Heli-Coil

[Giant1118]

I stripped my four bolt mounts (i meant to i swear). Anyway i got myself an m5 helicoil kit...which from searching was what i thought i needed. However when i took the heicoils out of the package and tried to thread my bolts in (just to see if it would work) they didnt grab in the helicoil. They can just sort of slide in and out. The only reason im asking is so that i dont tap out my frame and end up with the wrong shit.

Basically i just want to know first off if my bolts could possibly be m4 (i have know clue) and i got the wrong helicoil kit OR if they some how become smaller or more streched out when they are threaded into something.

[rtorrenga]

The easiest way to know is to go to your local hardware store and find a nut, or something with the matching thread to check and see what thread the bolts are. I don't believe that the Heli Coils contract once they are threaded in, but I've been wrong before.

[rtorrenga]

The easiest way to know is to go to your local hardware store and find a nut, or something with the matching thread to check and see what thread the bolts are. I don't believe that the Heli Coils contract once they are threaded in, but I've been wrong before.
I retract my previous statement.

Check out this link.

http://www.toolsnextday.ltd.uk/Helicoil_Kits/helicoil_usage.htm

[Giant1118]

yeah i just gave it a try in a canti mount on an olb beater i had lying around and the m5 fits when its in there. So i guess they do stretch out when they are threaded in.

[WhiteRavenKS]

ive had better luck with a time-sert than a heli-coil. especially in high stress points like a brake post mount.

[dingus]

ive had better luck with a time-sert than a heli-coil.
Yap. Harder to find though.

[chronic]

Can you get those time serts from online bike shopsbecause of the use, or at automotive stores? That is what I will use if I ever have a thread problem for sure.

[WhiteRavenKS]

i found some in the back bottom drawer of an old busted ass toolbox at a shop i used to work at. my super duper rad (by which i mean not at all) px mod used up all the time serts i found. i had to special order new ones from a local hardware store when i needed some more.

[chronic]

Awesome, I'm set then.

[dkoppric]

i wouldnt mess with your frame unless you dont care if you mess it up. i took my bike to a local machine shop and he did 3 of the 4 brake holes for like $25.

[[BMF]Andy]

hmmm, so this time-sert thing is just a solid heli-coil? Never heard of it before this thread.

[WhiteRavenKS]

it's similar to a heli-coil. it's like a sleeve that goes into a larger drilled out hole. unlike a heli-coil, it's one solid piece rather than... well, a coil. i have found they work a lot better for smaller bolts than a heli-coil does.

[THEDMAN]

Been there, go to the hardware store and get a bolt slightly bigger bolt than the one you used. When you thread it in, it'll make new threads..you can even use an standard bolt as well..



That would work,
THEDMAN

[Giant1118]

GHETTO

[Tanner]

Andy']hmmm, so this time-sert thing is just a solid heli-coil? Never heard of it before this thread.
Get it? Get it?

Yeah, those timesert things are new to me, too.

[jaydenn]

Helicoils are very strong when prepared and installed correctly.
the helicoil threads are always stronger than the original thread.
Every single aluminum thread in an airplane receives a Helicoil insert. That should speak volumes about the strength...

And they do compress when installed...That is partially what holds the insert in place...Friction from the compresive forces.

Sorry, I'm an engineering geek....

[mikesnow]

hello, sorry to hijack the thread a bit but this seems somewhat relevant:
i asked this question once before but was wondering if anyone might have more advice. my truvativ holzfeller (or similar) drive side crank is stripped very badly. i tried jb weld, that someone recommended this did NOT work.

i already ordered new cranks, but would like to salvage these anyway if there's anyway. would a machine shop be able to insert a heli coil that would work in a high stress spot like that? i know they would i guess i'm asking would you recommend that to salvage cranks.

what are your thoughts on having the pedal permantly welded to the crank. i guess for that matter it would be better to just weld over and retap hey? thanks for help.

[Donkay]

jb welding to the pedal insert of the cranks wouldn't do much i believe, should've just gave the cranks to a lbs or an engineer of some sort and they'll do a helicoil job no probs :hsugh:
I've got mine done on the cranks, still holding up till today (6months now by the looks of it) but best if you also installed a pedal washer if installing the pedal to crank

[Tanner]

@Mike: Do what I did to my stripped out crank arms. Take yours to a weldor (I did mine myself), and have then TIG weld the pedal eye completely shut, and completely solid. Then, take it to a machine shop, and have a machinist mill/drill out the weld, and then retap. Should work wonders.

[jaydenn]

would a machine shop be able to insert a heli coil that would work in a high stress spot like that? Remember, the thread will not be taking the brunt of the forces...The flange contact between the pedal axle and the crank face do most of the work...

That is why you'll notice that most things designed to take a side load (i.e. pedal) will have a flange and anything designed to be only in tension (i.e. wheel axle, stem bolt etc.) does not have a flange.

So, yes. Any heli-coil, properly installed, should hold up just fine.


Tanner's idea is also awesome, but may be a little pricy unless you have some friends in a shop

[mikesnow]

thanks for the help guys, i was using a used crank as a replacement that was a hussie with 2 of 4 chainring bolts stripped, it lasted about 10 minutes and ripped the other 2 bolts out, so once again i'm bikeless. i had the hole welded shut, just waiting on another set of cranks in the mail to see if i should bother getting the hole retapped. machine shops in london are sketch, no one really wants to do it for less than about 50 buxs, bike shop will do heli coil for about 30. i don't want to have to buy the tools.....