Square hole

[Chipmaker]

Greetings, anyone out there that has an idea how to make 9/16" square hole. In a steel boss. Broaching would be good but expensive for one hole. Key slotting would work but I do ot have a slotting attachment for the mill. Anything but filing as I dread the thought of that.

[Lou66]

Make your own broach. I have seen a few videos on Youtube on how to make one.

[C-Bag]

A while back Frank S. Posted this in Tool tips part of the forum

http://www.homemadetools.net/forum/p...e-broach-40067

Not tried it but it struck me as a cool way to possibly get 'er done.

[Toolmaker51]

All these suggestions work; but one solution hasn't materialized. If you have a quill or area you can clamp a 'fitting', make a single point shaping tool. Mine is bored to fit Bridgeport, split for clamping. Has a blind hole 1/2" diameter about 1.25 deep. Holds high speed blank, like a broken endmill shank or drill blank. If you can surface grind, a bit of negative clearance in front and a triangular shape will make sharpest corner you could want. Something like a cutoff tool, but cutting on the 'face' instead of top.
Drill undersize of 9/16" and use smallest endmill to square up inside as far as you can. Put the 'shaper' on and shave .001 increments from each (creating) 4 sides. It works well. Have done narrow slots and a hex once, with a rotary table for 60 degree sides.
Another way is to use an endmill holder, just lock the spindle brake.
If a sketch would help, I'll edit this and insert here. Just click on this illustration

[C-Bag]

I think I know what you're describing but a pic of your setup sure would be nice and to make sure I'm not misinterpreting

[ncollar]

This young man makes a square broach and makes it look so easy.

Check out Chris's entire site, very gifted.

[PJs]

This young man makes a square broach and makes it look so easy.

Chris (Clipspring) makes it look easy for sure but he is broaching brass. Simple but effective but on brass, not sure how the hardened 01 (silver steel) would hold up on steel. But if you only need one...might work. I might consider the hole and broach method with a good hardened tool like Toolmaker51 suggests in your mill spindle.

~PJ

[Toolmaker51]

For decades, Oil and Water hardening tool steels were standard for cold work punches and dies. Machinability is good, like 4130,+ simplest to heat treat and anneal. Also the most widely distributed, over the counter everywhere. Can't beat drill rod for a project like this. Best reference text to have around is one of the printed EMJ, Ryerson, Crucible, DuCommon, or other metal suppliers 'catalogs'. They are filled with info; term catalog minimalizes their content. The MacMaster-Carr even if out of date, you see one grab it! You'll cross reference details you never dreamed of.
For shorter tools though, use broken end mills and common punches from diesets, as heat treat is already done.

[kutzbill]

I have some old lathe tooling, and I have used the steel to make a type of broach. All I did was take a 1/2" tool, sharpen it so one surface would cut, and tapped it in with a bronze or brass hammer. You don't want to use a hardened hammer as you know because it will shatter the tool. It takes some time, but I have made up to a 1" square with this set up. You will have to use a file to finish it out, but I have done this and maintained a .001 tolerance. Of course a broach is faster, but they are pretty pricey too. Hope this helps.

[toyvolvo]

I have only ever used a set of templates (with square holes) and a 3-sided articulating drill bit called a broach. This pretty much works best with softer metals, but if you have good quality tools (Dumont, Enco) you can do pretty well with almost any material including mild steel.

I like the broaches best because, although they are expensive, you get great quality machine-work, AND you can use a drill press. I try really hard to find an excuse to NOT buy a new tool, but none of my excuses EVER work!!!

Filing a square hole is no fun, although I have used a knock-out punch for all sorts of sheet metal work. Depending on the thickness of your stock, I have used a very small drill to "make corners" but you still end up with a radius, AND you never end up with a REALLY square hole!!

Hope this helps!