Help wiring drum switch

John TV

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Wiring a Drum Switch on Logan 820 lathe

I don’t pretend to know a lot about electricity but I have done a fair amount of home wiring and I have studied several YouTube videos on my problem and I still am stumped. I need your help.

In replacing the old motor on my 1947 Logan lathe, the motor on the machine did not have a drum switch and the old motor had a built-in forward reverse switch on the motor itself. Very inconvenient and the motor was a bit undersized at 1/3 hp.

I had a 1970s Craftsman 1hp motor that had not seen much use so I have decided to use that motor as the replacement. (I know this motor is a bit overpowered but I have it on hand). I ordered a drum switch from eBay and it was for single phase, 115 or 230 volt motors. The configuration of the switch is in a picture below.

On the motor housing it states that to change rotation of the motor you switch the red and black leads. A picture of the electrical connections are below as the motor was first opened up (I had cut the hot and neutral wires and removed the ground wire for the picture). The black and red leads are visible in the picture and use female spade connectors. (In my amateur opinion it looks like the male spade connectors on the circuit block are for connecting the red and black leads to the hot and neutral poles and the red and black wires run back into the motor to the starter windings)

I wired the motor up as seemed logical from looking at YouTube and drawings and the wiring at the motor looked like the third picture below (again without ground) and the switch was wired as the diagram below shows (again ground omitted).

Here is where I am stumped…the motor works at this point using the switch and will change direction but it is not sounding at all like the correct hookup and makes quite a racket. I did not run the motor for long and wanted to double check the correct sound so I put the original wires back on and the motor again runs smoothly and quietly in both directions when I change the red and black leads.

Needless to say I went back to the drawings, tried different configurations and nothing else worked. The only thing that seems to work but defeats the purpose of the switch is to bring four wires from the motor into the drum switch representing both ends the male and female ends of both the red and black wires and using a separate single pole switch for the line power wires. Runs smoothly with that but obviously isn’t right.

I am thinking one of you may have had this problem and might offer a few suggestions. I don’t have much hair left as it is and pulling it out has not solved the problem. Thanks for any suggestions you have.

Ops, if this is in the wrong place, of course move it where you think is best suited.

John from Minnesota
Pictures may be out of order, fat fingered...
 

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Latinrascalrg1

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I must admit i don't quite follow along with what you are describing and i don't know much but since no one has answered yet l i will share what little knowledge I have on the matter for you to mull over until the real pros jump in!

Ok first the directions for switching the red and black wires (fwd/rev directional power lines) within the motor housing is for having the motor run in 1 direction using a simple single throw on/off switch.

Coming from outlet you should have 3 wires (black, white, green) the white wire should bypass the drum switch going directly to the motor. The ground may or may not be grounded at the switch and motor or just the motor (not really sure on the code with the ground so double check) now the black from plug stops at the switch to direct power flow into either the black or red directionsl lead wires coming from the motor housing. Hope this helps
 

wa5cab

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I could tell you how to wire the switch but you haven't yet given enough information to determine what to run the wires from the switch at the motor end. I can say that the Hot and Neutral wires from the line plug only go to the switch. Only the green (ground) wire would continue on to the motor. Post a photo or the High Voltage connection drawing for the motor. That might answer the question of how the motor is actually wired behind the panel that the male spade connectors are mounted on.

Do you have an analog (not digital) multi-meter? With ohmmeter function?
 

John TV

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I only have a digital multimeter, sorry.

Regarding line wires, I only had them going into the drum switch then using the switch configuration to send power thru to motor. But this did not sound right as stated. After a number of other thoughts and trials I did try one configuration that did kind of work but was not correctly using the drum switch.

Here is a pic of the high voltage wiring ( mine is on 115). IMG_2285.jpg

Sorry about the glare.
John in Minnesota


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wa5cab

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OK. It had me puzzled for a while, until I realized that BRN in the motor went to LINE 1, not to a winding.

In the motor, connect BRN to 3 and W to 4. Do not connect the R and BK wires to anything in the motor. From the R and BK wires in the motor, run two extension wires to the switch and tie them to 3 and 4 on the switch. Run two more wires from the motor connected to Line 1 and Line 4 in the motor and connect them to either 1 and 5 or 2 and 6 on the switch. Connect the BK and W wires in the line cord to either 2 and 6 or 1 and 5. It does not matter whether BK and W in the line cord go to either 1 or 5, or 2 or 6. If the motor runs in the opposite direction from what you would like for each of the RUN positions, swap the R and BK extension wires from the short R and BK wires in the motor from 3 and 4 to 4 and 3..

Do not forget to ground the Green wire in the line cord to the switch frame and also run a Green wire from a ground point in the switch to a ground point in the motor.

To test, if the breaker panel is in your shop (as it should be), turn OFF the breaker for the lathe. plug in the line cord. Turn on the breaker and confirm no smoke or sparks and arcs. Turn off the breaker. Operate the drum switch to one of the ON positions and turn on the breaker. Note the motor direction of rotation. If backwards, turn off the breaker, unplug the line cord, and swap the R and BK extension wires on 3 and 4 on the switch. Repeat the test using the breaker. Then repeat it leaving the breaker ON and using the drum switch.

One of the very few good things about a single phase capacitor start AC motor compared to a 3-Pnase or DC one is that if you get carried away with the drum switch lever and instead of turning it off, you let it flip over to the other RUN position, nothing will happen, at least not immediately. Because the centrifugal switch is open and the motor will continue to run in the same direction. Of course if you don't recover PDQ, you will probably have a CRASH. So practice starting and stopping the motor a few times before you start using the lathe. They do make switches that you can't do that with. But they are considerably more expensive.
 
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John TV

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This is awesome, really thank you for the directions. It will be a few days now before I can work on this but I will let you know how it comes out.

I'm a very big believer in grounding properly and thanks for the "testing" procedure too.

Wish I could go work on it now but somehow work gets in the way. Thanks again.

John in Minnesota


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Bi11Hudson

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Late finding this, per usual. I haven't figured out how to link to another post ande I don't feel up to deciphering your drawings at the moment. So I quote myself with the following. The wire colors will, of course, be different but the overall information is the same.
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Electrical hookup for a non-electrical person is confusing. No question there, it's a given. Start with the switch; an industrial motor reversing switch has the following connections that may well vary from switch to switch. Doesn't matter where they are physically, they all do the same thing. There is an ON-OFF switch that operates in both directions. Then there is a double pole switch that operates in different directions for different throws. One way will be straight across, the other way will be crossed. Centered will be open, no connection. Sit down with a cold drink (or beer, depending on preference) and the switch, operating it side to side until you can see each of these switch contacts. When you can see this, and not before, can you hook up the switch to the motor.

Now, to the motor; The black wires connect to the line cord, one to BLACK, one to WHITE. Make sure the capacitor is in the blue(?) circuit. Then connect the two blue wires to the two black wires. When plugged in, the motor should run. Then, swap the two blue(?) wires. The motor should run the opposite direction.

Then, and only then, add the switch into the circuit. From the line side, one of the black wires will run through the switch that is an ON-OFF. Then connect the two blue wires through the reversing switch. Depending on the model of switch, those two wires may be on opposite sides. Connect the other side of those to the neutral (white) and the black after the ON-OFF switch.

I normally make up the connections at the motor, with a six conductor cable to the switch. It is quite possible to bring in the line cord through the switch and have fewer conductors to the motor. That would be your choice, depending on how the wires were routed. The connections will be the same, it's just a matter of where they make up.

There are a couple of very important points to remember. The first is the GREEN wire. It is a frame ground and has no active part other than tying the metal parts together. The BLACK conductor in the line cord MUST go through an ON-OFF switch before it is used. In residential (home) electrical systems, the white wire is normally a reference point. There are exceptions, but very rare. In most (99+%) systems, it can be left connected. Only the black wire must NEVER be hot until it is in use.

Bill Hudson​
 

John TV

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wa5 & Bill,

Update on drum switch wiring. So I finally got a chance to work on the motor and drum switch and after following wa5's instructions. I realized this was basically how I had wired the switch as my first attempt and I am still stumped. As before, it seems to work but something is wrong. The motor starts and stops in forward and starts and stops in reverse but it is making strange sounds and seems to be vibrating a lot. I only ran it for a second or two because of the sound and vibration. But when I just switch black and red at the motor ,as in the wiring diagram on the motor, it runs smooth as silk. At this point I can only think of two things to try, open up the motor case and look at the wiring or take the motor and switch to a motor wiring shop and pay the freight. Or just get a different motor

Thought I was pretty good with this stuff but this really has me scratching my head.
The part that has me most stumped is it works so it has to be basically correct. No blown circuits or smoking wires but something is wrong or it would run just as smoothly as it does when not using the drum switch.

If anyone has a different option I am happy to try.
John in Minnesota.


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markba633csi

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Hi John, I suspect something is unusual about your motor configuration regarding the start circuit. Try this test: disconnect the red and black leads and measure between them with an ohmmeter (analog type preferred)
You should see the meter swing toward zero ohms then climb towards infinity. Reverse the test leads and you should see this again. If you see a steady low reading then that would be the reason you are having such difficulty- it means red and black represent the start winding not the start leg (big difference there)- also means you will have to open up the motor and do some detective work. Or, what's easier: use two switches as you had mentioned in your first post. Nothing wrong with that.
Mark
 
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John TV

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Thanks for the thoughts Mark, another friend pointed out that with the Logan screw on chuck, do I want reverse? Yes, but two switches may add a safety factor to lessen the likelihood of accidentally hitting reverse and having the chuck spin off. I need to ponder that a bit. John V


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wa5cab

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As far as whether you want a reversible motor on a threaded spindle lathe, my answer would be yes. You know not to try to do turning, facing or threading in reverse. But there are at least two scenarios where you must be able to reverse the spindle motor.

One is if you are ever doing OD grinding with the machine. The surface of the work piece and the surface of the grinding wheel must be moving in opposite directions. The way in which grinders are normally set up, the surface of the grinding wheel where it contacts the work is moving downward (so that the spark stream will be down toward the chip pan and not up towards the operator's face). And the front surface of the work with the spindle motor properly wired is also moving downward. So the relative surface feet per minute would be the difference between the SFM of the work and the SFM of the grinding wheel. It's never likely to actually happen but if the surface velocities just happened to be the same, the relative velocity would be zero and no grinding would ever be done. So the spindle motor would be put into reverse for any OD grinding.

The second one is if you are ever doing an operation where once the half nuts are closed and the lead screw is turning whenever the motor is running, you cannot open the half nuts for the duration of the job. So at the end of each pass, you stop the motor without disengaging the half nuts, back the cutter out with the compound, and reverse the motor to run the carriage back for another pass. The most common case would be cutting metric threads on an Imperial lathe.

There may be other cases that I haven't thought of.

Back to the drum switch wiring, Mark's thought that the red and black leads go only to the start winding and not to the start circuit could be the reason for the problem. the result would be that the start winding would always be energized. And will eventually burn up. The start winding is not intended to be energized all of the time that the motor is running and usually has fewer turns and smaller wire than the run windings. You should unplug the line cord and run the checks that Mark gave.

If that turns out to be the problem, you can still use the drum switch to reverse the motor but it does not have enough contacts to stop the motor in the OFF center position. Which means that if you do it that way, you must NEVER leave the drum switch in the OFF position because the main motor switch will still apply power to the run windings (only). And a few minutes of that will burn up the motor.
 

markba633csi

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Agree with Robert above, the start switch and start capacitor would potentially be bypassed, not a recipe for a good-running motor. So you need to do the ohmmeter test
If it passes the ohmmeter test then you must still have something wrong with your external wiring
M
ps these motors don't instantly reverse, so you don't need to worry about that John. They need to come to a stop first, because of the centrifugal switch inside. If you flipped the drum switch from forward to reverse quickly the motor would continue running in the forward direction (assuming it's wired correctly)
 
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John TV

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Thanks for your knowledge and suggestions. In looking over the situation and hearing from other friends on the matter too this is what I'm thinking about as a solution. Please give me any feedback, best part of this forum is access to your thoughts!

I think I'm going to take a little advice from several people here.

Several folks are rightly advising to be careful of a screw on chuck in reverse. Very good advice. Additionally I am upping the horsepower and that will lead to more of a "start up jerk" than the old motor. I know the flat belt will slip a bit but still more of a risk with higher hp.
That said, I still think I want reverse capability, and here is what I'm thinking about to make it a bit safer.

I did get the motor to work correctly using two switches, the rotary for direction change and a single pole switch for power.

I'm thinking of using the two switches, rotary and single pole. The single pole will let me use one of those industrial start stop paddle switches for power and that seems like it would work well up in front by the headstock. The rotary switch will control forward and reverse only and I'm thinking I will make a "reverse lockout cover plate" that would prohibit accidental hitting reverse without removing the plate. Then if I ever want to do grinding or metric threading I would have to take the extra cover physically off to use reverse and hopefully then be more mindful of the additional risk. The rotary switch would be located near the rear of the machine.

If you have any feedback give me your thoughts. As it is working out, I'm glad I had the wiring problem as it seems to have led me to a better and hopefully safer solution.

John V




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markba633csi

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That sounds fine John, safety is a good thing
A simple hinged cover would work for the direction switch, something to focus your attention
I have a similar control for my small lathe
 

wa5cab

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I will add one comment. You still do not ever want to leave the FWD/OFF/REV switch in the OFF position as the OFF/ON switch is still active. In this scenario, it would be safer with a 2-position FWD/REV switch.
 

John TV

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Thanks, a good reminder. Thought I would make the "safety cover" so that it could only be in forward. Then make a label reminding myself , or successors not to have it in the off position when the cover is off.


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wa5cab

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Actually, it shouldn't be in the OFF position ever. If it is and anyone turns the Off-On switch to the ON position and leaves it, the motor will eventually burn up. As with the Start winding disconnected and the OFF-ON switch in the ON position, the motor will have power on the Run windings but it will not start. That's why I suggested that the other switch should be only a two-position DPDT, not one with center OFF.
 
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