Broaching a small square hole

[dhamblin]

Thanks both.

Jason - I have tried with two square files, a diamond one from Laser and a needle one from Kennedy, both on a 2.3mm pilot hole in the 1.5mm thick steel plate. It's probably my filing skills / technique at fault but I'm struggling to stop the square wandering off centre and get the 30 degree angle consistent. I suspect it's because I'm only working with a short section of the file in the hole, which has kind of stalled at about 10cm penetration and doesn't seem to want to cut further.

Hence my interest in the broach to get a reasonably accurate square hole. I might give the files a last go, as there might be a smaller needle file in my model railway toolbox that would be more suitable.

Regards,

Dan

[uuu]

For a square hole, a triangular file is often easier than a square one. You can cut to the extent of the corner, then smooth out each side individually.

Wilf

[firebird]

Hi
Just seen this thread. A method I have used when making small handles is to mill a 1/8'' (or whatever size is needed) slot along the material then silver solder a square piece into the slot leaving the square hole in the centre. Turn away the waste to clean up then part off 3 or 4 handles at a time.

Cheers

Rich

[dhamblin]

Thanks again gents, both useful tips and Wilf's one was used with my Draper set of needle files to complete the task.

Internals of the blowdown valve appear to have broken though, but that's for another thread...

Regards,

Dan

[miken]

I've made a few small square holes in my time. Using a square needle file I've just roughed it out by hand. Then to finish I've put the file in the chuck of my drill press and "up and downed" it a few times to finish it to size. The file is tapered, the drill has a depth stop. It's not hard.