Helicoils

[atomant48]

I need to helicoil some M8 studs back into some aluminium / magnesium components. The studs are high usage with nuts going on / coming off.

What’s the general wisdom on using loctite - should I :

1. Loctite the helicoil into the components
2. Loctite the helicoil and stud
3. Loctite just the stud.
4. No loctite

??

Thanks !

 

[Turbo]

Loctite both. But fit your stud just after installing the helicoil.

 

[knighty]

I'd locktight the lot...

guessing there's no option to drill and tap to a larger size and fit a bigger stud?

 

[atomant48]

I'd locktight the lot...

guessing there's no option to drill and tap to a larger size and fit a bigger stud?

No there’s not enough meat on them (and I’d need a very precise stepped stud - not impossible of course). They’re for the front / rear hubs on a kart. Typically folk chuck them when they pull the studs … a bit pricey for me to keep doing that !

 

[Robotstar5]

We had ally plates on our test rigs, they came with tapped holes which soon wore as they had bolts run in and out a few times per shift so we fitted helicoils without loctite and they lasted years.

 

[Erie Fred]

I like Keenserts for hi usage, however in this case the hi usage is not in the actual
helicoil threads, so I'll simply suggest red loctite (the strongest) use heat to remove.

On both the stud and the helicoil, I would try to do it all in one go, or very quickly.

 

[bricol]

I seem to recall Bollhoff don't recommend using thread locker on their inserts, they mechanically lock into the new thread.

They do do a screw locking version that avoids the need to use thread locker on the studs themselves.

If you do us high strength thread locker, be careful you don't end up locking the insertion tool in the insert - it does tend to grip pretty quick once you exclude the air when winding it in.

 

[hotponyshoes]

Check what material the helicoils are, most are stainless steel so you'll need the activator as well if you want to use locktite.

If you don't have the meat for a bigger stud then a keensert probably won't fit either but they do do a thin wall version which might not be much bigger than a helicoil?

 

[Seadog]

guessing there's no option to drill and tap to a larger size and fit a bigger stud?

That's exactly what you're doing when you Helicoil.

 

[hotponyshoes]

Another (cleaner) option is a screw-locking helicoil.
If you are changing the wheels regularly it's not likely the nuts will get corroded so they'll probably grip just fine.

 

[atomant48]

Another (cleaner) option is a screw-locking helicoil.
If you are changing the wheels regularly it's not likely the nuts will get corroded so they'll probably grip just fine.

They look like an interesting solution. The nuts are brass (or similar) and can go on/off up to 20 times in a day. And always when you’re in a rush so no time to have studs pulling !

 

[oldbikedavey]

Received wisdom is not to use locking compounds on helicoil applications unless absolutely needed by reason of sloppy insert engagement..
Timeserts may be another kettle of fish, however.

 

[knighty]

That's exactly what you're doing when you Helicoil.

eh?

helicoil you drill and tap, screw the helicoil in, screw the stud in

I was asking if there was any option to drill and tap then screw a larger stud straight in

 

[Seadog]

The Helicoil is, by necessity, a size larger then the stud.

 

[atomant48]

I took the larger stud suggestion as putting in say a M10 stud (and in my case would have to step back to M8 for the protruding length). It’s certainly the way I would design these hubs if I was starting from scratch ! They are close to £100 each and this seems to be a common problem.

I haven’t measured the helicoil but it must be close to 10mm so I guess you are both saying the same thing.

Anyway I’ll have a go tomorrow. If it works out ok I’ll go round the pits scooping up broken ones !!

 

[Keithmac]

I prefer the Wurth Timeserts over helicoils but the kit is expensive.

 

[hotponyshoes]

I prefer the Wurth Timeserts over helicoils but the kit is expensive.

That's were keyserts have the advantage for a one-off job, nothing fancy needed to install them.
You'll be around 12mm for a keysert though whereas a trisert will be closer to 10mm

 

[dan.taylor.1]

Is there any way to use a stud with a shoulder on the back, which pulls or is pressed through from the back and has spline to hold it (like on a car) rather than threaded into the flange?

 

[northwest]

Received wisdom is not to use locking compounds on helicoil applications unless absolutely needed by reason of sloppy insert engagement..

Do not use loctite on helicoils, I have had a really bad experience doing this and as @oldbikedavey says, it is not recommended by both Loctite and Bollhoff (manufacturers of Helicoil)

 

[atomant48]

Is there any way to use a stud with a shoulder on the back, which pulls or is pressed through from the back and has spline to hold it (like on a car) rather than threaded into the flange?

Not really. The part is pretty similar to the below. We are also very limited by modifying anything - you are allowed to make repairs to threads but I think fundamentally changing the design would open you up to challenge. These things are considered tuning options / they come in a few different lengths, different materials, different profiles …. And I imagine changing too much could affect the behaviour.