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Workshop Practice (Lathe Machine & Welding) Essay

LATHE MACHINE

a. Describe FOUR (4) main parts of lathe machine.

Headstock

The headstock contains the headstock spindle and the mechanism for driving it. In the belt-driven type, the driving mechanism consists of a motor-driven cone pulley that drives the spindle cone pulley through a drive belt. The spindle can be rotated either directly or through back gears. When the headstock is set up for direct drive, a bull-gear pin, located under a cover to the right of the spindle pulley, connects the pulley to the spindle. This connection causes the spindle to turn at the same speed as the spindle pulley.

When the headstock is set up for gear drive, the bull-gear pin is pulled out, disconnecting the spindle pulley from the spindle. This allows the spindle to turn freely inside the spindle pulley. The back-gear lever, on the left end of the headstock, is moved to engage the back-gear set with a gear on the end of the spindle and a gear on the end of the spindle pulley. In this drive mode, the drive belt turns the spindle pulley, which turns the back-gear set, which turns the spindle. Each drive mode provides four spindle speeds, for a total of eight. The back-gear drive speeds are less slower than the direct-drive speeds. Tailstock

The primary purpose of the tailstock is to hold the dead center to support one end of the work being machined. However, the tailstock can also be used to hold tapered shank drills, reamers, and drill chucks. It can be moved on the ways along the length of the bed and can be clamped in the desired position by tightening the tailstock clamping nut. This movement allows for the turning of different lengths of work. The tailstock can be adjusted laterally (front to back) to cut a taper by loosening the clamping screws at the bottom of the tailstock. Before insert a dead center, drill, or reamer, carefully clean the tapered shank and wipe out the tapered hole of the tailstock spindle. When hold drills or reamers in the tapered hole of the spindle, be sure they are tight enough so they will not revolve. If allow them to revolve, they will score the tapered hole and destroy its accuracy.

Carriage

The carriage is the movable support for the crossfeed slide and the compound rest. The compound rest carries the cutting tool in the tool post. The carriage travels along the bed over which it slides on the outboard ways. The carriage has T-slots or tapped holes to use for clamping work for boring or milling. When the carriage is used for boring and milling operations, carriage movement feeds the work to the cutting tool, which is rotated by the headstock spindle. Can be lock the carriage in any position on the bed by tightening the carriage clamp screw. But do this only when do such work as facing or parting-off, for which longitudinal feed is not required. Normally the carriage clamp is kept in the released position. Always move the carriage by hand to be sure it is free before engage its automatic feed.

Bed and Ways

The bed is the base or foundation of the parts of the lathe. The main feature of the bed is the ways, which are formed on the bed’s upper surface and run the full length of the bed. The ways keep the tailstock and the carriage, which slide on them, in alignment with the headstock.

b. Name FOUR (4) kind of jobs that a lathe machine can perform and give a simple explanation for each job.

FACING

Facing is the machining of the end surfaces and shoulders of a workpiece. In addition to squaring the ends of the work, facing provides a way to cut work to length accurately. Generally, only light cuts are required since the work will have been cut to approximate length or rough machined to the shoulder.

TURNING

Turning is the machining of excess stock from the periphery of the workpiece to reduce the diameter. In most lathe machining operations requiring removal of large amounts of stock, a series of roughing cuts is taken to remove most of the excess stock Then a finishing cut is taken to accurately “size” the workpiece.

Boring

Boring is the machining of holes or any interior cylindrical surface. The piece to be bored must have a drilled or cored hole, and the hole must be large enough to insert the tool. The boring process merely enlarges the hole to the desired size or shape. The advantage of boring is that a true round hole is obtained, and two or more holes of the same or different diameters may be bored at one setting, thus ensuring absolute alignment of the axis of the holes.

TAPERS

A taper is the gradual decrease in the diameter of a piece of work toward one end. The amount of taper in any given length of work is found by subtracting the size of the small end from the size of the large end. Taper is usually expressed as the amount of taper per foot of length or taper per inch of length

c. List FIVE (5) lathe machine work holding device.
* Chucks
* Face plate
* Drive plate
* Lathe Dogs
* Steadies

OXY – ACETYLENE

a. Name and sketch THREE (3) kinds of flames in Oxy-Acetylene Gas Welding.

1. Acetylene in air flame.

2. Neutral flame.

3. Oxidizing flame.

b. State FIVE (5) differences between oxygen and acetylene attachment accessories.

Acetylene| OXYGEN|

Acetylene gas hose (Red)| Oxygen gas hose (Blue, Green)|
Left handed regulator thread connection.| Right handed regulator thread connection.| Acetylene connection nuts have chamfers or grooves cut in them.| Nuts are plain without chamfer or grooves.| Colour band on acetylene regulator in maroon or red.| It is either blue or black on oxygen regulator.| The inlet pressure gauge up to 8 bar.| The inlet pressure gauge up to 100 bar.|

c. Determine FOUR (4) types of gas welding defect and its prevention.

Defect| Prevention|

Uneven weld| By making a straight line before welding.|
Too much heat weld| Limit the amount of acetylene and oxygen pressure.| Not enough heat weld| Control the amount of acetylene and oxygen pressure ratio.| An oxidized weld| Control the amount of oxygen.|


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