Types of Jig Bushes. Fixed Bush, Liner Bush, Renewable Bush, Slip Bush, Screw or Clamping Bush
What is jig bushJig bushes are used to locate and guide the tools like drills, reamer, and counterboring cutters. They are generally referred as drill bushes. Jig bushes are fitted into bush plate of the jig. Even though the bushes drill bushes are hardened and made into exact size, they will subject tear and wear by the action of chips. So the one of the design consideration of jig is that giving a necessity of replacing of bushes.
Mild steel is the common material for Drill bush it is usually case hardened
Types of Drill bushDrill bush classified in to
These bushes are pressed directly into a jig and intended to remain there until they wear out. Fig shows plain type and head type bushing. Flanged or headed type of bush used when the jig plate is thin. Headed portion increase the length of bush. The head also acts as a stop for tool.
These are similar to fixed bush, press-fitted into jig body. But it can also function as a hardened guide for renewable and slip bushes. So it is also known as ‘master bushing’. Similar to fixed bush, these are either headed type or plain type.
Renewable bushes are intended to easy replacement of it when it wears out. These are the flanged type and fit into the liner bushing. The retaining screws are used to prevent rotation and lifting of the renewable bush with a drill. Once it wears out, it can take out by removing the retaining screw. fig shows the renewable screw in position.
Read: 3-2-1 Principle of Location (Six Point Principle)
Slip bush is used where more than one bushing needs to be interchanged during the operation. Similar to renewable bush they are fit into liner bush (slip bush having different inside diameter but have same outside diameter fitted into a liner bush of fixed inner diameter). It uses a permanent retaining screw in the bush mate. It is lock and unlocks by simple clockwise and anti-clockwise movement. It helps to interchange the slip bush during mass production with minimum time loss.
Screw or clamping bush
These types of bush have an external thread, and they not only guide the drill but also clamp the workpiece. The outer threads are susceptible to wear, so they are not preferred for accurate work.
These are designed to meeting special drilling conditions such as
- Drilling in inclined surface
- Drill two holes that are close together