Keeping The X On A Round Column Mill

Canuck75

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Jan 1, 2014
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Two years ago I posted a thread on keeping the X on my King PDM 30 by fixing the rack to the column and attaching tight fitting guide blocks on the head. I was getting .001" repeatability. As a method of checking I set a 1-2-3 block in the vise, edge found the X and Y, set both the DRO and lead screw dials to zero, moved the head, edge found again seeing the lead screws and DRO rereading zero.

I recently watched a You Tube video posted by Cuppa Jo in which he used a linear brg and shaft, plates clamped top and botton of the column( 8.5" between column C/L and shaft C/L), and replacing the hood with a plate to anchor the brg relative to the head. As a check on the resulting accuracy he set a DI against the extended quill and moved the head up and down. His results were impressive to >.001". Moreover, because of the sturdy design, the head doesn't wiggle when being moved.

Today I decided to re-test my mill the same way and have attached this video to show the results. I know the ratio between the guide blocks and the column C/L, vs the distance between the column C/L and the quill C/L, is not ideal for control, but it seems to work well enough. Cuppa Jo's mill has a split head casting and two clamp bolts, as mine does, but in his case it doesn't seem to matter about how you retighten the bolts. On mine it does. In the video you can see how much the head comes adrift after unclamping and if I don't fully retighten the top bolt first it will be off a few thou, as it was in one case in the video. Just the interaction between the rack and the split head as it comes back together I guess.

Anyways, it was a bit of relief to see that the setup is still accurate.

Canuck75
 

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