Need Assistance On Drum Switch Wiring

On the motor date versus lathe date, I doubt that Sears would have sold a 12" lathe already equipped with a split phase motor. By 1948, the default would probably have been a capacitor start motor. Do you know for certain the model number and/or serial number? If not, try to post a front view photo with the change gear cover closed and a left front quarter view with cover open.
 
As I understand it, Sears sold the motor separately from the lathe? It's also interesting the chucks were purchased optionally. Guess it was part of their marketing strategy allowing them to publish a low purchase price for a lathe. This was during the time when radio and heaters were options when buying a new car.

Glad to provide model/serial numbers. They are 101.27430/30576 respectively. Below are a couple of shots taken soon after I got it home. My initial plan was to just clean everything up and leave the original patina but OCD got the better of me. Will post final photos when done. I will also provide the spindle bearing dates when I get the headstock apart which is the next phase of restoration.

SN 30576 L.jpgSN 30576 R.jpg
 
OK. I'm not sure why but I had assumed that it was an earlier model. The QCGB equipped 101.27430 (and 101.27440) first appeared in the 1951 Craftsman Power Tools Catalog. Given typical catalog lead times, that means that the first ones were probably built 3rd Quarter 1950. From the serial number of this one, until we get the bearing dates I'll estimate its date at 1951/12/xx.

The motor could have been bought at the same time as the lathe. But I would imagine that the salesman, if asked, would probably have recommended a 1/2 HP capacitor start motor.

The only non-original part that I see is the right lead screw bearing. It is the earlier one from the late 1930's, and it has been repaired. The design of the bearing was that in the event of a crash while under power feed, the bearing would break and the lead screw would be ejected from the QCGB, hopefully reducing the damage. However, the way in which it was repaired makes it more likely that something else would break before the bearing did.

One comment that I'll make is that the half-nut lever visible in the second photo is in the engaged position. Get in the habit of never leaving it engaged. It won't damage anything per se to start the lathe with it engaged. But as soon as the motor starts turning, the carriage will begin to move. If the cutter was near a shoulder at the time, depending upon the setting of the QCGB you could have a crash almost immediately. Always remember that there are only about two valid excuses for a crash, sudden death of the operator or a nearby thermonuclear explosion.
 
I checked the S/N against your spreadsheet soon after purchase and your 12/51 prognostication falls inline with what has been reported. Am hoping the bearing date will confirm. It seems the 24" model wasn't very popular as I didn't see any of the 27430's listed.

If anything should happen to this 1/3 HP motor, I will definitely replace it with more power. I came close to getting a Craftsman half horse motor on eBay but I couldn't persuade the seller into more reasonable shipping costs. Patience is a virtue - Mine will come along soon enough.

The lead screw bearing has been replaced with an original as well as the power feed lever. For a 70 year old lathe, I haven't had to replace too many parts. Several of the back gears appear to have swelled and fell apart as well as the hand wheels (the chrome split apart). Also, I had to drive the lock sleeve out of the tailstock and turn it down (first job) before it would work. Does Zamak expand with age or high humidity?

Great advice on leaving the lead screw disengaged. I had to fill in several cutter bites on the tool post slide and wondered how they got there - Now I know.

Thanks for all your assistance!!
 
Does Zamak expand with age or high humidity?

Pure Zamak no, but even a miniscule amount of contamination in it during production and it will. Unfortunately it happens often enough that there are several nicknames for it, "zinc pest" and "Zamak disease".
 
Pure Zamak no, but even a miniscule amount of contamination in it during production and it will. Unfortunately it happens often enough that there are several nicknames for it, "zinc pest" and "Zamak disease".
Thanks Robert - Guess I got some of the contaminated castings.
 
Zinc pest is the accepted term. It can affect any zinc alloy, not just Zamak. "Zamak disease" was most likely dreamed up by an Atlas hater. I could probably name the brand of lathe he owns but doing so would violate one of the house rules. In any case, zinc pest usually shows up within 20 or 30 years. So basically any original parts on any Atlas machine that haven't already failed because of it will most likely not fail from it in the future.
 
I checked the S/N against your spreadsheet soon after purchase and your 12/51 prognostication falls inline with what has been reported. Am hoping the bearing date will confirm. It seems the 24" model wasn't very popular as I didn't see any of the 27430's listed.

Actually, counting yours, there are 6 101.27430's in the database. However, there are 14 101.27440's. So, there's no doubt that most people who could afford either model went for the longer bed. Although less obvious, as the earlier Craftsman model numbers did not determine the bed lengths, that is generally true across all reported Atlas built 9", 10" and 12" lathes. 206 have 36" beds and 190 have something shorter. Up until 1947, the shorter beds could be 18". 24" or 30". From 1947 until 1972 the choices were 24" and 36". And from 1973 until March, 1981, only 36".
 
Zinc pest is the accepted term. It can affect any zinc alloy, not just Zamak. "Zamak disease" was most likely dreamed up by an Atlas hater

Zamak disease is a more commonly used term among model railroaders and other die cast model collectors where it is a far more common problem, with about a 90% failure rate among some models. Interestingly enough some of the N scale trains that suffered notably from this were from the "Atlas Tool Company", later renamed the "Atlas Model Railroad Company" which was not related to the "Atlas Press Company" that made the lathes.

If the lathe maker used the same Zamak supplier the model train company used, there probably wouldn't be enough of them left to have this forum for.
 
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