What is a Jig Bush?
Jig bushes are the tools that are used to locate and guide the cutting tools like drills, boring bars, reamers, counterboring tools, etc.
Jig bushes can be used on multiple faces of the component which requires machining.
Jig bushings are made of which material?
Jig bush is made up of either mild steel or cast iron that have holes in which the bushes are driven. Some jig bushes are also made of hardened steel plate with machined holes in it that guides the cutting tool.
Types of Jig Bushes
8 Different types of jig bushes used in jig and fixture are mentioned below.
- Headless or plain bush
- Headed bush
- Shaped bush
- Extended bush
- Renewable bush
- Slip bush
- Screw bush
- Bushes with flats
Let’s discuss each of these bushes one by one.
#1) Headless or plain bush
Headless bush (or plain bush) is used for cases where the drill depth is not more important.
This bush is the cheapest bush and it is generally used for drilling the top free surface.
#2) Headed bush
Headed bush (or flange bush) is widely used where the controlled hole depth is required.
The flange section is provided on the top of the bush which increases the length of bush as well as it acts as a stop for the cutting tool.
The position of drill bush can be close to the workpiece or it can be away from the workpiece.
If the drill bush is near to the workpiece, then the machining chips will escape easily from the bush (see figure (a)).
If the bush is away from the workpiece, then the chips will escape from the space between the bush and workpiece (see figure (b)).
#3) Shaped bush
Shaped bushes are generally used where the drilling axis is not perpendicular to the workpiece surface.
In this case, it is necessary to locate the end of the bush as close to the workpiece surface.
In the above image, you can see that the end of the bush is also inclined which prevents the drill from running down the workpiece surface. And it also prevents the tool bending and breakage.
There can be different shapes of the bush as per the shape of the workpiece surface.
The end of the bush can be even curved if the workpiece surge is curved.
#4) Extended bush
Extended drill bush is used for guiding a long drill where the surface to be drilled is some distance away from the drill plate.
#5) Renewable bush
Renewable bushes are generally used where the wear of the guide bushes occurs rapidly in large batch production.
As the name suggests, the renewable bushes require a replacement due to its wear.
As shown in the above image, the retaining screw is provided with the bush, which prevents the rotational and axial movement of the cutting tool.
For replacing the bush, the retaining screw is moved and new bush is fitted in place of worn-out bush.
#6) Slip bush
Slip bushes are used where there is a need for multiple operations like drilling followed by reaming, etc.
For example, if a workpiece requires drilling and reaming, then it is first drilled using a bush that is suitable for drilling. After this, the drilling bush is removed and the reaming bush is used to guide the reamer.
In order to prevent the rotation of the bush, the retaining screw is provided.
Slip bush is similar to that of the renewable bush, but the renewable bush is replaced only when the bush gets worn out due to large batch production.
#7) Screw bush
The screw bush is like a semi-fixed bush that is screwed into a jig body which not only holds the bush in its place, but also makes the bush adjustable.
#8) Bushes with flats
Flat bushes are the bushes that are used to drill two or more holes that are close to each other.