Replacement Motor For Saw

[Jerry Bruette]

So I found out the "sleeve bearings" in the motor on my Craftsman contractor table saw aren't fairing so well. I have it patched up with an oillite bushing for now. I have a spare motor laying around but the RPM are 1725 and not the 3500 like the original. The pulleys on the saw are a 1:1 ratio. If I double the ratio and make the arbor turn at 3450 will I be cheating myself out of torque? It sounds like too easy of a fix. Can someone school me about RPM vs torque?

[Mike Kees]

I think it will work just fine. My Delta jointer is set up like this.

[Thomas Canfield]

Horsepower is the product of rpm x torque. A 1 HP motor at 1750 rpm will produce twice the torque of a 1 HP motor at 3500 rpm but you need to see the delivered rpm of driven equipment and at 3500 delivered rpm the torque would be identical for each application. Using 2:1 speed increase on the 1750 rpm motor will produce the same torque at the saw blade. The problem comes with the diameters of the pulleys, belt contact, and clearance. The 3500 rpm motors are lighter weight, smaller frame size, and less expensive and those are some of the reasons for going with the higher speed motor on the saw.

[Van Huskey]

Thomas got it right. The low speed motor has to produce roughly twice the torque to have the same HP rating as the high speed motor this offsets the loss of torque with the change in the drive ratios. The 1800 rpm motor is a 4 pole motor and the 3600 rpm motor is 2 poles this is what is the basis for the low speed motor making more torque and also being more expensive and larger/heavier.

[Bill Dufour]

As long as the oilite bushing is the correct size it should be fine. keep it oiled and it should last for years. sawdust will wick lube out of a bearing.. I doubt if it was reamed after installed at the factory.
Bill D

[Jerry Bruette]

Thanks for the responses. I'll have to check the spare motor to see what the horsepower is and if I'll have enough clearance to tip the blade at 45*



As long as the oilite bushing is the correct size it should be fine. keep it oiled and it should last for years. sawdust will wick lube out of a bearing.. I doubt if it was reamed after installed at the factory.
Bill D
I took the motor apart and put an oilite on one side, but couldn't get the sleeve bearing out of the other end bell. That's the end I'm worried about dying in the middle of a project.

[Bruce Wrenn]

That's the end I'm worried about dying in the middle of a project. Anything other than a bottle of glue, in you shop got a "Best By" date? Run it till it pukes.