Drum Switch

I just got a 10" SB. Some previous owner replaced the motor with a 3/4 hp capacitor start. There is no info inside the original drum switch so they just wired in a light switch.
Can anyone out there post a sketch of the SB drum switch schematic. If I can see that I can sort out the motor part.

Hi Gas,
You might try here:

Look for the drum switch layout.pdf
Hope that helps,

Thank you Malcom
I was still confused so I took it to a friend who has a motor rewind shop.

I still have mine wired as it came off my lathe...I can take a picture for you if it helps. The motor is disconnected however waiting to go back to the shop for a rebuild, I can take a picture of the switch if it would help you out. But here is a question for the group, the existing wire that goes from the motor to the switch is an SJ type wire- five lead ( I have a reversing motor on my lathe, I believe some didnt come this way) where can I get a replacement wire for that?. That wire isnt sold at the local electrical supply house. I was going to use thhn wire in a plastic type flex tubing short of finding that wire. Paul Burkhardt

You have just identified the one single problem with those reversing drum switches.
EVery machine with one will have some unique form of wiring between the motor and the
switch. Doubled-up SJ cord, taped up wiring, all kinds of whacky stuff.
My suggestion for this is to bite the bullet and do it right: go get a length of
liquid-tite conduit and the correct fittings to connect it to the motor and the drum
switch. Often the drum switch gets a straight fitting, the motor gets a right angle.
But your situation may require something different, the connectors also come in
45 degree versions.
Then it's only a matter of pulling the correct conductors (I suggest number 14
stranded THHN wire) and hooking it all up. Because you are likely to purchase a roll
of all the same color wire, be sure to tag each one at each end, and be sure to
tag the grounding conductor with green tape to identify it. Make a diagram
and stuff the diagram and a couple of copies in a safe place for the next owner.

here is a couple of pics of the switch itself...hope it helps you out some

monkfe posted good pics, but I just wanted to add that most all drum switches seem to be very basic switches, 6 poles with 3 in and 3 out.
I have an old one on my Nichols mill that is very similar, but different part than pic'd.
I need to find an original for my 9A, it has a 3-way toggle switch that replaced the original, and I would rather have an original for it.

monkfe posted good pics, but I just wanted to add that most all drum switches seem to be very basic switches, 6 poles with 3 in and 3 out.

Not all switches are the same. There is a different type out there. It was used on the 9/10K with "Instant Reversing" single phase motors. This is a true 3P DT swithh and has 9 screw terminals. On the Instant reversing motor either 7 or 8 terminals are used.
I have one on my Heavy 10 and they are recognized by having 9 screw terminals with a row right down the middle.
The diagram on the upper right describes this one.
It was standard on some South Bends.
Jim B.

Not all switches are the same.

Yes, you need the schematic for the proper drum switch poles, but the drum switch just routes the power to the proper poles. They certainly are not 3 on each side, maybe that is what you thought I meant, and if so I didn't mean to.
The drum switch I was working on recently was an old Allen-Bradley from the 40s, and it had the schematic inside.
Most all drum switches are marked with corresponding Tx and Lx poles, as I recall, could be wrong on that. Mine seemed pretty straight forward when I wired it up recently.

The words I was having trouble with are the "All Drum Switches" part.
Yes most are very basic and similar. There are, however some out there that are very different.
I posted a thumb-nail. This is as large a thumb-nail as allowed. This is a true 3PDT switch on my Heavy 10. It can be wired for any application, Single phase, three phase and "Instant Reversing." It can do anything the above pictured drum switch will do and it will handle the 'Instant Reversing" motors, which the above switch will not do. It has 9 terminals. The three center terminals will connect to either the poles, on the same level, on the left or the right. The center position of the lever is open to ALL terminals.
I am not in general taking issue with any of your statements but since we have a lot of Newbee's who might have an application for this type of drum switch they should know its available.
I myself was not aware of the difference until last summer when a friend got an Instant Reversing motor for his 9" and I agreed to wire it. I spent most of a week tracking down the right parts.
Jim B.



Hi jim,
Thats that one cutler hammer switch with the 9 connectors for the instant reversing motors. Took me and my brother 3 days to figure it out( well most of two and part of one) and we have wired many motors up. Had one heck of a blue streak coming out my workshop!!! Works great on my lathe, and probably better than some of the other drum switches i have( gotta love the instant reversing motor!).

My '47 9A has the instant-reversing feature with a 6-terminal drum switch. It's actually a fairly complex and interesting design.
There was a rather long-winded discussion of the supporting theory in this thread:
1947 Model 9A
...in case anyone's interested.

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