I thought I saw that on YouTube some time ago as a real operation, I may have been mistakes as I could not find it again, but maybe it was a “square” hole.
Here it is for a square hole…
That’s pretty slick.
Drilling was done so quickly.
I thought the guide would have gotten a little more banged up.
Excellent find
Well I’m NOT a machinist, (I’m a sparky and wood butcher), But let me postulate on the video and the apparatus used.
I suspect the “square guide” is hardened tool steel along with the rest of the apparatus…
I think the author mentioned he suggested softer metal like aluminum to drill the final hole in.
The triangular bit adapter has a free moving wobble that is hard to figure out for me. But that and the tool steel square guide with a triangular bit is one crazy invention!