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342 Posts
Discussion Starter · #1 ·
Hi all,
I have a Delta Unisaw that I have owned for over 10 years. I bought it used off of Craigslist. From my research, it is around a 1986 model, 3hp, right tilt, 220v.
Just recently, it has been giving me issues starting up. I push the on button, and sometimes it starts right up. Other times, it hesitates, then starts up. I’m afraid the time will come that it won’t start at all. I’m pretty sure it will be an easy fix, however, I don’t know much about electricity. I’ve read other people having this issue, but I can’t remember what the cause was. Capacitor?, switch?, something else? Would someone please steer me in the right direction, and if possible, inform me of a part number and where to purchase the part or parts I need to fix it?
I don’t want to be stuck without my saw.
Thank you in advance for any guidance or direction.


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Premium Member
1,866 Posts
the usual culprits are dirt/dust in the on/off switch
dirt/dust buildup internal to the motor - interfering with the centrifugal starting switch.

unplug, check the on/off switch first....

337 Posts
I agree with them. My Unisaw is also a mid 80's saw. The start and stop switch contacts have needed cleaning in my saw. With the saw power disconnected, I used a piece of fine emery cloth folded and placed between the switch contacts, then I held the contacts tightly together and pulled out the emery cloth. I repeated this several times for each contact.

For the centrifugal start switch, the non- shaft end of the motor needs to be removed. Again, with the saw power disconnected, it's best to remove the motor and place it on a workbench. Then remove the non-shaft end cover. Do it carefully, because wires connect it to the internal windings of the motor. The 4 long bolts hold the ends of the motor together and need to be removed. Then, using a blunt large flat blade screwdriver and a hammer or mallet, drive the motor end cover free of the center portion of the motor. In the inside of the end cover you will find the centrifugal start switch. It should be spring loaded to touch the stationery contact, so you will need to spread these contacts carefully apart to clean them. These contacts frequently get pitted, due to the high current arcing when in use. With a small file that fits between the contacts, you can file off these bumps and pits, at least enough so the surfaces are again pretty flat. The goal is to have no small points trying to carry the high current as the contacts separate in use. The current flow needs to be spread out across the flat surfaces so as not to melt the contact surfaces. Finish the process with the fine emery cloth like you did on the start and stop switch contacts. The contacts should now be touching each other tightly. If not, you have bent something.

One more thing to do with the centrifugal switch - On the motor shaft there is a fly weight / spring assembly that moves a hard plastic collar on the motor shaft as these weights swing out when the motor spins. The springs and weights never seem to have any problems, but the plastic collar sometimes has trouble sliding on the motor shaft. You can usually see the shiny area where this collar rides on the motor shaft. If this area has any surface rust or dirt, it needs to be cleaned off. Again, this emery cloth will be handy for cleaning the rust and dirt off. When clean, a very thin coat of a synthetic grease or oil will help, but use only enough to coat the surface and not enough to fly off when the motor spins.

If you have the motor this far apart, you should also replace the start and run capacitors, located on the side of the motor case. Two screws hold the bump cover on. Inside are the capacitors. They need to be replaced with the same size ratings printed on them as well as the same physical diameter or the replacement won't fit inside the cover. and they must be AC rated, as DC capacitors won't work very long in this application. Motor start capacitors are available from Grainger, Fastenal, Amazon, and local electric motor repair shops, etc.

As you are re-assembling the motor, it would also be a good idea to replace the bearings. The numbers that you will need are etched on the sides of the bearings and they are very common sizes available from industrial suppliers like Grainger and Fastenal, power transmission stores, and Bearing suppliers. Even Amazon has them. You should also be able to get replacement belts at the same time.

Do all of this, and your motor may never need to be repaired again in your lifetime. It isn't hard work, except for pulling the motor out of the saw and putting it back in. Do it once. Do it right. Then enjoy the saw for likely the rest of your life.

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