JB Weld vs Bondo vs Helicoil

Not sure how much "outside" room you have for going oversize, but they make "inserts" which are standard or metric sizes OUTSIDE threads so you can use a regular tap to rethread the hole, then these inserts are threaded into the hole with a screwdriver (and they have a dry type of locktite on the external threads so it won't back out) and the inside is threaded for the size you need (10mm x 1.25). Saves the expense of the helicoil and you can use regular size taps to prepare for the insertion (albeit the hole does have a be a smidgeon larger than would be needed for a helicoil) HTH Ken.

Loctite makes a product called Form-a-Thread for restoring threads. I've used it on a similar application. Works OK.

"Gary Brady" wrote: Loctite makes a product called Form-a-Thread for restoring threads.

^^^^^^^^^^^^^^^ I think Loctite and Permatex both have such products. They work fine, as long as you keep away from rod bearing caps, and things like that. You should be fine with a bike mirror mount.

DON'T use Bondo!! It's not really structural and even though this isn't a critical application I still wouldn't use it.

Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com

"I'm not grown up enough to be so old!"

And from my extensive experience with helicoils, probably far better in the end, if you have the room for the solid insert.

shame on you just the same... and doing it to a fellow biker no less!

get down to a wreckers, and you'll get the mount for $10, no need for helicoils, glue, subterfuge

Shaun

Forget Bondo. Screw it in with some JB or PC-7 and it should be fine.

Loctite IS permatex, last I checked. Same company.

Unless you want to adjust the mirror. Instead of doing the job poorly, just tell the buyer it needs repair. A used grip cap can be had at a bike wrecker for $5. Beats having the mirror fall off and break.

Thanks for all the replies. To those that thought I would do a sloppy job, I want to remind them that the mirror, which is a male stud, also has a decorative locking nut which would make the mirror easily adjustable. My approach would have been to us a dummy bolt with the "Form-a-Thread" and, after all is set up, unscrew the dummy and install the mirror.

INSTEAD, I do have enough material to drill oversize, and make a threaded bushing in the lathe. The only metric thread that I own is a 10mm x 1.25. Very lucky on that one. So, I will make a threaded bushing that is 10mm inside thread and, say, 7/16" outside thread. It's been so long, I will have to learn how to do outside threads again.

GET TO USE MY LATHE!!!

Thanks all,

Ivan Vegvary

So make it easier on yourself and start with a 7/16 bolt and then drill, tap and part off your insert.

According to Ivan Vegvary :

Hmm ... I fear that will not work with the suggested size. The fine thread for 7/16" is 10 TPI, and with that the root diameter of the thread is 0.351, or 8.91mm -- noticeably smaller than your desired metric thread of M10x1.25

Do you have room for 1/2"? That will get you to 10.5mm at the thread root with 20 TPI, and that should suffice. It is even pretty close to the 1.25mm pitch (which calculates out to be 20.32 TPI).

Good Luck, DoN.

Thanks Don & Roger! It never would have occurred to me to start with a bolt. Yes, I have bolts all the way up to 1" diameter. Been picking up hardware from the streets since I was 11 years old (53 years ago). Wow, didn't realize that's a half century of scrounging.

Ivan Vegvary

Keep in mind that left side mirrors often have left hand threads, so that wind resistance tends to tighten the mirror.