Atlas Half Nuts OEM vs Brass

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Wildman326

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I have a 12X36 101.07403 Atlas lathe that I have to push the lever all the way down to make it engage.

I’ve seen the half nuts for sale on eBay.

Are the brass ones worth the extra $30?
 
I have no knowledge of the Atlas lathe, but I think the brass ones would be worth it.
The stock gears are made of zamack zinc alloy and are much softer than steel, so I am assuming that the half nuts are also made from zamack
 
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the OEM half nuts are Zamak.
Zamak was chosen to minimize post formation machining, it casts very well and has moderate wear and strength characteristics
Bronze or Delrin may be very well suited materials to construct half nuts from

brass would be a step up from Zamak
i would become religious about lubrication of the feedscrew if/when you swap to brass- for longevity of the screw as well as the half nuts

there is another part inside the apron that helps to engage the half nuts.
i cannot recall its proper name, but it it connected to the engagement lever and runs transverse across the apron.
it has a couple half circle channels cut into actuator face that is distal in proximity to the engagement handle
these half circles can become worn and no longer move the half nuts as efficiently.
as a result, the travel between open and closed diminishes with the wear in the system
 
The factory name for the part that Mike is describing is "Scroll". The normally visible half nut engaging lever is mounted on the outer end of the scroll shaft. The other three parts of the mechanism that are subject to wear are the Guide and the two studs.

I disagree that brass half nuts are superior to or will outlast the OEM Zamak ones. On average, both materials will wear at about the same rate. There are two reasons that all of the after market halfnuts are made of brass instead of Zamak V - they can make unsubstantiated claims that their brass product is superior to the Zamak V OEM ones, and they couldn't machine them out of Zamak V if they wanted to because AFAIK no one markets Zamak V bar stock. There is a third reason why no one makes them out of Naval Bronze which is that they would be too expensive to compete. In general, the brass ones tend to ba a little more expensive than OEM, which they get around by claiming that their brass ones will outlast the OEM ones. Or by depending upon their customers not knowing that the OEM ones are still available.
 
Would naval bronze be superior to regular bronze or zamak? I would think a leaded bronze like SAE 660 would be a good choice
-Mark
 
Thank you very much for all the replies and information. I ordered the OEM half nuts. I’ll have to look at the scroll when I take it apart to see how much wear they have.
 
Just agreeing with Robert D. on a different note.
Lathes have half-nuts. They're made of all kinds of materials for all kinds of reasons.
The Atlas used Zamak. Low power. Low speeds. Low loads. Works fine. Zinc is a good lubricant, which is why we put it in certain motor oils.
The original equipment Zamak lasted longer than i've been alive, probably with dubious upkeep. How do I improve on that?
Brass? Not really.
But if I get another Zamak, and took care of things, it will only last another generation and then some. If I got another Zamak and a spare, I'd have the half-nuts covered for my great-grandchildren. That'll do,.
 
In my opinion, cast iron is the best material for half nuts, evidenced by the fact that all lathes, other than Atlas use it for half nuts.
 
after having personal experience rebuilding an Atlas TH42, zamak is junk
you can keep the low grade stuff
 
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