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?

Have you checked for sawdust build up in the moving parts of the brake? Maybe just blow out the motor with compressed air.

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.

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.

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Originally Posted by Lee Schierer

Have you checked for sawdust build up in the moving parts of the brake? Maybe just blow out the motor with compressed air.

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Yeah, I did that. No luck.

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Originally Posted by Mike Kreinhop

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.

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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.

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Originally Posted by Tom M King

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.

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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.

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

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....

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.

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Originally Posted by Julie Moriarty

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....

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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.

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

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Originally Posted by Ken Fitzgerald

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.

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Thanks, Ken. I'll open it up and take a look.

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Originally Posted by Jim Becker

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.

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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.

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.

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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Originally Posted by Tom M King

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.

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I never thought of that but it makes sense. But doesn't the blade want to dig in and jump forward, kind of like a router?

Not if you're used to it, but yes, you have to control it. Decades of use with a RAS makes it second nature to me, so I don't even have to think about it.

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Originally Posted by Ken Fitzgerald

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.

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I opened the handle. The switch assembly has three wires. This is the assembly
https://www.ereplacementparts.com/im...1641911558.gif

The hot attaches to the top, opposite the switch, of the electronic controller (beige rectangle) and the other two wires connect to the other side. I'm thinking that electronic controller is the culprit. Unfortunately, the switch assembly is obsolete.

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Originally Posted by Jim Becker

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.

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Research says - it's not worth the gamble. Thanks for the heads up, Jim.

Now, what saw will make me happy? I have (2) 10" Chopmaster blades and I rarely have found the need for a 12" so I'm going to stick with a 10". From everything I've read so far, the Makita LS1019L seems to have the best ratings. There is no 10" Dewalt SCMS. The Bosch CM10DG gets high ratings but I've read dust collection is horrible. If it's anything like the Bosch I have, I believe it.

The loss of the brake worries me. I'm programmed to take the piece out right after cutting. One forgetful moment is all it takes.

hartville tool has the kapex with the new motor for 1106.00 ...for how long I do not know..

Julie,
FWIW - I have had the DEWalt 12" SCMS for about 6-7 years (I also have 3 other 10" chop saws dedicated to various specific tasks). I spent a great deal of time setting up the Dewalt to pretty exacting personal specs and could not be more pleased with it. I have been using it for last month trimming out a house I designed and it is still dead nuts on. The additional cutting depth and width have come in quite handy, much more that I had anticipated.

I believe I have heard that the Bosch has less initial play (a good thing) and requires less space behind the unit.

It's the switch.

Might be worth flushing out the switch guts with contact cleaner. I fixed a non-functioning, obsolete switch on a 1/2" right-angle drill like that, and it's worked for a couple of years since then with not a single stutter.

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Originally Posted by Julie Moriarty

Research says - it's not worth the gamble. Thanks for the heads up, Jim.

Now, what saw will make me happy? I have (2) 10" Chopmaster blades and I rarely have found the need for a 12" so I'm going to stick with a 10". From everything I've read so far, the Makita LS1019L seems to have the best ratings. There is no 10" Dewalt SCMS. The Bosch CM10DG gets high ratings but I've read dust collection is horrible. If it's anything like the Bosch I have, I believe it.

The loss of the brake worries me. I'm programmed to take the piece out right after cutting. One forgetful moment is all it takes.

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Julie, I'm always good for a Makita LS plug when the opportunity comes up so...

I currently have two, a 1013 and a 1018. The 1013 is nearing 20 years old, the 1018 is a couple. The 1013 (discontinued) is a better saw. It has more power and stays adjusted better if it gets dropped or slapped by a board or something. The 1018 is no slouch though, both work well. I pick Makita over the others for several reasons you mentioned. 10" blades are easily sourced, cheaper and I have no reason to need a 12" slider. Portability is relatively (for a SCMS) nice on both, meaning you can set the miter all the way to a lock, lock the slide, and carry one through a door without beating up the jambs. I haven't owned the 1019, but I have used one a little. They have the same Makita accuracy that I really like, I just dislike the current fad of moving sliding mechanisms higher. In my opinion it serves no practical benefit, but raises the center of gravity, and you lose some stability. Bosch, Dewalt and that one Makita are all guilty of it. One more thing, the Makita guard is far better than the others I've used, especially on the 1013. In my opinion, Dewalt guards are pretty bad.

Oh, more to the point of the thread, I had was doing the same thing, it was a Dewalt, a switch fixed it.