Knee hight adjustment screw tightness issue

Kind of winging it here, but how about taking the knee to the top of travel and blocking it with a wood block at the bottom. Remove the cap screws on the knee nut and spin it by hand up the screw. If it moves easily you're burr and chip free.

If that's the case, spin the nut back in place and loosely install the nut cap screws. Run the table down and watch the nut. If it shifts back and forth, the screw may be bent. You'd think it'd move in the same spot on the screw if that's the case.

With the knee blocked up, you could turn the crank and watch the screw and see if it's orbiting.

To check the table up/down on the ways, maybe use an engine hoist from above and slowly lift the table through it's range of travel. Look for hard spots on the way up or down.

Good luck!

Bruce
 
I don't think the problem is in the screw/nut system. That whole system is pretty loose and it would take a lot of misalignment to affect the operation. I'm going to suggest that the problem is in the gib adjustment.

My mill is tight both at the top and bottom. This actually improved somewhat when I tightened the gib.

I would try Bruce's suggestion of lifting and lowering the table with a hoist. I'll bet you will find some tight spots.
 
I would be looking for galling in the ways, but a loose tapered gib could also be a culprit, it would likely run tight when going up, and loosen when going down.
 
A couple of things:

a) the acme screw is supposed to be covered in grease...................
b) you can access the bottom of the acme thread by removing a panel under the base and clean it from there.
 
Thanks everyone for input!
I fingured it out! I apologize it looks like I haven't made my self clear enough. First thing I did as some suggested I loosened that nut on the bottom and ran it up and down and brushed the screw likely getting rid of some chip that caused problems in the firs place. The trouble was that nut housing thing had just one way of being bolted and sit perpendicular. No surprise there really , the mill got plenty of parts that have been finished by hand with an angle grinder or sit catiwampas.
 
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