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CENTRE LATHE
The Centre Lathe Picture  and Parts description by http://www.americanmachinetools.com/lathe_

Diagram of Engine Lathe and all its parts Apron: Attached to the front of the carriage, it has the mechanism and controls for moving the carriage and cross slide.

Bed: Usually made of cast iron. Provides a heavy rigid frame on which all the main components are mounted.

Carriage: Moves on the outer ways. Used for mounting and moving most the cutting tools

Chuck: 3-jaw (self centering) or 4-jaw (independent) to clamp part being machined.

Compound Rest: Mounted to the cross slide, it pivots around the tool post.

Cross Slide: Mounted on the traverse slide of the carriage, and uses a handwheel to feed tools into the work piece.

Feed Rod: Has a keyway, with two reversing pinion gears, either of which can be meshed with the mating bevel gear to forward or reverse the carriage using a clutch.

Follow Rest: Bolted to the lathe carriage, it uses adjustable fingers to bear against the work piece opposite the cutting tool to prevent deflection.

Gearbox: inside the headstock, providing multiple speeds with a geometric ratio by moving levers.

Headstock: mounted in a fixed position on the inner ways, usually at the left end. Using a chuck, it rotates the work.

Lead Screw: For cutting threads.

Quick Change Gearbox: Controls the movement of the carriage using levers.
Split Nut: When closed around the lead screw, the carriage is driven along by direct drive without using a clutch.

Steady Rest: Clamped to the lathe ways, it uses adjustable fingers to contact the work piece and align it. Can be used in place of tailstock to support long or unstable parts being machined.

Spindle: Hole through the headstock to which bar stock can be fed.

Tailstock: Fits on the inner ways of the bed and can slide towards any position the headstock to fit the length of the work piece. An optional taper turning attachment would be mounted to it.

  Tailstock Quill: Has a Morse taper to hold a lathe center, drill bit or other tool.

Tool Post: To mount tool holders in which the cutting bits are clamped.

Ways: Inner and outer guide rails that are precision machined parallel to assure accuracy of movement.

 

 

Centre Lathe   http://mmu.ic.polyu.edu.hk

The term Centre Lathe is derived from the fact that in its operation the lathe holds a piece of material between two rigid supports called centres, or by some other device such as a chuck or faceplate which revolves about the centre line of the lathe.

The lathe shown is a typical example. This machine is usually used in a jobbing (one off) situation or for small batch work where it would be too expensive to specially 'tool up' for just a few items.

 

Setting the Tool height. The Lathe Tool should be set at the same height as the central rotating axis of the machine. It is done by lowering or raising the tool (held in the tool post) to the height of  the tail stock centre.

Failure to do so will result will result in uneven cutting  during operation and higher than usual wear of the tool. Furthermore as the work rotates and hits the tool it results in uneven cutting which causes vibrations resulting in a poor finish on the work piece.

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lathe setting tool height by  http://www.jjjtrain.com

 

Producing a cylindrical surface  As the workpiece held in the chuck turns, the cutting tool held in the tool post is fed incrementally in passes into the side of the work piece. As the cutting tool progresses along the workpiece, it reduces the diameter of of the workpiece. 

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I-Turning by  http://www-me.mit.edu/MachineTools/Videos/l_turning.mpg

 

Facing off   - a flat surface is produced at the end of a workpiece . The cutting action is perpendicular to the axis of rotation of the workpiece.

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facing off by  http://www-me.mit.edu

 

Drilling with a lathe  (Text information derived from http://www.mini-lathe.com)

 

This is a 2 stage process

 

The alignment between the headstock and tailstock of the lathe enables you to drill holes that are precisely centered in a cylindrical piece of stock. Before you drill into the end of a workpiece you should first face the end.

 

STAGE 1 Centre drilling

The next step is to start the drill hole using a center drill - a stiff, stubby drill with a short tip. If you try to drill a hole without first center drilling, the drill will almost certainly wander off center, producing a hole that is oversized and misaligned. Choose a center drill with a diameter similar to that of the hole that you intend to drill.

 WATCH A DEMO click 

 Centre Drilling  by  http://www.jjjtrain.com

 

STAGE 2 Drilling into the workpiece

Always use a cutting fluid when drilling.  You only need a few drops at a time,

 

Remove the center drill from the chuck and insert a regular drill. Slide the tailstock until the tip of the drill is about 6mm from the workpiece and then lock the tailstock in place. Place a few drops of cutting fluid on the tip of the drill, then start the lathe and drill into the workpiece as before, at the correct speed for the workpiece.

 

 After advancing the drill about twice its diameter, back it out of the hole and use a brush to remove the metal chips from the tip of the drill. Add a few more drops of cutting fluid if necessary, then continue drilling, backing the drill out to remove chips about every 2 diameters of depth.

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 Drilling  by  http://www.jjjtrain.com