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Bought a aluminum frame with rear suspension, got it sanded and powder paint. While they matched the color perfectly, it's smooth and evenly distributed BUT UNFORTUNATELY totally forgot to cover any threads.

Managed to remove the paint from bottom bracket threads, seat post tube and frame head tube with a copper brush, sandpaper and gently using an awl.

Problem is the #5, #6 threads for equipment and derailleur which is a part of a frame.

Could use a tap on #5 and #6, but the threads aren't damaged so there's no need as they are undamaged.

Any way to remove the paint chemically? Tried a hydrocarbon solvent that I left for 4 hours without slightest effect.

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  • 2
    Have you asked the paint shop what solvent would be appropriate? Seems a better bet than having us guess.
    – David Richerby
    Commented Jun 17, 2019 at 13:32
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    If you have a tap, just use it to cut out the paint.
    – Eric S
    Commented Jun 17, 2019 at 14:12
  • Benco B17 if you can find a supplier near you, #disclaimer use at own risk and avoid zinc and magnesium surfaces. Use the relevant safety measures, it will dissolve most paints and glues in around 20 mins
    – Dan K
    Commented Jun 17, 2019 at 14:37
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    If the thread is OK the tap won't cut into the metal. It will just remove the paint.
    – Carel
    Commented Jun 17, 2019 at 16:09
  • 1
    @ChrisH Got it! Sorry for my confusion.
    – Eric S
    Commented Jun 19, 2019 at 14:13

3 Answers 3

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Taps are useful for cleaning threads, and much better than forcing a screw down the hole (though that can sometime be enough).

Derailleur mounting bolts are an unusual size, but assuming you've got a removable hanger that should be held on by a normal metric screw (M6). Metric M5 screws are common for bottle cages, mudguards etc.

Normally you'd put a few drops of oil on the tap for actually cutting a thread. When cleaning a thread, grease can be better as you'll pick up more of the muck with it (and leave the threads nicely greased). If you've got a full set of taps, a second cut tap or even plug tap is enough for cleaning threads, and easier to start without cross-threading than a taper tap.

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A die (of tap & die) is exactly what you need to use. It will clean the powder off the threads in a single pass. When you use the die, remember they are directional and you want the bottom of the die facing away from the wheel.

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    A die cuts outside threads and a tap cuts inside threads. You can’t use a die on inside threads.
    – Eric S
    Commented Jun 18, 2019 at 13:48
  • Sorry, for some reason I thought he was talking about the threads on his wheel axel.
    – Gary E
    Commented Jun 18, 2019 at 23:41
  • No problem. You may want to edit your answer to reflect that. Otherwise it is ambiguous. I thought it was pretty clear the original question was about a painted frame.
    – Eric S
    Commented Jun 19, 2019 at 0:55
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I got my frame powder coated and asked what to use to degrease it should I want to paint some pin striping or place some decals. They told me not to use acetone because acetone will make the powder-coat dull and will soften it.

So perhaps try acetone (the same the ladies use to remove their nail paint, only they use the small bottles and men use the litre bottles) to soften the coating where it needs to be stripped? Be careful not to run it on the surfaces that must stay intact.

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    FWIW, the men use acetone to remove paint from their nails too.
    – Paul H
    Commented Jun 19, 2019 at 18:20

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