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Is repairing a burned tool/drill motor easy? Answered

I assume this applies to all tools. So, I have a burned out grinder motor (wires). The spining axle 'thing' looks fine. Can't I just re-wound those wires on outer ring of the motor and reconnenct it (good as new?) also I may have scraped (with pliers) the replacement/wounded copper wire when bending it away from center . Will I need to rewind it with another set of wire....have I ruin it given there's some sort of non-conductive coating on the copper wire which I scratched off. I would appreciate any specific advice on reconnecting the power source wires to the wire/magnetic field area as well. Or should I just spend $200 on a new one :)


This magnetic field can be rewound. I rewind motor fields by hand all the time. The last one I rewound was a Ridgid 700 power pony. Take the old field out of the tool being sure not to damage the copper windings on the armature. The windings on the field are normally two separate windings. Be sure to match the copper wire size exactly. Count how many windings are on one side of the field. The easy way to ensure the right count is to cut the middle of the windings in half and count the strands. Once you get your count you need to put a piece of felt into the center of the field just to cover the sharp edges on the iron assembly. Now start winding your wire being sure to get the proper count. Once you’re finished with one side go to the other. It’s really easy. This is far cheaper than buying a new tool or even the replacement parts. A new Ridgid 700 power pony cost well over $1200. The replacement field can cost over $170. A 1lb 18 gauge spool of enameled copper wire cost $15.16. It takes 1.5 hours to rewind the field. I think this is the best deal if a new replacement part is over $50.

And don’t forget to put a high heat protective coat of enamel over the finished windings.

It wouldn't be practical to repair it. If you had the time, and a serious amount of manual dexterity, you MIGHT do it, but it would not be easy. These will be wound with something not dissimilar to a sewing machine I suspect. Unwind the wire, measure its thickness, and then weigh all the wire you take off, very very accurately (<0.1g) to calculate the length of wire you need to wind on. WInd THAT onto a long bobbin, which can pass easily through the hole in the stator. rewind the winding on the stator, taking care to wind evenly, until the wire runs out on the bobbin.

You can't "repair" the enamel on a scratched wire.

....or buy a new motor for the machine....

so the new wire should not be scratched when rewounding it? (as I did with pliers) Also, I just wound the wire to what looked right. Will it weaken the magnetic field of the motor if off by a few grams.

No, it must not be scratched. It WILL weaken the field if you are off a little, but it will probably still work.


If it burned out once already, I'd say there's a significant degree of risk involved with this?


I think it depends on why its burned - if you take a really hot spark from the grinder into just the wrong place, it can kill it, or they can fail from sheer age. When my Bosch 100mm grinder died, a new one, with 100 cutting disks, was 40 quid.

Sorry, I should have expanded: If it's high-ish current, probably mains and there's missing lacquer on the re-wind - it could be a short-lived rewind?


ok, gotcha.  but this grinder was pretty old so I assume that was a bigger factor. My question is (one question at least), is it a fact/high certainty that it short (in the new wound magnetic field) if I have scratched lacquer from two touching wires. It's a 110-volt  motor. Sorry, I'm just looking for really specific info :)

If your insulation (lacquer) is compromised you're taking a risk plugging it into the mains. If you do it right, right wire, no scratching, do that. But for a mains-supply, don't do it while you know there are defects in the construction. I know what a 30A circuit can do, and it can be quite destructive...


Yes, I got the impression he'd knackered the existing wire and wanted to patch it ? So he should have been on fresh stuff anyway.

alright you guys, I went to radio shack and asked for the burn wire. I've replaced the burned wirethis, as seen by the shiny copper. I 'm having trouble find how these/ac motors are wired (to the magnetic field.) By the way, this babe is just an old 'American ....something' I got for $10.   

It looks like a Bosch.  You should'da checked the warantee before you tore into it.  You might'a got a new  unit or at least a refurbed one for free or may be shipping.  Next time thing before opening it up.

Just got new Delta faucet cartridges even though they were out of warranty.  They said "they don't like unhappy customers".

Buy another one and mess around with the old one. If you fix it, that's good, if you don't, it won't really matter. Put it in the spare parts box.