# 3996 Leadscrew Height Adjustment



## gymbo (Mar 31, 2015)

First I,ll say hello as this is my first post, you know the lurker thing. Also would like to thank you guys for the effort you put into this site makes it one of the better ones out there.
The problem seems to be the lead screw is sitting to low on the bed when I engage the half nuts the lower half actually pushes the lead screw up. So after doing a search and reading the manual it says to adjust the lead screw bearing assembly to fix this. However there is no vertical movement in mine , the bracket that bolts to the bed with two 1/4-20 bolts sits tight to the underneath of the bed against the ways and the two holes for the bolts are not slotted. 
The lead screw is 3/4" with the clutch and newer rear bearing assembly, the half nuts are the 10f-12
I do have a small mill and could machine the bracket to make it adjustable but thought I should ask first.

Thanks Jim


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## Tony Wells (Mar 31, 2015)

I would look more into adjustment of the half-nuts. If the bed of the machine has been resurfaced, that lowers the carriage, not raises it. I don't think I have ever seen an adjustable leadscrew. But, like an older gentleman I worked for told me...."Boy, there's a lot of things you ain't seen".


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## Nammar (Mar 31, 2015)

Dear Jim,

I bought a Polish made Andrychowska TUE-40 lathe from a fishing boat that was been scrapped, for the scrap price. During testing, when I wanted to engage the half nuts onto the leadscrew, the half nuts did not want to engage and they also caused the leadscrew to deflect. After stripping the apron to have a look see, the threaded parts of the half nuts were packed tightly with brass shavings. They must have turned a lot of brass on that ship. Nevertheless, a good clean-up of the half nuts and re-assembly solved this problem.

So, before going to adjust the height of the leadscrew, have a look at the half nuts. They may just be packed full of gunk. A simple cleaning job may just solve your problem. Geoffrey.


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## gymbo (Mar 31, 2015)

Atlas has no way of adjusting the half nuts the bracket that holds them is bolted directly to the apron and has two registry pins for alignment
Geoffrey that was the first thing I checked pulled the old (4 months old) nuts out to clean and saw the lower nut was shot, upper nut not quite as bad. Put in new nuts but its not engaging smoothly at all and the lower nut is pushing the lead screw up towards the ways long before the upper nuts engages the screw. If the ways had been ground I would think the upper nut would be engaging first. The half nuts open and close smoothly when lead screw is removed.  Jim


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## Strtspdlx (Mar 31, 2015)

I noticed on my lathe if I didn't have the jam nuts at the end of the lead screw adjusted correctly the lead screw would say and do the same thing your describing. I'm afraid yours may be a lot worse then mine but it's worth a shot


Sent from my iPhone using Tapatalk


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## Nammar (Mar 31, 2015)

Dear Jim,

Then I can only assume that it's an assembly issue and should be a quick fix. These brass half nuts are normally machined as a pair and should you remove them and place them on the leadscrew by hand, they should line up exactly with each other. You may just find that one of them is 180 degrees out and a simple turn around of one half, to properly align them up, may solve your problem. Lathes are pretty simple in their construction. Pictures would help a lot. Geoffrey.


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