# Need Assistance On Drum Switch Wiring



## Dollar Bill (Dec 5, 2019)

Over the last couple of weeks, I’ve read way too many posts about how to do this and it seems the more I read, the less I understand. The motor data plate and terminal box are shown in the first photo. The second photo shows the drum switch I’m using and the third photo shows the internal motor wiring. I’ve numbered them for ease of reference as most of them appear to be yellow except for the two green wires. The last photo shows how I wired in the drum switch and it spins in the right direction both ways but I’m unsure if it is running on the start windings. Also, I capped off and did not use wires 1 and 2 (3rd photo) which is where the cord was originally connected - Is that OK or is there a more correct way to wire in the reverse switch?

I truly appreciate any help you can offer as I’m quite ready to move onto the next phase in my lathe restoration.






NOTE:  See Post #4 for correct diagram for the Furnas R-1 drum switch.  The diagrams above are for the "other" type of switch.


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## RobertB (Dec 6, 2019)

Dollar Bill said:


> Over the last couple of weeks, I’ve read way too many posts about how to do this and it seems the more I read, the less I understand. The motor data plate and terminal box are shown in the first photo. The second photo shows the drum switch I’m using and the third photo shows the internal motor wiring. I’ve numbered them for ease of reference as most of them appear to be yellow except for the two green wires. The last photo shows how I wired in the drum switch and it spins in the right direction both ways but I’m unsure if it is running on the start windings. Also, I capped off and did not use wires 1 and 2 (3rd photo) which is where the cord was originally connected - Is that OK or is there a more correct way to wire in the reverse switch?
> 
> I truly appreciate any help you can offer as I’m quite ready to move onto the next phase in my lathe restoration.
> 
> View attachment 307198



Your picture is a bit hard to follow. You said you capped off #1 and did not use it yet you show it connected to terminal 3 on the drum switch and you do not show #7, is that mis-labeled?

Take a look at post #23 in this thread https://www.hobby-machinist.com/threads/wiring-help-needed.80487/ in your case the Red and Black would instead be your #'s 5 and 7


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## wa5cab (Dec 6, 2019)

Bill, 

If you have an ohmmeter, confirm that wire #1 is connected to or is the same wire as #4. 

Confirm that 2 and 3 are connected together (not through a winding).

Confirm that 5 and 6 are connected through a winding (specifically the Start winding).

As RobertB pointed out, in your 4th photo, you say wire #1 goes to switch #3.  Don't you mean wire #7?

Also, in your photo #4 you have the switch terminal numbers swapped left to right from how they are shown in the switch diagram in your photo # 2.  That makes it not possible to say whether that is safe or not.


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## Dollar Bill (Dec 6, 2019)

Gentlemen, I do apologize for the errors you pointed out. Having less than zero experience with A/C motors, I really got wrapped around the axle trying to figure this out myself and my confusion showed up in the graphics. Also, the schematics for the drum switch in my original post are incorrect too. At any rate, I've corrected the mistakes in the attached photos. 

RobertB & wa5cab, I will follow both your recommendations and report back tomorrow. Thank both of for the kind assistance!!


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## wa5cab (Dec 7, 2019)

OK.  Note that the Furnas R-1 (and other brands wired like it) is the better choice switch configuration for single phase Capacitor Start and Split Phase AC motors.  If you run the AC line cord to the switch and only run the ground and four motor control wires from switch to motor, when the switch is OFF, there is no AC in the motor.  

Anyway, that looks correct to me.  Numbered wires used externally are 3, 4, 5 and 7.  FWIW, 4 is connected to 1 and 3 is connected to 2 internally.  So 1 and 2 must be capped (insulated).


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## RobertB (Dec 7, 2019)

Dollar Bill said:


> Also, the schematics for the drum switch in my original post are incorrect too.


*Do not refer to the post I directed you to, that would only apply to the switch you showed you had at first, not the one you actually have!*



wa5cab said:


> Anyway, that looks correct to me.  Numbered wires used externally are 3, 4, 5 and 7.  FWIW, 4 is connected to 1 and 3 is connected to 2 internally.  So 1 and 2 must be capped (insulated).


^^^This^^^


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## markba633csi (Dec 7, 2019)

RobertB: Sounds like you have it wired correctly from your description if it starts and runs in both directions- your motor is called a "split-phase" type with no starting capacitor, hence the starting torque will be less than a capacitor-start type, but that may not be a problem for your application.
Mark


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## Dollar Bill (Dec 7, 2019)

*"If you have an ohmmeter, confirm that wire #1 is connected to or is the same wire as #4. *_*
Confirm that 2 and 3 are connected together (not through a winding).*_
*Confirm that 5 and 6 are connected through a winding (specifically the Start winding)." 

wa5cab*, As promised, I wanted to follow up with your original reply.... I did confirm wires both 1&4 and 2&3 Ohmed at .6 Ω with my 40 year old Radio Shack digital multimeter and wires 5&6 read 4.5 Ω which makes me think 5&6 are the starting coil as you indicated. Just for comparison, where would I take a reading for the run coil? Just to ease my mind that during my op test last week it wasn't running on the start coil. My research over the past couple of weeks indicates the run windings will have greater resistance than the start winding?


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## Dollar Bill (Dec 7, 2019)

markba633csi said:


> RobertB: Sounds like you have it wired correctly from your description if it starts and runs in both directions- your motor is called a "split-phase" type with no starting capacitor, hence the starting torque will be less than a capacitor-start type, but that may not be a problem for your application.
> Mark


Hi Mark, thanks for the reply. The motor seems to power my 12x24 Craftsman lathe OK. I just got the lathe this summer and was not able to speak with the original owner. Motor has likely been on the lathe since it was new. It has a build date of 11/48. I haven't torn into the headstock to check the date on the spindle bearings - That's my next move, hopefully next week.


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## wa5cab (Dec 7, 2019)

Dollar Bill said:


> *"If you have an ohmmeter, confirm that wire #1 is connected to or is the same wire as #4. *
> _*Confirm that 2 and 3 are connected together (not through a winding).*_
> *Confirm that 5 and 6 are connected through a winding (specifically the Start winding)."
> 
> wa5cab*, As promised, I wanted to follow up with your original reply.... I did confirm wires both 1&4 and 2&3 Ohmed at .6 Ω with my 40 year old Radio Shack digital multimeter and wires 5&6 read 4.5 Ω which makes me think 5&6 are the starting coil as you indicated. Just for comparison, where would I take a reading for the run coil? Just to ease my mind that during my op test last week it wasn't running on the start coil. My research over the past couple of weeks indicates the run windings will have greater resistance than the start winding?



Regardless of relative resistance, 5&6 or 5&7 are clearly the start winding or start circuit as 6 and 7 are connected to the centrifugal switch.  The Run winding is connected between 1 and 2, and between 4 and 3, whichever is the easiest to get to.  

The Start winding may have fewer turns than the Run winding, which lowers the resistance.  However, it may also use smaller gauge wire, which raises the resistance.  So it isn't in general safe to ID Start and Run windings solely by resistance.  However, in this case, Wire 6 is obviously connected to the start switch so it must go to the start winding. Therefore, the other winding has to be the Run winding.


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## wa5cab (Dec 7, 2019)

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.


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## Dollar Bill (Dec 8, 2019)

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.


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## wa5cab (Dec 9, 2019)

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.


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## Dollar Bill (Dec 9, 2019)

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!!


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## RobertB (Dec 9, 2019)

Dollar Bill said:


> 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".


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## Dollar Bill (Dec 9, 2019)

RobertB said:


> 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.


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## wa5cab (Dec 9, 2019)

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.


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## wa5cab (Dec 9, 2019)

Dollar Bill said:


> 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".


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## RobertB (Dec 9, 2019)

wa5cab said:


> 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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## wa5cab (Dec 9, 2019)

Good point!


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