Atlas/craftsman 16/32 Combo Gear ?

Report - Success!!! This is one of my first successful projects, so pretty happy about it.

I called Clausing this morning to check prices on a leadscrew and half nuts. Leadscrew, 3/4" 54" bed - $700!! Crazy, but the half nuts were $33.....yes, $33 plus shipping. That's cheaper than I've seen any half nuts on Ebay in unknown, usually poor condition.

I will either buy from Clausing or buy the brass half nuts....trying to decide which would be better. The brass are about $75, but may be worth it.

For the leadscrew I will likely just buy an ACME threaded rod and have a shop make it (or maybe I will try it, minus the keyway down the length, I don't have a mill.) But the wear on my leadscrew is only in about a 2" area very close to the chuck in a somewhat odd location. I don't see myself replacing it anytime soon unless there's an obvious problem.

For gears I doubt I will buy Zamak again, if given the choice of steel or cast iron. Looking at my Zamak gears, it appears the smaller gears are the ones with the most wear. My 20T gears are pretty much useless, while the 64T's appear brand new. Given the forces involved, it makes sense.

Thanks again, love the forum.
 
You can flip the leadscrew end for end, but this entails cutting the ends off and re-attaching somehow.
Pierre
 
The Zamak half-nuts should last longer than the brass. And new Zamak gears will probably outlive you. :D
 
I agree with Robert that the Zamak will wear as well or better than brass. Also the smaller gears will wear faster than the larger gears. This would be true with either Zamak ones or steel ones as the teeth on smaller gears are used more than on larger ones. If you drive a 40 tooth with a 20 tooth it will be worn twice as much. A 60 tooth with a 20 tooth 3 times as much. Spiral Chips did convert to mostly Boston Change gears and he mentioned that the drive train makes more noise than with ZAMAK. You do drive a steel gear with a ZAMAK in going to the QCGB. On my lathe the 40T drive gears do appear to have worn faster than the ones in the QCGB. This is a good thing as replacing the 2 40T is cheaper than replacing the compound gear they drive in the QCGB.

Also here are a couple of links to when Iron Man made a new lead screw for his lathe. http://www.hobby-machinist.com/threads/atlas-lead-screw-replacement.18061 http://www.hobby-machinist.com/threads/cutting-a-key-for-an-atlas-lead-screw.18159/#post-222724
 
Rob,
Good info on the gears. I noticed right away that the smaller gears, especially the 20T-40T were worn to points, I can't believe they were still making contact, albeit with tons of slop.

I've now replaced then 16/32 combo gear, the three 20T, two 24T, one 32T and a 40 T all with steel. These were all purchased cheaper than their Zamak counterparts or close enough in price to justify the steel gears. Once you get to 44T and larger the Zamak are usually cheaper (buying used.). Also all of my 44T and larger gears were in mint condition.
I'm not sure if that's because they "spin" x number of times more vs the larger gears or if it's because the forces applied to the smaller gears are higher....?

I'm not a gear theory expert but it was apparent that, as you mentioned, the smaller gears, worn to nubs, wear more quickly. That also gave me more reason to buy steel in those sizes. I will replace gears with steel/cast iron as they wear.

I'm also going to go with the Zamak half nuts on your recommendation, cheaper too!

Thanks again....now just need to get this thing cutting!
 
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