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Thread: Blade to Miter Slot Alignment - Cab Mount Trunnions

  1. #1
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    Blade to Miter Slot Alignment - Cab Mount Trunnions

    I finally broke the saw down to add another wing and shift the whole rig 12" to the left as the final step in a recent re-org. I took advantage of the effort to pull the top, clean out real good, check all the fasteners and adjust anything like backlash and such.

    I like my machines level with Mother Earth so I get the machine level first. There will be some table adjustment that will kill “perfection” so I just get real close front to back, left to right and corner to corner. I set the blade at 90* and begin.

    Grab your alignment tool of choice:

    22124 Alingment 004.jpg

    Choose the miter slot that will be used for all the following steps and check the blade front to rear in the same tooth area. No surprise, mine is out after having the top reattached. I loosen 3 of the 4 bolts and tap my way to zero change front to back.

    22124 Alingment 007.jpg

    Lay the blade to 45* and repeat the front to back checks. Mine is out so I will have to shim one or more corners of the top to adjust for this.

    22124 Alingment 010.jpg

    The long LV feelers make this really easy and I find that everything is pretty close but, I need to elevate the right front corner by .015".

    22124 Alingment 012.jpg

    Four layers of Coke can is .0155" so I'll try that.

    22124 Alingment 013.jpg

    Now I return the blade to 90* and recheck, readjusting if required. Return to 45* and recheck, readjusting if required. OK, I'm dead-on at 90* and heeled away from the fence by .001" at the rear. I wasn't trying for the heel-out but after a reasonable effort .001" seemed like as close as I was going to get on this machine and I'm OK with it.
    She said “How many woodworking tools do you need?”
    I said “Why? Do you know someone who is selling some?”


  2. #2
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    Yet another thing that I need to now check and true on my machine. It never ends.

  3. #3
    Glenn Bradley,

    You made the comment "Lay the blade to 45* and repeat the front to back checks. Mine is out so I will have to shim one or more corners of the top to adjust for this.'

    I have the same problem, but do not know how to shim the corners. In my case, the distance from the miter slot to the blade increases from front to back (wider at the back than at the front).

    Can you spell out how to do the shimming to correct this?

  4. #4
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    You are raising or lowering a corner to put (or rather remove) twist from the top. I find it easiest with the wings removed. Before you roll your eyes and say how much trouble that is, you will be realigning your wings anyway Most tops will have shims already in place that look like washers. Woe be to the man who disregards the location of these when dismantling his saw . We want to add or subtract from these to correct the problem. I found that washers were good for a rough start and then used strips of aluminum can that I had cut out (actual shim stock works too of course). My method was:

    - take a front to rear reading with the blade (or plate) at 45*.
    - loosen the front right corner and slip a piece of shim stock in.
    - tighten the corner back down and take another reading.

    We now know which way we want to move. If the deviation increased, we want the opposite action. If it decreased, we are on the right track. If the deviation is approaching a hundredth of an inch, I do not try to solve the problem at one corner. If additional thickness is needed, I will go to the opposite corner (front right to rear left for example) and remove height. It is a personal matter but, I generally move the top to allow for the most room for my hand to get into the throat for blade changes before I start. This would be shifting the table to the left for a left tilt saw for example but, that's just me. I also set the top level with mother earth as best as possible while arriving at a good alignment.

    I set aside a morning to do this so I do not feel hurried. I take my time as once this is done, you probably won't do it again until you move your saw. Any sled throats or ZCI's will usually need to be redone but, those are wear parts anyway. So, in a nutshell; you are raising or lowering a corner to determine if the problem gets better or worse. Then you continue on the corrective path till you arrive at your tolerance for deviation (we all have our own threshold, mine's .001") at 90* and at 45*. You will go back and forth a few times so don't get frustrated. Make peace with it by knowing that once done, you can pretty much kiss burning and mill marks goodbye
    Last edited by glenn bradley; 02-02-2012 at 4:24 PM.
    She said “How many woodworking tools do you need?”
    I said “Why? Do you know someone who is selling some?”


  5. #5
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    You're goal is not to "twist" the top ... it is to make the axis of tilt parallel to the miter slot in the z axis. Your solution is the same, but the stated problem is incorrect.

  6. #6
    Quote Originally Posted by Bob Wingard View Post
    You're goal is not to "twist" the top ... it is to make the axis of tilt parallel to the miter slot in the z axis. Your solution is the same, but the stated problem is incorrect.
    I understand that I don't want to twist the top, but isn't that what you are doing by only shimming one corner? It seems like either both front corners or both back corners (depending on which way the alignment is off) should be shimmed at the same time so that the top stays "untwisted).

  7. #7
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    In theory, what you suggest is correct ... but ... that assumes that the four mounting pads are all in precisely the same plane and you simply wish to raise/lower the front or back (your choice) in order to align the "z" axis'. In reality, that is not usually the case, so you would need to adjust for mounting pad deviation and also for alignment.

    Kind of like shimming a short table leg ... THEN ... shimming to level the top ... if that makes any sense.

    I think most manufacturers do a pretty good job of making sure the top rest solidly on it's mounts ... it's the axis alignment where they fall short.

  8. #8
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    Quote Originally Posted by Dan West02 View Post
    I understand that I don't want to twist the top, but isn't that what you are doing by only shimming one corner? It seems like either both front corners or both back corners (depending on which way the alignment is off) should be shimmed at the same time so that the top stays "untwisted).
    I realize from some posts that the description is overly simplified. If the front right corner is raised the front left and right rear would also be elevated to some degree and the left rear bolt would be loosened a bit. You don't want your top to look like ribbon candy, you want to tilt it. Picture a book balanced flat on your finger tips. Elevate a corner and the other fingers adjust as well to maintain contact. A bad choice of words by me in using "twist". It is an adjustment of the plane of the table top in relation to the plane of the blade in rotation, n'est-ce pas?
    She said “How many woodworking tools do you need?”
    I said “Why? Do you know someone who is selling some?”


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