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Powermatic 3520A Switch Repair

Ronald Plumley

Ronald Plumley

Joined
Aug 4, 2015
Messages
38
Likes
27
Location
Talking Rock, Georgia
Greetings!
My club has a PM 3520A and it has been somewhat neglected since I've known it as far as maintenance goes. I've been doing some repairs and general work on it this year and I've noticed that the power switch has gotten a bit loose where it it mounted. I have not just dug in and tried to repair it, since it's not *mine*... but I do want to get it repaired if I can. I'm mostly concerned that if I start trying to get too 'forceful' with it, I'll end up breaking the switch and making the situation worse.

I've done some googling and looking around, but I've not found any good "This is how it goes together and this is how it works" kind of documentation. I was hoping that one of you kind souls might have information about the switch, or perhaps a link to documentation.

Looking at the switch itself, it appears that there is a knurled nut behind the mounting plate which would be twisted to tighten the switch up to the plate, but the nut then appears to be broke/cut/non-continuous (see photo with the broken/non-continuous knurling circled in yellow).

Hopefully, the collective wisdom will be able to shed some light on my issue.

Thanks!
Ron Plumley
Apple Ridge Woodturners - Ellijay Ga

20180208_165122_576x768_L8.jpg 20180208_165314_1024x768_L8.jpg
 
This is a pretty common industrial type switch body. My experience is that retaining ring is bad about snapping. A quick fix would be a zip tie around the ring pulled as tight as possible then twist the ring tight. Otherwise a look in a Graingers catalog will likely find a similar switch. It usually doesn't even need the wiring undone as the switch is a snapout assembly in the housing.
 
Thanks, Gary.
After posting, I was doing more research on the numbers shown on the main body of the switch and I was reaching similar conclusions. I actually think that the ring is okay, based on what I've been seeing in my research. I see a number of button/switch heads which have similar items on them and they show the same thing that looks like a break. The next time I have access to the lathe, I'll pop the cover and see if I can just twist the knurled nut and tighten up the button.

Ron Plumley
Apple Ridge Woodturners - Ellijay Ga
 
Scrap it and buy a new lathe? No particular excuse is needed, is there? OK, Gary is right on the $$$$. Give it a try.
 
The notch in the nut is for using a flat screw driver as lever to tighten the nut with several light taps
on the handle of the screw driver.
 
Mine has the same problem but it's working fine so I haven't worried about it. I'll repair it tomorrow and tell you what I did. It appears from the photo that it takes a special wrench which I think I have. I forget the name of those wrenches but I buy them at the flea market when I see them so hopefully will have the size i need.
 
John, they are either vise grips or Channel locks. Otherwise, known by many, as the Redneck socket set. :D
 
Yes although what I called a spanner wrench when I was doing camera repair was quite a bit different. Here is a photo of the switch and my spanner. Took me about a minute to tighten it up. You could do it with some large needle nose to snug it up and then gently tap the slot with a flat blade screwdriver for the final snug. Don't know why didn't fix it sooner. I guess the loose switch just didn't bother me much.

spanner wrench2.jpg
 
From your description of the problem it does sound like tightening the knurled retaining ring should fix the looseness. But, if you have to get in to switch replacement you might try GALCO. I bought a OEM replacement inverter for my Powermatic from them recently and was very impressed with their service. Here's what they show for your switch: https://www.galco.com/buy/Telemecanique/ZB2-BE102?type=ac_search. Scroll down and you'll see they offer a like-for-like equivalent for about $3. Hope you can get it all fixed up.
 
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