Is it safe to use a metal file on a polarized plug to make the bigger prong (neutral) a little smaller? But not as small as the hot wire so that I can still tell the difference between the 2.

enter image description here

Reason i would like to file it is that this single appliance with the polarized plug does not fit in my polarized wall outlet. It fits in a universal adapter then i plug that in the wall outlet.

All other appliance with polarized plug fits in the wall outlet, only this appliance. I know I can replace the outlet but filing a little bit would be a quicker fix.

Do you foresee any problems with filing this?


  • 2
    Better would be to replace the plug itself. Can you upload a picture of the problem plug, maybe showing it next to a "good" plug for comparison? Commented Jul 13, 2021 at 2:31
  • 1
    safe? yeah. Legal? maybe.
    – dandavis
    Commented Jul 13, 2021 at 8:01
  • @manassehkatz-Moving2Codidact, here is a pic. [link] ibb.co/6YmtdCK
    – edit12
    Commented Jul 13, 2021 at 16:06
  • 1
    Based on the picture, the plug is out-of-spec. Commented Jul 13, 2021 at 17:06

1 Answer 1


TLDR: you have an appliance that is polarized for safety. You are trying to plug it into an adapter that is not polarized (in or out). Get an adapter which is polarized.

No, you cannot modify things like that. NEC 110.3(B).

The polarized plug blade is supposed to be 5/16" (8mm) tall.

Measure it. If it is taller than 5/16", then the plug is defective.

If it is <= 5/16" (8mm) tall, then it is not defective, and the problem is the socket you are trying to plug it into. The socket is either defective, or is very old and pre-dates polarization, or is built in a way that can't guarantee polarization on the other end of the cord.

Based on the picture, the plug is not defective.

Take a close look at the non-conforming thing. Look for a UL in circle mark*. If it has that mark then there is a very good reason for the slot being too small.

If the biggest mark on it is CE or CCC or FCC or RoHS or no mark at all, then the item is NOT UL-approved and you cannot use it in North America. NEC 110.2. Back to Amazon it must go! ... And don't buy electrical equipment on Amazon.

* or any of the other NRTLs, including CSA and ETL... but definitely not CE.

  • Thanks for the comprehensive reply.. but my problem is the width of the plug, not the height.. pls see pic for reference ibb.co/6YmtdCK
    – edit12
    Commented Jul 13, 2021 at 16:09
  • 2
    @edit12 Based on the new info from your picture, I understood exactly what you meant in the first place, and my answer is dead-nuts on-point; the only difference is we are disagreeing on the meaning of "width" and "height". I think of a plug oriented as if you were about to plug it into the wall. Commented Jul 13, 2021 at 16:15

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