Mini mill table binding

[redvan22]

My mini mill table screw is really tight in one direction only. In the other direction it's smooth.

I took everything apart cleaned and oiled and still, one direction only is tight.

Any suggestions?

 

[Asm109]

gib on dovetail is moving sligthly. In one direction it moves loose, other direction it goes tight. Assuming the gibs are tapered.

 

[homebrewed]

Mini mill gibs are not tapered so that's not the issue.

For clarity, when you say "tight in one direction only", do you mean something like "it's tight when I move the table to the left but not to the right" (or substitute "forward" and "back"), or "the Y axis is tight but the X axis is loose"?

Since you refer to a single table screw I'm guessing the problem is specific to a particular axis but I could be wrong. Even if my guess is correct, there are significant differences regarding the X and Y axis. The X axis has thrust bearings in the bracket, so the nut on the handwheel can be tightened down pretty good without making it difficult to move the table, but the Y axis uses thrust washers, which require a lighter touch to prevent the feed screw from binding up. It would be nice if both axes had thrust bearings but for some reason that's not the case.

So we need to know which axis you are referring to.

 

[redvan22]

Mini mill gibs are not tapered so that's not the issue.

For clarity, when you say "tight in one direction only", do you mean something like "it's tight when I move the table to the left but not to the right" (or substitute "forward" and "back"), or "the Y axis is tight but the X axis is loose"?

Since you refer to a single table screw I'm guessing the problem is specific to a particular axis but I could be wrong. Even if my guess is correct, there are significant differences regarding the X and Y axis. The X axis has thrust bearings in the bracket, so the nut on the handwheel can be tightened down pretty good without making it difficult to move the table, but the Y axis uses thrust washers, which require a lighter touch to prevent the feed screw from binding up. It would be nice if both axes had thrust bearings but for some reason that's not the case.

So we need to know which axis you are referring to.

X axis.
When I crank the table to the left, it's easy. When I try to return, crank to the right, it's tight.

 

[silence dogood]

X axis.
When I crank the table to the left, it's easy. When I try to return, crank to the right, it's tight.

I had a problem similar to yours, except it was on the Y axis. Cleaned like you did. Found that there were dry areas or no oil. Also, cleaned and relubricate the screw and nut. Carefully redid the gibs. Found a couple of burrs. Not sure where the problem was, although I suspect it was the gibs were the main problem, but the other things must had added to it. It works fine now.

 

[benmychree]

I have seen graduated dials that bind/drag against thrust surfaces cause that problem.

 

[ChazzC]

Adjusting the nut on Mini-Mill lead screws is more than a little finicky. LMS has a good breakdown of the procedure in their Users Guides and this Bulletin.

 

[redvan22]

Adjusting the nut on Mini-Mill lead screws is more than a little finicky. LMS has a good breakdown of the procedure in their Users Guides and this Bulletin.

Never saw that bulletin but I will do what it says tonight after work. Never knew exactly how to adjust both those screw nuts. Thanks.

 

[redvan22]

I have seen graduated dials that bind/drag against thrust surfaces cause that problem.

This is the exact problem I'm having with my compound slide on my mini lathe. It drives me mad.

 

[homebrewed]

Adjusting the nut on Mini-Mill lead screws is more than a little finicky. LMS has a good breakdown of the procedure in their Users Guides and this Bulletin.

The problem could be indirectly due to the nut. IIRC the pocket it sits in isn't machined (or not machined very well) so it could be rocking back & forth. That could result in a change in the effective amount of clearance between the feedscrew and nut, so the friction between them would vary under those conditions.

The X axis nut has two set screws so if the nut is rocking on a high point it may be possible to play around with them to adjust the alignment & reduce or eliminate the described problem. It really depends on where the high point is. It wouldn't hurt to play around with the set screws some -- loosen one then tighten the other one down, see what happens, then do the same with the other set screw.