View Full Version : Cutting a radius
10-17-2001, 07:06 PM
Probably hoping for magic here...
When cutting a shoulder on a piece in the lathe, I HATE to leave a sharp inside edge; stress-risers and all that.
I've tried all sorts of 'sneaking up on it', but the final cut in that corner with a radiused tool gives me chatter at whatever speed and feed I can find.
10-17-2001, 07:54 PM
Sounds like slop or flex in the lathe to me.
Have you tried locking the slides before that final pass? Maybe face the shoulder after turning to get the radius. A tiny undercut on the turned diameter shouldn't hurt in this case.
Oh yeah, a tailstock center works great to take out chatter. That's my two cents worth.
Just try cutting from the outer diameter to the final diameter of the shoulder. Worked for me again today
10-17-2001, 09:17 PM
I use a "v" or "w" style insert for shoulders with a small nose radius and positive geometry. A small HSS tool ground to plunge cut a small undercut in the corner might be the best solution as Snorman suggests.
10-18-2001, 06:45 PM
Try leaving material in your the corner, and when you get to where you want the radius to start turn off the power feed and run the carrage and crossfeed by hand to make your radius. Atfer a couple of years of practice you can do it second nature!
10-18-2001, 07:25 PM
I've tried most all of the methods, 'cept the carbide tool, but I'm afraid the lathe may be just not rigid enough.
I do that on outside radii. It looks good, but it still leaves some sharp cuts, so I'd rather use the 'nosed' tool.
10-18-2001, 09:03 PM
Well, how about cleaning up those chatter marks with a chain saw file. They come in several fractional diameters and cut great. I've used them for years for lots of stuff; making shims, deburring slots, "moving" bolt holes, you name it.
Put a handle on it unless you like the idea of running it through your hand. Ouch!
[This message has been edited by snorman (edited 10-18-2001).]
10-18-2001, 09:33 PM
Grind a radius on your parting tool and plunge. Leave a few thou on face and od to clean up.Use parting tool to clean face to size and turning tool to finish od to size. This way you do not have to take the turning tool to the face (shoulder). Use small file or emory cloth to dress if necessary.
10-19-2001, 07:05 AM
I like the grinding a radius on the parting tool trick myself. Might use a radius gauge
11-28-2001, 08:53 AM
Turn your tool up side down and run backwards
But don't do this with a screw on chuck!
Rear tool posts are great for parting off and heavy forming operations.
All machine components are in tension which tends to eliminate vibration.
Ever hear of a draw cut shaper? Used for heavy slotting in railroad shops in the past.