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best way to check for a bent arbor?

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  • best way to check for a bent arbor?

    a friend of the family gave me an old craftsman 10" direct drive table saw a few years ago. just recently i've been trying to get it up to speed - made a throat plate, cleaned it up, and have been trying to cut with it. it works okay, but the blade has a slight wobble. i noticed it more last night when i installed a 10" blade - it wobbles maybe 1/8" or 1/16" from side to side, very noticeable.

    the washers looked good on my passing glance and there's no noticeable play in the motor bearings, so what's the likelihood of the arbor being bent as it comes out of the motor? what's the best way to check this? i don't own a dial indicator, but i'll buy a cheap one if need be cause it'd be handy to have anyways.

    thanks for any advice,


  • #2

    Re: best way to check for a bent arbor?


    It's possible that the arbor is bent and ... it could also be that the blade arbor flange is not perpendicular to the arbor.

    A dial indicator will give you the most accurate measurement and I agree that it's almost a necessity for anyone working on or setting up equipment, but for a start you can make a very simple indicator from a piece of wire and a piece of cardboard. I'm not a great explainer, but here goes .... the indicator will simply be a lever that has a fulcrum (pivot point) somewhere along its length.
    • Unplug the saw
    • Remove the blade table inert
    • Remove the blade and all blade retaining hardware
    • Cut a piece of coat hanger long enough so that one end can rest on the arbor shaft and the other end goes out to either the front or rear edge of the saw table
    • Let the wire rest on the table saw top so that the longer end points either to the front or rear and the shorter end rests on the arbor
    • Tape the cardboard to the table top at the free end of the wire and mark where the wire points to when the wire is touching the arbor
    • Hold the wire gently but firmly down on the arbor, rotate the arbor by hand slowly
    • The wire will pivot where it touches the table top and IF the arbor is bent, the free end of the wire will move up and down, changing it's position from where you marked it.
    • Do the same thing for the blade flange - wire will now move sideways instead of up and down
    Coupla' things - it's not accurate - it's pretty crude, but it WILL tell you if the arbor is bent, or if the flange is not rotating perpendicular to the arbor - the longer the wire from pivot to cardboard is, the easier you will be able to read the movement - No, it's not a dial indicator, but it'll get you started at least

    cheers eh?


    • #3

      Re: best way to check for a bent arbor?

      You can also check the blade, just put it on a flat surface and check if the blade is OK. If the blade is fine, just spend the +/- 45$ and get a dial indicator with a magnetic base. Remove the blade and tilt the saw to the max, this should give you an easy access to the arbor flange. Set the dial indicator so that it touches the flange and slowly rotate the arbor (or course with the power removed) and check if the needle is boucing around or not.

      Even if the saw turns out to be bad and not worth repair the dial indicator will find many other usage around the shop...


      • #4

        Re: best way to check for a bent arbor?

        A quick check to see if it is the blade or arbor:
        Unplug saw
        Remove insert
        Use a wooden block (from the opposite side of the blade attach nut) on the saw table to find the spot where the maximum deflection is, clamp the block and use a marker to mark both the blade and arbor at that angle.
        Loosen the blade and rotate 1/2 turn relative to the arbor, and retighten.
        Rotate the blade and again check where the maximum deflection is: if it is at the blade mark the blade is probably the cause, if it is at the arbor mark it is most likely the arbor that has the run out.