Overheating Table Saw
Is it the belts? The pulleys? The motor? Pros help troubleshoot a too-hot saw. November 12, 2005
Question
I've got a 5hp 3ph Delta Unisaw. The motor pulley and arbor pulley are both getting very hot to the touch. This may be normal but I am just noticing it now. The Delta tech said it could be belt slippage, but that didn't seem to change when I really cranked on the belt tension. The heat starts with the motor pulley and eventually is also found in the arbor.
A year ago I had the bearing redone in the arbor. The motor runs cool with no belts on it, spins free and makes no bad bearing sound. The belts don't look worn. My questions for other Unisaw owners are as follows:
Do your pulleys heat up, and if so, how hot is normal?
If this is not normal, do you have any suggestions how to fix it?
Forum Responses
(Cabinetmaking Forum)
From contributor A:
I would double check that the pulleys are lined up properly.
From contributor B:
Excess belt tension is bad for your saw's bearings and trunions. Check your manual and adjust the tension properly, or you could break something expensive. Check that the pulley grooves are in line with each other. If they aren't in line, excess heat will build up from the sidewall friction of the belt. You'll also wear your pulleys out faster.
If the motor runs without heating up, then the problem is either the pulleys or the arbor bearing. Since both pulleys are getting hot (equally hot?) then it's probably the belts, but try this test: Run the saw without a blade until the upper pulley just starts to get hotter than warm. Check the blade flange of the arbor for heat. Is it as hot or only lukewarm? If hot, then it's the bearings. If only warm, then it's more likely the belts or pulley alignment. Use some sort of thermometer to check the heat of each part. The easiest way to do this and check alignments is with the table off the saw.
From the original questioner:
I found that it was slightly out of alignment, so I realigned them. The pulleys still got hot. The belts looked very good as far as I could tell. None of them had shiny spots or apparent wear. The motor pulley gets hot first and is definitely the hotter of the two.
How free should the arbor spin without any belts on it? Mine is nowhere as free as the motor.
From contributor B:
Check that the motor pulley is securely fastened to the shaft. If it's loose then it'll wobble and create heat and wear. The arbor shouldn't be free spinning whereas the motor should almost freely spin.
From the original questioner:
The motor pulley is tight on shaft. To contributor B: How hot is the motor pulley on your saw?
From contributor B:
The pulley isn't any hotter than I could hold in my hand after 30 minutes of use. However, I don't push the saw and also use link belts. The motor is wired 240v single phase and is the old style repulsion/induction type motor with the 5" pulley and spins at 1750 RPM. This doesn't equate to your 3ph, 3450 RPM, small 3" pulley modern motor.
But, if your pulley is hotter than what you can hold in your palm, then it's over 105 degrees -110 degrees and that's bad. I'd suspect either a bearing or motor problem or slipping belts. The motor shouldn't get that hot even under intermittent heavy load. I'd recommend a tear down of the motor and check the bearings. Then reassemble and replace the belts.
From the original questioner:
I was wondering about link belts. Do you have 3 on your saw? What has been your experience with them?
From contributor C:
When the saw is just free-wheeling the load is on the motor pulley. The armature in the motor is heavy, and that’s why it spins longer than the blade arbor. The cooling fan in the motor is blowing heat towards the pulley. It’s a triple pulley running 3 belts. That’s the reason for some heat. The belts should be snug but not real tight. Run it with just 1 belt with no load, and then run it with no belt at all. The pulley should be hotter than the shaft. Feel the shaft between pulley and motor - it should be warm but not burn your fingers. A 3 belt pulley that has been free-wheeling for 30 min will burn your fingers. Check your jointer - it will do same thing, but not as hot, if it has 1 belt. If you don’t have a bearing screaming, don’t worry about it. Just back off on the belts, and don’t crank on them or you really could do some damage.
From the original questioner:
I ended up putting link belts on the saw and it practically eliminated the heat in the arbor pulley. The pulley on the motor is still hot, but if that is normal, that's all I needed to know.
