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12" Atlas Reverse Tumbler Gear Stud

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paul s

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Just got a 12" Craftsman/Atlas, going through it and making it usable.

Regarding the two smaller single gears - were the nuts on the back side staked? I took the assembly apart for cleaning, and there doesn't seem to be any provision for keeping the nut from tightening all the way against the casting. There's a shoulder on the stud where it meets the front of the tumbler casting, but not on the back.

Also, why does the headstock pulley have indexing holes, just like the bull gear?

Paul
 

wa5cab

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To answer your second question first, in any given year up until the end of WW-II (roughly the Summer of 1945), Atlas built three models of 12" lathes, 101.0736x, 101.0738x and 101.0740x. where "x" = 0, 1, 2 or 3. The first group of four models had no back gears, so the right face of the step pulley had the indexing holes. The first two groups had babbit bearings and the third had Timken bearings. There is probably no way to prove what happened, but either the factory installed the wrong pulley (either by mistake or because they had a lot of them in stock after production of the babbit bearing lathes ceased) or a PO somehow damaged the pulley and maybe the factory was selling off the pulleys with the holes cheaper to get rid of them.

On your first question, no. The two nuts are torqued against the back side of the Tumbler which locks the L3-48A Shoulder Bolt against the tumbler and prevents it spinning with the gear and double keyed bushing. The two gears are standard A-suffix Change Gears with 20T and 24T. Although the parts drawings have never shown it, the A-suffix gears still have the same 3/8" face as the original no-suffix gears supplied on the x=0 and x=1 models but they have a 1/2" long hub, which sticks out from each face or side of the gears, 1/16" to each side. Note that all of the parts shown for the tumbler and change gears with an "A" suffix have the 1/2" hubs or are 1/8" longer than the original parts. These are used on all machines with x=2 and x=3, which includes your 101.07403.

Not that it matters to you, but the change gears and 1" long bushings were all carried over to the late 12". For some reason, they changed the two tumbler gears on the late 12" instead of using change gears there.
 
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paul s

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Regarding the pulley; anything's possible on this machine - I pulled it out of an estate and the history is unknown. The bull gear was rubbing up against the index pin and I couldn't turn the spindle, until I loosened the set screw and moved the gear inboard. So, I suspect it's not completely original.

Regarding the tumbler gears; you're saying the shoulder bolt is stationary, while the gear and keyed bushing rotate? That's what I would expect, but that doesn't seem to be the case here. The gear will not rotate with respect to the shoulder bolt, in fact, it appears to be a press fit. I put it on the arbor press and pressed the shoulder bolt out roughly 1/16" and there's still no relative motion. I notice that my tumbler casting is L3-21A, while the parts list shows what appears to be L6-21.

Meanwhile, I've almost got the spindle out, but I'm fighting the woodruff key on the bull gear.
 

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Remove the gears, bushings and shoulder bolts from the tumbler. Press the shoulder bolts out of the bushings and clean up the bolts and the bore of the bushings until the bushings will spin freely on the bolts. Then reinstall and tighten the bolts and then install and tighten the nuts. And confirm that the gears still spin freely on the bolts. Apply a few drops of SAE 20 oil to each bushing and bolt.

As to the question of L3-21A or L6-21, I will try to remember to call Clausing and see whether anyone knows what the story is. All of the 12" flat parts lists that we have show L3-21A, the "A" appearing with the appearance of the "A" suffix gears. The later Illustrated or exploded view parts lists show L6-21. The one model where we have both types of parts list shows L3-21A on the early one and L6-21 on the later one. And to further confuse the issue, back in 2012, I started downloading all of the parts lists off of SearsPartsDirect. And all of those lists still show L3-21A,
 

paul s

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Thank you, Robert.

One of the gears/bushings had some old lubricant that hardened - I used isopropyl and 4/0 steel wool. The other, however, had more issues. The bore was distorted slightly near one face of the gear, which was remedied by forcing the bolt through and turning with a wrench, repeatedly. The distortion was enough to keep the gear from freely turning. Even worse, the shoulder of the bolt did not protrude through the gear. I fixtured the gear with an expanding arbor on my South Bend and took a few cuts off the face. I was surprised at how far off square the faces were to the bore. And I don't think it's a consequence of the bore being distorted, I think it's still on-axis. I put the tumbler back together, and there's no binding between the two gears, everything turns freely.

Any advice on that woodruff key on the backgear? I tried prying up the outboard end with a screwdriver, tried needlenose pliers, wouldn't budge. I thought maybe I could rock it back and forth, so I hit with a pin punch on the inboard end, no go. When I hit it with the pin punch on the outboard end, it rocked a bit - of course, that doesn't help much, maybe even worse off now.
 

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I assume you are trying to pull the spindle. Although this works best if you are using a drawbar and receiver (which keeps the spindle centered), try moving the bull gear and everything else on the spindle to the rear. Then extract the spindle until most of the key is visible. Dribble a little penetrating oil down both sides of the key. Wait a few minutes and then use a pin punch on top of the rear end of the key.
 

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Back on the original subject, if one of the shoulder bolts is too short, it is probably the original "non-A" version.

The gear with the damaged bore sounds like a hammer blow damage.
 

paul s

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I assume you are trying to pull the spindle. Although this works best if you are using a drawbar and receiver (which keeps the spindle centered), try moving the bull gear and everything else on the spindle to the rear. Then extract the spindle until most of the key is visible. Dribble a little penetrating oil down both sides of the key. Wait a few minutes and then use a pin punch on top of the rear end of the key.
Yes, I need to replace the two spindle gears that interface with the backgear, apparently, the zinc "pests" got to them. I don't think I can expose any more of the key at this point - it's all the way up against the inner bearing cover and the gears/pulley/collar are all the way up against the other inner bearing cover. I've tried penetrant and I'll try the pin punch again.
 

paul s

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Regarding the short shoulder bolt - do I have mixed parts from different versions? The SN on the bed is 30478.
 

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If the short shoulder bolt looks like the long one except for length, that would be my guess. Most commercially available shoulder bolts are socket head. So if the too short one is hex head, it's probably an Atlas part. But the gear hub length change dates from about 1938 and your lathe from early 1951. So it is unlikely that the mistake happened at the factory.
 

paul s

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The too short one is hex head and is identical to the other one, but about 0.003" too short. I'm guessing that the gear got changed at some point.
 

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OK. Then your problem is not mixed version parts. The Rev A part is 1/8" longer that the base or original parts. Your problem is an out of tolerance part. As it is unlikely that wear from use is the culprit, my guess is that it came from the vactory that way. You have two choices - replace it (Clausing may still carry the part). or shim it. Check on some place like McMaster for bearing shims, inner race shims, outer race shims. You might also try a place like Ace Hardware. You would pay more for one shim, but you won't have to buy a box of them to get one. The shim OD must NOT be any larger than the shoulder diameter. It can be a few thou smaller.

Another possibility, if you have the necessary tooling, would be to reduce the thickness of the hex head.
 
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paul s

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Actually, I solved the problem by skimming down the face of the gear on my other lathe.
 

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Well, that's also a viable solution. But now you have two non-standard parts on the machine.
 

paul s

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As long as it makes chips - and the lathe is going to be a gift for someone who doesn't have a lathe, so I think they'll be able to look past it.
 

paul s

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Finally got that woodruff key out. I ended up drilling and tapping for a 6-32 screw near the outboard end, and used a slide hammer.

Spindle is out, inboard bearing is still in the headstock. I'd like to take it out for a full cleaning/inspection - do I remove the inner or outer dust cover and do I pry it with a screwdriver, or use a pin punch? Also, is it common practice to replace the "filter" material in the Gits oilers?
 

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wa5cab

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Glad to hear that you got the key out. I think that this is the first time I've heard of drilling and tapping a hole in it and using a small slide hammer.

Yes, to remove the cup, you will need to first remove the inboard dust cover. Then you can try the pin punch but the best choice is an aluminum disk just smaller than the hole that the dust cup fits into and either a slide hammer or better a length of 5/8" or 3/4" dia. threaded rod and a larger shoulder disk that fits the hole where the outboard dust cover fits.

Yes, replace the felts. They also serve as filters. Clausing still has them but you should preferably also have something else to order as they only ship UPS and UPS has a one pound minimum.
 

paul s

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Regarding the back gears and mating spindle gears on my 12" - would a babbitt head have the same gears as the timken head?
 

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Short answer is Yes. Longer answer is that throughout the production of the 3/8" bed lathes (except for the 9" and the models of 10" and 12" that did not have any back gears), both the 10" and the 12" used the same components throughout the back gear assembly except that the 10" and 12" did not use the same left back gear bracket. This is even partially true of the late 12" made from 1957 though March of 1981 in that the two back gears, sleeve (that ties them together) and bushings and two spindle gears are the same all the way back to about 1934.
 
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wa5cab

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Yes. The Atlas part numbering system identified whatever type or size of machine a part was originally used on. At least up until the palace coup that changed the company name from Atlas back to Clausing, for the most part Atlas did not assign a new part number to an old part simply because the part was used on a different machine than what it started life being designed for. If you look at almost any parts list for any type machine, you will see examples of part numbers that do not match the machine that the part is being used on. So if a part number is 10-242, it is still 10-242 even though the machine it's being used on is a 12". If a table saw had needed a gear like that, the part number would still have been 10-242. Or to put it the other way around, if the part number isn't 10-242, then a 10-242 won't work there.
 

RobertB

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The too short one is hex head and is identical to the other one, but about 0.003" too short.
Was that as measured compared to the other bolt, or as compared to the gear?

Just speculating, but the bolt may have been fine and the gear could have been the problem. You mentioned other gears suffering from "Zamac disease" or "Zinc pests" and one of the first symptoms of this is parts beginning to swell. It's possible you gear may have begun to swell a bit.
 

paul s

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Was that as measured compared to the other bolt, or as compared to the gear?

Just speculating, but the bolt may have been fine and the gear could have been the problem. You mentioned other gears suffering from "Zamac disease" or "Zinc pests" and one of the first symptoms of this is parts beginning to swell. It's possible you gear may have begun to swell a bit.
Good point - that's estimating, just by looking at the gear/bolt combination assembled. I never did measure the two bolts, just skimmed the face of the "fat" gear on my other lathe.

So, am I sitting on a time bomb, as far as these gears falling apart? Or are they good for another 20 years?

Paul
 

wa5cab

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The Suffix A gear hub lengths were 0.500". Probably +/- 0.005". Same is true of the early and late bushing lengths. Measure the hub length of the gear that you didn't modify and the one that you did.

As far as the Zinc Pest problem is concerned, it is generally thought that at this late date, if the parts haven't already failed, they aren't going to.
 

RobertB

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Well if it took 70 years for it to swell a few thousandths, I would expect many more years of service left in it.
 

paul s

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I measured the bushing lengths at about 0.574" - each was within 0.001" of the other. I didn't measure the gears, mute point now.

I did order a backgear off of ebay, and made an offer on one of the spindle gears, as well. The only one I can't locate is the bull gear. I did call Clausing, just for the heck of it - they have a new bull gear, they quoted $202.95. All I see on ebay are entire headstocks or entire spindles. I may end up buying a whole spindle, taking the bull gear off it, and selling the rest.
 

wa5cab

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Yeah. It is good that Clausing still offers some parts support for the Atlas machines. But unless they overstocked on a part 50 or 60 years ago, it is going to cost what it costs in 2019 dollars and wage scales, not 1940's or 50's. Just price a similar part for some newer US built machine (if there are any).
 
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