Gallery, Projects and General > How do I??
Cutting a concave hole
Mike K:
I need to cut a concave depression that'll be used to grip a 1" plastic ball. Is there any way to do this on the mill? The plans for the part suggest simplifying it by making it 30* instead, but it would be nice to have the curve to limit wear on the ball. Also, the position on the part prevents me from using the lathe anyway, as my lathe doesn't have enough swing.
I recently read in Guy Lautard's "Machinist's Bedside Reader" (great book, by the way) of cutting curves on the lathe without using a radius cutter, by moving the cross slide and saddle to a set of coordinates and then filing/sanding. I was thinking about doing this with a boring tool in the mill.
Any thoughts?
Mike
John Hill:
In to what material?
How about drilling a series of steps (using different sized drill bits) to rough out the hole then finishing the job with a shaped bit cut from a flat piece of steel, or maybe put a ball end on a rod then grind it to half diameter to make a combination 'D' bit and form tool?
sbwhart:
I think I can remember Bernd making a D bit and posting it on her, if my memory serves me correct he turned a disc up on the lathe the required diameter silver soldered it to a shank, backed it off an used it in a mill to put a rad round some plate, may be worth doing a search.
Good luck
Stew
arnoldb:
I also remember seeing it Found it
You could also make it in the mill with a rotary table and coordinates... Cut successively deeper rings toward the middle of the workpiece... A ball-end mill would do a good job, and if you use close coordinate spacing it should come out pretty good...
Cheers, Arnold
Mike K:
Thanks, guys. You've armed me well. Now to try it! That D bit looks interesting. It'll be my first. I'll let you know if I manage not to goof it up. I'm also going to test out the rotary table idea, since I haven't used mine yet (only been using the mini-mill for a couple months).
Mike
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