Question regarding helicoils.

I just bought a recoil kit as I have a thread that needs repairing.

Question is, the coils in the kit are only about 8mm in depth, yet the thread that is buggered is probably tapped to a depth of 15mm maybe?

So, do you need to match helicoil depth with that you are drilling out or are helicoils that much stronger that you generally use a shorter depth? (as they seem to come in one size only)

Cheers
Luke

[yorkie_chris]

Because the coil is steel you will probably find it still stronger than the alloy around it, or the tensile strength of the bolt even.

helicoils are much stronger than the base material as you increase the effective surface area for thread pullout. You wont pass the yeild strength of the bolt tho. whats it for?

Originally Posted by AndyBrad

helicoils are much stronger than the base material as you increase the effective surface area for thread pullout. You wont pass the yeild strength of the bolt tho. whats it for?

Engine case cover bolt. Stupid mistake on my part. 8 bolts hold the cover in place - 2 of which are 5mm longer than the other 6. I didn't notice that and put a 20mm bolt in a 25mm hole and stripped the first few threads out.

Did it about a year ago and up until now I have just used the correct bolt and slightly under torquing it, but it needs fixing properly- especially as I'm about to install a woodcraft cover instead!

[Spanner Man]

Good morning all.


You will find that even though the tapped holes are 15mm deep the original bolt probably only went in for 10-12mm or so.

Helicoils are at least twice as strong as a given thread in Aluminium, so all will be well.

Just make sure you use the correct size tapping drill even if it means going out to buy one. Don't be tempted to use ones that's 'close enough' If it's slightly larger there's the danger of pulling the helicoil out when you refit the cover. If it's too small the bolt may bind.

For an M6 thread helicoil the tapping drill is usually 6.3mm or1/4 inch in old money.


Cheers.

stripping the threads on an engine cover, i mean who would do such a thing........

yea it will be fine. At least you used a torque wrench....

[punyXpress]

. . . and drill at least the length of the old thred in ( ie remove it all) or when you put the new bolt in it'll bind & cause problems. ?

Originally Posted by Spanner Man

Good morning all.


You will find that even though the tapped holes are 15mm deep the original bolt probably only went in for 10-12mm or so.

Helicoils are at least twice as strong as a given thread in Aluminium, so all will be well.

Just make sure you use the correct size tapping drill even if it means going out to buy one. Don't be tempted to use ones that's 'close enough' If it's slightly larger there's the danger of pulling the helicoil out when you refit the cover. If it's too small the bolt may bind.

For an M6 thread helicoil the tapping drill is usually 6.3mm or1/4 inch in old money.


Cheers.

Yep - using the correct drill bit

[yorkie_chris]

Originally Posted by Spanner Man

For an M6 thread helicoil the tapping drill is usually 6.3mm or1/4 inch in old money.


Cheers.

I tihnk if you get "recoil" brand kits they come with correct drill and tap included.

Originally Posted by yorkie_chris

I tihnk if you get "recoil" brand kits they come with correct drill and tap included.

Unfortunately not

You get the tap, but I didn't get a drill bit. Had to go out and buy the correct one.