Rotary Broach Holder?

Thanks David, this is very useful. Not only the pre- dill info but cutter size man you are awesome!!
 
Great work David, I'm very impressed. Even though you said the wrench fit in nicely, I'm pretty sure you can use a smaller pilot hole diameter than the recommended 3% if you want to . The trade off is faster tool wear and increased pressure, but sometimes a better 'looking' hex. They key is never to go below the flat-to-flat dimension so that you always have separate chips. Beautiful.

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Markknx, if you make your own take a look at the picture of the broach above. You can just barely see the rake angle ground into the face of the broach. The rake angle is critical for getting the chip to start curling up when rotary broaching. I'm sure it would help if you have a way to machine it. Hope that helps.
 
The faces of factory rotary broaches are hollow ground. Shouldn't take much to dress a ball or narrow disc for a TPG and get an acceptable face. It will make a huge difference in thrust pressure required to cut the shape. Also, if you don't want to leave the chips in the bottom of the hole, after you drill/bore/whatever, but a narrow relief groove at the bottom and the chips from the corners will be free to fall out. Ive spent more than a few hours pushing a Slater, and while they do the job, it's not quite the same as a cold headed product, or one cut on a shaper or slotting head.
 
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Broach,are you saying I need less of a dishing On the face of the cutter? Could not find the above photo you mentsioned. Thanks for the input.

broach said:
Great work David, I'm very impressed. Even though you said the wrench fit in nicely, I'm pretty sure you can use a smaller pilot hole diameter than the recommended 3% if you want to . The trade off is faster tool wear and increased pressure, but sometimes a better 'looking' hex. They key is never to go below the flat-to-flat dimension so that you always have separate chips. Beautiful.

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Markknx, if you make your own take a look at the picture of the broach above. You can just barely see the rake angle ground into the face of the broach. The rake angle is critical for getting the chip to start curling up when rotary broaching. I'm sure it would help if you have a way to machine it. Hope that helps.
Click to expand...
 
On the one cutter I had made, I hollowed out the tip with a cutting disk on a rotary tool mounted on the tool post. Worked pretty well. I have not messed with it in a while as I have had other things going on that have kept me out of the shop.
 
I used wobble broaches on screw machines and CNC lathes for years. I found that proper setup of these tools was essential to production broaching.

The tool isn't just offset, it is at an angle to the centerline. Properly adjusted, the rear of the broach will oscillate around the centerline. This lets the tool cut on one edge at a time as it penetrates the work.

Here is a description of wobble broaching that gives a pretty clear explanation of how they operate.

http://www.slatertools.com/customer...l-rotary-broach-toolholder-setup-instructions
 
I dish out the broach by spinning it up in the lathe and running my dremel tool with a narrow disk on edge to the end of the broach That will give you a relief nearly the same as the tangent section of arc of the dremel disk.
 
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