HF #981 mill/drill

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powderhorn01

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I have a older HF #981 mill/drill, and am wondering if any one has had to replace the table feed screws or not. Mine seems to have an excessive amount of play in them, causing the table to jump around when I am trying to mill something. The gibs are snugged up. I have pulled the table off and cleaned every thing, and the screws have a lot of side slop in there threaded boss, that I can not adjust out. ANY Ideas????
 
There's a bunch of stuff on backlash on the net. I think the tables on the various HF mills are of similar construction, so the same sorts of fixes should work. Tightening up the jibs may work, but it's basically just masking the problem - the Acme threads used aren't very high precision. The added friction may, however, be just enough to get you through your project. In extreme, you could lock the stationary axis in each pass, but that's probably a lot of tighten/loosen/tighten cycles that you'd rather not do.

It's kind of like a hot rod - how fast can you afford to go? Well, how much play do you want to take out? Replacing the screw and nuts with ball screws and ball nuts is the ultimate way to go, it seems, but there are other alternatives (well documented on the net).

Good luck!
 
This is a little update about the play.
I ended up replacing the leed screws with an American thread of 5/8-10, as the original was 17mm -10 thread. Which is a size that I could not find, but the 5/8-10 was available in precision thread, from McMaster. I also ordered a set of precision blank nuts to go along with the rod. When I ordered I had to get a right and left thread rod.

What I ended up doing, was to take the original threaded mounts for the leed screws, and bore them out for the precision nuts, which were then brazed into the mounts.

I stuck with the 10tpi so that my dials would still read the same.
 
Great! Did this solve the problem you were having? What kind of backlash do you now have in your table?

Thanks,
 
So far it has been working great. I was able to get the play down from about 1/32", to less than .001". I am still watching it close, but it seems to fixed all of my problems.
 
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