Jig Bushes

To position and guide the cutting tool for cutting we use bushes to reduce the wear and tear.

Tool Guide or Jig Bushing:

• Sometimes the stiffness of the cutting tool may be in sufficient to perform certain machining operations.
• Then to locate the tool relative to the work, use is made of guiding parts such as jigs bushing and templates. These must be precise, were resistance and changeable.
• Jig bushes are used in drilling and boring, a bush fits into the hole of the jig, through which the drill passes.
• The diameter of the bush depends on the diameter of the drill.
• Different types of bushes are spot welded or screwed with the jig. Headless type bushes are press fit into the hole of the job. Bushes are general made of a good grade of tool steel to insure hardening at a fairly no temperature and to lessen the danger of fire cracking.

• Sometime the bushes for guiding tools may be of cast iron. Hardened steel bushes are always preferable for guiding drills, reamers and taps etc.

  1: press- fit wearing bushes

  2: renewable wearing bushes

  3: linear wearing bushes

  Press fit wearing bushes:

These bushes are used when little importance in put on accuracy or finish and tool used is a twist drill. These bushing are installed directly in the jig body and are used mainly for short protection. There are two design of press fit bushing

1. Plain or headless bush

2. Headed or flanged bush

• Headless Bush most popular, expensive and light axial load is least expected.
• Headless press fit bushes are generally used where replacement due to wear is not anticipated during the life of the tooling, and where a single operation such as drilling or reaming is performed.
• Their benefits are that they can be mounted flush with the jig plate, and where space is at a premium they can be placed closer together than headed bushes.

Renewable bushes:

• When the guide bushes requires periodic replacement (due to wear of the inside diameter of the bush). Its replacement is simply by using a renewable bush.
• These are of the flanged types and sliding fit into the linear bush, which is installed press fitted into the jig plate.
• The linear bush provides hardened wear resistance, mating surface to the renewable bush.
• The renewable bushes must be prevented from rotating or lifting with the drill. One common method is to use a retaining screw.

Linear bushes:

• These bushes are also known as master bushing, are permanently fixed to the jig body.
• They act as guides for renewable type bushing.
• These bushes are with or without head.