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Rear of the rip fence moves when locking

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  • Rear of the rip fence moves when locking

    Hi everyone,
    I have been using my BT3100 occasionally for the past 10 years. These have been for home repair projects and my cuts were usually pretty accurate. However I have been wanting to get into more precision work and have started reading and learning about properly aligning the SMT and rip fence. I have noticed that when I am locking down the fence the back of the fence moves to the left before it locks. I think that it has something to do with the adjustment of the sliders on the front of the fence. I have set both of the sliders to the same position but I still get movement. The only way I can lock the fence straight is to physically hold the back of the fence while locking it down. Even then I'm not 100% sure it still doesn't creep over.

    One thing I did notice about the sliders is that the part that rides in the t-slot is significantly smaller than the t-slot itself. The tab on the slider measures 13.5mm and I believe the t-slot is at least a couple mm larger. I would think that the fit should be close enough to just allow the slider blocks to move freely but in its current form there is a lot of front-back play. I even reversed-engineered the sliders in CAD so I good try decreasing the amount of play on the sliders.

    Has anyone seen anything like this or have any ideas? I'll try to grab some pictures tomorrow.

    Thanks!

    Joe

  • #2
    Hey Joe,

    Mine does the same thing (the far end of the fence moves to the left a little when I lock it down). I always assumed it was the fence aligning itself to be perpendicular to the front rail (and parallel to the blade). I have set my fence scale, and indicator, to be dead-on accurate and almost always use the fence scale when making rip cuts (unless I am trying to get down to thousand's precision) and since the front of the fence (and scale indicator) don't move when locking, it's never been a problem for me. When setting the fence, I almost always slide the fence beyond the desired rip width, and then tap it back to the left (taping on the front fence block) until the scale indicator is lined up precisely and then lock the fence. In my case, I just assumed the slight leftward movement of the far end of the fence was that end trying to line up perpendicular again (since taping on the front of the fence would naturally cause a slight misalignment). All that being said (and sorry if it's confusing), when I lock down the fence and it pulls parallel to the blade, I get very accurate cuts. However, now you've got my curiosity up - so I'll have to take a closer look at the mechanics of my fence the next time I'm at the saw.

    John

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    • #3
      Yes, the movement when locking down is correct. Any Adjustment should factor this in. You want it to be either dead on or the thickness of a dollar bill to the right of the blade to prevent pinching. Some wood boards warp with the stress being relieved and that is the reason that the set up is towards the thickness of a dollar bill to the right instead of perfectly straight. But that is an individual preference. Now, back to the movement. (I think I remember this but it has been a long time since I went over the explanation.) ON the BT3000/3100, the fence is aligned in two stages, the front first and then the pulling into alignment the rear. Most big saws used to (and probably still do) align from the front only. The BT3x00 aligns and locks from the front, but locks the back as well in the second stage - which is the movement that you see.

      Here is the basic alignment procedure as mentioned on page 29 of the manual:

      1. Raise the locking handle to permit the rip fence to be moved.

      2. Place a framing square beside the blade and move the rip fence up to the square. Take the dimension on the rip scale.

      3. Move the fence back and turn the framing square 180 degrees to check the other side.

      4. If the two dimensions are not the same, loosen the two screws on the fence and align it. See Figure 45.

      5. Retighten the two screws.

      6. Make two or three test cuts on scrap wood. If the cuts are not true, repeat the process.


      IN THE VERNACULAR: That is somewhat misleading but is technically correct. 1. Alignment is done by loosening the two top screws on the rip fence, 2. align the fence to the square against the blade as you push the locking ever down. 3. Check to see if it is aligned. 4. TIGHTEN the screws. 5. Lift the locking handle and watch the back swing about a degree to the right away from the blade. It will swing back into alignment when the lever is locked again.

      A misunderstanding is that it swings OUT of alignment; No. When understood and properly done, it swings INTO alignment and then locks on BOTH ends.
      Last edited by leehljp; 05-19-2019, 09:08 AM.
      Hank Lee

      Experience is what you get when you don't get what you wanted!

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      • #4
        Thanks for the responses and explanation. Iíll try this out and let you know.

        Update:
        I reassembled my rip fence and used a set of feeler gages to set both fence slide blocks to the same distance (approximately .071 inches from the fence housing). I aligned the fence with the instructions above and dialed it in. I did some test cuts and they are coming out exact.

        Thanks for the assistance!
        Last edited by CajunJoe; 05-19-2019, 08:23 PM.

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