Group Project: Rotary Broach-- Building complete, all shipped out!

John O said:
Is the cup needed? I saw an article where they didn't put the cup and it cut the same.
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I made a rotary broach for fun, and a 1/2” hex tool out of O-1, but did not harden it. With a flat, not cupped, bottom, it had no trouble punching a hole in (as I recall) 1/8” aluminum. it worked surprisingly fast, looked none the worse for wear, and then I put it in a drawer, have not used it since. I did post on this, if anyone is interested.
 
GunsOfNavarone said:
Now that this is over.... this tool post mounted version looks pretty awesome.
Tool post broach
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I think i saw the video on that one at one point! I think it is pretty cool how simple he was able to make it, though I think we chose to do bearings to avoid wear.

I also don't really see the advantage of putting it on the tool post vs the tailstock. I would think you'd spend a ton of time 'centering' the broach with the carriage, both up and in. I'm sure it is useful, it just seems less practical.
 
Got mine in today. It looks great on the bench! Unfortunately, I neglected to order an arbor until the last minute, so I can't give it a try, but that's alright. If I decide to be in a hurry, I can make a straight shank real quick on the lathe, but I suspect the one I ordered will get here before I get shop time to make one. :)

I need to look up how to use these things again. But it looks like I can use the set screw in the front to swap cutters, then it should work like any other rotary broach, right?
 
Ye
ttabbal said:
Got mine in today. It looks great on the bench! Unfortunately, I neglected to order an arbor until the last minute, so I can't give it a try, but that's alright. If I decide to be in a hurry, I can make a straight shank real quick on the lathe, but I suspect the one I ordered will get here before I get shop time to make one. :)

I need to look up how to use these things again. But it looks like I can use the set screw in the front to swap cutters, then it should work like any other rotary broach, right?
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Yep this is a traditional rotary broach.

The key is that you predrill a few percent over the flat-diameter, then add a champher larger than the OD to lead the cutter in, the rotate the broach into the material (or rotate the material into the cutter).
 
I feel ya @ttabbal I ordered my arbor last night. I can't say I have any immediate plans for it....it was more the experience. Been welding in a hot shop all day....too burnt out to even go check the mail! I kinda let the instructions how to set these up prior to cutting (center it/off center it) go in one ear/out the other. Do you use an indicator?? Damn my short attention span!!
 
I hope we will see some video of this in action?!
Robert
 
I clamped a dumore grinder with a 3/8 spherical stone to my tool post, put the cutters in the 1/2 collet, spun both up to speed and within seconds had concave grinds in the hex cutters.

No big deal. I know, no pictures, it didn't happen, Pix on my cell phone, won't send to me, dumb cell phone.

Edit: correct typo
 
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