# Atlas 12 in half nut "Brass ?"



## Redneck79 (Feb 2, 2019)

I put new half nuts in my 12x36 and used it a couple months and the teeth are gone in it.  Is this common with zamak??  I see brass replacements on ebay, any experience with these?

Really sucks i had the whole weekend to work on lathe projects and now im done till i get it repaired.


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## Ulma Doctor (Feb 2, 2019)

zamak is a mixture of zinc, aluminum, magnesium, and copper.
zinc is the base metal, aluminum, magnesium and copper are added in small concentrations to create the alloy.
is is not an especially strong nor is it wear resistant
it is a cheap metal that casts well, without the need for much machining after casting.

brass will wear a lot better, bronze would be even better than brass-
but i'm concerned that you may have an unknown issue that may be eating up the half nuts,
being that you replaced the zamak nuts not long ago

further investigation should take place before you buy another set of nuts

another consideration may be to make a set from delrin
it has a lower drag coefficient and is surprisingly tough being a plastic


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## Norseman C.B. (Feb 2, 2019)

Bronze is a go to for that, but as Ulma doc said you may have other issues to look at ......................


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## Redneck79 (Feb 2, 2019)

What would cause that??  The miter gears arent in it, that leaves no resistance i can see.


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## wa5cab (Feb 2, 2019)

I would agree that something else may be wrong.  My 3996 has the same part number parts in it as yours does.  It was bought new in 1981 and is still not worn enough to consider replacing.  I would suggest calling Clausing and asking for Tech Support.  But remove the new nuts first so that you can look at the wear pattern.


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## benmychree (Feb 2, 2019)

Especially, see if they are closing completely.


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## Redneck79 (Feb 2, 2019)

went out to check the rest of the lathe over and with the apron off the carriage was harder to move than i think i tshould be.  I may have overtightened the set screw on the back.  would that be enough resistance to do it?


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## wa5cab (Feb 2, 2019)

Removing the apron shouldn't have any effect upon the force required to move the carriage

I assume that you mean the four Carriage Gib adjusting screws.  With them properly tightened, the increased force required to move the carriage should just be noticable.  But even if they were significantly over-tightened, wearing the half nuts out in two months shouldn't happen.  Maybe two years or twenty years.  I assume that you are oiling the threads on the lead screw and thrust bearings daily or before each day of usage.


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## Redneck79 (Feb 2, 2019)

Always oiling.  I am OCD when it comes to lubrication be it the lathe or me diesel 3/4 ton.  I dont know what else it would be.  the lead screw is in excellent shape, all other apron parts "except mitre gears are absent" are in great shape, It hasn't crashed and i watch my feed rates close.


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## wa5cab (Feb 2, 2019)

OK.  Check the wear pattern on the half nuts and confirm that they close fully.  And call Clausing next week.  Talk to someone in Tech Support, not the parts people.


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## Redneck79 (Feb 2, 2019)

will they help being an old atlas?


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## wa5cab (Feb 3, 2019)

Yes, if they can.  It may help to be a known regular customer but I've never been made to feel unwelcome by anyone there.  I didn't actually ask you whether or not you got the new half nuts from them - just assumed that as they were supposedly Zamak that you had.  Did you?


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## Redneck79 (Feb 3, 2019)

No, ebay.  I really didnt think they would have much for a machine that old and i assumed the prices would be rather high if they did.  Was i wrong on both accounts?


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## Redneck79 (Feb 3, 2019)

I actually need the cross feed mitre gear bearing and bushing as the lathe was missing it when i bought it.


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## wa5cab (Feb 3, 2019)

They do still have a fair number of parts for the lathes and a few for the mill.  Almost none for the shaper.  Prices are generally about what you would pay today for similar parts for newer lathes (in other words not cheap Chinese prices but generally fair.  Of course, if you have preconceptions based on 1940's catalogs or Harbor Freight, you will be disappointed.  Prices on gears that you can buy and modify to work on an Atlas will be around what you would pay for the US made blank plus what you would pay a shop to modify it.  What did you pay for the half nuts on eBay?  And did they claim that they were factory?

Factory probably has the cross feed parts.  All that you can do is to call them and ask.  But as you didn't buy the half nuts from them, forget what I wrote earlier about calling them, unless you think that they were actually factory.  In which case they won't refund your cost but should be willing to try to help you figure out what happened.


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## Redneck79 (Feb 3, 2019)

paid $60.  yes they were supposed to be factory.  Ordering new from clauseing mon. went through and readjusted the carriage and found it moves Alot easier now, have to watch close when i get the new ones in to see if anything is binding.  I thought the half nuts i got were kinda soft.


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## Bob Korves (Feb 3, 2019)

Watch out when adjusting the carriage.  Most all lathes get most of the wear to the bed ways with the tool close to the chuck, in a fairly small area of the total bed ways.  If you adjust the gibs in that area, and you move it closer to the headstock or closer the the tailstock end of the bed, you will be sliding on metal that is much less worn, so the gibs will be too tight if they were adjusted where the most wear is.  This is a common problem on all slide way machines, and must be understood and taken into account when adjusting the gibs.  Often, when there is differential wear on the bed ways, the gibs would be adjusted so they are just a little tight, but still sliding freely near the far right of the bed, where there is normally much less wear.  In the most worn areas of the bed, with the same gib settings, the gibs will be somewhat loose.  That is about the best compromise you can make  If you want better, the ways will need to be ground or scraped parallel and in the same plane along the entire length of the bed.  That is not an easy project.


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## Redneck79 (Feb 9, 2019)

Found the problem.  Although i thought they were closeing all the way they were not!  Play in the end at the scroll stroke allowed the half nuts to to move.  the bottom was dropping and the top could raise slightly causing them to not engage fully.


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## Jan the man (Sep 26, 2019)

I encountered  that problem while trying to clean my Th42! When I put it back together, I found that their was not enough shim under the saddle and it was way to tight.
When I got the lathe, the gears in the gear box  for the forward and reverse was destroyed as well as the Half nuts. I added shim and the problem went away.


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