What?!!! Cupped cuts (start & end of cuts not even)

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  • randelph

    What?!!! Cupped cuts (start & end of cuts not even)

    Not sure how to ask this question, really bizarre. Working on a big project and absolutely want square lumber to work with.

    Using the sliding miter fence on my 3100 at 0 degrees to cut the end of boards that are 3-4 long (and therefore too long to use the rip fence). I'm cutting about 14".

    When i use a straight edge to check the cut i just made, the start and end of the cut, about an inch or so on each end, is shallower, with the body of the cut deeper (about 1/16").

    What the heck? How is that even possible?

    I already adjusted the miter fence relative to the blade using the hex nuts on top of the miter table. Even a cut using the rip fence has some of the same qualities.

    Please help!

    Thanks,
    Randy
  • JBCrooks
    Forum Newbie
    • Feb 2006
    • 44
    • Seneca, SC

    #2
    I had something similar happen, if I understand you correctly. Your fence on the SMT is square to the blade, but the SMT itself is slightly out. That's what I had, anyhow. Even though the piece is held square, mine was slightly moving into the blade as I pushed it across. As it started the cut, the teeth would nibble sideways slightly until the start of the board would contact the blade and deflect it out. That would leave a cut slightly dished out in the center.

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    • davwho
      Forum Newbie
      • Oct 2006
      • 16
      • Petawawa Ontario
      • BT3100

      #3
      Wow, i have had the same problom since i bought the BT3100,ive tried everything to fix it, but its so out of wack now,im lost!!!
      same as randy
      please help!!

      Comment

      • JR
        The Full Monte
        • Feb 2004
        • 5633
        • Eugene, OR
        • BT3000

        #4
        Ok, I see several new members posting about similar problems. I'm not best tune-up guy around, but I'll try to get things started. If I'm a little too basic, please bear with me, because it's important to get the basics right.

        There are two main steps to SMT alignment - table alignment and fence alignment.

        I was little confused by the OP's post about adjusting the screws on the SMT. For clarity, I'll point out that it's important to have all that kind of adjustment done before trying any crosscuts or aligning the SMT fence. There are a couple of articles in the Articles section of this site which give good suggestions for aligning the SMT table. Rod Kirby's can be found here http://www.bt3central.com/articles/files/kirbalign.pdf and Dave Hawkins' here http://www.bt3central.com/articles/files/smtalign.pdf. The user's manual also works here.

        I use a slightly different technique, but the paramount issue is making sure the SMT table moves exactly parallel to the blade. A single point on the table must have the same distance from the front of the blade as it is from the back of the blade after moving the SMT. Exactly, to a poofteenth, with no slop or sideways play.

        Once the table is aligned, then you can worry about the SMT fence. You'll need a trusty square - I use a framing square and it seems to work for me. Raise the blade all the way and loosen the SMT fence. Place one leg of the square against the blade, making sure it doesn't touch the teeth. Now snug the fence against the other leg and cinch it down (it helps to leave the table free to move forward and backward while doing this part).

        You should now be aligned. Now it's time to make a couple of cuts. Proper technuique here can also contribute to the problems described. The most important thing is to assure the piece being cut is snug against the fence the whole time. There's a hold-down thingy that comes with the saw (I'm acutally not sure if this is a standard part or comes in the optional accessory kit), that works like a champ. It's designed to hold the piece down and pull it into the fence at the same time.

        Don't force the cut. Depending on the distance of the SMT from the blade, the hardness and thickness of the material, it may be possible to experience some flex in the assembly. Just take it easy and smoothly push the material through so it gets cut, but still remains square to the blade.

        HTH,
        JR
        JR

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