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Question about nickel test.

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  • Question about nickel test.

    I just finished assembling the 3650 and thanks to this forum with all the tips and experience it went well for the most part. Had an issue with some squeaking from the front rail but that was taken care of with a little WD40 (thanks Bob and Lorax for the help).

    I tried doing the nickel test and was not too successful. When I start the saw the motor jolts a bit and causes the nickel to fall over. When running at full power the saw runs very smooth, only at the start it's pretty rough. The funny thing is every once in a while maybe 1 out of 5 or 6 starts it starts up very smoothly without the jolt and the nickel stays up. I've tried fiddling with the belt tension thinking this may have something to do with it. The looser the tension the smoother it starts except there is a screeching noise which sounds like at the intial start the belt is slipping a bit. Any suggestions will be greatly appreciated. Thanks!

    After thought- does the motor need breaking in at all? Is that why it jolts at the start most of the time?

  • #2
    The nickel test isn't a very good really doesn't prove much, and there's alot of variability between nickels. I've stood several on my saw and had some fall over and some not....they're different thicknesses. It's only as good as the nickels and the belt on the saw. If your saw shakes badly enough to be a problem you'll know it without the nickel test.


    • #3
      So the shaking is typically caused by the belt? It shakes pretty severely only for a second on the intial startup. It really isn't too bad, the thing that really concerns me is that sometime it does start up smoothly which tells me something must be wrong. Now if it always started up with a jolt I would accept it and live with it but that isn't the case.


      • #4
        Sounds like you need more super glue on the nickle.

        There are more reasons for your saw to have 'the shakes' than just the belt itself.

        Pulley alignment
        Belt Tension
        Physical condition of the pulleys (and belt)
        Motor mounting

        How about the motor fan? Its mass is low compared to the motor, blade, etc but it might be enough to cause some wobble on startup/shutdown. Once it spins up to speed the off-balance of the fan would be overcome by the heavier rotating parts. Its kinda like an out-of-balance wheel on your car that is only noticeable at certain speeds.
        Last edited by Bob D.; 02-03-2006, 09:15 PM.
        "It's a table saw, do you know where your fingers are?" Bob D. 2006


        • #5
          Thanks again for the feed back guys.

          Do you guys notice on your saws that it's a little rough at startup compared to running at full power/speed? What is the proper tension for the belt. Is there a way to set the proper tension? Thanks.


          • #6
            Check trunnion bolts

            Are your trunnion bolts tight? (The ones that bolt the trunnions to the table). Some owners have reported finding their trunnion bolts only finger tight!
            "Did you put the yellow key in the switch?" TOD 01/09/06


            • #7
              I will be checking that first thing in the morning. I need to adjust the blade a tad bit anyhow. Planning to check all the alignments again in the morning. Thanks.


              • #8
                Okay I checked all the alignments and everything seems to be in order. I took the belt off and tried starting the saw and the jolt at startup is still there. I'm thinking it's the motor itself that is the cause of the problem. Keep in mind it's very minor and maybe I'm being overly sensitive or critical on just how smooth the start up should be. Not sure if it's worth pursuing any further on resolving this issue, maybe i'll just have to live with it. Anyone else notice a jolt or rough start when the starting up the saw? It's a momentary thud or a bang for a split second. Not sure how to describe the sound.
                Last edited by ryan.s; 02-05-2006, 03:09 AM.


                • #9
                  Keep in mind that this is not designed to be a soft start like on a router, its like launching the Space Shuttle, you're taking 10 pounds or more of metal at a standstill and spinning it up to 3450 RPM in 2 seconds or less. There is bound to be some resistance to the initial acceleration (remember Newton?).

                  Also, I think that since the motor assemblys' rotating mass is not centered on the support bracket there will be a torquing affect which can cause a slight twist or jump of the motor on startup. Remember the motor is not rigidly mounted, it has by design the freedom to float left/right a small amount to help maintain alignment with the arbor pulley and will rotate (within a defined range) up and down to maintain belt tension as the blade is raised or lowered.
                  "It's a table saw, do you know where your fingers are?" Bob D. 2006



                  • #10
                    Lots of induction motors will rock a bit at startup. My saw tends to have more shimmy at shut down. As long as it doesn't persist during operation, I can't imagine it ever affecting the cut. Like I said, even though my saw passes most of the time, the nickel test is worth... well... about a nickel IMO. (maybe it would mean more to me if it didn't pass! )


                    • #11

                      Are you running the saw on 220V, motors on 220 tend to start with an instantaneous jerk much more so than on 110?



                      • #12

                        You said:

                        "I took the belt off and tried starting the saw and the jolt at startup is still there"

                        I dont have an intimate knowledge of motor design, and this may be way off base, but in the back of my mind (along with a lot of other clutter) I seem to remember that some motors need a capacitor linked in to put the current out of phase with the voltage just to get the initial momentum started, then after the unit is spinning, this capacitance is not needed so perhaps there is some switch to disconnect this capacitor after inertia comes in from spinning, and if it were intermittant as to when it worked properly and when it didnt, that could be your problem.

                        It is impossible to make anything foolproof because fools are so ingenious.


                        • #13
                          Thanks again for all the feedback guys.

                          Woodslayer - I'm running it on a 120V circuit.

                          I still can't figure it out but what you guys commented on makes sense and it's something that I can live with as long as it's smooth at full power. I tried a few test cuts finally and I'm lovin it. It cuts like butter. I decided that the jolt at startup isn't really bad at all, hardly noticeable actually but I'm the type that spent an hour aligning the blade and fence within 1/1000 of an inch to the mitre slot. When it does start up smooth every once in a while I'm guessing the position of where the motor came to rest at shut down probably has something to do with it. Anyhow I'm very happy with the saw so far but will get a better assessment once I really start using it. Thanks again for all the help guys.


                          • #14
                            Nickel Test

                            Don't lose any sleep over the so-called nickel test. The Nickel test is more of a marketing ploy than a true test of how well your saw runs. If you align your blade properly and get your belt pulleys in the same plane your saw should run very smoothly-at least as smoothly as any other contractor's saw. If balancing a nickel amazes or amuses you forge ahead.