Help a new guy ID a lathe?

[Bi11Hudson]

Welcome aboard, Sir. While I don't remember the Sears part number, I have a 101.27440. A 12X36 machine. There are a couple of shorter machines that use 101.274?? part numbers. The only difference between those and your's is the lack of a "QC" threading setup. Otherwise identical. . .

Someone should be along shortly with the correct part numbers. Although a relative lightweigt, it is a solid machine with plenty of attachments when you get crazy ideas. In the meantime, use the 101.27440 as a reference ignoring the QC threading box.

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[wa5cab]

I assume that the 35" is the estimated maximum distance between centers rather than the actual bed length. It is actually 36" with an actual length of the front or rear ways of 54".

On the Atlas 10" which had as many changes to them as the Craftsman 12" did, only once did they briefly start the serial numbers over at 1. So the serial number is of some help in guessing the age of the machine. But unfortunately, Sears had them start every new model number's serial number over at 1. So the serial number is no help in guessing age or model number. There are 14 different model numbers to pick from. However, the method of locking the compound swivel does help somewhat, although we do not have much to go on with the Sears machines as they don't seem to have documented at what model and serial number the change occurred as they did with the 10". Your machine has both the early compound swivel lock method and the early tumbler lock but the later change gear cover and motor switch arrangement. And its change gear set is the earlier version which includes two 96T gears. I cannot tell from your photos whether or not it has back gears. But considering what I do know, it should be a model 101.07360 if it does not have back gears or a 101.07380 if it does.

And regardless of which model number it is, the correct model/size of QCTP for it is the AXA. Over the years, a few people have made the mistake of buying a BXA QCTP. They fall into two groups, those who wish that they hadn't and admit it and those who wish that they hadn't but won't admit it.

 

[DeepLogic]

I still don't understand this. It looks new.

 

[DeepLogic]

Here a couple of shots showing better detail of the back gears, etc. That measurement of 35" was from the face of the headstock to the end of the bed.

 

[wa5cab]

OK. It has back gears so it is a 101.07380, made near the end of 1936, as it has a few things on it normally considered as part of 101.07381.

Note that the back gear actuating lever and knob, part number 10-254, is missing. It or they go in place of the round head machine screw that is screwed into the right eccentric. See any 3/8" bed Craftsman or Atlas illustrated parts list for a drawing of what they look like. I would call Clausing and see whether or not they still have any, If not, ask for a TIF of the part drawing.

To correct what I may have written before, your machine should have a 48" bed and the size would be a 12x30. Note that unlike with the Atlas machines, the ear;y Sears model numbers do not specify the bed length. In 1936, neither does the catalog number. It wasn't until 1939 that they fixed it so that at least the catalog number specified the bed length. At any rate, the 12 model numbers covered 48 different lathes. Only the last two 3/8" bed model numbers (101.27430 and 101.27440, for a total of 14) were unique to only one machine.

The blank serial number plate on the right end of the bed is not original. At the time that your machine was made, the model number was stamped on a similarly sized plate mounted on the rear of the bed. Is by any chance the plate on the right end actually two plates stacked? Part of the photo looks like it is and part looks like it isn't.

 

[DeepLogic]

Thanks for all of this very helpful information. I figured it was pre-1937, but wasn't sure how much before it might be. Like many things this old, you have to figure that people have changed or replaced parts over the years and it can get confusing. I found a few things that were in question. I found that altering the motor mount a little and getting all the pulleys lined up sure quieted things down. Nice a smooth and relatively quiet now. I did break one of the 96 tooth gears (barely touched it) only to realize it had been broken into several pieces and glued back together with JB Weld by a previous owner. Really wish I would have gotten the change gears with the lathe. Luckily I did get a decent amount of tooling and chucks.

I assume with the bolt-down spindle bearing caps mean that I have Babbitt bearings? They seem nice and tight.

I looked on the back of the machine for an ID plate, but didn't see any evidence of it. Pretty sure the serial number plate isn't on top of a plate.

That lever you mention for the back gears is actually there, but was tipped away in the other photo. Is this what you were referring to?

 

[wa5cab]

Yes, all four of the 101.0736x and all four of the 101.0738x had babbit spindle bearings. When shipped, new, each bearing cap had a 0.010" shim pack under each end. They consisted of five 0.002" shims laminated together.

The 12" first appeared in the 1936 Sears catalogs. The 1936 and 1937 Power Tools catalogs are in Downloads under the

Atlas/Craftsman\A/C\Catalogs folder.

Your machine mostly matches the one shown on page 28 in the 1936 catalog but part of it matches the 101.07381 shown on page 18 of the 1937 catalog. So it might have been originally badged as a 101.07381. It has the later gear cover and tailstock but the earlier compound slide.

on the back gear lever, engage backgears and see whether or not the lever sticks straight up.

 

[DeepLogic]

Ah, that may explain all the trouble I've had trying to get the new top and upper rear belt covers to fit. There is little or no room for adjustment and they just aren't right. Close, but not really right. The back gears do engage properly, but the handle kind of flops back when disengaged. I'm going to check out that old catalog. Thanks again for the info.
On a side note, I visited a guy that lives down the road from me today, and he has a full machine shop in his garage. He has one lathe about the size of my car from the 1940's. 3 tons. He has a crane like thing for removing the huge chuck. Really neat to see.

 

[wa5cab]

Unfortunately in this case, my 3996 (same except for badges and nameplates as the 101.28990) has a radically different setup for the back gears (although the four gears themselves are the same) than did all of the 3/8" bed machines. So I have no feel for what the back gear lever should feel like. I do, however, understand how it works. The two eccentrics must be "in sync", meaning that their peak movement must occur at the same lever position. If that part of the machine hasn't had any parts replaced, that should be OK. There may be one or more shims under each pf the brackets that attach the two gears to the headstock casting. Nominally, there would be the same thickness of shims under both brackets. But in practice, this may not be the case. So if you remove the brackets and gears and this isn't the case, don't forget which shim(s) went under which bracket.

Starting with the lever in the fully disengaged position, the gear teeth on the two removable gears should not touch the teeth on the two spindle gears. As you move the lever toward the engaged position, the teeth on the two rear mounted gears should begin to mesh with the teeth on the Bull Gear and small spindle gear. As you continue to move the lever (knob), the teeth engage deeper and deeper and then start to move away. The shims were made in 0.002" and 0.003" thickness. Yours may have some of either or both. To check that the shims are the correct, remove on of the thinnest shims from under each bracket. Rotate the two rear mounted gears. The gear teeth should not touch. And you should be able to pass a 0.002" feeler gauge between each pair of gears with the pairs held toward each other with thumb and fingers of the left hand. Then try to engage back gears. When the teeth in each gear-pair are at their deepest mesh, they should not bottom out. It should not take significantly more effort to move the lever past the deepest mesh point than in other parts of the arc. I don't know which case will happen first. If neither case happened, remove another shim and repeat the checks.

Everyone must sooner or later decide how large a lathe is large enough for them. And remember that although within reason, a large lathe will turn small parts, it may not do it as conveniently. And pick your own poison, so to speak.