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Lapping: Principle, Advantages and Disadvantages of Lapping

Lapping:


Lapping: 
In this article we are going to learn about lapping, lapping is a simple process used to improve the surface finish, by using this method we can remove the minor imperfections on the surface. by using lapping process we can obtain high accuracy in dimensions. this method is highly useful to get perfect contact between two mating parts.
This type of process mainly used in gauge blocks finishing, flat surfaces etc.
Lapping process make the surface smooth by removing a small amount of material about 0.005 to 0.01 mm.
Lapping tool is made by abrasive particles which can retain and receives abrasive grains. to hold thise abrasive particles cast iron along with graphite is used and this material also provides lubrication effect.

when the workpiece is placed against the lap and moving to obtain smooth surface In this operation a suitable cutting fluid is used to control extent cutting action and useful in preventing cuts on work surface.
The surface roughness is obtained by about 0.005-0.04 micrometers. and lapping pressure is from 0.01 to 0.7 MPa.
In this, if the cutting speed increases, this may increase in tool life, and also smooth surface decreases the coefficient of friction which gives result in increasing the tool life.


There are some important lapping techniques:

Vertical axis lapping:

  • Vertical lap consists of two vertical spindles in which workpiece is opposed between this spindles, by this, there is a flat or round surface is formed.

Centreless lapping:

  • In this, the workpiece is placed between the spindles to get a required object. this is used for piston pins, bearing races, shafts etc..

Abrasive belt lapping:

  • In this, there is an Abrasive belt machine which is used to pass over the workpiece with high speed by this the surface smoothness can obtain. this is used in bearings, cams etc..
  • Abrasives which is used to make smooth surface are iron oxide, chromium oxide etc..


Advantages of Lapping:

  • This gives the high surface finish.
  • Rate of production is high.
  • By the absence of clapping parts, no heat is generated.
  • Less skilled labors can do this work.
  • On any material this operation can perform.
  • This can remove burrs on materials.

Disadvantages of Lapping:

  • It can remove only a limited amount of material.
  • Surface finishing is not uniform in this.

Applications:

  • Used for the ball and roller bearings.
  • Used for Jigs Bushes.
  • Making smooth Holes and Pins.
  • Surface Plates.
  • Injectors in diesel engines.

Improving the Characteristics of the work piece by lapping process:

  • This improves in High dimensional accuracy.
  • By this they can obtain close fitting between the parts.
  • This improves in geometrical accuracy.
  • Burrs on the workpiece is removed with accurate.
  • It reduces imperfections on the workpiece.
  • It can correct any deviations in shape of the workpiece.

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