reference circle [mm]� = angle of friction [°] ≈ 0.2° to 0.35°

If a torque is to be converted to a longitudinal force,then:

When a longitudinal force is converted to a torque:

Lifetime

The lifetime (better, nominal life) is expressed by thenumber of revolutions (or number of operating hours atconstant speed) that 90 % of a sufficiently large num-ber of identical ball screws achieve or exceed beforethe first signs of material fatigue occur. The nominallifetime is designated with L or Lh if the figure isexpressed in revolutions or hours respectively.

The dynamic rating C is to be understood to meanan axial load acting centrally (given in N) of unvaryingmagnitude and direction under which a sufficientlylarge number of identical ball screws achieve a nomi-nal life of one million revolutions.

The static rating C0 is to be understood to mean anaxial load acting centrally (given in N) which causes atotal permanent deformation of 0.0001 x the ball dia-meter between the ball and the ball track.

As ball screws are sensitive to radial and eccen-tric loads, these should be avoided if possible.

L = lifetime [revolutions]Lh = lifetime [h]C0 = static rating [N]C = dynamic rating [N]Fam = average axial load [N]Fa max = max. axial load [N]nm = average speed [rpm]fn = utilisation factor

Duration of use KGT (h)Planned utilisation of the machine (h)

Guide values for machine life:

1-shift: 10,000 to 20,000 hours2-shift: 20,000 to 40,000 hours

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Lifetime diagramMini-KGT (Ø 8 – Ø 16)

Load

Fam

[kN

]

Lifetime L [106 revolutions]

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Lifetime diagramKGT (Ø 16 – Ø 160)

Load

Fam

[kN

]

Lifetime L [106 revolutions]

32

Example – Calculation of lifetimeGiven load and speed values:Fast speed: n1 = 1200 rpm, Fb1 = 7,500 N, q1 = 25 %Roughing work: n2 = 60 rpm, Fb2 = 25,000 N, q2 = 40 %Finish machining n3 = 150 rpm, Fb3 = 18,000 N, q3 = 35 %Lifetime of the machine: Lh = 10,000 hUtilisation factor of the ball screw: fn = 0.5Required nominal diameter of the ball screw 40 or 50 mm, lead 10 mm.(These two diameters are derived from the critical speed and the installation conditions).

1. Calculating the average speed (nm) [rpm]

2. Calculating the average load (Fbm) [N]

3. Required lifetime (L): L = 60 · Lh · nm · fn

4. Calculation of the required dynamic loading capacity (C)

Here, a ball screw with a nominal diameter of 50 mm, nominal lead = 10 mm and 4 load-bearingthreads with a dynamic rating of C = 63,200 N is chosen from the dimension sheets.5. Re-examination of the expected lifetime (L and Lh)

Speed limits referred to the nut systemThe maximum speed possible for a ball screw depends above all on the type of construction and the ball feed-back system. Furthermore, it is dependent upon the size and type of the lubrication system (oil or grease).Under the assumption that the ball screw is relatively lightly loaded and that it is well lubricated, the maximumpossible speed can be calculated by a formula.Speed factor for grease lubrication K ≈ 60,000 – 80,000

oil lubrication K ≈ 90,000 – 150,000

nmax = max. speed (rpm)K = speed factord = spindle diameter (mm)

vmax = max. possible traverse speed (mm/sec)P = thread lead (mm)

The maximum possible traverse speed can be calculated from the formula:

With speed factors above 20,000, the dynamic rating of the ball screw should include a safety margin of at least 20 %.The same can be achieved by an appropriate tapering off of the load. However, too small a loading should be avoi-ded at maximum traverse speed as otherwise the wear factor (lifetime) will be adversely affected.These figures are purely for guidance. It should be especially noted that above speeds of 3000 rpm, technical consul-tation with our engineers is necessary.

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Calculation of critical bending speed

Calculation of the critical bending speed nkrTake speed limits of the nut system into account (see Page 32)

0.8 = safety factornkr = critical speed from the diagram [rpm]fk = correction factordm = average thread diameter, see table belowF = weight of the unsupported spindle length in Nla = bearing spacing [mm]nzul = permissible speed [rpm]

Average thread diameter = dmWeight of the spindle/metre = N/m

case 1

Correction factor

case 2

case 3

case 4

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Critical bending speed diagram

Crit

ical

ben

ding

spe

ed n

cr[rp

m]

Unsupported spindle length L [103 mm]

Speed limits of the nut system are to be observed, see Page 32.Correction factor depending on bearing type to be observed, see Page 33.

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BucklingCalculation of the buckling force Fkn as a function of the spindlelength Lk and the core diameter of the spindle.

dk = core diameter of the spindleLk = unsupported spindle lengthfk = correction factor for bearing type

Correction factor fk fortaking the type ofbearing into account:

CoreØ

Buc

klin

g fo

rce

F kn

[kN

]


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Buckling – diagramKGT (Ø 20–160)

Buc

klin

g fo

rce

F kn

[kN

]

Buckling factor see Page 35

Buckling length L [103 mm] (unsupported spindle length)

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Leads – Overview

Spindleø Lead – standard

We can supply any lead on request (maximum lead =2 x diameter). The spindle length can be up to 6000 mm depending on the diameter. Even speciallengths are no problem for us.

preferred standard range

Pre-loaded flanged double nut

Cylindrical double nut

Flanged single nut or internally pre-loaded flanged single nut

Pre-loaded centre-flanged double nut

Single nut with and without screw flange

Nut systemsCylindrical single nut

How accurate are the leads and how are theyproduced?The lead accuracies are in accordance with DIN 69051, Part 3: 3/5/7/10. Test certificatescan be provided. Depending on the application,the leads are ground, fine turned or rolled.

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Single nut without flangeto DIN 69051

(lubrication connection)

Wiper

For exact outside diameter of spindles see page 37

Any special leads and imperial threads can be provided on request.

DIN dimensions and lead

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Single nut with flangeto DIN 69051

Lubrication connection

Wiper

Drilling diagram 1 Drilling diagram 2

Forms of flange


DIN dimen-sions and lead

Drillingdia-gram

Lub. conn.No. ofholes

40

®



Double nut without flangeto DIN 69051

(Lubrication connection)

Wiper

DIN dimensionsand lead

41

®



Double nut with flangeto DIN 69051


Wiper

Drilling diagram 1 Drilling diagram 2

Forms of flange

DIN dimen-sions and lead

Drillingdia-gram

Lub. conn.No. ofholes

42

®



Single nut

Lubrication drilling

LeadP

Lub.conn.


43

®



Single nut without flange


Wiper

Dynamic ratingcdyn

Static ratingcstat

44

®



Double nut without flange

(Lubrication connection)

Wiper

45

®



Single nut with flange


Wiper

Drilling for M … DIN 6912

Lub.conn.

46

®



Double nut with flange

Drilling for M … DIN 6912


Wiper

Lub.conn.

46/1

®

Left-hand threads and special leads can be provided on request.

Kammerer normFlange nut

Drilling diagram 1

Forms of flange

Drilling diagram 2

Lubrication connection:

KGT 16 – 32 = M 6KGT 40 – 80 = M 8 x 1

Ball

46/2

®

Left-hand threads and special leads can be provided on request.

Kammerer normCentre flange nut

Lubrication connection:

KGT 16 – 32 = M 6KGT 40 – 80 = M 8 x 1

Ball

47

®

Miniature balls screws

Assembly department for miniature ball screws. A high degree of precision and dexterity is required here. Thehighest standards of cleanliness and precision engineering skills are needed during assembly.

48

®



Miniature single nut

o = single nutx = double nutinternally pre-loaded

49

®



Miniature single nut without flange


on requestd (lubrication connection)

Wiper

50

®

Any special leads and imperial threads can be provided on request. *) = on request (special)


Miniature single nut with flange



Wiper

Lub.conn.

51

®

Spindle ends

KMT nuts

Spiral spring covers

Lubrication –Lubricants

52

®

Standard spindle ends

BearingZARF/LTN

Lock nut

53

®

Needle axial cylinder roller bearings

Range ZARF .. LLight duty range


Range ZARF .. LHeavy duty range

Shaftdiameter

Weight

kg

DimensionsFixing

screws DIN9121)

Ratings Limiting speed Axial rigidity

cal

N/µmng greaserpm

ng

oilrpm

Code

Shaftdiameter

Weight

kg

DimensionsFixing

screws DIN9121)

Ratings Limiting speed Axial rigidity

cal

N/µmng

greaserpm

ng

oilrpm

Code

54

®


BearingZARN/TN

Lock nut

55

®


Range ZARNLight duty range


Range ZARNHeavy duty range

Shaftdiameter

Weight

kg

Dimensions Ratings Limiting speedAxial

rigidity cal

N/µmng

greaserpm

ng

oilrpm

Code

Shaftdiameter

Weight

kg

Dimensions Ratings Limiting speedAxial

rigidity cal

N/µmng

greaserpm

ng

oilrpm

Code

56

®


Rikula 2RSSize

Bushø x ø x L4

Circlip DIN 471

CirclipDIN 471

Bush

57

®

Shaftdiameter

Weight

kg

Dimensions Fixing screwsDIN 912 10.9 Qty

RatingsConnection dimensions Axial rigidity

cal

N/µm

Limitingspeed

ng greaserpm

Code


Axial angular-contact ball bearings

Double-sided actionRange ZKLN … 2RS

Table of dimensions. Dimensions in mm

Bearing ZKLN/RS KMT Shaft Nuts

58

®

Shaftdiameter

Weight

kg

Dimensions Fixing screwsDIN 912 10.9 Qty

RatingsConnection dimensions Axial rigidity

cal

N/µm

Limitingspeed

ng greaserpm

Code

Axial angular-contact ball bearings

Double-sided actionRange ZKLN … 2RS

Double-sided action, screw fixingRange ZKLF … 2RS



BearingZKLF/2RS

Lock nut

Withdrawal slot

59

®

Spindle end machining

Machining nuts and spindle ends on the latest CNC machines

60

®

Shaft nut KMT

The KMT shaft nut secures without damaging theshaft

The KMT nut is secured with three brass locking pinsdistributed equally around the circumference and whichare set into the nut at an angle. The slope angle of thepins is equal to the flank angle of the nut thread, whichis also cut into the end surfaces of the locking pins inone continuous process.

The KMT shaft nut does not need a keyway

As a result, the shaft diameter can be made smaller.Costs for the manufacture of the keyway and the keycan be avoided.

The KMT shaft nut locking system does not sufferfrom material fatigue

The locking pins are pressed against the shaft threadwith the help of adjusting screws.Axial forces are absorbed by the flanks of the threadand not by the locking pins. Securing the nut againstturning is based exclusively on the friction between thepins and the screw thread. As the locking pins do notbecome distorted, KMT shaft nuts can be used asoften as required with the same high accuracy.

The KMT shaft nut locking system is reliable

Even when the generously sized adjusting screws areonly gently tightened, a high locking force is achieved.The force applied by the adjusting screws is usedexclusively for locking the nut, i.e. – load is not taken off the flanks of the nut thread– the nut is not distorted.

The KMT shaft nut is adjustable

When securing the KMT nut, the three locking pinsarranged equally around the circumference enable anexact right-angled adjustment to be made. Variationsor inaccuracies of other components sitting on theshaft can be compensated for by means of the KMTnut.

Material: High-strength steel (similar to StE47)Surface treatment: phosphatised, oiledLocking pins: hard drawn brassAdjusting screws: P6SS (ISO 2343/DIN 913),hardness class 12.9 – 14.9Nut thread tolerance: 5 H (ISO 965/3)Tolerance 6G is recommended for the shaft thread

FA = axial force

Shaft nutKMT/KMTA

Code

Permissibleaxial load

FAKMT/KMTA

Breakawaytorque1)

Tightening torquefor adjusting screws, max.

KMT

1) Applies for adjusting screws tightened to max. tight-ening torque.

61

®

Shaft nuts KMT – Data

Slotted nuts

KMT nuts are to be used where simple fittingand reliable locking with high accuracy arerequired. They can be tightened and releas-ed using simple tools such as open-endedspanners, adjustable spanners, hookedspanners or impact spanners.

Shaft nut thread

GCode

Dimensions Weight Suitable hookspanner

Code


Threadd

Code Weightkg

Dimensions Axial breakingload FaB

62

®

Spiral spring covers… protect shafts, spindles, columns and screws againstcontamination and damage and reduce the risk of acci-dent in this area.… can be used in all swarf-producing and swarfless ma-chines, etc.… are made of high-quality, hardened spring steel andhave optimum characteristics due to their special methodof manufacture.… are designed in a spiral shape and are manufactured inthe diameters and installation lengths shown below.Different strip widths guarantee faultless operation for thedifferent stroke lengths.… achieve very good sealing between the individual turnsin any position. Simple centring flanges are all that arerequired for mounting the springs, as shown adjacent.The flanges must however accomodate the rotary move-ments of the spring that occur. The centring flanges arenot included in the scope of supply.When installing vertically, it is recommended that the largediameter is fitted at the top and when installing horizontal-ly it is fitted towards the accumulation of swarf.No maintenance is necessary. However, it is recommen-ded that cleaning be carried out depending upon thedegree of contamination and that a light film of oil be sub-sequently applied.For functional reasons it is necessary when enquiring orordering to state whether the HEMA spiral springs are tobe fitted horizontally or vertically. When fitted horizon-tally, the dimension Da is increased by ca. 3–5 mm.HEMA spiral springs help to maintain the precision of yourmachines and also increase their life.Design: spring steel, blued, stainless on request.

Explanation of drawing:

d = max. diameter of the part to be coveredD1 = inside diameter of springDa = outside diameter of springLmin. = minimum installation lengthLmax. = maximum installation length

DF1 = outside diameter of the centring flange (D1 – 2 mm)DF2 = inside diameter of the centring flange (Da + 4 mm)Stroke = largest possible travel

All dimensions in mm

As ball screws are sensitive to dirt and swarf, they must fundamentallybe protected by sealed covers such as bellows or telescopic springs.

Can be fitted horizontally and vertically

Spiral springcover

for KGT type

63

®

All dimensions in mm

Type Type

64

®

Lubrication of ball screws

Basically, the same lubricants can be used for lubri-cating ball screws as for anti-friction bearings, i.e. bothoil and grease.

In contrast to anti-friction bearings, the maximum oper-ating temperature is of far more importance with ballscrews, as it affects the accuracy of the ball screw dueto the longitudinal expansion along its axis. A single fil-ling of grease for the ball screw as a lifelong lubricationis not generally adequate, as grease is continually re-moved due to the spindle shaft repeatedly moving inand out of the lubricated area and thus damage couldoccur within a foreseeable time due to lack of lubrica-tion. If grease nipples are specified for re-lubricationpurposes, damage may also be expected if the maint-enance intervals are not observed or if the ball screwis over greased.

As central lubrication systems are available in manyinstallations, oil lubrication predominates with ball screws.

Oil lubrication

Oil lubrication by means of a central lubrication systemhas the advantage that it is always possible for anadequate film of lubricant to build up and for low heat-ing of the ball screw to occur due to the improvedheat transfer. Furthermore any excess oil is removedby the wiper.

Basically, circulating oils with active ingredients for in-creasing the corrosion protection and the ageing resist-ance in accordance with C-L to DIN 51517 Part 2, asare also used for lubricating anti-friction bearings, aresuitable for supplying ball screws. The viscosity of thelubricant to be used depends primarily on the speedand the ambient temperature as well as the loading. Inorder to guarantee an adequate film of lubricant at alltimes and under all operating conditions, a somewhathigher viscosity of lubricant should be aimed for. In mostcases it is sufficient to select the lubricant in accord-ance with the following table.

If the ball screw speeds are less than 20 rpm and/orhigh loading is to be expected, it is recommended thata circulating oil with active ingredients to increase theageing resistance of the corrosion protection as wellas additives for increasing the loading capability andimproving the protection against wear in accordancewith C-LP to DIN 51517 Part 3 is used.

The amount of oil required for each ball revolution isabout 3-6 cm3/h. With immersed lubrication, it is suffi-cient if the oil level is maintained at the centre of thelowest roller when installed horizontally.

Grease lubrication

Lubrication of ball screws with grease suggests itselfwhen it is not possible to install central lubricationsystems and low speeds are to be expected. Furtheradvantages are the improved sealing effect, the avoid-ance of running dry and the independence from theinstallation orientation. The re-lubrication intervals areto be agreed with Kammerer for each application inorder to avoid damage due to lack of lubrication.

Lubricating greases are divided into NLGI classesaccording to DIN 51818 corresponding to their flexingpenetration. In normal cases (operating temperature –20 °C to +120 °C), class K2k water resistant greasesto DIN 51825 are to be used for ball screws. In specialcases, greases to NLGI 1 (for very high speeds) orNLGI 3 (for highest loads or low speeds) are possible.

The mixing of greases based on different saponifica-tions should be avoided. Consultation with the manu-facturer is necessary if the operating temperatures lieabove or below the given values.

The amount of grease to be applied is such that thecavities are approximately half filled. In order to avoidunnecessary overheating of the ball screw due to overgreasing, it must be ensured that the design enablesused or excess grease to escape.

65

®

Lubricants

ViscosityISO

No ISOnorms

Aralub HL 2, LF 2 multi-purpose grease Avia multi-purpose greaseAvilub special grease EP

Avilub special grease A

No ISOnorms

No ISOnorms

DesignationDIN 51 517

ViscosityISO


ViscosityISO


66

®

Trapezoidal screwsApplication examplesExample 1:

Lift table system Problem: Lifting of machine parts

Solution: The trapezoidal spindle is adjusted by means of anelectric motor. The design gives a progressive force charac-teristic and does not require a stopping brake.

Example 2:

Co-ordinate table

The co-ordinate table shown in section is inte-grated within a numerically controlled proces-sing centre for rough milling operations.The co-ordinate table is positioned using thetrapezoidal screw. It has a clamping area of1600 mm x 550 mm and can be traversed inthe X-direction by up to 900 mm.Due to the high traverse speed, a particularlyrigid bearing arrangement is required for thespindle of the trapezoidal screw.For situations requiring accurate processing, itis preferable to use ball screws.

Design solution

The trapezoidal spindle is mounted in a needle axial cylinder rollerbearing ZARF..TN at the drive end and in a ZARF..L bearing at theother end. The stepped shaft disc of the ZARF..L TN bearingprovides optimum support for the bearing at the other end of thespindle in spite of the small spindle shoulder. Both bearings can bebolted directly to the surrounding construction so that adaptationwork and additional flange covers are not required. Sealing of thebearing positions is not necessary here, as the lubricant is allowedto escape.

67

®

Problem: electrically actuated entrance gate

Solution: Trapezoidal screw with electric motor and strokelimiter. The spindle is covered to avoid risk of injury and con-tamination (bellows).

Example 3:

Entrance gate opener

Example 4:

Ventilation flap

Opening and closing a skylight or ventilationflap

The gearing with drive and fittings is mountedusing a cardan adapter.The end points (fully open and fully closed)are restricted using limit switches.

Example 5:

Linear stroke gearbox

The lifting spindle travels through the linearstroke gearbox without rotating.When using a single linear stroke gearbox,measures should be taken to prevent thespindle from turning.

68

®

Trapezoidal screw spindles

Sold by the metre, spun

Trapezoidal thread to DIN 103, tolerance class 7e

Standard lengths are 1m, 1.5m, 2m, 3m

Other lengths possible on request

The adjacent materials are available from us as standard

Other materials and tolerances on request

Two quality classes available (see table below)

All sizes can also be supplied as left-hand thread

Ordering example:Screw spindle Tr70x10 x 2m long, left-hand lead, spun QC2

Thre

ad

Thread

Quality classes to Kammerer norm

Other accuracies possible on request.Quality classes

Lead variation

Straightness

Outside ø tolerance

Further dimensions on request

69

®

Trapezoidal screw spindles

Sold by the metre, rolled

Trapezoidal thread to DIN 103, tolerance class 7e

Standard lengths are 1m, 1.5m, 2m, 3m

Other lengths possible on request

Material: C15


Two quality classes available (see table below)

Ordering example:Screw spindle Tr20x4 x 2m long, right-hand lead, rolled QC2

Thre

ad

Quality classes to Kammerer norm

Other accuracies possible on request.

Quality classes

Lead variation

Straightness

Flaking


Thread Right Left Thread Right Left

not permissible permissible

70

®

Rolled screw spindles

The rolling of threads is an economic manufacturing process. Based on swarfless cold defor-mation, it has a positive affect on the characteristics of the base material.

The natural course of the grain is not destroyed unlike with machine manufacturing processes(e.g. thread spinning, thread cutting, thread milling or thread grinding).

Thread rolling has a positive affect on the following physical and technical characteristics:

– higher resistance to wear, tensional strength and bending strength– higher surface quality of the die-burnished flanks of the thread– less corrosion– high thread profile accuracy depending upon the quality of the rolling tool– high flank diameter accuracy (parallelism) due to accurate pre-material tolerances

Plastic nuts are particularly well suited to rolled threads. The efficiency of the spindle drive is higher due to the high surface quality of the flanks of the rolled thread and the low friction of plastics.

According to DIN 103, the core diameter of rolled trapezoidal screws can be 0.15 x P less thanwith machined trapezoidal screws (flow radius required on the thread-rolling tool).

Rolled threads can display the so-called closing fold (undercut) on the outside diameter of thethread. This has no effect on the quality or the function of the thread. The undercut is only a criterion for making a judgement of the roll technology.

The disadvantages of rolled compared with spun trapezoidal screws:

– very high tooling and setup costs– strong influence of the material characteristics on the accuracy of the lead (changes with each

batch of material)– spindles with larger form elements than the outside diameter of the thread cannot be rolled or

can only be rolled at great expense.– too high a surface quality due to polishing of the flanks of the thread can lead to a detachment

of the lubricant film between the spindle and the nut and thus to “a tendency to seize” whengrease lubrication is required (e.g. with steel or bronze nuts).

– not suitable for the manufacture of individual components and small production runs, as theaffect on the thread rolling process (machine and tooling) is cost and parts-intensive.

71

®

Trapezoidal screw nuts

Round nut, short or long

Trapezoidal thread to DIN 103, tolerance class 7H

Max. runout error up to Tr 22x5 = 0.2 mm; from Tr24x5 = 0.3 mm

These nuts are provided in the adjacent materials


Short design: L = 1.5 x nominal diameter

Long design: L = 2 x nominal diameter

Ordering example:Round nut Tr 44x7, left-hand, made from CuSn12, short, in accordance with Kammerer catalogue


Plastic

Thread D1 LTr 8 x 1,5 18 12Tr 10 x 2 22 15Tr 10 x 3 22 15Tr 12 x 3 26 18Tr 14 x 4 30 21Tr 16 x 4 36 24Tr 18 x 4 45 27Tr 20 x 4 45 30Tr 22 x 5 50 33Tr 24 x 5 50 36Tr 26 x 5 60 39Tr 28 x 5 60 42Tr 30 x 6 60 45Tr 32 x 6 60 48Tr 36 x 6 75 54Tr 40 x 7 80 60Tr 44 x 7 80 66Tr 48 x 8 90 72Tr 50 x 8 90 75Tr 60 x 9 100 90Tr 70 x 10 110 105Tr 80 x 10 120 120Tr 90 x 12 130 135

Short design

Thread D1 LTr 8 x 1,5 18 16Tr 10 x 2 22 20Tr 10 x 3 22 20Tr 12 x 3 26 24Tr 14 x 4 30 28Tr 16 x 4 36 32Tr 18 x 4 45 36Tr 20 x 4 45 40Tr 22 x 5 50 44Tr 24 x 5 50 48Tr 26 x 5 60 52Tr 28 x 5 60 56Tr 30 x 6 60 60Tr 32 x 6 60 64Tr 36 x 6 75 72Tr 40 x 7 80 80Tr 44 x 7 80 88Tr 48 x 8 90 96Tr 50 x 8 90 100Tr 60 x 9 100 120Tr 70 x 10 110 140Tr 80 x 10 120 160Tr 90 x 12 130 180

Long design

72

®


Flanged nut, short or long


Max. runout error up to Tr 22x5 = 0.2 mm; from Tr24x5 = 0.3 mm

These nuts are provided in the adjacent materials


Two designs (long or short), with or without fixing holes

Ordering example:Flanged nut Tr 20x4, right-hand, made from RG7, short, in accordance with Kammerer catalogue


Plastic

Thread D1 D4 D5 D6 L (short) L (long) L1 L7Tr 8 x 1,5 22 32 4 40 12 16 4 8Tr 10 x 2 25 34 5 42 15 20 5 10Tr 10 x 3 25 34 5 42 15 20 5 10Tr 12 x 3 28 38 6 48 18 24 6 12Tr 14 x 4 28 38 6 48 21 28 9 12Tr 16 x 4 28 38 6 48 24 32 12 12Tr 18 x 4 28 38 6 48 27 36 15 12Tr 20 x 4 32 45 7 55 30 40 8 12Tr 22 x 5 32 45 7 55 33 44 8 12Tr 24 x 5 32 45 7 55 36 48 8 12Tr 26 x 5 38 50 7 62 39 52 8 14Tr 28 x 5 38 50 7 62 42 56 8 14Tr 30 x 6 38 50 7 62 45 60 8 14Tr 32 x 6 45 58 7 70 48 64 10 16Tr 36 x 6 45 58 7 70 54 72 10 16Tr 40 x 7 63 78 9 95 60 80 12 16Tr 44 x 7 63 78 9 95 66 88 12 16Tr 48 x 8 72 90 11 110 72 96 14 18Tr 50 x 8 72 90 11 110 75 100 14 18Tr 60 x 9 88 110 13 130 90 120 16 20Tr 70 x 10 88 110 13 130 105 140 16 20Tr 80 x 10 118 130 15 160 120 160 18 22Tr 90 x 12 118 130 15 160 135 180 18 22

73

®


Hexagonal nut


Not suitable for motion screws

Material: 9SMn28K


Ordering example:Hexagonal nut Tr 10x3, right-hand, in accordance with Kammerer catalogue


ThreadThread SW LTr 28 x 5 41 42Tr 30 x 6 46 45Tr 32 x 6 46 48Tr 36 x 6 55 54Tr 40 x 7 65 60Tr 44 x 7 65 66Tr 48 x 8 75 72Tr 50 x 8 75 75Tr 60 x 9 90 90Tr 70 x 10 90 105

Thread SW LTr 8 x 1,5 14 12Tr 10 x 2 17 15Tr 10 x 3 17 15Tr 12 x 3 19 18Tr 14 x 4 22 21Tr 16 x 4 27 24Tr 18 x 4 27 27Tr 20 x 4 30 30Tr 22 x 5 32 33Tr 24 x 5 36 36Tr 26 x 5 41 39

74

®

Technical data

Metric ISO trapezoidal thread to DIN 103

Nominal Ø . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . dLead for single start threads andPitch for multi-start threads . . . . . . . . . . . . . . . . . . . . PLead for multi-start threads . . . . . . . . . . . . . . . . . . . . PhNumber of starts . . . . . . . . . . . . . . . . . . . . . . n = Ph : PCore Ø of bolt thread . . . . . . . . . . . . d3 = d – (P+2 · ac)Outside Ø of nut thread . . . . . . . . . . . . . D4 = d + 2 · acCore Ø of nut thread . . . . . . . . . . . . . . . . . . D1 = d – PThread flank Ø . . . . . . . . . . . . . . . d2 = D2 = d – 0.5 · PDepth of bolt and nut threads. . . . . . . . . . . . . . h3 = H4 = 0.5 · P + acFlank overlap . . . . . . . . . . . . . . . . . . . . . . . H1 = 0.5 · PHeight of tooth tip . . . . . . . . . . . . . . . . . . . z = 0.25 · PTip clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . acRounding . . . . . . . . . . . . . . . . . . . . . . . . . . . R1 and R2Three chisel width . . . . . . . . . . b = 0.366 · P – 0.54 · acFlank angle . . . . . . . . . . . . . . . . . . . . . . . . . . . � = 30°

Dimn. For lead P in mm

Thread designation

D x P

Nut thread

Bolt thread Flank ød2 = D2

Thread dimensions in mm

Core ø

Boltd3

NutD1

OutsideøD4

Threaddepth

h3 = H4

Ph Lead: Distance along theline of the flank diameter be-tween adjacent flanks of thesame orientation of the samethread.

P Pitch: Distance along theline of the flank diameter be-tween adjacent flanks of thesame orientation.

Multi-start (n-start) threadshave the same profile as single-start threads where the lead Ph = the pitch P.

Only the permissible values forthe lead P (equal to the pitch P)of the single-start thread maybe selected for the pitch P ofthe multi-start thread. A multi-ple of the pitch P of the multi-start thread does not howeverhave to correspond to a per-missible lead value for a single-start thread.

Single and multi-start threads

single-start

Pit

ch =

Lea

d

Pit

chLe

ad =

2 .

Pit

ch

Pit

chLe

ad =

3 .

Pit

ch

two-start three-start

75

®

Thread diameters and leads

Dimensions in mm

Lead P of the single-start trapezoidal threadNominal thread diameter dSeries Series Series

1 2 3

Material CuSn and CuAl alloy/steel Cast iron GS, GTW

permissible surface compression in N/mm2Sliding speed in m/sreferred to flank Ø

The size of thread can bechosen from the thread andlead table.

For example:chosen diameter = 40 mm,Preferred range = 7.Designation = Tr 40x7

A maximum of only threeleads is recommended foreach thread diameter. Oneof these is identified as thepreferred lead in order torestrict the number of trape-zoidal threads to be usedstill further. If, in specialcases, other diameters arerequired in place of thoselisted, a lead should be cho-sen that is associated withthe nearest diameter.

Permissible sliding speeds (guide values):

76

Max. loading of trapezoidal screwsreferred to the nut lengthThese values do not include any safety margin! Furthermore, buckling must be taken intoaccount. Based on a surface compression of 10 N/mm2

Length of nut F in N/dyn Length of nut

®

77

®

Efficiency of trapezoidal screws

Single-start Two-startcast iron

drycast ironlubricated

CuSn, CuZndry

CuSn, CuZnlubricated

plasticdry

cast irondry

cast ironlubricated

CuSn, CuZndry

CuSn, CuZnlubricated

plasticdry

plasticlubricated

plasticlubricated

The efficiency of trapezoidal spindles is significantlyless than that of ball screw spindles due to the slidingfriction.

However, the trapezoidal screw is technically simplerand less expensive. A holding device (e.g. brake) isonly required in rare cases due to the self-brakingaction of the trapezoidal screw spindle.

For an exact calculation, see Page 82 onwards.Friction values, see Page 83.

ball screw

Lead angle in degrees

Effi

cien

cy in

%

conventional trapezoidal spindle

78

®

Critical bending speed – Diagram


Crit

ical

ben

ding

spe

ed n

cr[rp

m]

For an exact calculation, see onwards. Flank ø for trapezoidal spindles is tobe taken into account, see Page 74.Note max. sliding speed at the flanks, see Page 80.

79

®

Buckling – diagram


Buc

klin

g fo

rce

F kn

[kN

]

For an exact calculation(buckling factor), see Page80 onwards. Characteristicdiameter for trapezoidalspindles is to be taken intoaccount, see Page 74.

80

®

CalculationsCarrying capacity:The ratings of trapezoidal screws are influenced by many factors. The most important factors are material pairings, surface quality, surface compression, duty, lubrication and temperature.Select a screw according to your requirements (required feed speed, fitting space, etc.) and calculate thenecessary length of nut for your application.

Arithmetical determination of the nut lengthLm = nut length required [mm]F = axial loading force [N]P = thread lead [mm]pzul. = permissible surface compression [N/mm2]d2 = flank diameter [mm]H1 = thread bearing depth [mm] (0.5 x P)z = number of starts

Pvorh. = existing surface compression [N/mm2]F = axial loading force [N]P = thread lead [mm]Lm = nut length required [mm]d2 = flank diameter [mm]H1 = thread bearing depth [mm] (0.5 x P)z = number of starts

vg = sliding speed [m/s]n = rotational speed [rpm]d2 = flank diameter [mm]

s = feed speed [m/min]n = rotational speed [rpm]P = lead [mm]

The permissible surface compression is dependent upon the sliding speed and the material used for the nut. Avalue of 10N/mm2 can be taken as a rough estimate. Approximate values for common materials can be found inthe table below.

Existing surface compression depending on nut selected

Sliding speed

Screw feed speed

Approximate values for the permissible surfacecompression for sliding screws. Exact particularscan be requested from the material manufactur-ers.

Material: Sliding speed Pzul.

[m/s] N/mm2

Steel 1,5 10CuSn alloy 1,5 10CuAl alloy 1,5 10Plastic PA 0,6 1

81

®

Calculations

Drive torque

Mta = drive torque [Nm] when converting a rotary toa linear movement

Mte = drive torque [Nm] when converting a linear toa rotary movement

F = axial loading force [N]P = thread lead [mm]� = efficiency�’ = efficiency

� = efficiency (torque to linear force)�’ = efficiency (linear force to torque)� = lead angle [°]� = friction angle [°]

� = lead angle [°]P = thread lead [mm]d2 = flank diameter [mm]

� = friction angle [°]µG = see table below

Pa = drive power [kW]Mta = drive torque [Nm]n = rotational speed [rpm]

Friction values for common nut materials.

These values can be affected by lubrication,roughness, loading, etc.

Efficiency

Lead angle

Friction angle

Drive power

The thread is self-retarding if the lead angle < the friction angle

Nut made from

Cast iron GC

dry lubricated

Steel

Bronze CuSn Plastic

82

®

Calculations

Critical bending speed

Permissible speed

fkb = 0.32 (case 1)

Correction factor fk for calculating the permissible speed.

fkb = 1.0 (case 2)

fkb = 1.55 (case 3) fkb = 2.24 (case 4)

The critical bending speed is dependent upon the deflection of the spindle and thus upon the diameter and thedistance between the bearings. The permissible speed can now be calculated from the way in which the spindleis mounted and from a safety factor.

ncr = critical speed due to weight and length ofspindle [min-1]

d2 = flank diameter of thread [mm]F = weight of the unsupported spindle length [N]la = distance between bearings [mm]

nzul. = permissible speed [min-1]ncr = critical speed due to weight and length of

spindle [min-1]fkb = correction factor for deflection0.8 = safety factor

83

®

Calculating the buckling force

The buckling force of the screw spindle is dependent upon the unsupported spindle length and the core diameterof the spindle.

Correction factor fk for taking into account the type of mounting.

Calculations

FKn = buckling force for the spindle [N]d3 = spindle core diameter [mm]fk = correction factor for type of mountingLK = unsupported spindle length [mm]

fk = 0.25 (case 1) fk = 1.0 (case 2)

fk = 2.0 (case 3) fk = 4.0 (case 4)

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All about us

In 1938, Franz Kammerer founded a small commer-cial enterprise in his own home. This was mainly forthe manufacture of components for the domesticclock industry.

The Second World War put a complete stop to pro-duction. Manufacturing was restarted after 1946.

From the manufacture of clocks via the production ofprofiled components, by 1963 things had progressedto trapezoidal screw spindles and the associatednuts. This step saw the entry into a field, whichdemanded a lot of patience, skill and precision.

Following the all too early death of the company foun-der in 1967, his wife and two of his sons continuedthe development of the business up to the precisionmanufacturing of trapezoidal screw spindles, crossroll spindles and the associated nuts and bushes ofthe present day. The supplying of top quality goodsresulted in a rapid growth of the business and thus toan expansion of the production capacity. The factoryarea available was becoming too small.

In 1970, the company was forced to move to rentedaccommodation following the purchase of a modernthread turning machine.

Longer and stronger screw spindles were more andmore frequently in demand so attention was turned tothe construction of a new production facility. This wasstarted in 1977. A suitable site was found in Tribergand the company had moved into the completed fac-tory buildings by 1978.

The present day operation, led by the brothers Klausand Wolfgang Kammerer, with its approximately 100employees, numbers amongst the most sought-afterspecialist manufacturers of trapezoidal screw spind-les, worms and worm shafts, cross roll spindles andball screws at home and abroad.

Clients include companies from the machine toolindustry, general machinery manufacture, precisiontechnology, manufacturers of automatic handlingmachines and telescopic spindles, the aircraft indu-stry, the automobile industry, medicine, manufacturersof robots and many other branches of industry.

The extraordinarily positive development in the lateryears made it necessary to open up extra capacityand to find additional space. In 1990, the companywas able to rent an additional manufacturing area inthe buildings of a formerly different commercial enter-prise in neighbouring St. Georgen and to fit out mostof it with new machines.

It can already be foreseen today that even the pre-sent total production area will not be sufficient. Theconstruction of an additional production area inTriberg was completed at the end of 1995. Thesemeasures made it possible to move the outside pro-duction completely back to Triberg once more.

Kammerer has also made significant investments inrecent years in order to be able to offer the best qua-lity that is currently technologically possible using themost up-to-date, future-orientated manufacturingprocesses. The organisation has set itself the task ofextending this technological advantage even further.

These days, yesterday’s visions become concretereality at ever increasing speed. Meeting the steadydevelopment of our firm in the future forces us toexpand our production and administration premisesto a total of 5500 m2. This expansion is not possibleat our current company location.Despite our close ties with the city of Triberg, the onlychoice open to us is to build on our own land in theHornberg-Niederwasser industrial area.

As a company with innovation in mind, Kammerer willalso be striving in the future to be able to offer itscustomers the definitive product that, as perhaps youwill find, is a little better than the normal.

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The headquarters of today’s Kammerer organisation in Hornberg, which in the meantime concentrates on themanufacture of ball screws, trapezoidal screws, worms and worm shafts.

Our production facility is situated where others go on holiday – in the middle of the Black Forest. How about a visit?

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The finish-machining of thenuts takes place on two 3-axisCNC thread-grinding ma-chines each with 2 grindingspindles for internal and exter-nal machining. The machiningof the ends of the spindleswith a new cylindrical grindingmachine can be seen in thepicture on the right.

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One of the first steps in thepreparation for spindle manu-facture is the centring, theaccuracy of which is a deter-mining factor in the later workstages (grinding, straightening,…). Our spindles are preparedon this centre-grinding ma-chine for this reason.

Straightening is an importantpart of the process in themanufacture of precisionspindles. For this reason, thelatest technology is employedhere too.

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A new Waldrich machine isavailable just for the manufact-ure of ball screw spindles. Thequality of the spindles that canbe achieved is well above thatof rolled and nearly as goodas that of ground spindles.The lead accuracy is toleranceclass 3 according to DIN69051 (G 10).

4-axis controlled machiningcentre with the most up-to-date CNC dialogue control formachining KGT nuts andreturns as well as complicatedprofiled components andother CNC machine-groundparts.

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We manufacture larger quanti-ties of trapezoidal screwspindles, ball screw spindles,worms and worm shafts up toØ 20 mm on CNC controlledthread-rolling machines.

The KGT is assembled ingenerously appointed rooms.The bright working areas areergonomically designed andseparated from the swarf-producing manufacturing area.

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Questionnaire Part 1Customer: _________________________ Customer No: __________Address: __________________________________________________Telephone: __________________ Telex: ________________________Department: _______________ Contact: _______________________New design: � Re-design: �Enquiry dated: _____________________________________ Order dated: _________________________________________

Order confirmation dated: _____________________________ Order No: Customer drawing No: _______________________________ dated: ______________________________________________

No: _______________________________ dated:_______________________________________________No: _______________________________ dated: ______________________________________________

Standard spindle, type: ___________________________________________________________________________________QuantityCall-off of: _______________ items ____________________ monthly, yearly ________________________________________________________ per order, or ____________________________________________________________________________

We would ask you to provide us with as many technical details as possible. Our offer can then be worked out morecarefully and appropriately for the application. If possible, please attach an installation drawing or draft sketch of the ball screw to this request.

Comments (or sketch)

1. Operating data1.1 Drive via spindle shaft � nut �1.2 Static max. loading, axial (Fa) Tension: _____________ N, Compression: _________________________ N1.3 Dynamic max. loading: Tension: _____________ N, Compression:__________________________N1.4 Non-axial loading: Fr = _______________ N, Fp = _________________ N, r = ______________________________ mm

1.5 Safety factor in the loading figures: ______________________________________________________________________1.6 Loading direction: single-sided � two-sided �1.7 Speed at the stated loads: v = _______________________ mm/min, n = __________________________________ rpm1.8 Max. speed: nmax = _______________ rpm1.9 If the loads or speeds should vary, please provide details in the table below.

Collective load

Type of load or or

Utilisation factor:ball screw duty (h)machine duty

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Questionnaire Part 21.11 Spindle mounting

1.12 Distance between bearings: ______________________________________________________________________ mm1.13 Installation orientation: vertical � horizontal � at an angle of ___________________________ degrees1.14 Max. permissible play: ___________________________________________________________________________ mm1.15 Required rigidity:_______________________________________________________________________________ N/µm1.16 Permissible no-load torque: _______________________________________________________________________ Nm1.17 Required life: __________________________ operating hours, _______________________________ x 106 revolutions

2.0 Operating conditions2.1 Dust/dirt � Moisture � influence of chemicals �2.2 Seal type: Bellows � Telescopic spring � Plastic wiper � Felt wiper �2.3 Operating temperature: _______________________ °C, Ambient temperature _______________________________ °C2.4 Type of lubrication: ___________________________________________________________________________________2.5 Unusual operating conditions: __________________________________________________________________________________________________________________________________________________________________________________

3.0 Characteristic data of spindle3.1 Required nominal diameter ø A: ___________________________________________________________________ mm3.2 Lead P: _________________ mm3.3 Lead direction: right-hand � left-hand �3.4 Permissible lead variation �p/300 mm at 20 °C ______________________________________________________ µm3.5 �p/thread length at 20 °C ________________________________________________________________________ mm3.6 Permissible lead variation according to drawing No: ______________________________________________________3.7 Actual lead variation diagram required: �3.8 Max. wobble error: _______________________________________________________________________________ mm3.9 Thread length:___________________________________________________________________________________ mm3.10 Total length: ___________________________________________________________________________________ mm3.11 Spindle in tension � Compression � pre-loaded at Fv = ________________________________________ N 3.12 Material: _______________________________ to ISO, DIN: ________________________________________________3.13 Material No: ____________________________ Quality norm: _______________________________________________3.14 Surface treatment: __________________________________________________________________________________3.15 Hardness: ______________________________ Depth of hardening zone: ____________________________________3.16 Ball screw surface: _______________ Roughness class: __________ Reference roughness value Ra:__________ µm3.17 Accuracy class: _____________________________________________________________________________________

4.0 Characteristic data of nut4.1 Max. length:_____________________________________________________________________________________ mm4.2 Max. diameter: __________________________________________________________________________________ mm4.3 Housing to drawing No: _______________________________________________________________________________4.4 Single nut � max. axial play ___________________________________________________________________________4.5 Double nut: Type of construction: ______________________ pre-loaded at Fv =______________________________ N 4.6 Max. axial displacement δa = _____________ µm at Fva = ________________________________________ N4.7 Max. reversal span δu = _____________ µm at Fva = ________________________________________ N4.8 Material: _______________________________________ to ISO, DIN __________________________________________4.9 Material No: _____________________________________ Quality norm: _______________________________________4.10 Surface treatment: ___________________________________________________________________________________4.11 Hardness: _______________________________ Depth of hardening zone: ____________________________________4.12 Ball screw surface: __________________________________________________________________________________4.13 Accuracy class: _____________________________________________________________________________________

Checked and approved (customer) Checked (Kammerer)

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