nut and bolt loading curves
TRANSCRIPT
UNCLASSIFIED ORNL-578
AL RESEARCH LIBRARY
UMENT COLLECT-3ON
NUT AND BOLT LOADING CURVES
CENTRAL RESEARCH LIBRARY
DOCUMENT COLLECTION
LIBRARY LOAN COPY
DO NOT TRANSFER TO ANOTHER PERSON
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OAK RIDGE NATIONAL LABORATORYOPERATED BY
CARBIDE AND CARBON CHEMICALS DIVISIONUNION CARBIDE AND CARBON CORPORATION
ITTW
POST OFFICE BOX P
OAK RIDQE, TENNESSEE
UNCLASSIFIED
UNCLASSIFIED
Contract No. W-7^05, eng 26
OBNL-578
This document consista 55pages.m
n"ry__/- of 1fr* Series A.
TECHNICAL DIVISIONBnginoering Development Section
HUT AND BOLT LOADING CURTIS
C. P. Coughlen
DATE ISSUIDsFEB 151950
OAK RIDGE NATIONAL LABORATORYo-o@rated by
CARBIDE AND CARBON CHEMICALS DIVISIONUnion Carbide and Carbon Corporation
Post Office Box P
Oak Ridge, Tennessee
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ORNL 578
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W. L.
J. P.W. E.
J. R.
R. E.
C. L.
F. L.
H. E.
F. C.
R. J.
R. P.F.-N.
W. G.
W. E.
T. H.
C P.
rW?^«^lS«S^^a<WWffi)«1»3*^^S™«l' "•<
Scott, Jr.Gill
Sholl
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EngbergSegaserCuller
Goeller
McCulloughKlotzbach
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Browder
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UngerThomas
Coughlen
Rsnd CorporationSandia Bs.se
Sylvania Electric Froducts, Inc.Technical Information Branch, OREU. S. Public Health ServiceUCLA Medical Research Laboratory
(Warren)
University of California RadiationLaboratoryUniversity of RochesterUniversity of WashingtonWestern Reserve University(Friedell)Westinghouse
- 3 -
TABLE OF CONTENTS
1.0 ABSTRACT .....
2.0 INTRODUCTION .
3.0 TEST PROCEDURE
k.O TEST DATA ..r .
5.0 DISCUSSION OF RESULTS
APPENDIX
I TABLE OF OBVIOUS DEFECTS.........................
II SHIFT IN LOADING CURVE ON SECOND RUN-DOWN OF NUT,
III EXCERPT FROM MEMO UNDER DATE OF 23 MARCH, 19^9BIB. VAN WINKLE
ORHL-578
Page
k
k
5
6
*7
*9
50
51
- k - ORNL-578
1.0 ABSTRACT
Tests of nut and bolt sets were made wherein were measured the bolt
loads resulting from controlled torques applied to the nuts. Torques were
applied using calibrated torque wrenches. Loads were measured by a
Tate-Emory Universal Testing Machine in which the specimens were mounted.
Metals of construction, bolt sizes (l/2" to 1 l/8") and thread
surface conditions were varied.
Normalized curves are presented with little comment, the data being
considered too scanty to permit firm conclusions.
As appendices are (I) a table of comments on certain irregularities
noted during the test work, (II) a table listing qualitatively the shift
in the loading curves on the second run-down, and (ill) a reprint of an
analysis of the data (by R. Van Winkle) that was included in a memorandum
of very limited distribution. The analysis includes some additional data
developed by Van Winkle.
2.0 INTRODUCTION
A specific design under consideration specified the use of unlubricated
stainless steel nuts and bolts of sizes within the range of l/2M to 1 l/8w
(standard). Concern was expressed that maintenance operations would be
complicated by the 'freezing' of nuts on bolts and studs.
The subject investigation was undertaken in an effort to develop
information that would serve as a basis of prediction of maintenance
difficulties and aa a basis for specifying bolting materials.
~5 - ORNL-578
2.0 INTRODUCTION (Cont'd)
Time being available at the inception of the work, the decision was
made to expand the tests somewhat, to include the use of some non-stainless
materials and the effect of conditions not called for by the above mentioned
design.
3.0 TEST PROCEDURES
Special holders were constructed for use with a Tate-lmory Universal
Testing Machine. The holders consisted of a shaft about lh inches long
and 3 inches in diameter which attached to a wedge block that locked the
shaft into the bottom movable platten. The bolt head was locked by set
screws into a heavy duty cap that screwed onto the upper end of the shaft.
The bolt extended through the cap and thence through a heavy duty plate which
rested on the upper platten of the machine, A lubricated washer was usually
used. The nut was run down until the nut threads were full, the platten
adjusted to give a nominal load reading on the testing machine, and the
bolts further loaded by hand operated torque wrenches.
The torque wrenches used varied in size from 50 ft-lbs. maximum to 420
ft-lbs. maximum. Each was calibrated by loading th® wench with lead brick
and shot.
The bolt loads at a number of applied torques were recorded.
- 6 - ORNL-578
3.0 TEST PROCEDURES (Cont'd)
Test groups normally consisted of nine bolt-nut pairs each. These
were randomly separated into three sub-groups; (1) for testing in the
'as received' condition, (2) for testing in the 'degreased' condition
(2 washes of carbon tetrachloride), and (3) for testing in the 'greased'
condition. For the latter condition the Testing Machine threads were
robbed of a little grease.
k.O TEST DATA
The data are presented as normalized mean curves. No single curve,
with but one exception, was developed from more than three individual run
curves. Anomalies are present and will be discussed briefly later.
In all cases, the abscissa Is 'foot-pounds' of applied torque and the
ordinate is the resulting load in thousands of pounds (kips).
The curves are grouped in three ways. First, the metal pairs and
surface conditions are held constant for each plot with the curve family
representing different sizes. Second the size and surface condition are
specified with the family of curves describing different metal pairs.
Third, the metal pairs and the size are specified resulting in a curve
family of conditions of surface.
The shifts in the loading curves and successive run-downs of the nut
are presented in appendix II.
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8 -
FIGURE 4.1.1.2
303 S. S. Nut303 S. S. Bolt
"IBB 15o—' ' 250' 255"
Torque Applied to Nut-Ft-Lbs.
Condition - Degreased
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o
(15
O
20-
- 9
FIGURE 4.1.1,3
303 S. S. Nut
303 S. S. Bolt
100 150 200 250
Torque Applied to Nut-Ft. Lbs.
Condition - Greased
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20
TlJUL —
FIGURE 4.1.2.2
303 S. S. Nut304 S. S. Bolt Condition- Degreased
Torque Applied to Nut-Ft-Lbs.
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3
i-4
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20
- 12 -
'V'"'%/«Si^:SjAl^
FIGURE 4,1,2.3303 S. S. Nut
304 S. S. Bolt Condition - Greased
Torque Applied to Nut-Ft-Lbs,
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/
//
FIGURE 4 .'1.3 «1
Condition - As Received
Curve 1 - Steel Nut
304 S.S. Bolt
Curve 2 - Steel Nut
303 S.S. Bolt
3/4"
3/4w
50 ioo 150 . 200 250
Torque Applied to Nut-Ft.-Lbs.
300 350
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20
15
14
Condition - Degreased
Curve 1 - Steel Nut" 304 S.S. Bolt - 3/4'
Curve 2 - Steel Nut~ 303 S.S.Bolt - 3/4"
50
Curve 3 - Steel Hut304 S.S. Bolt - 1
3.00 150 200 250Torque Applied to Nut-Ft.-Lbs,
300 350
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50
15
FIGURE 4.1.3.3
Condition - Greased
Curve 1 - Steel Nut~ 304 S.S. Bolt - 3/4"
Steel Nut
303 S.S. Bolt - 3/4B
Curve 3 - Steel Nut~ 304 S.S. Bolt - 1 1/8"
100 150 200 250Torque Applied to Nut-Ft-Lbs.
300 350 400
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64
20
16
FIGURE 4.1.4.1
Carbon Steel Bolt Condition- As ReceivedCarbbn Steel Nut
25 50 75 100 150 200Torque Applied to Nut-Ft-Lbs.
300 350
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20
50
17
FIGURE 4.1.4.2
Carbon Steel Bolt Condition - Degreased
Carbon Steel Nut
100 150 200 250
Torque Applied to Nut-Ft-Lbs.
300 350
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//
S"
/
/
*» $°
' j£$•>
FIGURE 4.2.1.3
Comparison of Various Metal Pairsat 1/2w Size
Condition - Greased
J0 1() 2 0 3<3 40 5«5 60 7<5 8 0 90 100
Torque Applied to Nut-Ft-Lbs.
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64
22 -
16—
ill
•
IP
10
c#X
^ 3: ^*r
R
^^^ FIGURE 4.2.2.1
Comparison of Various Metal Pairsat 5/8" Size
Condition - As Received
6
/ &
k-4
2
— /
1 1 1 11', 10 ?ni1 | _L 1 1 I | 1 | , jj i
0 2 0 4(3 £ 0 8<3 1 00 u 20 1*0 L60 180 200
Torque Applied to Nut-Ft.-Lbs
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14
12
10
8
23 -
C onTnArlaon
FIGURE k
nf TTnT"4 mis
-.2.2.2
Ma+.a 1 Pn 1 vq
at 5/8" Size
Condition - Degreased
s
s
—
—
—
>^1%;^2r
&>-^^
—
— ^0^^^'
• -
—
^ ^| , ! ^ , _u i 1 1
! , • ( ! , !
40 60 80 100 120 140
Torque Applied to Nut-Ft-Lbs,
20 160 180 200 220
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25 -
St-St
St-303
St-304
303-303303-304
°fl—
^6FIGURE 4.2.3.1
Comparison of Various Metal Pairs
at 3/4" Size
Condition - As Received
24
'tHH '
2U
18
—
•
16
14
-"
12
1 0
—
^ — •„ ^
—
•^
*
8
6
4
?
—
0 >* ff fi& &**"
1 I 1 |_i__l_ | | 1 1 | | 1 1
0 10 20 30 40 50 60 70 80 90 100 120 130 140 150 160 170 180 190 200 210 220
Torque Applied to Hut-Ft-Lbs.
co
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M 22
o
03
a 20
«
n ltthi
•pHI 16O
«
H) 14-Pr>
64
12
40
26 -
80 100 120 140
Torque Applied to Nut-Ft-Lbs.
FIGURE 4.2.3.2
Comparison of Various Metal Pairsat 3/4" Size
Condition- Degreased
200 220 240
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13
12
11
10
9
8
FIGURE 4.2.4.2
Comparison of Various Metal Pairsat 1 1/8" Size
Condition- Degreased
- 28
Torque Applied to Nut-Ft-Lbs,
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S ?
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1-4
i
FIGURE 4.3.1.2
Hut- 303 S.S.Bolt- 303 S.S.
Size 5/8"
31
*5o" 80 100
Torque Applied to Hut-Ft-Lbs.
FIGURE 4.3.2.1
304 S. S, Nut304 S. S. Bolt
Size 1 1/8"
Curve 1 - As ReceivedCurve f^A - Greased-Shipment 1Curve 2-B - Greased- Shipment 2Curve 3_ - Degreased
- 33 -
150 200 250 300Torque Applied to Nut-Ft-Lbs.
Lll 1 1 I 1.450
To
tal
Bo
ltL
oad-
Lbs
.x
10"3
oro
•To
n0
00
ro
js-
O CD)12Torque
N_
.......
..-_
S£
£m
&
01602AppliedtoHut-Ft-
W O&
4H
1e
c4-
c*
co'
'«
H-
CO
CO
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®.p
-co
a
1co
coii
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=-
Oo a
co
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XV
94
c0
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ro
.\
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FIGURE 4.3.3=4
Nut - 303 S.SBolt - 304 S.S
37 -
TSC ISo SOO 240"
Torque Applied to Hut-Ft-Lbs.
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- 38 -
As Racelved
/ Degreased
FIGURE 4.3.4.1'
316S. S. -*-»- Hut304 S. S. -*— Bolt
Conditions as labelled.
Size 5/8'
200
Torque Applied to Mut-Ft-Lbs.
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10
8
40 -
—
/
I-
—
/ /
fa1 ISi
—
—
/M/
•
—
—
II—
/ /
/ £f JS/
—
—
—
FIGURE 4:3.5.1h
Hut - Carbon Steel
Bolt - 304 S.S.
Size - 3/4"
—
—
—
—
—
— M J
mi
40 80 120 160 200 240Torque Applied to Nut-Ft-Lbs.
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42 -
ic
-
FIGURE 4.3.6.1
8Nut - Carbon Steel
Bolt - Carbon Steel
Size - 1/2"7
6
~
4
5
<*>
•
31
*&y
2
1
0 sK J 1 1 | | 1,
j_ • ii 1 , | 1 L
Ci 1 0 2/>'' 3 0 Vc> 5 0 o£) 701 8o
Torque Applied to Nut-Ft-Lbs,
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- 44
-
FIGURE 4.3.6.3 t
20— Nut - Carbon Steel
/
Bolt- Carbon Steel //
Size - 3/4"18
—
/
/
-/
/
1.6 / f
— / /
14 / •*/ /
/
55 /
12w
t/—
4V
in
8
6
4
J
olr\ 1 l I 1 | 1 i 1 \ | ! | I 1 10 4 ) 80 ll20 16 0 2(30 240 2(50
Torque Applied to Nut-Ft-Lbs,
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45
20
18
16
FIGURE 4,3.6.4
Hut - Carbon Steel
Bolt - Carbon Steel
Size - 1"
/
/
/ '
/ j.
/
/14
TO
—
J/i/*v/Jo/
V
//
/
10
^
«/
7
/
—
8
6
—
—
4
o
r v\ i I | 1 1 1 1 1 1 1 1 _L
i
1
0 5 0 1C0 1 ^o 2C)0 250 3C)0 350 \^00
Torque Applied to Hut-Ft-Lbs.
enioH
a
*3
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!
- k6
It_ 1
—i
9 i
//
As R joeiwd
Q
/
i
0
:
l
7
: i /
! ' 1/ax eased /
/ /! /
Tin6 ! /
l! / /
//
/ "^
5
—
— i
\ ,
k
—
—
-/
Everdur NutTSvnyAur' Bolt
3
—
Conditions as labelled.
Size 1/2"/
1
12
—
FIGUBE M.7.1
—
J
!
1
i
1
1,—
/ /
0 K\ 1 >l 1
1
i ,I
, ,4—J—
1*00 10 20 30 ko 50 6o 70 80 90 100 120Torque Applied to Hut-Ft-Lbs.
_ kj - ORNL-578
5.0 DISCUSSION OF RESULTS
The number of data available for each curve are statistically
inadequate to permit any claims that they may be used as design bases
unless a wide uncertainty is allowed. Lack of manpower, economically
spendable, forced the investigation into a suspended category. The
preservation and dissemination of the data obtained to date is the only
excuse for this report at this time. At some later date, additional effort
may be expended to develop sufficient additional data so that the sum total
then available may be statistically adequate for firm conclusions.
The curves may be considered to describe the loading characteristics
of only the test groups.
Qualitatively, considerable can be said. Orders of bolts and nuts,
manufactured supposedly to meet purchase order specifications, were found to
be little better than surprise packages. Material specifications were not
met in over 50$ of the orders. The specified No. 2 fits were often doubtful.
Further, careful examination of a test group usually led to the
conclusion that all members of the group were structurally identical with
comparable thread surfaces. Yet quite divergent results were often obtained.
Re-loading results were often unpredictable. Improvements resulted when
degradations were expected, and vice versa. Further, the entire range of
•degradation through no change to improvement' was found in three-member
test groups in more than one instance.
- 48 - ORNL-578
5.0 DISCUSSION OF RESULTS (Cont'd)
Speculation Is in order as to the effects of various variables, i.e.
the condition of the bolt machine cutters, the disposition of the bolt
machine operator, etc. It is suspected that variables such as these play
Important parts in determining the loading of any given nut-bolt set.
To sum - the data are inadequate but are here presented as a matter
of record to satisfy numerous requests that they be so presented.
- 49 - ORNL-578
APPENDIX I
TABLE OF OBVIOUS DEFECTS
1/2" Hut 303 S. S. ———————— in degreased condition, threads ofBolt 303 S. S. both nut and bolt galled badly.
5/8" Hut 303 S. S. — .—.——__ in degreased condition, two setsBolt 304 S. S, froze after second run-down.
1 1/8" Nut 304 S. S. — -- In degreased condition, two setsBolt 304 S. S, froze after second run-down. In
all conditions, threads were badlygalled,
- 50
APPENDIX II
SHIFT IN LOADING CURVE ON SECOND HUH-DOHH OF HUT
ORNL-578
Result of Second Run-Down
Hut Bolt As
Condition
Material Material Size Received Degreased Greased
303 S. S.303 S. S.303 S. S.303 S. S.
304 S. S.304 S. S.304 S. S.304 S. S.
1/2"5/8"3/4"7/8"
AD
AD
AI
SD
AD
AD
WV
SD
V
LC
LC
303 S. S.303 S. S.303 S. S.
303 S. S.303 S. S.303 S. S.
1/2"5/8"3/4"
SD
AD
AD to LC
SD
AD
V
SD
SI
LC
304 S. S. 304 S. S, 1 1/8" AD to V WV AI to LC
C. Steel
C. Steel
0. Steel
C. Steel
C. Steel
C. Steel
C. Steel
C. Steel
1/2"5/8"3/4"
1"
AD
SI
LC
WV
AD
AD
AD
AD
AI
AI
V
SD
316 S, S. 304 S. S. 5/8" AD LC AI
Everdur Everdur 1/2" SD AD V
Steel
Steel
304 S. S.304 S. S.
3/4"1 1/8"
AD SD
SD
AI
LC
Steel
Legend
AD
SD
LC
SI
AI
V
WV
303 S. S. 3/4" SI
Appreciable degradation of loading curve.Slight degradation of loading curve.Little change in loading curve.Slight improvement of loading curve.Appreciable improvement of loading curve.Variable change.Widely variable change.
SI
- 51 -
APPENDIX III
Excerpt from memorandum under date of 23 March, 1949, by R. Van Winkle.
"According to the piping handbook, an initial bolt stress of 30,000
to 60,000 psi to set the gasket in place is common practice. The initial
tension secured in bolting depends on the method of control, if any, used
in tightening the bolts. Experienced pipe fitters usually tighten the bolts
in high pressure flanges to give a bolt tension of approximately 60,000 pel
with raised-face Joints. In the case of ring-type Joints, a bolt tension
of 30,000 psi has been found adequate. Bolt tension may be controlled to
some extent by use of torque wrenches adjusted to permit application of only
sufficient turning effort to secure the desired bolt stress.
The turning required to secure bolt stresses of 30,000 and 60,000 pel
with different size alloy-steel bolts threaded in accordance with the
American Standard Screw Threads is given in Table I.
TABLE I
Nominal
Diameter
of Bolt,
Number of
Threads
per
Area at root
of
Thread
STRESS
30,000 Ib/sq.in. 60,000 lb/sq.in.Torque Force per Torque Force per
Inches Inch Sq„ Inches ft-lbs. bolt,lbs. ft^lbs. bolt,lbs.
1/2 13 0.126 30 3780 60 75605/8 11 0.202 60 6060 120 12,320
3/4 10 0.302 100 9060 200 18,1207/8 9 0.419 160 12,570 320 25,1401 8 0.551 245 16,530 490 33,060
1-1/8 8 0,728 355 21,840 710 43,6801-1/4 8 0.929 500 37,870 1000 55,740
- 52 - ORNL-578
APPirogjEII (Cont'd)
This table is based on tests conducted by Crane Company and represents
results obtained with well-lubricated thread® and bearing surfaces. Tests
with no lubricant on threads aad bearing surfaces showed an increase of
almost 100$ in the torque required to secure a given bolt stress.
The use of stainless steel bolts and nuts for bolting components
together presents the problem of obtaining adequate bolt tension without
galling the threads.
Careful tests conducted by C» P, Coughlen"s group indicate that in no
case could stainless steel bolts and nuts fe® tightened sufficiently to give
bolt stresses as high as 60,000 psi without serious galling of the threads.
Table 2 shows a summary of the torques that war® required to produce a stress
of 30,000 psi in 1/2", 5/8% 3/4", 7/8'B and l-l/8w stainless steel bolts and
nuts. Comparison of Table 2 with Table 1 shows that stainless steel bolts
and nuts require almost 100$ more torque for a given bolt stress than do
the alloy steel nuts and bolts tested by the Gran© Company,
In order to circumvent the problem of tte"@a& galling by the use of 303
stainless steel nut® on 303 stainless steel bolts, it has been proposed to
use hardened chrome steel nuts on 303 bolts, which are two dissimilar
metals.
53
APPEHDH III (Cont'd]
TABLE 2
COUGHLEH DATA
ORHL-578
Bolt
Diameter
Bolt
Material
Hut
Material Treatment
30,000 psi Stress 60,000 psi Stress
Torqueft .lb.
Force perbolt,lb.
Torqueft.lb.
Force perbolt,lb.
1/2--l/2«l/2M
303303303
303303303
As Rec"d
DegreasedGreased
48-6052-62
62
378037803780 -
756075607560
1/2"1/2"
.1/2"
304304 ,304
303303303
As Rec'dGreased
Degreased
40-4-743-4755-58
378037803780 -
756075607560
5/8-5/8-5/8"
303303303
303303303
As Rec'dDegreasedOreased
106-118115-143115-119
606060606060
- 12,120w
It
5/8"5/8"5/8"
304304304
303303303
As Rec'd
DegreasedCreased
118-134166-210
92-93
606060606060 -
»
It
w
3/4"3/4"3/4"
303303303
303303303
As Rec'd
DegreasedGreased
191-202200-223169-183
906090609060
- 18,120
18,120
3/4"3/4"3/4"
304304304
303303303
As Rec'dDegreasedGreased
200-220*
2l8-230f172-175
906090609060
- 18,120«
n
3/4"3/4"3/4"
303303303
Steel
Steel
Steel
As Rec'd
DegreasedGreased
134-140205135-131
906090609060
-
18,120n
M
7/8"7/8"
304304
303303
As Rec'd
Degreased(240)1(240 )X
12,57012,570 -
25,140
1-1/8"1-1/8"
304304
Steel
Steel
DegreasedGreased
440440
21,84021,840 -
- 54 -
APPEHDH III (Cont'd)
ORHL-578
Tests were performed with a torque wrench to determine the effect of
heavy torques on the 303 stainless steel bolt threads using hardened chrome
steel nuts. Ho thread damage was observed in any of the tests. Table 3 is
a summary of the tests.
TABLE 3
Bolt
Diameter
1/2"*1/2"7/8"7/8"
1"
Torqueft-lb.
100-140120
240-340305-400450-500
Estimated
Bolt Load
9000-12,00011^,00014,000-20,00018,000-23,00022,000-25,000
Estimated
Stress
70,000-95,00067,00033,000-48,00043,000-55,00040,000-45,000
* Twisted bolt in two using a torque of 175 ft-lbs. Threadswere undamaged and the nut ran freely on and off the threads.
In Table 3, the bolt loads were estimated by combining Coughlen's
experience with the results given in Table 1. For instance, in Table 2,
using a steel nut on a 303 stainless steel 3/4" bolt (as received condition),
a torque of approximately 134-140 ft-lbs. was required to give a bolt load
of 9060 pounds, while in Table 1, for the same bolt size, a torque of only
100 ft-lbs. was required. Thus, about 1.35 times as much torque needs to be
applied to a steel nut on a stainless steel bolt than on the materials used
in the test of Table 1.
Estimated bolt load = Force per bolt (Table 1) x ^1^1 Torque x1735Estimated stress =
Estimated bolt load
- 55 - 6RHL-578
APPEHDIX III (Cont'd)
According to these assumptions, then, the required torques to produce
30,000 psi and 60,000 psi are given in Table 4.
TABLE 4
ESTIMATED TORQUES FOR VARIOUS BOLT DIAMETERS
Bolt
Diameter Bolt Hut
STRjess
30,000 psi. 60,000 psi.Torque Bolt Torque Bolt
Inch Material Material ft.lbs. Load ft.lbs. Load
1/2 303 S.S. Hardened 40 3780 80 75605/8 n
Chrome 81 6060 162 12,1203/4 it
Steel 135 9060 270 18,1207/8 « « 216 12,570 432 25,140
1it « 330 16,530 660 33,060
'Date
/gd