In the middle of a project, I turned the table saw off and the blade started slowing normally. Then it suddenly stopped. Turned the power back on again and got electrical buzzing, but no blade rotation.
With the power off, I could rotate the blade, but it had a new ‘silent’ resitance to it. No grinding or mechanical noise. After a few manual rotations, the saw would start again, run normally, and then come that sudden stop as the blade slowed. Got the buzzing with no rotation when I turned it back on.
It’s a 10″ Steel City 35911 (non-granite) and it’s now in the lemon category of power tools. I’m hesitant to lift the hood as I am running a fairly new TS miter sled that I have perfectly dialed in. There is an access panel of the left cabinet side that gives access to the pulley head and trunion.
Before I do start taking the thing apart (right in the middle of a Christmas project deadline), any ideas on what might be causing this sudden ‘braking’ ?
Replies
Could be a shorted capacitor. Unplug and check the connections. If the starter cap is bulging, leaking or smells bad then that is your culprit.
I had much the same happen to my planer last year, just before lockdown :-(
Probably a job for a motor specialist though if you are confident of the capacitor, they are cheap to purchase and not a difficult fix.
Definitely sounds like a motor issue but I don't think it's a simple as a capacitor. Capacitors supply a power boost to overcome start-up resistance, but after that serve no purpose. The fact that you motor runs and stops and you feel resistance tells me it's a more serious internal issue and needs to be either rebuilt or replaced. My local motor shop generally won't rebuild most imported motors citing low quality so I might plan on a new motor.
"With the power off, I could rotate the blade, but it had a new ‘silent’ resitance to it. "
That sounds mechanical to me. Like something getting hot/warm and expanding and binding. Bearing can go bad without any noise too. A capacitor wouldn't cause any resistance.
If that is a belt driven saw the simple check it remove the belt, try the motor and try spinning the blade too. You should be able determine which one has the issue.
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I tried to find specs on your motor, without much clarity. Assuming a relatively normal motor (not a brush type like a big router motor), there are only a few parts to this system.
Arbor: Here the bearings can go bad. They don't have to make noise, just start adding more resistance. Check by loosening and removing the drive belt, then feel the arbor for resistance or smoothness. Most sensitive test is turning the arbor without a blade on it. This is not likely the problem, as it would not cause the system to hum instead of starting unless it were totally locked up.
Belt: only cause a problem like this if it had some large crud stuck to it; even then not likely to cause the symptoms.
Motor:
Here there are multiple parts that could affect things:
Single phase motors have starting circuits to get them running. These include windings (the circuit) and a switch. If the windings have a problem, the saw would not start, but just hum when you turned it on. No amount of turning the system would change that. The switch is another matter. It has contacts that can get corroded or burnt, in which case you would get the humming symptom. Turning the system by hand can sometimes move the starting contacts enough to get them to work again. The starting switch is operated (disengaged) by centrifugal force generated by the motor as its speed increases. As the motor slows down after you shut it off, the starting switch closes again, hopefully ready to help start the motor the next time you need it. The starting system adds a noticeable amount of friction to the system, so that the saw will slow much faster after the switch re-engages.
The main windings: These are what actually powers the saw in use. They are typically only damaged by overworking the saw while it is running (bogging it down) tho they can occasionally decide their life is over on their own. The fact that your saw ran again after humming means they are not likely the problem.
The motor bearings: these can go bad at random times, and sometimes gradually, sometimes suddenly and drastically. If they are going bad here, it would be the gradually version, as the saw would not run if they had locked up, and you could feel that at the blade, as it would not turn at all.
So the most likely problem is the starting switch, unless you have the bad luck to have 2 problems at once, which can make diagnostics really difficult. But start with checking out the starting switch. If you take the motor out and remove the end where the wires go in, you can find the starting switch, and use a thin file to file the points (like folks used to do with the points of a car's engine.) This is a temporary fix, as the filed surface doesn't last as well as the original smooth, domed surface. But it can help with diagnostics, and get you going for quite a while. You should also suspect increased resistance to turning from the starting switch, the motor bearings, or the arbor bearings. That in addition to the starting switch's resistance could cause the saw to stop even more rapidly, making it appear like a brake.
Good luck! Rarely is it convenient to have a breakdown!
Don’t know the drive configuration of the saw but suspect it has a belt drive like most. Unplug the unit, remove the belt, reconnect the plug and turn the unit on. If it seems to be OK let it run for a while (a minute or more) to see if the motor fails when it warms up. If that seems to be OK unplug the unit and try turning and spinning the blade. If it freewheels (turns easily and doesn’t have any resistance then try turning the idler/tension pulley. You should be able to eliminate one or the other mechanical issues this way. Capacitor issues usually show up as a motor starting issue. Their purpose is to assist the motor with an extra boost of electrical current at start-up to overcome “dead” inertia. Once the motor starts they are not usually active. You should be able to do all this troubleshooting without effecting the alignment of the table to arbor. If it’s the motor and you replace it, you won’t usually effect the alignment. The same for the idler bearing. However if there is a bearing issue at the arbor you might lose the alignment. Bearings usually have a universal model number stamped on them and if you need a replacement then the model number will serve to help purchase a replacement. No need to go back to the manufacturer, which in your case may not be an option. I had great hopes for Steel City. Fixing the unit will still be cheaper than buying a new one. Good luck to you.
Don't most table saw motors have a reciprocal brake, or something like that?
If it were frozen that might cause the problem?
Thanks all. Finally had a chance to troubleshoot and follow ya'lls suggestions.
With the pulley off, the motor runs fine. The 'silent' resistance is in the arbor shaft. Looking at the exploded schematic, there appears to be two circular ball bearing housings that support the arbor shaft on either side of the arbor bracket. Should I now assume the issue is now that one or both have failed? (#181 & 187)
The only way to know for sure it take it apart and see. But that is exactly what I would suspect and where i would start looking.
You only want to do this once. Get the specs on the bearing (universal model #) and replace all of them on the arbor. Get a reputable bearing, don’t go cheap. The number is usually stamped on the side plate of the bearing. The universal number might also be spec’d in the schematic. Bearings have been standardized for many years. Designers use standard sizes. It’s too expensive to use custom bearings. Don’t want to start a product discussion but Swedish, German, Japanese or American (Timken) brands are suggested. The number is usually four or five digits. If you’ve replaced bearings before, you know the challenge. Whatever you do protect the bearing and the receptacle. I’ve seen folks use wooden dowel rod to remove and install the bearings. That prevents damage since metal will booger-up everything it touches. Something the same size the the outer race of the bearing. Or take the arbor to a machine shop to R & R the bearings. Stay away from using metal objects to remove the bearings. You can end up damaging the receptacle and or the shaft.
Good luck….
If the resistance is in the bearings, you will need new ones. It looks like the arbor shaft comes out from the pulley end toward the blade end. You will need to remove the pulley first. There will be some way that the shaft is fixed in place, possibly an Allen set screw. Find it before something gets torn up. It looks like #185 is a spacer between the bearings. Depending on the fit tolerances, it may take a hydraulic press to disassemble it, or it may come apart with just gentle persuasion.
If one of the bearings is bad, as we suspect, I would replace both of them. Tho there is no guarantee the non-damaged one is on the way out, it is used, and might have been made the same Friday afternoon as the bad one.
Good advice - thank you
PS: Please let us know what you find. Again good luck. Hope it’s not something more than a bad bearing. That shaft appears to have a bushing (part # 185) also. When I looked at a couple of Steel City parts diagrams (not your model) they listed the universal number of the bearing with the part description.
Thanks again to everyone and the plan now is to replace the bearings. RevBob is correct -- the bearings are 6004 2z and they are available on Amazon with a Swedish Co. (SKF) being the manufacturer. Grainger also carries a good selection of bearings.
I'm going to give this repair a good college try but default to taking the whole bracket it to a machine shop it falls outside my DIY abilities.
Once I get it back up and running, I'm trading it in for a SS :)
Way to go. FYI - The bearing had three main parts - The hub which slides onto the shaft and is sometimes called the inner race, the bearings and the outer race. The races are the part on which the bearings roll or race along. There are more parts depending on whether they are sealed or not.
I was hoping you would get back to us. Thank you and good luck to you. You built the sled once and can get it aligned again, no worries.
Circling back here. Got the race bearings replaced and one was the culprit. They were a common size available on Amazon. Removed the trunion/arbor assembly from the saw (had to take the top off) and a local machine shop replaced both bearings while I waited. Problem fixed.
Now to put the saw back together and try to get my sled to cut square again. Thanks to RevBob and JHarvey for good guidance.
Pic of repaired assembly with bad race bearing on the side.
Could be a shorted capacitor. Turn off and actually take a look at the associations. Assuming the starter cap is protruding, releasing or smells terrible then that is your guilty party.
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