Pm 727m issues, help please!

B

Brad125

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Mar 12, 2020
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Hey fellas,

I been fighting my machine for hours. If i have the.Z axis locked down and indicate the X axis( .0002 over 10 inches) as soon as i raise the Z axis a few inches lock down the Z axis and try again, the table is way off. Like 5 or 6 thou off. I have the Z axis gib adjusted tight but not to tight, there is a 1/2 inch of gib sticking out fron under the head of the mill. What in the heck is causing this? Its driving me nutz!!! I am using an Edge Technology indicator holder and a Browne and Sharpe BesTest indicator and using precision 123 block accuracy to .0002. Anybody have any ideas? I thought square column mills were suppose to hold the position when raising and lowering the head?
 
Can we assume that the column/head is clamped when setting zero, and also clamped when moved and re-indicated?
 
You mentioned the 1/2" of gib sticking out- that sounds wrong. If it moves as you move the head you need to investigate that. Usually, on non-tapered parallel gibs there are dimples in the gib that engage the adjustment screws to keep it from sliding around.
-Mark
 
I believe this machine gas tapered gids, and yes the machine Z axis is locked down before indicating. Something doest seem right and i can figure it out. The 1/2 inch on gib sticking out the bottom is from having to adjust it enough to take the slack out, or maybe someone else has a procedure they would be willing to share.
 
I had a similar issue on my 833TV on the X axis. I had to cut the gib because I had so much sticking out.
 
Gutting the gib off is fine with me, i just want to know whats causing the head "tilt" to be off that bad when traversing the Z Axis
 
Sounds to me like your column could be out of plumb.

Are there any adjustments on that? Or have you checked it for squareness recently?
 
The only adjustment is head tilt, i know thw machine has a nod of .004 but that shouldnt affect the squareness to the table at various distances. I have not checked the squareness for the head in relation to the table, the only way to do that is to extend the quill the 3" and run it up and down a angle plate, which i dont have one currently.
 
I would bounce it off PM and see what they say- Maybe they will send a new gib strip or give some adjustment info
Ask them what the maximum repeatability deviation of the head is when traversing vertically
-Mark
 
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