Riving Knife Alignment

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  • Riving Knife Alignment

    My BT3100 riving knife is placed too far to the left with all the shims (except the bent one) on the left. I plan to clean it out and put it together again. The only change I made was placing the splitter within a 1/8 of the blade. If I move it further back, would it be more forgiving and not hang up the wood as it passed by. Any suggestions on what I should look at or adjust?

  • #2
    Moving the knife further back is not a desirable work-around for a knife that can't be aligned to the blade. Anything that "moves the workpiece" improperly is reducing safety.

    Typical riving knife-to-blade alignment issues:
    1: Knife is bent. It should be dead-flat.

    2: incorrect spacers on saw arbor. For a thin-kerf simple blade (not dado stacks or other odd-width blades basically) there should be two spacer rings on the arbor along with two large blade stabilizing washers. The order should be:
    nut-washer-blade-washer-ring1-ring2
    The two spacer rings are different widths; it doesn't matter what order they're used.
    ring1 = quarter inch width
    ring2 = slightly less than half an inch width
    washers = about a quarter inch wide

    3: incorrect blade stabilizer washers. The factory stabilizer/washers are somewhat dome-shaped. They have flat spots in the center hole that must be aligned with the corresponding flat areas of the arbor. Incorrect stabilizer/washers may not be thick enough which shifts the blade left or right on the arbor.

    4: Any chance the arbor itself is improperly mounted in the supporting bracket assembly?

    5: aluminum bracket structure bent, damaged, or otherwise "edited" by a prior owner. I.e. the part that supports the riving knife assembly has been shifted out of place. Look at the area that clamps to the riving knife: if the clamping faces aren't parallel with the blade then something is amiss in the bracket assembly itself. If there are no obvious defects - no bends, no cracks - then I'd disassemble the bracket assembly and use a file to remove some of the material, moving the splitter to the right.

    On my early model BT3, the left face of the blade lines up with the end of the smooth part of the arbor. So the nut and left washer are 100% on the threaded part of the arbor.

    mpc
    Last edited by mpc; 01-13-2021, 10:56 PM.

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    • #3
      MPC had some really good advice.
      I just reinstalled my riving knife after doing some dados.SO this is fresh in my mind.

      One thing is to make sure that the knife is perfectly vertically aligned with the blade. Sight down the blade and make sure first that the knife is perfectly parallel to the blade over the whole length, not just lined up with the blade at the tip!!!

      The riving knife is mild steel, and can be persuaded right or left to line up parallel with the blade. This is important for deep cuts. Only after you get the knife parallel to the blade, then work at getting the knife between the right set of shims.

      On my saw I have one shim to the right and the rest to the left.

      Getting the height of the knife is also important. You should have the knife set down as far as possible so it is resting on both bolts. It should then be forward so that the back of the knife does not drag on the table as the blade is lowered; it should be straight up and down and have a constant clearance to the metal table. Also the curve of the knife should be safely 1/8 inch or so from all the teeth on the blade or bad things will happen when you turn the saw on.
      Only if you can't satisfy both criteria should you try raising the knife off the bolts. I don't have to.
      Finally if you have the cut down shark guard knife, make sure that the line across the top of the knife (use a straight edge to extend it) is a hair lower than the highest tooth on the blade...this will allow you to make kerf dados (non through cuts a blade width wide) and pass over the knife.

      .
      Last edited by LCHIEN; 01-16-2021, 01:10 AM.
      Loring in Katy, TX USA
      If your only tool is a hammer, you tend to treat all problems as if they were nails.
      BT3 FAQ - https://www.sawdustzone.org/forum/di...sked-questions

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      • #4
        All great advice. Since I have owned this saw since buying it new, some of MPC suggestions are N/A, but will recheck the arbor mounting and the splitter flatness ( which is possible). Suppose another look at the clamping area for flatness wont hurt. Loring's saw is just like mine as far as shim alignment in that it really too far left to be able to adjust in the middle of shims. I have one last shim to move to the left. I am considering if everything else checks out, that I can shim the arbor with a thin washer on the right.

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        • #5
          It was flatness. Trying to persuade it to be flatter.

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