PM30 Tram

Oops! I should have mentioned that I already checked the column some time ago. I have a granite square which I placed on the bed and by moving the headstock up and down, I measured the deflection using the dial test indicator bearing against the vertical face. I measured the squareness with the granite square facing forward and then turned the square around and measured with the square facing rearward. By averaging the error, the contribution to the error of the square is zeroed out. It turned out the column is within .0006" over 5" of travel on the granite square. By minimizing the movement of the headstock when making cuts, this error is virtually eliminated.
 
RodSME said:
Oops! I should have mentioned that I already checked the column some time ago. I have a granite square which I placed on the bed and by moving the headstock up and down, I measured the deflection using the dial test indicator bearing against the vertical face. I measured the squareness with the granite square facing forward and then turned the square around and measured with the square facing rearward. By averaging the error, the contribution to the error of the square is zeroed out. It turned out the column is within .0006" over 5" of travel on the granite square. By minimizing the movement of the headstock when making cuts, this error is virtually eliminated.
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Sounds like you covered that base then!
 
Here's some more conversation on tramming column mills.
www.hobby-machinist.com

Tramming my PM-833TV

All of my experience in the past was on full size Bridgeport mills. I'm discovering that these column bed type mills are a different animal as far as tramming goes. I've done some research but would like to hear from others the techniques they use. Here is what my gut and a little research...
www.hobby-machinist.com www.hobby-machinist.com
 
I can’t leave well enough alone, I have the forward and aft tilt of the column zeroed but now it tilts to the left .0005 over 8” of the granite square. Should I try and shim that out or let it ride?
 
Livnpaintball said:
I can’t leave well enough alone, I have the forward and aft tilt of the column zeroed but now it tilts to the left .0005 over 8” of the granite square. Should I try and shim that out or let it ride?
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Don't "settle" for "almost good" - go for it. :)
 
Seems like it would require a really thin shim; is that possible? What about differential tension on the bolts?
 
Livnpaintball said:
I ended up with a shim of .0025 on the left side.
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I don’t understand how a 0.0025” shim on one side of a support with 8” separation can cause a 0.0005” change across an 8” travel. Something isn’t adding up.
 
jwmelvin said:
I don’t understand how a 0.0025” shim on one side of a support with 8” separation can cause a 0.0005” change across an 8” travel. Something isn’t adding up.
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I guess the weight of the column and head compress the Shim material? .0005 shim material I bought is like a Mylar ballon, but it’s stainless.
 
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