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I have this Milwaukee corded drill: 1/2 in. Pistol Grip Dual Torque Hammer Drill.

Recently, I pushed the motor too hard while mixing thinset mortar. I got a burnt motor smell and bit of smoke. I have now learned that bigger mixing paddles are not always better! Have I caused serious harm to the motor? Is there anything I can do to ameliorate some of that harm? Or maybe drill motors are designed to survive such occasional abuse.

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    Nope - you let the magic smoke out.
    – Ecnerwal
    May 26 at 16:10
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    @Ecnerwal I hope that you mean "Nope, you didn't cause serious harm" but I fear you mean "Nope, there's nothing you can do." May 26 at 16:13
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    Motor windings are insulated with a thin layer of varnish. The smoke is usually some of that varnish being burned off, and then some of your motor windings are no longer insulated one from the next, so that part of the winding is shorted out, which usually leads to further heating and further damage. Repair was economically sensible some decades back. These days, not so much. The new parts frequently exceed the price of a new tool, and as for a motor rewinding shop, good luck finding one at all; finding one that will work on a small tool; and having that not cost more than a new tool.
    – Ecnerwal
    May 26 at 16:23
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    Nothing you can do about it now, repairs really aren't possible. I'd address this practically: If it works, use it, if not replace it. But bc the insulation may have breaken down enough to cause a short, I'd be sure to only use it on a GFCI protected circuit. May 26 at 17:27
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    @Ecnerwal You're probably right, but I'd open it up and see what the motor is and whether I can get a replacement (assuming it doesn't work now, or fails soon). Drill motors are fairly standard - I've specced one for something completely different so looked into them a few years back
    – Chris H
    May 27 at 9:46

3 Answers 3

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This has happened to me before and in general the tool continues to work mostly fine. I suppose there might be a drop in power output but I’ve never really noticed it.

I realized that slightly more expensive brushless motor drills often come with an electronic control that will shut off the motor before it gets damaged from being overdriven. Those are useful for avoiding the problem altogether.

Bottom line in my experience is, keep using the tool until it stops working unless you have a good reason for an upgrade.

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    Think it would depend if it was a little wisp of smoke or a few seconds of smoke.
    – crip659
    May 26 at 17:36
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    @crip659 I’ve definitely made a mess of smoke with both cordless and corded drills and in general they still work. May 26 at 18:42
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    many motor winding wire coatings like varnish or lacquer produce A LOT of smoke when over-heated or burned. While a wisp from an LED or transistor signals death, you can probably fill a room with motor smoke and still have no measurable performance impact.
    – dandavis
    May 26 at 20:19
  • @dandavis: On the other hand, if one continues to use a smoking drill it may eventually burst into flames quite dramatically, so think of the smoke as being a warning not to keep abusing the drill.
    – supercat
    May 28 at 2:33
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Usually overheat and smoke means replacement.

Smoke is from something burning/melting usually electrical insulation.

Once the insulation is damaged it needs replacing.

Might be able to get a new motor, but probably cost close to a new drill, unless lucky.

Would contact the maker to make sure if they have replacement motors and the cost.

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    If a motor replacement is required, I'd suggest searching online for parts. I've purchased factory replacement parts from 3rd party sellers for much less than they were from the official factory web site. Also, many times, there are well made videos on how to break down the tool and do the repair. There are also many not so well made videos full of "let's try this", and "oops". While I support the "it can't be much more broke than it already is" spirit of these folk, I recommend not putting to much trust in them.
    – FreeMan
    May 26 at 18:08
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What should I do if I overheated my drill motor and made it smoke?

Let it cool down in front of a fan for an hour and try using it again. If it doesn't feel right then you will quickly know.

Have I caused serious harm to the motor?

There's really no way to answer this question without taking it apart and inspecting the motor. The pre-requisite is of course that you know what you're looking for once you've disassembled it.

Is there anything I can do to ameliorate some of that harm?

What's done is done. The main thing is to let it cool down adequately before using it again. If it's warrantied then send it in for repairs.


Realistic assessment:

That drill has a 5 year warranty; I hope you registered it and can make use of the warranty.

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So you've learned what that drill's max potential is, now you have to ask yourself whether that potential satisfies your needs. If your needs exceed the drill's capabilities then the realistic question is, which drill should you buy to satisfy your needs?

If the drill is still within the store's return window then I suggest returning it; why move forward with a hobbled drill?

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