A Shop-Made Compact Rotary Broach

that's a good writeup, but I am confused by the feedrate part of it.
Maybe someone else has some insight as to the problem.
I don't think it's your relief.
 
I don't know what the problem is.Al I know is that it is frustrating, especially when I worked of a plan and my broach aint workin.

Don't know,but maybe I must increase the offset????
woodchucker said:
These require a lot of force.
Click to expand...
I am giving it beans,but I dont want to break my mill now.
 
Thinking about it now,could it be that the fact that I did NOT give the cutter a 0.0500 clearance in the holder,therefore another 0.0500 offset,that that could be the problem and the broach not wobbeling enough???
 
I don't think so.
That would be the last place I would be concerned about.
 
I think you're closer to 2 degrees as it is if I guesstimate the length of your tool form tip to pivot knowing the face is 1/2". Plenty of dish for your lead angles, cutter looks sharp. There was a dimension that was missing in the prints when I peeked at them yesterday, and that's the groove width or groove to set screw clearance that limits your maximum angle on the ball pivot. The offset ground into the shank is what provides the "action" though. The action is what determines your (theoretical) feed. The importance of feed rate will matter if you are setting up a screw machine.

I wonder if your shank offset is cancelling out the wobble. I have to go back and look at the prints to see if that can happen, but I would imagine so, the shank offset and deflection from the ball may be netting near zero inward motion.
 
Just checked the prints, the design requires a tool offset (at the tip, from the ball) to be greater than the shank offset's contribution.
 
Suzuki4evr said:
How do I achieve that then?
Click to expand...
That darn drawing doesn't show critical clearances and fits. It doesn't spec dimensions for the bit holder and socket/driven part. It needs to rock in order to cut. What happens if you loosen the set screws a bit to provide clearance on their contact tips and see if it cuts? If you have clearance for good gyrating movement in the ball joint, then I'd say your problem is not enough offset in the shank.
 
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