Rotary Broach holder

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RSG
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Rotary Broach holder

Post by RSG »

I know this topic has come up many times as I've searched it and found information, however some of the info is old and the links associated are now dead.

I'd like to do some rotary broaching in aluminum and was looking for a broach holder. I contacted Slater tools and they want almost $1000.00 (CND) for a holder and one broach bit which I thought was ridiculous so I thought I'd maybe make one. Anyone have a set of plans they would share? I'm not certain about a few things, one being dos the bit require a certain amount of slop (or free play) so to speak?

Thanks in advance.
Vision is not seeing things as they are, but as they will be.
drmico60
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Re: Rotary Broach holder

Post by drmico60 »

Here is my version:
http://mikesworkshop.weebly.com/rotary-broaching.html for use in the lathe.
The same simple principle can also be used on a mill:
http://mikesworkshop.weebly.com/rotary- ... -mill.html
These simple tools work well but they are designed for occaisional use by hobbyists rather than industial full time use.
I hope this is useful
Mike
Russ Hanscom
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Re: Rotary Broach holder

Post by Russ Hanscom »

Model Engineers Workshop had an article on one a few years ago - Looked pretty much like the commercial ones -I do not remember the Issue #.

Might have some luck on ebay.
pete
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Re: Rotary Broach holder

Post by pete »

Youtube channel Randy Richard in the shop did a full build series of the Hemingway Kits rotary broach. Plus numerous other videos on YT should provide just about anything needed to build the tool or broach.
fenichel
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Location: West Vancouver, BC

Re: Rotary Broach holder

Post by fenichel »

My variation on Mike Cox's model is described on my Web site at http://www.fenichel.net/pages/Indoor_Ac ... gidity.htm.
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SteveHGraham
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Re: Rotary Broach holder

Post by SteveHGraham »

Lathe or mill?

For a lathe, you just need a straight holder with a bearing from a car parts store in it. You put it in the QCTP, and you put the QCTP at a small angle to the lathe's axis. Because the holder is at an angle to the lathe's axis, you don't need to incorporate a wobble into the holder. People have argued with me about this, but I have done it, and it works. You don't need to put any angles in the tool holder or cutter.

I don't have a photo of my holder, but it looks like an old-fashioned flashlight. The handle goes into the tool holder, like a boring bar. The big part of the flashlight holds a bearing, a little cup with a set screw, and a cutter that goes in the cup. The screw holds the cutter in place. I made a lid that screws onto the holder's big end, to keep the cup and cutter from falling out.

For a mill, you do the same thing, but you have to make the cavity for the bearing angled with respect to the axis of the holder. As the holder rotates in the mill spindle, the cutter precesses with regard to the work, presenting one cutting edge to the work at a time. I probably made the angled cavity by tilting my mill's head a little.

I used $5 bearings. It only takes a few seconds to broach a hex into a drilled hole, so it's not like you need top-quality bearings.
Every hard-fried egg began life sunny-side up.
johnfreese
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Re: Rotary Broach holder

Post by johnfreese »

I have a dwg drawing and Solidworks models & drawings for a rotary broach with radial and thrust bearings. Send me a PM with your e-mail address if you want copies. I will try to get as many e-mails out before Friday evening. Requests later than that will be answered in about 3 weeks.

eDrawings viewer is free and you can vie the drawings with it.
whateg0
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Re: Rotary Broach holder

Post by whateg0 »

SteveHGraham wrote: Wed Jan 30, 2019 7:25 pm...You don't need to put any angles in the tool holder or cutter.
...
How does that work? If the tool is held at an angle, and there aren't any angles cut into the tool, doesn't the near side of the tool interfere with the part?
broach-interference.jpg
Dave
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SteveHGraham
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Re: Rotary Broach holder

Post by SteveHGraham »

Your cutter should have relief on the sides. I don't know if there is such a thing as a prefab cutter. I make them on the mill.
Every hard-fried egg began life sunny-side up.
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tornitore45
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Re: Rotary Broach holder

Post by tornitore45 »

I made one with the shaft angled 2 degrees on a vertical plane but I wish I learned from Steve that by rotating the thinking 90 degree one cam achieve the inclination by rotating the tool post. Steve I don't see what the argument is about, is just geometry.
Mauro Gaetano
in Austin TX
whateg0
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Re: Rotary Broach holder

Post by whateg0 »

SteveHGraham wrote: Thu Jan 31, 2019 2:45 pm Your cutter should have relief on the sides. I don't know if there is such a thing as a prefab cutter. I make them on the mill.
Ok. I knew that from having watched videos of them in use. I wasn't sure how you were doing it without cutting any angles on them, as in your earlier post. What angle are you talking about, then, that isn't needed?
RSG
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Re: Rotary Broach holder

Post by RSG »

Thanks for the feedback guys!

I'll review everything above. I can buy a cutter from Slater Tools for $75.00 but that seems rich for what it is. I'll likely make my own, just need a steel recommendation from you guys if I could! Perhaps O1 ?
Vision is not seeing things as they are, but as they will be.
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