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Thread: Loud Jolting Sound When Starting Tablesaw?

  1. #1

    Loud Jolting Sound When Starting Tablesaw?

    I just got a used Delta Unisaw. The newer version with cranks on the front. 2012 mfr I think.
    5hp single phase and prior owner put a big Powertech magnetic switch on it (just saying in case its the reason for the jolt)
    When I start it up with a blade installed it makes a loud jolting sound for a fraction of second then a nice smooth whir.
    I dont know what this saw should sound like but the jolt sound doesn’t sound right to me. Here is a video... hope it works….
    https://photos.app.goo.gl/b7wePa5ohk1hNWmq5

    Without a blade installed, at start up no jolting sound and just nice smooth whir.
    I adjusted the belts per manual and when watching them with a blade in at start up, they expand out coincident with the jolt.
    Without a blade the belts just hug the pullys, no expansion or flyout.
    Do you think its just the belts need replacing or do I did I get a bummer used saw?
    If its the belts would the link belts be better to use then the stock Delta part?

    Any experience here?
    Appreciate any help
    Thanks!

  2. #2
    Join Date
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    It sounds to me like shot bearings in the motor. There is definitely more noise/tingling at the fan end of your motor than it should have. Should be silent except for sound of air moving.

  3. #3
    Join Date
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    My Unisaw has always started with a bang since it was new in 1993. I just assumed it was a little 'take up' on the belts. I have seen others do the same thing.
    Rick Potter

    DIY journeyman,
    FWW wannabe.
    AKA Village Idiot.

  4. #4
    Join Date
    Apr 2018
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    Cambridge Vermont
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    You can always pull the belts and turn the arbor and motor separately by hand to feel for a bad bearing. However my PM66 kind of does the same thing. It's just a very powerful motor with almost no resistance getting up to speed pretty much instantly.

  5. #5
    Join Date
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    Motor start up is fine. But you need to pull the fan cover off end of motor and figure out what is up with the fan.

  6. #6
    Thank all. I did find after I removed the belts that that both pulleys were loose, jiggling back and forth. I tightened the allens and the jolting start up reduced significantly. I continue to tinker and look at the fan for its noise..

  7. #7
    Join Date
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    olmsted falls,ohio
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    Sure sounds like bearings unless the cooling fan is rubbing.

  8. #8
    Quote Originally Posted by orren countin View Post
    Thank all. I did find after I removed the belts that that both pulleys were loose, jiggling back and forth. I tightened the allens and the jolting start up reduced significantly. I continue to tinker and look at the fan for its noise..
    Did you check the keys and key ways for damage? The loose set screws may be only part of the problem.

  9. #9
    I ran the motor unattached or no belt attached and without the fan....it was very very quiet.
    I spun the arbor with a blade attached and it spun for a very long time. No movement or grinding when I turn the arbor
    https://photos.app.goo.gl/rpPdE6VjGK4royED9
    The delta belts look good but worn on the side and threads are showing through.
    Delta Belt.jpg
    I went to 2 auto stores and they could not find a replacement for it.
    From what Ive found the delta belts are $71 each and I need 2. I was hoping to find a suitable replacement for a reasonable price so I can still feed my family
    Any clues on a belt substitute?
    thanks!

  10. #10
    Quote Originally Posted by Lee Schierer View Post
    Did you check the keys and key ways for damage? The loose set screws may be only part of the problem.
    I agree. I should do that. It will always be a nagging concern. If I go to all the work to pull the pulleys to check the keys I might as well replace the bearings.

  11. #11
    Its been suggested that since the blade spins so easily (see video above) when not connected to the belts that the bearings are bad. How does that make sense?

  12. #12
    Join Date
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    Check and see if one belt is a tad longer than the other. It is possible someone replaced one belt, and they have to be the same. That is quite a bit of belt slap, but it sounds just like mine has since new.

    If they look like a pair, I would just tighten them up and see if you can get a drop of oil on that fan shaft, while you are checking it for being loosely fastened, or rubbing.

    The motor sounds fine to me, except for that fan noise.
    Rick Potter

    DIY journeyman,
    FWW wannabe.
    AKA Village Idiot.

  13. #13
    Join Date
    Nov 2012
    Location
    North Dana, Masachusetts
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    119
    I would pull the table off, and make sure all the parts are bolted together, and not worn. That saw looks brand new inside. I run belts on a table saw loose, so that there is some give if something jams the blade. Those capacitor start motors can make some noise when they start. You could check the numbers on the capacitor(s), and make sure they are the right ones.

  14. #14
    Join Date
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    A new bearing with a rubber shield will actually give the bearing a little resistance. I replaced the bearings on my PM66 this past summer not because of noise but when I spun the blade with no belts on it just sounded dry. They probably still had years left in them but I decided to do them. At the same time I took the saw apart and cleaned up and adjusted everything. It's nice being able to tilt the arbor with just one finger on the hand wheel.

  15. #15
    Quote Originally Posted by Rick Potter View Post
    Check and see if one belt is a tad longer than the other. It is possible someone replaced one belt, and they have to be the same. That is quite a bit of belt slap, but it sounds just like mine has since new.

    If they look like a pair, I would just tighten them up and see if you can get a drop of oil on that fan shaft, while you are checking it for being loosely fastened, or rubbing.

    The motor sounds fine to me, except for that fan noise.
    Thanks for that. Im sure the belts are a matched pair as the stamped letters that go off the edge line up perfect when I put them side by side. Do you mean oil between the fan and the shaft?.

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