Rotary broach

Malave16

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Here's a rotary broach that i just made. It not my idea, the gentleman that goes by arduinoversusevil on youtube is were i got the idea from. Its made out of stock from some center punches that came with my lathe.
The trickiest part was turning the offset. I did it on the 3 jaw by putting .140" shims on one of the jaws. The hole for the bearing is just the profile of the bit i used to drill them, nothing special. I just made sure that the ball would stick out of the hole just under halfway on all the holes. The holes for the bit were supposed to be temporarly round until i could make them square with the broach, but they work just fine like that. Profiling the tools was the biggest pain. I used a dremel with a ball attatcment. So far i only used it on a drill press. It makes square holes. I was also considering making more dies for it using actual tool bits, like an actual allen key sharpened to make hex holes maybe torx and the like. They are hardened, so it should work. Any questions please ask.
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Impressive. I didn't know it was fairly simple to make one of these.

Did you get prints for dimensions or draw it up yourself?
 
I wonder how thick a piece of metal you can do this to.? woul this be a viable way to make a square hole in say a boring bar?


Mark Frazier
 
Thats the sole purpose why i built it, to make boring bars with it. So far i made one with the 1/4 bit trough 1" cold rolled. It worked fine. About 1/2 way trough had to stop and clear the chips, buy it went trough.
 
Does it hold itself together somehow or is it just held together with the spindle force?
 
Got the idea from youtube. No prints, i kinda eyeballed everything
 
Does it hold itself together somehow or is it just held together with the spindle force?

Just spindle force will hold it together. A bit of duct tape will make it usefull on the lathe, but not worth the risk
 
That’s a clever way to make a rotary broach! Nice Going, Dave.
 
I have heard of these, but I never saw one of these work. Seems like it would vibrate like a jack hammer or be hard on the equipment. If not maybe I should try it.


Mark frazier
 
I wonder how thick a piece of metal you can do this to.? woul this be a viable way to make a square hole in say a boring bar?


Mark Frazier

Mark, the tool bit does gyrations/rocks about a solid angle. Just as long as the tool bit has side clearance for the rocking/tilting it will go as deep as that clearance. The downfall is the more clearance on the bit, the weaker it gets, so you will need to compromise…Good Luck, Dave.
 
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