Modified square file.

[Gritineye]

I made a replacement part for a broken 85 yr old rotary switch today, I turned it on the lathe, drilled the center then used a hacksaw and files to finish it.

I have quite a few tools that belonged to my late tool maker neighbour, who passed around 98 yrs old. There was a square file the right 9/32" size but it had two sides ground smooth, it didn't take long for me to realise how much quicker and easier it was to get the square hole correct with only two sides cutting.

It worked a treat and the whole job only took a couple of hours, I presume he had ground the two sides smooth for the same reason as I can't find any mention of anything similar, unless of coarse you lot know different!

 

[Agroshield]

I think the general term is 'safe edge file'. As you say, if it is rubbing against something that you do not want even to mark let alone remove material from, it is the ideal tool.

 

[MetalMonkey]

Contrary to logic, I find a triangle file makes square holes a lot easier than a square one as you can get right into the corners while only filing one edge at a time.

 

[Gritineye]

I think the general term is 'safe edge file'. As you say, if it is rubbing against something that you do not want even to mark let alone remove material from, it is the ideal tool.

Yep most files I have are safe edge, but never seen a square one with a safe edge, let alone two, this file is the same size as the hole needed on the unground sides, so the hole came out very nicely.

 

[Gritineye]

Contrary to logic, I find a triangle file makes square holes a lot easier than a square one as you can get right into the corners while only filing one edge at a time.

I started with a triangle file to put 4 starter groves in the corners then went to the square one as it kept the hole shape better.

 

[Guzrik]

Pferd has rectangular lathe files with two safe sides; I always use them to brake a sharp edge on the lathe, it saves me a toolchange.