Table saw died.

John Pollman

Member
Messages
1,332
Location
Rochester Hills, MI
Hi folks,
Earlier this week I went to fire up my table saw and it just hummed. I figured it was a bad cap on the motor so I went to Grainger and spent six bucks for a replacement. Plugged it in and it's a no go. The motor still just hums and it even let out a little bit of that magic blue smoke. :( It's a probably 30 year old Craftsman saw and it's in pretty good shape. I'd love to have a nice new saw but that's just not in the budget right now. I went to Sears Parts Direct and they show the motor as no longer available. It's a 1 hp 3450 RPM capacitor start motor.

Harbor Freight sells a 1 hp "Farm Duty" motor but it's only 1800 RPM's. They have a 1-1/2 hp "Compressor Duty" motor that's 3515 RPM's. It's only about $140. I'm assuming this would be a suitable replacement until I can afford a new saw. What do you think?
 
Assuming the V&A are OK, if the motor mounts are acceptable, I'd go for it. The difference in speed @10" dia. is minimal;+ 65rpm, +170sfpm, < 2%.
 
I replaced a motor on an old Craftsman with a HF motor about 10 years ago. I believe it as a 1 hp (not sure) and ran at 3450 rpms. I later gave the saw to my son in law and it is still running. They have a 3 hp that runs at 3450, $159. I think most TS motors run around that speed. They also have 25% off coupon good on 1/1/2014 for any one item. That makes it around $120.
 
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Agree, the same specs will sub out your old motor. Alternate plan; look for a used C-man saw in your area. I picked one up for $50, kept the motor and scraped the saw which looked pitiful ;-) Motor is (queue the Energizer Bunny) still going.
 
Thanks guys!
I just printed out one of those January 1st only 25% off coupons. I like the idea of the 3hp for about $120. It never hurts to have MORE POWER. (In my best Tim Taylor voice) :)
It's the right shaft size and the rest of the specs are the same.
 
More power may need a beefier housing however. Sheet metal and cast parts are not nearly as strong as cast iron - like the big boy saws. Be careful out there. Just sayin'....
 
I hear ya Carol.

I think it'll be fine. This is an older saw and it has a pretty beefy mount on it. Another thing is I really think that the HP ratings on today's motors are not the same as they were 30 years ago.
 
To Carol's concerns on weight the mounting is not as much a concern as the trunnion style. If the mount hangs on a pair of rods like a contractor format saw, the weight can cause alignment problems as the weight will give you one set of readings while stopped, another while running and a real change when tilted. You know your saw and can judge well enough. I just hate to spend some money to "fix" something only to bring a new set of problems along with the fix. DAMHIKT ;-)
 
Thanks guys!
I just printed out one of those January 1st only 25% off coupons. I like the idea of the 3hp for about $120. It never hurts to have MORE POWER. (In my best Tim Taylor voice) :)
It's the right shaft size and the rest of the specs are the same.

The specs won't be the same, if it is a 3hp where you had 1 hp before. You will certainly have to go to 230 volts (the max you can run on a household 120 volt circuit is 1 1/2 hp). If you were wired for 230 before, you will have 3 times the current, if you were wired for 120 you will have 1.5 times the current and twice the voltage. Watch for new wiring and new switch inside the saw. You may also need to go to new belts, or dual belts, and different pulleys.

Back in the days when I ran a contractor saw, there were many horror stories on the forum from folks who tried to boost the HP on their saw, both in terms of the weight of the motor twisting things, and the substantially greater torque that the bearings were not ready to handle.

Without rereading the whole thread, I think you said the problem with the 1 hp motor is that it is 1800 rather than 3600 rpm. That is an easy pulley change - double the diameter of the pulley on the motor.

I am a HP freak as well, with seven 5 hp motors in my shop. But my machines are designed to handle the larger motors. And I did have to upgrade the dual belts on my Jointer/Planer, heavier than the factory original equipment.
 
.... Another thing is I really think that the HP ratings on today's motors are not the same as they were 30 years ago.
I was trained as an Electrical Engineer 50 years ago, and the HP ratings on an induction motor (what we are discussing here) have not changed. In fact they are the same as in my father's Engineering handbook from shortly after WW I . The ratings are calculated (746 watts = 1 hp) but the efficiency varies. Older motors might have taken 1000 watts to produce 1 hp, but more efficient (and larger) motors are closer to the calculated 746 watts, but the HP calculations have not changed.

The ratings on universal motors are based on the braking HP - rev them up to full speed then slam a load on them. Marketing people have too much influence on the testing procedures for Universal motors, such as how long they have to maintain the load before stalling.

I don't remember the exact details, but what I recall is that a Farm Rated motor is designed for long duty cycles, but not for 365 days per year use - the picture in my mind is spending all day loading a silo. I believe it can even withstand occasional rain. A compressor rated motor is designed for shorter duty cycles, but heavier overall use - every day type use. Either should be fine on a non-factory table saw.

And don't pay attention to the difference between 1725 and 1800 rpm - an induction motor slows slightly under load, that (or twice that in a motor with more windings) is the "standard" speed for 60 hz motors.
 
Thanks Charlie, I hadn't thought about it. But the spec sheet on the 3 hp motor shows it has an input of 115V/208-230V.

I guess I could go with the 1.5 hp because it's rated at 3600 rpm also.
 
HF seems to be the best source for motors at low prices. I got my 3 hp from them.
However, I learned from my old lathe that TEFEC motors are easily fixed (sometimes). If yours is a tefec, just take off the end cover and clean the parts inside. Hand spin the motor. Reassemble and try.
 
...TEFEC motors are easily fixed (sometimes). If yours is a tefec, just take off the end cover and clean the parts inside. Hand spin the motor. Reassemble and try.

The Sears saws didn't use TEFC (totally enclosed, fan cooled) motors. They were open frame motors, and the most likely problem was the centrifugal switch in the start winding being fouled with sawdust.

Since John says he already let the smoke out, his motor likely isn't easily reparable anyway.
 
.... But the spec sheet on the 3 hp motor shows it has an input of 115V/208-230V.

If you use the 115 volt wiring, be sure you don't plug it in a standard 115 volt outlet - it could draw 25-30 amps, and standard outlets in older wiring only supports 15 amps, in newer wiring supports 20 amps. On 230 volts it will draw 13-15 amps, more if your voltage is low (like 208 volts).

.... I guess I could go with the 1.5 hp because it's rated at 3600 rpm also.

But you would be overloading your bearings by 50%. Can the critical arbor bearings handle it? Probably. But do you want to take the chance to save the cost of a new pulley (sheave) on the motor to compensate for the lower speed 1 hp motor (probably around $10)
 
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