Square Broach
There are quite a few established methods for making a decent quality square hole in metal stock.
Probably the oldest method is to drill a pilot hole, and then get to work with a set of files. That is certainly the traditional approach, and if it's taken carefully, it can deliver a reasonable result. To be perfectly honest though, I never feel totally happy with my own efforts filing square holes - there's always a slight imperfection somewhere that bugs me, that of course can't be corrected because once you're at dimension, that's it.
Another method that I have seen (but not used) is a rotary broach. It certainly looks like it produces good quality results, although the retail price on the tools is prohibitive. I've got a design in the works for a shop built version, so that one is on the to-do list, and will pop up at some stage in a video.
That leaves us with the tried and true method of a multi tooth broach. Favoured by model engineers across the globe for many decades, this option has everything going for it - Easy to make, convenient to use, low cost, and most of all it delivers superb results. The broach made in the video is 3.4mm square, and will be used to cut a square for the motion work end cap on the current clock build, so keep an eye out for it in a future video.
You can download a free copy of the broach drawing here.
Probably the oldest method is to drill a pilot hole, and then get to work with a set of files. That is certainly the traditional approach, and if it's taken carefully, it can deliver a reasonable result. To be perfectly honest though, I never feel totally happy with my own efforts filing square holes - there's always a slight imperfection somewhere that bugs me, that of course can't be corrected because once you're at dimension, that's it.
Another method that I have seen (but not used) is a rotary broach. It certainly looks like it produces good quality results, although the retail price on the tools is prohibitive. I've got a design in the works for a shop built version, so that one is on the to-do list, and will pop up at some stage in a video.
That leaves us with the tried and true method of a multi tooth broach. Favoured by model engineers across the globe for many decades, this option has everything going for it - Easy to make, convenient to use, low cost, and most of all it delivers superb results. The broach made in the video is 3.4mm square, and will be used to cut a square for the motion work end cap on the current clock build, so keep an eye out for it in a future video.
You can download a free copy of the broach drawing here.
