PM66 Motor fried in middle of sale!

[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.