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] ******************************************************** The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. If you are not the addressee, any disclosure, reproduction, copying, distribution, or other dissemination or use of this transmission in error please notify the sender immediately and then delete this e-mail. E-mail transmission cannot be guaranteed to be secure or error free as information could be intercepted, corrupted lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message which arise as a result of e-mail transmission. If verification is required please request a hard copy version. ********************************************************