Drilling square holes
I’ll start by clarifying that I don’t actually have a need to make square holes at the moment but I am facinated by these techniques.
The maker of the above video Jacques Maurel also wrote an article for Model Engineer a couple of years back. The article outlines a home made square drill using a tool shaped as a Reuleaux rotor.
Jacques article includes how to machine the rotor, jigs for making the parts, grinding the tool and how to make the floating chuck. The floating chuck is based on an oldham coupling and can also be used for reamers and tapping. As seen the first video the solution works well and can produce blind square holes.
Model Engineer magazine issue N°4285 oct /nov 2006
Also see article by Mr Parkes in Model Engineer N°112
Applications of shapes of constant width by John Bryant and Chris Sangwin
Floating chuck and square drills
An alternative solution to producing a square hole is to use a broach which are good for though holes, keyways and even internal gears.
Michael Cox has written an interesting article for Model Engineer #185 (Jan 2012) where he has a free running rotary broach that works by being just a couple of degrees off of perpendicular to the lathe axis. It uses a single ball bearing as a thrust bearing based on Edgar Westbury’s rotating centre design.
Just spotted that Hemingway Kits now do a floating reamer holder which would make one of the more complex parts of Jacques project a little easier.
The skeptics over at hobby-machnist have suggested that this is a rotary broaching operation rather than a drilling operation. Here’s a site with closes up of the end of the square drill that shows you that it’s cutting process not broaching. However they are correct in thinking that the corners of the holes will be slightly rounded.
Another alternative would be to use a completely different machine for this. The Shaper is spot on for this and would make the job look easy. Dave Gingery’s book The Metal Shaper shows you how to make them.
Have you also considered looking into Rotary Broaching? See the tools and videos at: http://www.polygonsolutions.com
Thanks for the link, I wonder if it would be possible to make a rotary broach from an old hammer drill?
Make Magazine have also put together a selection of videos on drilling square holes.