GhostTownForge Posted April 25 Share Posted April 25 I was cutting some steel and stopped for a second to adjust the extension cord, then when I tried to start again, the grinder had stopped working. I tried other things on that extension cord, and it worked fine. I checked some wires in the grinder, and nothing seemed out of place. please help Quote Link to comment Share on other sites More sharing options...
Jimw3326 Posted April 26 Share Posted April 26 I just answered you on the blade forum. Haha! Brushes probably. Quote Link to comment Share on other sites More sharing options...
GhostTownForge Posted April 26 Author Share Posted April 26 update: now it works. I poked around the switch mechanism, and now it works somehow. i would still like to know why it stopped working Quote Link to comment Share on other sites More sharing options...
Frosty Posted April 26 Share Posted April 26 It over heated. Cut off disks require a LOT more power than grinding or sanding so unless you have a light touch the motor gets hot. When an electric motor reaches a set temperature it shuts off until it's cooled below the limit. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
GhostTownForge Posted April 26 Author Share Posted April 26 is there a possibility that the shut-off switch malfunctioned? because I had only been using the grinder for a few minutes. Quote Link to comment Share on other sites More sharing options...
Dogsoldat Posted April 26 Share Posted April 26 I've had switches and brushes fail. Also something to check is if the wire in the cord is broken. Most likely spot is right where it is pinched entering the body of the grinder. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted April 26 Share Posted April 26 I would tend to think bad connection in the cord, switch, or less likely, the brushes getting a crap connection. Frosty may well be right, but I don't think any of mine have a cutoff for overheating, so I'm not experienced with it. The cord you can jiggle (carefully) to see if it cuts out, or test for resistance. Switch you pull out and test for resistance. Brushes you take out and look at them and while you're at it, make sure the commutator is clean and not scored. And if you've got them out, why not replace them. You can clean a commutator by sanding with a VERY fine grade of sandpaper, lightly, then cleaning out the grooves with a probe or thin screwdriver. I just had an old favorite, a Bostitch start making popping noises once in awhile, acting weak, and getting hot while using the cutting disc, so I'm guessing I've fried the brushes and it's arcing to the commutator (the bit of the armature that the brushes touch). Or maybe some of the carbon has got down in there and is arcing. I'd fix it, even if it costs more than new. I've had that thing for around a decade and love it. You kinda get attached to them. I've got three, one Bostitch, one Dewalt, and an $11 HF Chicago Elecric special that just will not die no matter what I throw at it. I've bought three of the latter over the years, almost more out of morbid curiosity than anything. One lasted about 30 minutes before the windings started smoking, one lasted maybe six months before the brushes went and I gave it away, and the other has been going for maybe eight years now, zero maintenance. It's the Nash Rambler of angle grinders, clunky, awkward, and people look at you funny when you use it, but it just will not die. Quote Link to comment Share on other sites More sharing options...
Mike BR Posted April 26 Share Posted April 26 I think the last one I took apart had crimped connections between wires. Those are worth checking as well. Quote Link to comment Share on other sites More sharing options...
lary Posted April 26 Share Posted April 26 I've had a couple of the cheaper angle grinders start cutting out at the switch. There the type that have a plastic switch that slide to a locking position. Sometimes on sale at Harbor Freight for $9.95. I've had the best experience with the 15 amp paddle switch 4 1/2 inch grinders from Dewalt. I'm not talking about the name brand angle grinders when it comes to the slide type switch. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted April 27 Share Posted April 27 Took mine apart enough to pull the brushes this morning. No bueno. One was reasonably okay, maybe worn down between a third and a half. The other was around a quarter inch shorter, the wear was slanted, and there was a chip missing out of the shorter side. Gotta take it apart some more to get a look at the commutator. That thing is buried in there more than I thought. Turns out nobody local carries bloody carbon brushes either, so I'm ordering a variety pack and making Jeff Bezos a little richer. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted April 29 Share Posted April 29 Took the rest apart, worse than I thought. The windings are burned on the armature, just below the commutator. I'm not good enough to rewind one, and I've been losing my mind for two hours trying to hunt down a replacement. Seems like they sell one for every brand but the Bostitch BTE820. Anyone know if they call it something weird, or just don't carry them anymore? Well used or not, I don't want to throw out a $100 grinder over a $30 part. Quote Link to comment Share on other sites More sharing options...
Scott NC Posted Monday at 08:29 PM Share Posted Monday at 08:29 PM If you have the interest and time, consider ordering a copy of Gingery's "Universal Coil Winding Machine". Quote Link to comment Share on other sites More sharing options...
Florida Man Metals Posted Monday at 08:38 PM Share Posted Monday at 08:38 PM Not sure but have you tried to locate the part in Dewalt. Dewalt and Bostitch are basically identical. They are manufactured by the same company. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted Monday at 10:20 PM Share Posted Monday at 10:20 PM The ones I found for Dewalt grinders look a bit fatter and shorter. The ones for Makita actually look pretty close, but I'm hesitant to mix and match. Called the service center, and got a wonderfully helpful foreign national, Alejandro, who tried very hard, but didn't have much more to go on that what was on their website and I'm not sure knew an armature from a backhoe. Is there nothing Gingery didn't do at some point? Yeesh. I'm surprised he hasn't wrote a book on do-it-at-home gene splicing. Quote Link to comment Share on other sites More sharing options...
Frosty Posted Tuesday at 12:07 AM Share Posted Tuesday at 12:07 AM Johnson and Masters handled do it yourself gene splicing. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Nobody Special Posted Tuesday at 04:19 AM Share Posted Tuesday at 04:19 AM Well, found a close match...in a Makita 9556. All the dimensions work except the screw end going to the gear box, which is 6mm to the Bostitch's 8. But the 9556 is designed for 220V, so if I recall correctly, that would draw a bunch of extra current and burn up the windings. No bueno. And while I'm at it, picked up a caliper to measure all this mess, and it was reading exactly half what it should. Ended up having to pull the batteries and short the terminals to reset it before it worked right. Maybe rewinding is the way to go. It looks simple enough, but knowing how a motor works in theory and rebuilding it are two very different things. Screw up an intake gasket on a 318 and make a hidden vacuum leak say, and your Carter carburetor will never forgive you. I can't imagine it's better with electric motor. Quote Link to comment Share on other sites More sharing options...
Mike BR Posted Tuesday at 11:51 AM Share Posted Tuesday at 11:51 AM It seems like running the armature of a universal motor below rated voltage should have the same effect as running a permanent magnet motor at reduced voltage—the motor happily runs at reduced speed. But even if I’m right, that’s probably not what you want. Quote Link to comment Share on other sites More sharing options...
gewoon ik Posted Tuesday at 02:15 PM Share Posted Tuesday at 02:15 PM 9 hours ago, Nobody Special said: Well, found a close match...in a Makita 9556. All the dimensions work except the screw end going to the gear box, which is 6mm to the Bostitch's 8. But the 9556 is designed for 220V, so if I recall correctly, that would draw a bunch of extra current and burn up the windings. No bueno. And while I'm at it, picked up a caliper to measure all this mess, and it was reading exactly half what it should. Ended up having to pull the batteries and short the terminals to reset it before it worked right. Maybe rewinding is the way to go. It looks simple enough, but knowing how a motor works in theory and rebuilding it are two very different things. Screw up an intake gasket on a 318 and make a hidden vacuum leak say, and your Carter carburetor will never forgive you. I can't imagine it's better with electric motor. Install it and upgrade the shop to 220V. Quote Link to comment Share on other sites More sharing options...
Frosty Posted Tuesday at 03:50 PM Share Posted Tuesday at 03:50 PM About now I'd be looking at new angle grinders. You've spent an awful lot of time on this, I could spend a lot less mowing lawns, picking up dog poop, etc. and earn enough to buy new. There's a point where things are just not worth the effort and expense. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted Tuesday at 09:45 PM Share Posted Tuesday at 09:45 PM Another avenue would be to buy a used running one off eBay or Amazon and keep yours for spare parts, did a quick search and eBay has the same model for around $15. I can't control the wind, all I can do is adjust my sail’s. Semper Paratus Quote Link to comment Share on other sites More sharing options...
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