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Thread: SCMS Blade Brake Stopped Working

  1. #1
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    SCMS Blade Brake Stopped Working

    I have a 20 year old Bosch 10" SCMS that has worked fine over the years, dust collection excluded. About a month ago the blade brake failed to work. I snap-released the switch a few times and that seemed to work for a couple of weeks. Then that temp fix stopped working.

    Next I took a pencil eraser and cleaned the rotor through the brush opening until the copper looked polished. No luck.

    I ordered new brushes and installed them. I ran the saw for several minutes at a time, removing the brushes in between, until they had formed to match the curvature of the rotor. Still no blade brake.

    Any idea where to go from here?
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  2. #2
    Have you checked for sawdust build up in the moving parts of the brake? Maybe just blow out the motor with compressed air.
    Lee Schierer
    USNA- '71
    Captain USN(Ret)

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  3. #3
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    The problems with electric brakes on these saws are usually the brushes, switch, armature, or brake coil (if equipped). If you've changed the brushes, the next option is to replace the trigger switch, or at least remove it and try to clean it out. When the contacts in the switch are pitted or corroded, the current can't go to the brake coil.

  4. #4
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    The "fix" for my circular saw, that has a brake, is to hold the trigger, and let it run for about a minute. I never stopped to try to figure out why it works, but I read about it somewhere online, tried it, and it worked.

  5. #5
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    Quote Originally Posted by Lee Schierer View Post
    Have you checked for sawdust build up in the moving parts of the brake? Maybe just blow out the motor with compressed air.
    Yeah, I did that. No luck.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  6. #6
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    Quote Originally Posted by Mike Kreinhop View Post
    The problems with electric brakes on these saws are usually the brushes, switch, armature, or brake coil (if equipped). If you've changed the brushes, the next option is to replace the trigger switch, or at least remove it and try to clean it out. When the contacts in the switch are pitted or corroded, the current can't go to the brake coil.
    I haven't opened anything up yet but from what I've read, the brake on my saw is electric, by reversing the flow. All the advice has been to replace the brushes. If that doesn't work, you'll have to send it out or live with it. I'm hoping that's not the case.

    Quote Originally Posted by Tom M King View Post
    The "fix" for my circular saw, that has a brake, is to hold the trigger, and let it run for about a minute. I never stopped to try to figure out why it works, but I read about it somewhere online, tried it, and it worked.
    I just did this. I let it run for a couple of minutes but started wondering if the motor was designed for prolonged running. Anyway, it didn't work. I'll try it again after the motor cools.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  7. #7
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    When I have experienced this with my old Delta 12" CMS, cleaning and/or changing the brushes fixed the braking issue for some reason...
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
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    I told my SO about the braking issue and got this response, "That thing is pretty old. Why don't you buy that Festool one? We can afford it."

    And my head started spinning....
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  9. #9
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    Julie,

    Out of curiosity, how many wires go to the hand switch, you know, the switch you squeeze to operate the saw? The reason I ask, I am wondering if it might be a 2 section switch. One section turns on the motor while the other section disables the blade brake and they do the opposite when the switch is released.
    Ken

  10. #10
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    Quote Originally Posted by Julie Moriarty View Post
    I told my SO about the braking issue and got this response, "That thing is pretty old. Why don't you buy that Festool one? We can afford it."

    And my head started spinning....
    LOL. He's a keeper for sure.

    Do a bit of research before you order a Kapex. While many folks love them, some have had some issues. festoolownersgroup dot com might be helpful for you there.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  11. #11
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    There’s a kapex in the smc classifieds for $750.

  12. #12
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    Quote Originally Posted by Ken Fitzgerald View Post
    Julie,

    Out of curiosity, how many wires go to the hand switch, you know, the switch you squeeze to operate the saw? The reason I ask, I am wondering if it might be a 2 section switch. One section turns on the motor while the other section disables the blade brake and they do the opposite when the switch is released.
    Thanks, Ken. I'll open it up and take a look.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  13. #13
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    Quote Originally Posted by Jim Becker View Post
    Do a bit of research before you order a Kapex. While many folks love them, some have had some issues. festoolownersgroup dot com might be helpful for you there.
    In the back of my mind I was thinking I heard something similar. It's quite a leap in price from a Dewalt or Bosch to the Kapex. After accuracy, all I'd want is good dust collection. The Bosch I have now is so bad it would be worth it to me to buy a new one if I knew it would have great dust collection.
    “Travel is fatal to prejudice, bigotry, and narrow-mindedness..." - Mark Twain

    Diapers and Politicians need to be changed often... Usually for the same reason.

  14. #14
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    If you pull cut, almost any can have good dust collection. If you push cut, I doubt any will have decent dust collection. I never push cut, but started out just by habit from decades of using a RAS, and never had a good reason to switch to pushing. Pushing scares me.

  15. #15
    Seems to me I read that Festool has updated the Kapex to address some of the issues users have reported with them.

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