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Centerless workpieces are concave on specific diameter

mokemoon

Plastic
Joined
Jun 17, 2020
Has anyone ever encountered a problem which Centerless workpiece profile are concave only on a specific diameter?

My material is SUS306 with diameter of 0.330mm, I tried to Grind it down to 0.064 in tapered shape but somehow concave occurred on my tapered part just only at the diameter around 0.27-0.30 as in the attached pictureView attachment 291997, but on the different diameter even though it is tapered shape none concave occurred. I tried changing the alignment and such but it doesn't seems to help does anyone know what might cause this i'm kinda desperate now.profile circle.jpg
 
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Your picture did not attach, try again. I'm not a centerless expert, but could your regulating roll be losing contact with the workpiece at that diameter range? If you try a straight section of ~0.285mm does it rotate or is it stationary?

Is your grinder specifically for micro diameters?
 
I uploaded a new picture,Yes my grinder is build specifically for micro diameters but it use work rest blade instead of regulating wheel. Me too think that the workpiece might somehow lose contact with the support at a certain diameter but i don't know how. Right now i'm thinking about the contact angle and I testing it out, Thankyou!
 
OK, I see the image now. Is the profile you're grinding dressed into the wheel (so a plunge grind), or is this a Z move with a wheel that has just one taper ground into it, and X is adjusted for the different work diameters?

In any case, listing the machine you're using may help too, as well as any other operating parameters that could be affecting your work. Including whether this is a short individual piece grind, or you're cutting longer sections of rod.

As I mentioned, I'm not an expert with centerless grinding, so hopefully one of the more knowledgeable grinders will comment too.
 








 
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