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I got an old table saw, a Toro with 3/4 hp motor driving the spindle with a V-belt. It loses power and almost comes to a standstill when ripping 1/2" pine. I’ve bought a new belt, ensured it’s not slipping, changed to new blades and not much improvement.

With no load the machine is actually quiet, the arbor bearings are smooth, and there’s almost no vibration. When cutting, the motor doesn’t jam, the circuit breaker doesn’t trip even when the motor’s almost stopping.

Can anyone can tell me what’s happening?

Table saw is very similar to this image.

old print ad for a similar saw
Source: The Patriot Woodworker

The manual (PDF download.)

Photo of motor plate: saw motor info plate

I did replace the plug with a new three-pin plug. Cut the old one out as it had circular pins. Live wire (black) is on the left pin, neutral on right and the top as ground. Not sure if that would affect anything.

Update: Thank you for the voltage tip. I'm at 110V. And it looks like you folks are right, can you check the picture and confirm that this is indeed wired for 220V and that I need to follow the instructions on the plate to rewire to 110V? enter image description here

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    Possibly silly question but is it plugged into the right voltage?
    – Graphus
    May 24, 2022 at 14:39
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    I think first, you should check that your motor is wired for the voltage you're giving it. I am suspicious that the plug with "circular pins" means the motor is wired for 220V. If so, by putting a standard 3 prong plug on the cord, you're running the motor at half it's required voltage, which would explain your problem. It will also rather quickly overheat and destroy the motor. If that's not the problem, then I suspect the motor's windings are damaged from age/misuse, and have internal shorts. If so, then the motor needs to be rewound or replaced. May 25, 2022 at 12:52
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    I would recommend searching for the model number of the motor. AIUI, some older dual voltage motors required physical changes inside the motor housing to change the voltage. Your description of a plug with "circular pins" leads me to believe it's set to run at 240v (modern voltage, close enough to the 230v listed to not be a problem). If you're running it on 120v, it's definitely undervolted and that would cause the stalling.
    – FreeMan
    May 25, 2022 at 16:21
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    You might also consider asking about the wiring of the motor over at Home Improvement. There are a lot of licensed electricians over there, many who have worked with old equipment and would likely be able to tell you how to rewire this for 120V if that's necessary. Be sure to include that picture of the name plate so they know what they're looking at.
    – FreeMan
    May 25, 2022 at 16:28
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    Most welcome, it's literally the first thing that came to mind given it seemed like it could be a low-power situation. If I might suggest, give the tick to @FreeMan since his Answer most directly answers the question. I'm perfectly happy that mine will be a parallel Answer to the one selected here that might help future searchers who have a similar problem to diagnose their issue from the broader range of possibilities that didn't apply here.
    – Graphus
    May 26, 2022 at 12:22

2 Answers 2

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The update with the added picture of the wiring diagram indicates to me that this is wired for 240V operation since there are 3 wires connected to terminal 3. AIUI, it will run on 120V in this configuration, just not very well, which is what you're discovering.

I'd suggest that either you need to rewire this end for 120V operations or put a proper 240V plug back on the other end of the power cord.

Also, the wires are very old and dirty, so making out the colors from your picture is difficult. It looks like the wire that leads to the left from screw #3 is the red wire, while the wire that goes down, then loops and goes back toward the top is the white wire. The 3rd wire from that screw appears to be black, but that could be the green wire being very dirty. If you're going to rewire the motor, I'd suggest cleaning these wires with a mild cleanser to get the dirt off and make sure you can correctly identify the wire colors. It might be as simple as a wet rag to get them cleaned up enough for proper identification.

If you have, or can wire a 240V circuit for this, you'll be much happier with operations than if you rewire the motor for 120V operation. If you're comfortable with doing home electrical work (and it's legal for you to do so where you live), check out the Home Improvement sister site - there will be a ton of questions there already on wiring a 240V receptacle. If not, hire an electrician. It probably won't cost all that much, though copper prices are through the roof right now.

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  • I'm glad you could make sense of that new photo! Nice one.
    – Graphus
    May 26, 2022 at 12:22
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First: I would stop testing until you think you have diagnosed and rectified the problem as running the saw and having it stall can itself burn out the motor, since as soon as the rotor stops the stator begins to heat up. This is one of the classic ways a motor can burn out, either due to a locked shaft (e.g. from a broken bearing) or from overload forcing a stop.

The motor plate seems to indicate that this is a dual-voltage unit that can run on either 110 or 220. Or at least it was, there's no telling what has been done to it in the (50+?) years since it was installed.

You haven't indicated which voltage you're running it at, assuming it is still dual-voltage 220 would be preferable if available as per the consensus here and in other forum threads.

With no load the machine is actually quiet, the arbor bearings are smooth, and there’s almost no vibration.

You may be safe in assuming the windings are in good shape and the insulation also given the smooth running under zero load.

Assuming the voltage isn't the primary or sole cause of the issue, and you've apparently ruled out a slipping belt and dull blade, other possible causes are:

  • worn brushes
  • decayed power cord
  • slipping blade.

Investigate both the brushes and the cord while you're at it since it can't hurt to replace the two of them even if only one appears to be the culprit.

Presumably the washer is installed on the correct side of the blade! A slipping blade could be caused by a worn arbor washer. Obviously another possible cause is simply the nut not being tight enough, but this can be directly caused by a worn washer as the limited amount of threading cut into the arbor may not allow the nut to be tightened sufficiently if the washer is too flat or worn thin.

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  • thanks for the key second para. :)
    – Regmi
    May 25, 2022 at 19:40

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