Drilling a square hole

[habu68]

Here are two links that explain the math of a Watts square hole end mill.
http://mathworld.wolfram.com/ReuleauxTriangle.html
http://upper.us.edu/faculty/smith/reuleaux.htm

The math left me in the dust but I have seen this done and found it to be fun to watch.

Enjoy

Habu

[ApprenticeMan]

Interesting, it work roughly on the same principle as a rotary engine does.

[D Ravizza]

Alexander Weygers shows this technique in his book The Complete Modern Blacksmith. He shows how to make the triangular drill and a hardend steel guide. It is a facinating process. I am going to have to try it one of these days.

Dan

[ApprenticeMan]

I think it is WAY easier to drill a orund pilot hole, then drive a square bar pf appropriate size through.

[habu68]

Broaching is surely one approach, although, the equipment is expensive and specialized, another way would be to hot punch, not easy on a large piece. Now days EDM (electro discharge machining) would be the preferred approach for a high tolerance hole. That is the way I made my bolster plate and a small swage block, since my brother is a tool and die maker and the EDM was not in use. I just thought that the drilling a square hole was a great example of “how’d they do that”????

[Phil Patrick]

I took a look at the math,,, It made my brain itch.
I'll stick to round ones