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I bought a cheap power drill, so I didn't expect much of it, but still, I'd like to learn from it. After drilling less than 10 holes, I noticed it sparking a lot (just by turning it on, without any load). After failing to drill a small hole in concrete (using its impact driver), and having the drill bit bent, I wonder if the fault was caused by the latter (from a supposedly "premium" brand) or by the former.

I disassembled the drill and noticed this weird indentation in one side of the motor:

Drill motor with indentations

Is this normal? Could it be the cause of its malfunction? The "stator" part around it seemed perfectly fine, I didn't see any damage on it.

I also noticed a possibly small sign of burnt part in the white middle axis:

Possible damage in white part that spins?

Finally, I read that the sparks could be caused by carbon contacts being worn, but they seem new enough to me:

Carbon contacts from power drill

So, in the end I still don't know why it failed and/or caused the drill bit to become torn and unusable. Is there a clear sign that the drill was faulty, or maybe it was just under-powered for the task (500W, for drilling a 4cm, 6mm wide hole in non-reinforced concrete)?

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    The "weird indentation" looks like a balancing mill mark, where material was ground away to balance the rotating mass. I don't know why it failed, but I've also been victim of cheap imported power tool allure. I'll simply repeat a bit of wisdom I've accumulated since: The bitterness of poor quality remains long after the sweetness of low price is forgotten. In other words, don't confuse cost and value.
    – isherwood
    Commented Aug 14 at 19:16
  • There are times when a "disposable" tool that is Just Good Enough can be justified. On the other hand, if your library network maintains a Library Of Tools, you can donate a tool away after you're done with it, possibly take a tax credit for its used value, and borrow it back if you ever need it again, which can make justifying better one-time tools easier
    – keshlam
    Commented Aug 15 at 0:54
  • Thanks for the "balancing mill" comment, I didn't know it was a thing. I would love local libraries to offer such services but there is no such thing in my country. On the other hand, there are shops where you can buy such power tools for less than 20$ and hope that they will last for 3 months.
    – anol
    Commented Aug 15 at 6:47

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Bending/breaking a bit usually means you didn't have it in the chuck straight or were abusing it. Cheap bits are cheap bits, but user error is likely.

Sparking... The carbon brushes could be stuck in their guides and not making good contact; make sure the spring can push them firmly against the contacts. But sone samples if done drills just like to spark; I have a porter-cable which has always done so, and outside if not using it around explosive vapors that's been annoying but mostly harmless.

If it was still under warranty I'd say try yo trade it for another sample and see if that sparks too. But given that you have disassembled it, that's a moot point.

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    Even moderately priced bits can wear out after 10 holes… look at the tip of the drill bit if you haven’t tossed it out already. If it’s all worn down, that’s a data point. Don’t know how you drilled, but pulling out repeatedly to clear dust and keep heat down is good. And hammer drills are always worse than rotohammers for bit life.
    – Aloysius Defenestrate
    Commented Aug 14 at 23:58
  • I do believe the bit was not properly inserted in the chuck, or the chuck itself prevented me from doing so. About the sparks, the springs seemed fine, I guess it was just the model that was like that. About the warranty, it's the kind of shop that makes you prefer just throwing it away than trying to explain the issue to a human being. The amount of time spent is not worth it.
    – anol
    Commented Aug 15 at 6:51

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