helicoil inserts

[catalac08]

re-asembling daughter's renault clio having replaced all valves following timing belt failure(pathetic small puny belt for such a critical engine part).
Job going well but there is a stripped thread in the alloy head, thought it was loose when I disassembled it!
The thread is about 3/4" inch deep and is I think M8 (unless renault use some other threads?)
Never used a helicoil insert before but this seems the answer but the kits I can see for sale have the threaded insert 1.25" long.I have read where the tang used for driving the thread in is snapped off - is it feasible to then cut off the protruding insert.
I have never used a helicoil before having always been aware of tendency for threads in alloy to pull out - many threads on outboard are M8 so a kit and the other inserts will be usefull on the boat.
Any sources of kits & advice how to do this would be welcome - the hole is effectively blind so all has to be done from the top.

 

[saltwater_gypsy]

Most garages have a full Helicoil kit.
Its probably worth just towing the car to your local and asking them to "fix it". Otherwise you will have the expense of the insertion tool and probably three inserts left over.
Its about a five minute job so budget £20

 

[Cardiffcruiser]

Far better to cut it before insertion as it will be next to impossible to cut it off neatly afterwards. If cut before they are ussually quite forgiving as they are compressed into the outer thread, as long as they are not too badly mangled.

In work we have them in various diameters and lengths and usually can use the correct length, though we have been force to trim on occaision. m8 x 19mm are available, though I'm not sure where the company I work for get them.

 

[AIDY]

you should be able to get a helicoil kit from you local engineering shop. (loads on ebay - just bought and sold an M6 kit on the bay after a job)

Round about £25 for the kit and you will need a drill also for the tap. This should be the tapping size for helicoil thread.

Helicoil inserts are available in different lengths from 1D - 1.5D - 2D - 2.5D etc.... where D is the diametre of the hole.

The helicoil has a tang on the bottom which enables you to wind the coil in. It generally gets knocked of into the bottom of the hole afterwards.

Don't be scared of helicoils there easy to insert to an existing thread.

 

[alan17]

Your major DIY expense will be a correct size drill and the special tap to thread the hole before inserting the helicoil. A local mobile mechanic should be able to help.

 

[catalac08]

thanks for advice - I had the wrong end of the stick, as advised they come in multiples of the diameter so 1.5x8mm = 12mm which is about right.
as an alternative Ondrive do thread repair inserts - these are heavily knurled threaded inserts that knock in and then expand so that the knurls grip the sides of the hole (9.5mm) The torque is only 17ft lbs on these bolts and the alloy is reasonably substantial around the holes. Has anyone experience of these which would be cheaper and easier to fit?

 

[leomagill]

Check the thread diameter as the frogs use M7 quite often, theres a lot on my 1.9 pugs, helicoils are easy enough to fit as long as you have the tap that comes with them, go for a shorter insert rather than cutting one down as you get a better thread to start on.

 

[burgundyben]

I've no experience of ondrive, but i dont like the sound of it.

Helicoils are as strong as you like, I've fitted dozens.

 

[morgandlm]

I'm a great fan of helicoils having rebuilt loads of motorbikes. As others have said, the major cost is the right sized tap.

You might also like to look at Cross Inserts which do the same job. I've always found the Cross people very helpful.

In both cases the tang that is used to drive the insert down the tapped hole is broken off to lock the coil into the hole.

If you are just doing one or two - get a local garage to do it.

Morgan

 

[maxi77]

In aviation helicoils aresometimes used becausethe insert is actually betterthan the bnative thread, as long as youhave enough depth.

 

[martinb]

I use these kits from RS Components, although you can probably buy cheaper elsewhere:
http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0291846
As pointed out by others, you will still need the correct size. RS alos sell the inserts at various lengths in bags of 10. Note that the kits come with a second taper tap and to repair a short blind hole you will need to get a plug tap.

Martin

 

[savageseadog]

Hi
I've a pretty comprehensive set of Helicoil kits and I could drop it off for you

 

[dukes4monny]

I found this video useful

 

[Daedelus]

Ah jus lurve his accent!