OBJECTIVES

AIMI IZYANA BINTI ISMAIL 0226962

OBJECTIVES

To learn the skills involving the bench works such as chiseling, sawing, marking out and filing. To more understand about the process of bench work.

To get acquainted with operations of marking out, chiseling, sawing and filing.

To know the work holding, metal removing and tools used.

To more understand about the process of drilling

To identify tools for countersink and counter boring.

To get acquainted with various type of drilling machines that use to finish this project. Better understand the various features of a twist drill.

To gain more understanding of the drilling process and to get acquainted with the machines that involved in drilling process.

To familiarize with all the apparatus used and the drilling process.

To know the proper method and safe manner in handling drilling machine.

To familiarize and study the important terms that use in drilling process.

To know about the precautions that must be taken in doing this project.

APPARATUS

Work piece : Mild Steel (102mmx65mmx9mm)

Marking tool

Table

Hand Scriber

Engineer Dividers

Odd-leg caliper

Engineers Steel ruler

Center punch

Engineering square

Scribing block

Parallel bar

Metal removal

Cold chisel

Hack saw

Flat file

Half round file

File brush

Drilling

Drilling machine

Hammer

Twist drills

Oil

Center drill

Vernier caliper

Soft hammer

Countersink drill

Pillar Drilling Machine: H5 32

Two flute twist drill set:

Center drill: (6, (10, (8, (9 Counterbore drill

PROCEDURE

a) First, the work piece is clamped on the vice tightly to ensure that it does not slip.

b) Two sides of the work piece are chosen to be the reference plane. These two sides are filed using a flat file. The surface of both sides must be level so that it is balanced and would stand upright when placed on the parallel bar.

c) The filing process should be done so that the work piece is 90( to each other and until it is able to stand on its own over a smooth surface.

d) One side of the metal is filed using the double cut file so that a flat surface will be obtained. When the surface is almost flat, single cut files is used for finishing work.

e) The engineering square is used to check the flatness of the sides. During filing, there are some metal chips left on the file. The file brush is used to remove these chips.

f) Then the other reference plane is filed until the angle between the two reference planes is 90( to each other, which can be checked with the engineering square whereby if the square rests on the two sides without any gaps, the two planes are perpendicular.

g) When this is finished, the work piece is placed on a flat surface horizontally with the filed side on the flat surface. Using the height gage caliper a 25mm and 50mm mark is done on the work piece.

h) The work piece is then placed vertically with the other filed side on the flat surface and a 20mm, 40mm, 60mm, 80mm and 100mm mark is done.

i) Two quarter circles with a 20mm radius is sketched using engineers divider and the tangent of the circles to the 50mm line is marked.

j) The center punch is then used to mark the line in order to make it more visible while cutting is done. The center of the holes which are to be drilled are also marked with the center punch. Please refer Figure 1.

k) Next, the unwanted part of the work piece is removed using a hacksaw. Once the unwanted part is removed, the surface is filed until it becomes flat and smooth.

l) The drilling process is done after that. Four holes need to be drilled in this project which are, the countersink hole, a hole with an internal thread, a thru hole and a counterbore hole.

m) First the the work piece is placed on the drilling machine table and the machine is switched on. To star drilling, the arm is pressed down on the work piece.n) Then, the center drill is selected. This is to make the next drilling process easier.

o) The drilling process is done by drilling a smaller hole first then continued with the right diameter.p) Instead of using the twist drill with the actual diameter, each hole is drilled from a much smaller diameter and will be increased until the actual diameter is reached. q) For the hole on the right and the left countersink and counterbore is done using the countersink drill and counterbore drill respectively.r) Then the internal thread for the second hole is done by using the tap wrench. For safety, the angle file is used to file the sharp edges.

s) The work piece is measured again to make sure it is right.DISCUSSION

The workbench is the place where a craftsman carries out the most important parts of completing his project, which includes marking out, chiseling, sawing and filing. These operations need patience and skills for the project to come out beautifully. Of all metal removing operations, work holding is the most important aspect as work pieces need to be held tightly in place so that it does not move when filing, chiseling or sawing is taking place. A workbench is usually provided with a parallel jaw vice to hold the work piece. The best working height is when the hand elbow is about level with the vice jaws.

Marking out tools or equipment are required to provide visual indication of the outline of a component, position of slots, center lines of holes, by the use of described lines. The finished shape of a work piece can be obtained by use of tools at the work bench once its outline is marked out.NOTE: The figure shows the main hand metal removal methods. The accuracy decreases as we move upwards.

ACCURACY

Chipping action

COLD CHISEL

Accurate work difficult

Sawing action

HAKSAW

Straight lines only

Surface producing tool

FILE

Very selective metal removal

SCRAPER

Cold chisels are used for breaking down a surface rapidly. Its rate of metal removal is very small and so accurate work is very difficult to obtain. A typical flat cold chisel, shown in the figure below is made from high carbon steel and has a hexagonal or octagonal section to prevent it from rolling off the workbench.

Useless or unwanted part of the metal can be removed using a hand hacksaw. For each job, a correct blade should be chosen instead of using the same one for everything. Hacksaws cut only in the forward direction so on the forward or cutting stroke, the hacksaw is pressed downwards and pressure is eased on the return stroke. While cutting is done, it must be made sure of that at least two teeth is in contact with the material work piece at all time. It is classified by the pitch of its teeth, length of the blade and material of which it is made. Pitch is number of teeth in one mm.

The file has an important role in material removal and filing operations from roughing to finishing on flat and curved surface and can be specified according to its length, pitch and cross section. Without file, a flat and smooth surface cannot be obtained. The single cut file has a series of parallel teeth at an angle to file axis while double cut file has a second series of parallel teeth in the opposite direction and crossing the others at an angle of about 45 to file axis.

Most of the engineering components have holes drilled either in or through them. The machine tool to produce holes is then naturally called the drilling machine. For ordinary workshop purposes, there are three main types of drilling in use which are:

Sensitive drilling machine. Its vertical feed is actuated by hand, which enables the operator to sense how fast the drill is cutting and therefore is able to control it according to the condition of the moment. It is very necessary for holes of small diameters (less than 12 mm).

Pillar drilling machine. It is rigid and of heavy construction and equipped with a power feed. It is suited for holes up to 30 mm and a wide variety of operations such as reaming, counterboring, countersinking and spotfacing. Radial arm drilling machine. It is designed to drill holes in heavy castings or forging that are difficult to reposition for each succeeding hole. The drill arm is capable of vertical movement and of a radial swing, while the drilling head mounted on the arm is capable of lateral movement along the arm as well as automatic vertical feed. It is designed to drill holes in heavy castings or forging that are difficult to reposition for each succeeding hole. The drill arm is capable of vertical movement and of a radial swing, while the drilling head mounted on the arm is capable of lateral movement along the arm as well as automatic vertical feed.In all the drilling operations it is essential to ensure rigidly of both cutting tool and work piece. The drill must be correctly held and the work piece clamped to the table or held in a vice, and it is good practice to ensure that the drill sleeve is at its highest position and the worktable raised to reduce the distance between the drill and the work piece as shown in figure below.

Sleeve in highest position

NON-RIGID RIGID SET UP

SET UP

Excessive amount

Of sleeve protecting

Table raised

Correct setting of the drill sleeve

Cutting speed, Feed, and Depth of cut

1) Cutting speed

Cutting speed in drilling is the peripheral speed of the cutting edge V = DN where D is the drill diameter and N is the rotational speed (rpm). The cutting speed selection depends on both the work piece and cutter materials.

N = V X 1000 r.p.m

D2) Feed

Feed (f) is the distance the drill penetrates per revolution (mm/rev); the share of each cutting edge is f/2.

3) Depth of cut

Depth of cut is taken as half the diameter for drilling (D/2).

4) Drilling time

The drilling time (T) can be given by the equation:

T = L / fN

Where f is the feed (mm/rev),

N is the rotational speed (rpm),

L is the sum of hole depth, approach and over travel distances.

The approach is usually considered as (0.4 D) while over travel ranges from 1

to 3 mm.

5) Material removal rate

The material removal rate (MMR) in drilling is the volume of material removed by the drill per unit time.

MRR = ( D2 / 4) (f) (N)This project took a lot of time because it takes quite a while to master the techniques of filing and chiseling since two sides of the work piece has to be flat and perpendicular to each other. The flat surface took a lot of time to obtain because while filing, the force exerted on the work piece is different which resulted in some sides becoming higher than the other. This also occured in obtaining the 90( between the two sides. If the filing was done slowly and carefully maybe it would take less time to get the flat surface.

Due to the number of our group, there is no problem during the measurement is done. The equipment is enough for us. For marking operation, the problems are while drawing the curve and mark the line. The tools used for drawing the curve, which is engineer divider, does not have sharp end, so marking had to be done several times.

Because of wrong technique used during removing the excessive work piece using the hacksaw, a lot of time had been taken just only to remove the small part of the work piece. If correct technique is used when using the hacksaw, metal removal can be done in a short while. While cutting, at least two teeth of the saw must be in contact with the work piece and the right skills on how to use a hacksaw can also be very handy. Then the work piece had to be filed again. It was quite hard to obtain a flat surface so, the engineering square should always be used to make sure that the surface is indeed flat.The only problem during drilling procedure is to wait for turn, as there is a few numbers drilling machine in the workshop which is not enough. It is also hard to level the center drill since the accuracy of the table support lock is not absolutely correct. The table might move as we were setting the center of the drill and while fasten it.

There are some precautions that we have to take note like, the work piece should be clamp straight and tight and the position of the drill sleeve should be at highest position so that the elbow is at the same level as the work piece to reduce the distance between the drill and the work piece.

CONCLUSIONBench work is one of the most important processes when in the workshop. It is involved in most of all the projects here. Each equipment has its own style and skills needed to operate it. I have learned a lot of things from this project. It has taught me patience, as the project took quite a while to finish, and perseverance almost always bring good results. It has undoubtedly taught me about bench working and drilling. I learned the correct techniques of filing, measuring, chiseling, sawing and others, which are very important and should be mastered by all engineering students. Although the objectives of this project is successfully achieved, I still have to learn to improve my skill and knowledge. For now, Im satisfied with what I have done so far. But Insya Allah in the next projects will try my best to produce the desired work piece.

ANSWERS TO QUESTION

1. Sketch the tools shown in the table below.

NoTool or EquipmentPurpose

1Surface plate or tableTo provide a datum face or reference plane from which measurements can be made

2Hand scriberTo scribe lines on metal components

3Engineers dividersTo scribe circles on metal components

4Odd-leg calipersTo scribe line parallel to an adjacent surface

5Engineers steel ruleTo set off marking-out tools to prescribed distances and to check it.

6Center punchTo provide a location point for dividers, or a start for a twist drill.

7Try-squareTo mark out lines at 90 to an adjacent surface

8Scribing blockTo mark out lines parallel to a reference plane.

a) Surface plate or table

To provide a datum face or reference plane from which measurements can be made.

b) Hand scriber

To scribe lines on metal components

c) Engineer's dividers

To scribe circles on metal components

Engineer's steel ruleTo set off marking-out tools to prescribed distances and to check it.

d) Center punchTo provide a location point for dividers, or a start for a twist drill.

e) Engineering square

To mark outlines at 900 to an adjacent surface.

2. Sketch the hacksaw shown in workshop.

`3. Sketch the files shown in workshop

4. Sketch the cold chisels shown in workshop.

Draw a twist drill and a workpiece indicating the two motions and the chip movement.

Draw parallel and taper shank reamers.

HOMEWORK PROBLEMS:

1) A 20 mm diameter drill is on a drilling machine with cutting speed 25 m/min. If the feed is 0.25 mm/rev, what is the MRR? What is the MRR if the drill diameter is tripled?

Answer:D = 20 mm;f = 0.25 mm/rev;V = 25 m/min

N = V X 1000 r.p.m

(D

= 25 X 1000

3.142 X 20

= 397.8 r.p.m

MRR = (( D2 / 4) (f) (N)

= [ 3.142 (20)2 / 4 ] (0.25) (397.8)

= 31.248 mm3/min

= 520.8 mm3/s

If the diameter is tripled, the value of MMR is increased by 9 times.2) The hole of a diameter of 44.7 mm is to be drilled to a depth of 60 mm and reamed to diameter of 45 mm. The feed is 0.56 mm/rev for drilling. The cutting speed is 70.6 m/min. The reaming approach is 0.55 mm and over travel is 2 mm. Determine:

The feed and spindle speed for the reaming operation

The drilling time

The reaming time

The depth of cut for both drilling and reaming operations

The MRR for the drilling operation

Answer:

Given information

Diameter of the hole = 44.7mm

Depth of the hole = 60mm

Diameter of the ream = 45mm

Feed = 0.56mm/rev

Cutting speed = 70.6 m/min

The reaming approach = 0.55mm

Over travel = 2mm

A) The feed = 0.56x2

= 1.12 mm/rev

Spindle speed = ((1000V)/(D) )/2= ((1000x70.6)/(3.14x45))/2= 251.37 rpmB) The drilling time

(T) = L/fN

=(60+2+0.4(44.7)/(0.56)x70.6(1000/44.7)

= 0.2837min

= 17s

C) The reaming time (T)= L/fN

= (60+2+0.55)/(0.56x502.7)

= 0.22min

= 13s

D) The depth of cut both drilling and reaming operations

Depth of cut for drilling= D/2

= 44.7/2

= 22.35mm

Depth of cut for reaming = 45-44.7/2

= 0.15mm

E) MRR for drilling operation

MRR = (D/4) x fN

= (3.14x 20/4) x (0.56 x (70.6(1000/44.7))

= 441 815mm/s

REFERENCEi. MEC 1105 Workshop Technology Course Manual

Kulliyyah of Engineering, IIUM

ii. Machine tool Practices, 6th Edition

Richard R.Kibbe, John E. Neely, Roland O.Meyer, Warren T. White

Prentice Hall

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