# Alliant Mill Lead Screw sticking issue



## HadesHubs (Jul 27, 2014)

I have an Alliant vertical mill manufactured in 1990.  I acquired it at the company I worked for in 2002. It has a DRO and a Servo Type 150 power feed on the X-axis. Recently the X-axis lead screw has had a sticking issue.  When I move the table to the right all is well, but sometimes, when I reverse the rotation, and move it back to the left, the hand crank 'hangs up' or sticks, and I have to exert extra pressure to move it.  It does not take much pressure, but it is aggravating when making fine adjustments, and I fear that this will get worse.  It also seems to be a random occurrence.  Sometimes I can reverse the rotation on the crank and the table moves to the left without any hesitation.  Has anyone ever had this happen with their mill?  I would like to hear any suggestions before I tear anything apart.


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## JimDawson (Jul 27, 2014)

Make sure the gib is not ''floating'' It should have a screw on each end that will keep it in position, the two screws should be tightened against each other.


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## 12bolts (Jul 27, 2014)

Jim has most likely picked it.
If your gib screws are not tight against the ends of the gibs, locking it in place then when cranking your table one way the taper in the gib allows it to slip freely, but when you reverse direction the taper pushes it up tight creating excess friction. It would be worth removing the adjusting screws and pushing the gib key free of the table. Check it for bends, dings, cleanliness, etc and reinstall. Just make sure you note the way it came out and refit the same way. They are a parallelogram in section but tapered in profile.

Cheers Phil


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## HadesHubs (Aug 1, 2014)

Thanks for the advice, and of course you both were correct.  I should have maintained the gibs long ago.  When I removed the screws and gibs for cleaning I noticed the locking screw had been mistreated and was bent.  Luckily the threads were 5/16-18, so a little modification on a standard SHCS gave me a new locking screw.  All adjusted and working fine now. Thanks again~!


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