Inside Square Corners

I need to machine a few parts that will basically fit over a square hex, so will need to machine a inside hex with sharp edges. Machining most surfaces are straight forward, but now sure the best tools to use. Material will be AL and the hex size is about 3/4" across flats.

you dont say how deep your going but you can try pre drilling the corners with an 093 dia. drill then use maybe a 1/4 endmill to rough the hex followed by a 1/8 endmill and finnally a 3/32. i would think there should be almost the same radious on a 3/4 hex

Quote:

---

Originally Posted by hitachibos

you dont say how deep your going but you can try pre drilling the corners with an 093 dia. drill then use maybe a 1/4 endmill to rough the hex followed by a 1/8 endmill and finnally a 3/32. i would think there should be almost the same radious on a 3/4 hex

---

Whatever size you decide to drill the corners, drill them on the exact center of the corner.

This part is somewhat similar to a wrench. And a wrench does all of its work on the flats, and the corneers need not be a tight fit.

Tom

Quote:

---

Originally Posted by Magnum164

I need to machine a few parts that will basically fit over a square hex, so will need to machine a inside hex with sharp edges. Machining most surfaces are straight forward, but now sure the best tools to use. Material will be AL and the hex size is about 3/4" across flats.

---

you will need to broach the corners

if it's a Through hole you can buy a hex broach , msc has them

you could also remove the corners in the hex pocket

Ive had to do a few 'square' holes on internal features before. I rough it to size best i can, then peck full depth with a drill stepping over a few though at a time and then finish with a hand file

If you want to run all the work on the mill and can't do the big hex broach, you could also get a small rotary hex broach and use it in the corners.

I'll try and answer all the questions. This is not a through cut it's about .5" deep or so. I will probably go the route of cutting a hole on the center of the corners.

never done any broaching, so not sure if you can do that on a Tormach or do you need a different machine. The idea is to do everything on the Tormach.

i found this video a while back and i have been wanting to try it with a tormach.

if you machined away the rough hex shape only leaving the radius in the corners, with a properly ground tool, i don't see why this method couldn't be done on a blind hole as long as there is room to move the tool away at the end of the cut.

[nomedia="http://www.youtube.com/watch?v=8gC4nbVB1-8"]YouTube- Rick CNC Cutting a Internal Spline[/nomedia]

Thanks sniper. Actually one of my next projects also has a spline but I have been holding off.. But it will be a very small spline so I am sure there would be no problem doing that on the Tormach with it.

Any idea where I can get a tool for that. I'll start looking/searching later tonight. Doing some masking for painting right now. Hate painting:)

The tormach can definitely handle a rotary broach. For a selection of rotary broaches appropriate to that machine, I have seen them at littlemachineshop.com. I would buy the smallest hex one, broach the corners, then do the rest with an endmill.

I've been using the 1/4" hex broach from littlemachineshop - it works great on my PCNC770 !