Spindle drive gears on Atlas / Craftsman 12 x 36

[Bill1958]

Hi....just joined up and my first post here.
I could really use some input here as to what type of gear drive setup this is on my lathe. Craftsman tag on the bed: 101.07403, 12 x 36.
Just picked it up about a week ago...but the seller didn't have any info on it. A renter skipped out on him in a hurry and left the big stuff behind...to cover the back rent I guess.
From what I can find on google images it looks as it should...except the spindle gear drive assembly. No one has an answer so far...so I'm hoping someone here can shed some light on this mystery.
Has anyone ever seen this setup on a lathe before?
I don't believe it's completely custom...as the outer support plate for the gear train is stamped steel and fairly thick.
The one gear has chipped teeth but it still ran quiet.
I've got it about half apart for inspection and then strip and paint. I'm not fixing it up to sell and I plan to use it.
Whatever lathe this gear drive is from...I'm pretty sure the speed and threading charts won't match up.

Any thoughts on this gear drive would help....as I am lost.
Thanks!
Bill

 

[pdentrem]

First time I have seen this set up. There has been aftermarket makers of gear boxes as well as the units produced by Atlas. Maybe somebody has adapted from another company’s lathe.
Pierre

 

[Bill1958]

Hey thanks for your input Pierre! The plate is what made me think that it might be aftermarket. Hard to stamp that out at home.
I'm guessing it's an improvment of some sorts...otherwise why replace the original gear set with something that looks to be more expensive.
I don't know...just guessing.
Thanks again for your input!
Bill

 

[Orangetruckman]

That’s an interesting quick change gear setup. I’m only a couple year into the hobby, but I ain’t seen something like that. I’m sure the super knowledgeable Robert will be along shortly to hopefully help shed some light on your unique setup. Congratulations on the new to you lathe and welcome aboard Bill!

 

[Bill1958]

Thanks OTM! I'm pretty new too...got my feet wet restoring and learning on an old Unimat. I've got it bolted down to a granite inspection block to help with the vibration. It was good to learn the basics on...now I'm hooked : )
When I spoke with Mr. Davis (from Davis Machining) he told me for threading I can do the math on the gear train, which sounds like a nightmare, or just make test pieces with each setting and then measure the threads with a gauge and make my own chart from that. Probably what I will do this spring...after I paint it and get it back together.
I'm glad to be here and I'm sure I'm going to learn a lot.

 

[markba633csi]

It looks like a completely homemade quick change arrangement. Probably works just fine as is, you'll want to cut some test threads to check it.
-Mark

 

[epanzella]

Never saw a setup like that. I would guess that some one bought this lathe used and there was missing change gears so he set up his own. Use your threading chart and pick some random threads coarse, medium and fine. Compare the difference between your thread chart and the actual threads you cut. There may be a simple conversion factor you can use to make an accurate threading chart.

 

[Orangetruckman]

You’re very welcome. Another idea, aside from cutting threads, would be to setup a dial indicator against the carriage. Then, manually rotate the spindle one time and record how much movement you get from the carriage for each gear position. Maybe then a method can be developed by correlating the amount of carriage movement using the change gear/quick change gear charts provided by the folks that have done all that math stuff. No need to reinvent the wheel, ya know

 

[Bill1958]

Never saw a setup like that. I would guess that some one bought this lathe used and there was missing change gears so he set up his own. Use your threading chart and pick some random threads coarse, medium and fine. Compare the difference between your thread chart and the actual threads you cut. There may be a simple conversion factor you can use to make an accurate threading chart.

Thanks for your input Epan....a lot of good suggestion here. I was a little stressed about it at first but not now. A lot of good ideas!

 

[Bill1958]

You’re very welcome. Another idea, aside from cutting threads, would be to setup a dial indicator against the carriage. Then, manually rotate the spindle one time and record how much movement you get from the carriage for each gear position. Maybe then a method can be developed by correlating the amount of carriage movement using the change gear/quick change gear charts provided by the folks that have done all that math stuff. No need to reinvent the wheel, ya know

I'm a pretty smart fella....I have thoughts I haven't even thunk yet. But I don't think I would have came up with that one.
That is a simple and great way to get some answers on the threading. Thanks!