Wednesday, December 7, 2011

Material Cutting Processes – Production of cylindrical Surfaces

Machining techniques for production of cylindrical surfaces

1. Turning –
Turning is the process whereby a single point cutting tool is parallel to the surface. It can be done manually, in a traditional form of lathe, which frequently requires continuous supervision by the operator, or by using a computer controlled and automated lathe, which does not. This type of machine tool is referred to as having computer numerical control, better known as CNC and is commonly used with many other types of machine tool besides the lathe.

2. Drilling – 

Drilling is a cutting process that uses a drill bit to cut or enlarge a hole in solid materials. The drill bit is a multipoint, end-cutting tool. It cuts by applying pressure and rotation to the workpiece, which forms chips at the cutting edge.

3. Boring – 

In machining, boring is the process of enlarging a hole that has already been drilled (or cast), by means of a single-point cutting tool (or of a boring head containing several such tools), for example as in boring a cannon barrel. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole.

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4. Reaming – 

A reamer is a metalworking tool used to create an accurate sized hole. The process is called reaming. They may be used as a hand tool or in a machine tool, such as a milling machine or drill press.
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5. Knurling –
 
Knurling is a manufacturing process, typically conducted on a lathe, whereby a visually attractive diamond-shaped (cross-cross) pattern is cut or rolled into metal.
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Machining operations in lathe

  • Turning
  • Facing
  • Boring
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Tail Stock
  1. Hold the dead center
  2. Slides on bed
  3. Spindle Slides
  4. Spindle can be replaced
  5. No power feed
  6. Lubrication
Carriage / Tool Post
· Support moves and control the tool
· Tool head - tungsten carbide (costly, brittle, hard)







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(Tool should be like the 2nd picture (We call it the clearance angle))

Guidelines for turning
  1. Minimum tool overhang (???)
  2. Support WP rigidly
    1. No vibrations (Vibrations may be caused by incorrect alignment and centering (Using 4-jaw chuck we can make the cut eccentric)
  3. Use machining tools with high stiffness and damping capacity.
  4. If tool vibrates change process parameters.
Drilling
Center punch - We should have a center punch before we start drilling otherwise the tool will try to slide on top of the work-piece. If you hold it very hard, the tool may break off.
Reaming
  • Enlarge a hole or to produce a better finish.
  • Multiple-point cutting tool
  • Fixed size tool
  • Faster than boring
  • Can’t correct errors

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