Rotary broach

What a clever, brilliant idea, no less so the explanation on the way it works, thank you so much Mike, it certainly sounds a lot better than a "bl...dy"big hammer.

Thanks also to Mark for the design, excellent..! I am going to have a go building one.

Thanks,

Norm.
 
How much should the offset be on the eccentric and can you grind the relief on a bench grunder? Lastly is HSS toolbits sufficient.?
 
S-7 tool steel, mill to size and shape, then harden. Not to hard to get precise squares, hexes .
Hss is best but most likely you will be grinding it with abrasives,need a good jig.
The corners of the bit are the weakest link, so the less material you remove on the work the better.
 
I've made one and they work well; as far as broaching depth. That's dependent on the back angle you make and it's length. You still can't beat a "Slater" brand which I use in lathe, mill and yes, drill press. I make most of the needed broaches, but for about, $28.00 is the starting price point on store bought.
 
I gotta make one of these.
After hand filing a 1/4 square on a 1" pc of round steel, never again..lol:grin big:
 
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