PM66 Motor fried in middle of sale!

[Zach Duran]

I have a Powermatic 66 tablesaw that I recently arranged to pass on in a trade deal. The buyer was going to pick up in 2 weeks, and low and behold, this weekend the 1.5hp, single phase Century Electric motor stopped working! It made a loud hum when turned on, but the motor wouldn't kick on. Well, I unmounted it, discharged the cap, and removed the 4 bolts to slide the housing apart. When I did, the brushes and 2 metal clips/housing, 3 springs and a washer fell out. It appears that the phenolic board that the brush contact points were mounted on is cracked right down the middle. I thought I was going to be able to just clean out the contact points, but now it appears the problem is more severe.
I called up a few motor repair shops (Chicago) and one said I'm better off replacing the motor instead of repairing it, and another shop quoted me $570 for a new 3 hp c-frame motor. Considering this saw was almost out my door, I really really reeeeeallllly don't want to spend almost $600 on a new motor. I also don't know anything about buying used motors. Will any C-frame motor work that I find on eBay? My thoughts is to find a 1.5-3hp C frame motor used on eBay and price it out. Then give the buyer the option of me buying a used motor on eBay, or us splitting the difference of the new $570 motor. Of course timing was immaculate in this situation. Any insight or advice is much appreciated!! Or, if anybody has a C-frame 1.5-3hp motor that will fit my PM66 they would like to generously donate thanks all. :D

[Bruce Wrenn]

Any NEMA 56-C motor will work. Some swimming pool pumps use this type motor. Contact Century and see what parts will cost, or just buy another NEMA 56-C frame motor. Be sure it rotates the way you need, and has same size shaft.

[Zach Duran]

Thanks Bruce, I figured there would be a few factors to consider that I wouldn't have thought of (rotation direction/shaft size).

[Darcy Warner]

Thanks Bruce, I figured there would be a few factors to consider that I wouldn't have thought of (rotation direction/shaft size).

Frame size dictates shaft size and length. It's a fairly common motor, I would be inclined to order the parts and fix it.

[Michael A. Tyree]

I would not want a 1.5 hp motor on that saw which would have me on the web, ebay & Amazon looking for a minimum of a 2 and preferably a 3hp motor. I live in a fairly low cost labor cost area yet the last couple of motors I've had go kaput it was not logical to do a rewind as cheaper to buy a new one. Ebay typically has a deal if your patient. The 1987 PM66 I just bought came with a 2 hp/220v motor and seems OK compared to the 3hp Grizzly I sold/replaced.

[David Kreuzberg]

A quick peek at EBay: "https://www.ebay.com/p/1600712813?iid=324041428201&rt=nc"]www.ebay.com/p/1600712813?iid=324041428201&rt=nc[/URL][URL="https://www.ebay.com/p/1600712813?iid=324041428201&rt=nc"]

(What should​ be on that saw)



My bad! That's a 3-phase.

[Frank Pratt]

A quick peek at EBay: "https://www.ebay.com/p/1600712813?iid=324041428201&rt=nc"]www.ebay.com/p/1600712813?iid=324041428201&rt=nc[/URL][URL="https://www.ebay.com/p/1600712813?iid=324041428201&rt=nc"]

(What should​ be on that saw)

My bad! That's a 3-phase.

And it's only 1 HP

[David Kreuzberg]

Talk about brain freeze! Mea culpa.

[jeff norris 2011]

on the bright side at least it failed just before selling. I would heat to have something I sold fail a week after shipping or worse not work the day it arrived.

[Charles Lent]

Your motor problem is very likely a failed start capacitor (the bump on the top of the motor). It could also be a stuck centrifugal start switch, located in the non shaft end of the motor. Replace the capacitor with the same rating new capacitor first. If that doesn't fix it, remove the non shaft end cover of the motor and you will find the switch. Clean the contacts of the switch and make certain that the contacts are closed against each other. The other part of the switch is the actuator, and it's located on the motor shaft. Two spring loaded weights swing out away from the motor shaft as the motor comes up to speed, and return as the motor slows down. They move a plastic collar on the motor shaft, which presses on the centrifugal start switch to open the switch when the motor is coming up to speed. Usually what happens is that the collar does not slide on the shaft, especially if the motor has not been used in a while. You need to clean and polish the area of the shaft so the collar can slide easily. A tiny bit of light oil on the shaft at this point will help too, but keep it only a tiny amount, because you don't want it flying off when the motor runs.

Re-assemble the motor and try it. I'm quite certain that it will run fine now.

Charley

[Frank Pratt]

Your motor problem is very likely a failed start capacitor (the bump on the top of the motor). It could also be a stuck centrifugal start switch, located in the non shaft end of the motor. Replace the capacitor with the same rating new capacitor first. If that doesn't fix it, remove the non shaft end cover of the motor and you will find the switch. Clean the contacts of the switch and make certain that the contacts are closed against each other. The other part of the switch is the actuator, and it's located on the motor shaft. Two spring loaded weights swing out away from the motor shaft as the motor comes up to speed, and return as the motor slows down. They move a plastic collar on the motor shaft, which presses on the centrifugal start switch to open the switch when the motor is coming up to speed. Usually what happens is that the collar does not slide on the shaft, especially if the motor has not been used in a while. You need to clean and polish the area of the shaft so the collar can slide easily. A tiny bit of light oil on the shaft at this point will help too, but keep it only a tiny amount, because you don't want it flying off when the motor runs.

Re-assemble the motor and try it. I'm quite certain that it will run fine now.

Charley

Read the first post. He already knows what the problem is.

[Steve H Graham]

There are sites that have diagrams for NEMA motors, showing all the important measurements. Very helpful.

The idea of 1.5 HP on a Powermatic 66 makes my skin crawl. For some reason, the one I bought has 5 HP, and I always thought that was normal because I didn't know any better.

[Mike Monroe]

Might want to see what Grizzly has to offer. I picked up 1.5 HP 56 frame motor for a very reasonable price. There's also Electric Motor Wholesale on the web.

[Dave Sabo]

I'm no PM expert but I seem to recall that 80's and newer pm66's came with a 3 h.p. with a 5 h.p. as an option. I never paid much attention to what the 60's &. 70's saws had.

At any rate, a saw like that wouldn't cut it for me with 2hp and 1.5 would laughable.

[John K Jordan]

At any rate, a saw like that wouldn't cut it for me with 2hp and 1.5 would laughable.

I have three table saws at the moment, one of the last PM66s sold and a couple of portable jobsite saws for around the farm. The last two do not have powerful motors and can even be run from long 110v extension cords.

I think whether a particular motor is useful for a specific person depends on what is done with it. I have no problem using the smaller saws for many purposes. I wouldn't be happy with cutting thick hardwoods but for many tasks with stock less than 2" thick, plywood, etc the power is certainly enough. I've built several buildings and did a lot of remodeling with these. Nothing I'd laugh about.

I think my PM66 has a 3 hp motor and the power is easily enough for anything I've used it for. The precision is certainly better and it is easier to use, especially with the long table, good fence, and a slider.

JKJ

[Matt Day]

At any rate, a saw like that wouldn't cut it for me with 2hp and 1.5 would laughable.

A 1.5 or 2hp 10” saw will cut through anything you can ft through the blade. Feed rate might be slower than a 3 or 5hp but that’s about it. I’d guess half the Unisaws and 66’s had 2 and below hp.

Glad you get some laughs out of it!

[Dan Jansen]

The age of the saw really matters too. Back in the day, horsepower was more sold along the lines of a minimum rating whereas now it’s marked at the theoretical peak horsepower.

I have a 1996 PM 66 with a 5 hp motor. You can feed as fast as you want. Sitting next to it is a green 1979 PM 66 with a 1 1/2 hp motor. You can rip 2x4s with it just fine albeit a slower feed rate. I set it up with a crosscut blade but it can handle the occasional rip cut in a jam even without removing the crosscut blade.

Personally I think you can grab a great saw pretty cheap because people overrate the need for horsepower on a table saw.

[Mike Henderson]

The age of the saw really matters too. Back in the day, horsepower was more sold along the lines of a minimum rating whereas now it’s marked at the theoretical peak horsepower.


That is not ture, I'm afraid. The measurement of horsepower has been standardized for a long time and companies have not been minimizing the rating of their motors, not long ago and not now. And that "theoretical peak horsepower" only applies to universal motors and not induction motors. If you purchase an induction motor today, it will produce the nameplate horsepower all day long as long as the ambient temperature is within the specifications.

Some induction motors have a specification called "service factor" which will be something like 1.1 or 1.2. This is how much you can multiply the horsepower by and the motor will produce that horsepower. However, the motor will get hotter by (if I recall correctly) 10 degrees C and that will reduce the lifetime of the motor.

It's a myth that old motors in table saws (or other tools) were more powerful than their rated horsepower. You can check this by looking at the nameplate voltage and current. Given efficiency considerations, it takes at least 1000 VA (volts times amps) to produce one HP, and maybe more than 1000 depending on the motor.

Mike

[Just a comment on HP in table saws. A lot of the old ('50s and maybe '60s) saws were very low horsepower - some as low as 1HP. Many of the old Craftsman portable saws were only 1HP. And people got work done on them. I used an old Craftsman table saw when I first got started in woodworking. But then I upgraded to a 3HP saw. While you can get things done with a 1HP saw, it's much nicer using a 3HP saw.]

[Doug Garson]

Any chance you can repair the crack in the phenolic board using epoxy? Obviously a bit of an ethical issue involved if the repair is iffy but sometimes you can make a permanent (whatever that means) repair with epoxy or JB Weld etc.

[Matt Day]

Some older motors are much larger for the same HP of a modern one. A larger motor turns a larger stator which is harder to stall or slow down because of the momentum it creates. It can appear to have more HP.

[Mike Henderson]

Some older motors are much larger for the same HP of a modern one. A larger motor turns a larger stator which is harder to stall or slow down because of the momentum it creates. It can appear to have more HP.
I think you mean that they had a larger rotor. The stator is the part that contains the coils and doesn't turn.

But in any case, I doubt if that's true. The rotor in an old motor is not that much larger than one in a modern motor (of the same HP) and the energy in a rotating mass is directly related to the mass of the rotating unit (it's actually called the moment of inertia to be specific). There just isn't enough difference in the mass of the rotor of an old motor and the rotor of a modern motor. For that matter, the rotor of an induction motor of the size we'd use in a table saw just can't store that much energy.

Even if the rotor could store a sizeable amount of rotational energy, as that energy was used, the rotor would slow down and you'd quickly notice the slower speed. What I mean is that you can't recover all the rotational energy stored in a motor's rotor, you can only recover the energy between the normal speed and the speed when you'd consider it a stall - and that amount of energy is probably pretty small.

You'd have to have a very sizeable rotating unit to take advantage of the rotational energy - much larger than the rotor of an induction motor.

Mike

[And ideally, you'd want that rotating unit to have a large diameter because the other factor besides moment of inertia is the rotational speed of the center of mass along the radius. You can prove this to yourself by sitting on a rotating bar stool and spinning. If you stick your legs out you'll go slower. That's because your body has a certain amount of energy but you moved the center of mass outward. Since the mass didn't change - it just moved - and the total energy didn't change, you had to go slower to keep things even. Same reason an ice skater goes faster as s/he pulls his/her legs and arms in.]

[One additional comment: One reason older motors were physically larger is that they did have a larger stator. The insulation on the wires used in the coils was thicker than the insulation on the wires in the coils of modern motors - because better insulation has been developed. To house those larger coils, the stator had to be larger. That didn't mean the rotor was larger and it's likely the rotor wasn't - or certainly wasn't significantly bigger.]

[Dave Sabo]

A 1.5 or 2hp 10” saw will cut through anything you can ft through the blade

So can my arm and Disston handsaw. ��

I wouldn't want to cut much with either. What would be the the point of having a a big cabinet saw without the h.p necessary to use it optimally ? Just get a contractor saw or a jobsite saw. Cheaper, smaller and they will cut anything you can fit through the blade too.