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Harold Hall

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More Complex Requirements

Most applications for a drilling jig will of course be more complex than the single bush  but will range from quite simple to the very complex. They will also come in very many forms with two factors particularly having an impact on this. Obviously, the greater the number of parts to be made  the greater is the justification for making a more complex jig that will better achieve the aims, typically, productivity and accuracy. Secondly, and the one that cannot be covered in detail here is the very wide range of workpiece shapes. Because of this, only some pointers in their use can be covered.

 

Having chosen to consider a drilling jig for the part being made there are three factors that have to be decided upon.

 

First, will the jig simply be a flat plate requiring external devices to position and hold it in place, or will it be complete with provisions for locating and clamping the part into the jig.

 

Secondly, will the jig just mark out the position of the holes using a smaller drill than the holes ultimately required, or will it enable the holes sizes required to be drilled directly.

 

Thirdly, is the drill to be guided just by the plate with which the jig is made or are hardened bushes to fitted.

 

Whilst the above cover the basic design of the jig there is a forth decision that needs to be addressed, that is, what level of precision is required in the hole placing?

 

I should add at this stage that my comments relate to drilling what are essentially flat items, beyond that workpieces could range from a simple bracket to complex shaped items.

 

Flat plate jig

The simplest form of flat plate jig will be to use the first one of a batch of parts being made as a template to position the holes in the remaining ones. This is relatively straight forward but if the part is quite thin and has large holes, say 10mm diameter into 4mm thick, then it should be used solely to mark out the hole positions using a smaller drill, say 3mm diameter.

 

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Metalworking

Workshop Processes