Square Holes

I thought this was a great video showing off a Japanese tool to machine square holes.



Have people used this tool before or some other technique for making square holes in thick metal ?


Very cool. I’ve never used something like that before personally, but it does seem pretty interesting.


Here’s an animation of the principle. Note that it produces slightly radiused corners.

There’s a similar tool (called a mortiser) that does roughly the same thing for wood. It uses a different principle, though: brute force. (It’s a combination chisel and drill.)

Sort of like a Wankel Engine isn’t it?

I have used this technique for years to produce all manner of hole profiles, pentagons, hexagons, even triangles, that are significantly over sized for the drill bit being used. It works best using a very large diameter drill bit held in a small hand held drill. A badly sharpened drill bit works best, as does thin soft material that tends to produce a lot of drill chatter. By hand the technique is a bit difficult to reproduce. I seem to have the best luck getting them to come out with good sharp corners when I am overly rushed, and absolutely need round holes that are not over sized.


I never thought Chief Delphi needed a “like” button, until now

Yes, its based off the principle of the very same reuleaux triangle as the wankel engine.

Wankle engines actually don’t use a true reuleaux triangle for a rotor profile. A Reuleaux triangle is composed of three 60 degree arcs with centers on the opposite corners. Wankle rotors use an arcs less than 60 degrees with centers beyond the opposite corners. This is important to note because while a Reuleaux triangle is a shape of constant width, a Wankle rotor is not.

I owned an RX-4 a long time ago. Once you became accustomed to dealing with no low end torque, it was one fun car to drive. In the pre 55mph days, that car hit 70 at 4000 RPM. With a ten mph increase for every 500 rpm and a 7000 redline, you can get an idea of why RX-4 owners were pretty happy. It had a great suspension that made me take it off the highway often. The summer after I bought it, I was working nights on transmitter proofs. My wife would talk me into driving her downtown to work and then I would get out onto LSD (Lake Shore Drive) headed north just like the song. When LSD ends it turns into Sheridan Road and I would take that all the way up into Highland Park, riding through Evanston and the Northwestern Campus. Sheridan is a tree lined, curvy road with lot’s of turns, stone bridges and old mansions as it passes through the affluent neighborhoods north of Evanston.

Has anyone ever used something like this for milling with a drill press?

sounds like a good way to break bits… drill bits are too flexible and drill presses don’t have enough torque anyway.

it is good for bolting to the drill press to drill precision holes, however.

The video shows using mill bits in the drill press. I would worry more about wearing out bearings.

If they also sold a spindle that had additional bearings that could be attached to the drill press for use with the vise, then they would have something suitable for things like pocket milling.

I haven’t used one recently but it works ok on thin materials and plastics. It is not so much the wear on the drill press, it is the flexibility in the vise and drill press bed. If you try to do anything on heavier material, the chatter eats up the workpiece.


You would likely be fine doing that with small cutters and plastics.

I don’t think I would try it on metals. The spindle bearings in a drill press are intended for axial load only and would likely wear out very quickly with the radial loads you would see in milling metals.

Furthermore most drill presses are going to have the chuck held in place passively via a Morse taper. This is going to be your biggest problem as side loading such a setup can cause the chuck to break loose from the taper. This would be bad news.