I had to create the tooling once for a board requiring square holes.  I done exactly what Robert also suggested and drilled small diameter holes in each corner then routed using a normal routing tool.

This caused a lot of debate within the CAM department of the company where I'd remembered learning about special drill bits that could drill square holes based upon the releaux triangle.  No-one believed me!

The solution drilling the four corner holes also created some debate with a couple of people rightly saying that there could be a small dimple where the rout tool and drill bit meet so our team leader spent a good couple of hours working it out on paper before declaring it wasn't enough material to take notice off.  Actually he said it somewhat differently in a phrase involving a "gnat" which I can't repeat here.

James

James Head BEng CID MIIE MIET
Senior PCB CAD Engineer
Crowcon Detection Systems Limited
2 Blacklands Way
Abingdon Business Park
ABINGDON
OX14 1DY

Telephone:      +44 (0) 1235 557700 extension (9) 289
Fax:            07092024504
Email:  [log in to unmask]
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