Answered Stripped thread arrggghh!!

[RustyMTB]

I pride myself on being tidy with maintenance so this one aches a bit. I changed a headset bearing & while reinstalling the front brake hose guide bracket in the fork, I manged to strip the thread. In fairness, they are a crap design, a little M3 bolt with short threads but knowing that, I should have been a bit more careful.

For now, I've cable tied it which works ok but looks garbage, so I'm thinking options. Obvs, the fork lower is aluminium & soft, so it's either tap it for an M4 or similar, helicoil it or bodge it with something like metal putty or whatnot. Not interested in glue or stick on pads. I'm thinking helicoil is the best idea, Am I right?

This bit, if my explanation is a bit rubbish.

 

[Mikerb]

Nothing wrong with the design, it is only there as a guide for the cable and should the cable get snagged it is the fork bridge that needs to suffer the least harm. A rubber tie or similar on the fork leg will do much the same job.

 

[RustyIron]

Yup, you've got the right idea. A helicoil is the a sanitary option, with the added benefit of leaving you with more durable threads for future assembly/disassembly. But helicoil tools aren't cheap. You can buy a boatload of tie wraps for what you'll pay for helicoil tools.

Drilling and tapping for a larger size screw is also good. Keep in mind that the hole is shallow, so you'll need a bottoming tap. In situations like this, you can grind down the tip of the tap to make a "super bottoming" tap.

There is one more option that actually might be your best bet. Make a cylindrical insert that is drilled and threaded for those tiny screws you're working with. The OD of the cylinder might be 3/16" or so. Stainless steel would be a good material, but it's up to you. Drill your fork so the insert will slide in. It needn't be a super tight fit. Epoxy it in the hole, or use Loctite Retaining Compound. Such a repair is easy, cheap, and will be more durable than original.


Oh!!! I just thought of something else that can be economical and sanitary, but only a little more difficult that the Cylindrical Insert. Get yourself a screw that's bigger than the M3 you're working with. Stainless is best, but stainless isn't easy to work with. Chop off a threaded section of screw, of the appropriate length. Like the cylindrical solution above, drill down the middle and tap it for your M3 screw. Now drill out the fork and use a tap to thread it accordingly. Once you're sure everything will fit up perfectly, add a bit of epoxy or Loctite Retaining Compound to the threads, and install your insert permanently.

This last idea is even better than the Helicoil.

 

[KennyB]

I found that there is enough depth for a longer bolt.

 

[RustyMTB]

Nice one Rusty, good stuff.

 

[Mikerb]

sounds like a lot of faff for something that actually does very little! Given the complete lack of any strain on the fixing you could just fill the existing hole with epoxy and self tap the existing ally screw into that.