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STRIPPED THREAD RENEWAL

Posted: Wed Jun 24, 2009 2:37 pm
by Old Fogey
Although this subject comes up regularly I don't remember seeing anything about what it is or how it's done, so I though that a pictorial tutorial would be useful.

Thread renewal is a way of replacing a stripped thread with a coil of (usually) stainless steel carefully manufactured to mimic the dimensions of the original thread once installed.

It is a relatively simple procedure once you know how ( as are most things) but could be daunting to someone with little knowledge and some stripped threads!

There are various kits on the market, Helicoil being the best known (and usually the most expensive). Your local tool store should be able to help or there is always the ubiquitous eBay.
Usually each kit is for a dedicated size of thread.
The threads being renewed here are the 6mm x1mm for the rocker box screws.

OK, HERE WE GO!

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The tools you will need. Thread renewal kit, drill, hammer, tap wrench, small screwdriver, thread lock solution, grease.

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Make sure to cover everything with cloths or paper towels pushed into all the crevices to stop the swarf getting into places it shouldn't.
It still will, so be anal when cleaning up after you have finished the job!

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Check out how deep the drill has to go with the small screwdriver.

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Transfer that dimension to the drill. I used a bit of masking tape ; if you have a drill collar so much the better.

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This is the bit that usually goes wrong so check, check, check again. Borrow a friend's eyes so that you check from the top and they check from the side.
You need to be 90 degrees both ways!

Hold the drill very firmly and use a slow speed because it will likely try to grab!
A dab of grease on the flutes will help lubricate it and also trap some of the swarf.

A good tip. If I'm drilling down an existing hole in a soft metal such as aluminium I dull the cutting edges of the drill with a sharpening stone :-? to reduce the chance of it grabbing (note! Dull not blunt!)

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A little grease on the end of the tap will help lubricate it and trap some of the swarf.

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You'll need you friend again when you go to tap out the hole. Very easy to run off with a tap so make doubly sure it's at 90 degrees.

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Loads of swarf trapped but there will still be more down there. Use the small screwdriver with some grease to remove the rest.

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The new coil is slipped over the installation tool with the coil tang towards the bottom of the tool.

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In this instance we want the top of the coil to be slightly below the surface so the installation tool collar is set as above.

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Put a little thread lock solution in the outside of the coil before inserting it.

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Screw the coil into the hole slowly down to the stop collar.
REMEMBER. YOU CAN SCREW IT IN FURTHER IF NEED BE; YOU CANNOT SCREW IT BACK OUT IF IT'S TOO DEEP!

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Once the coil is in place use the thin metal rod to knock the installation tang off the coil.

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Finally, check that the intended bolt fits the new thread.

Only another seven to do! To give you an idea (admittedly I've done this kind of thing before) all eight were done in about half an hour.

Time for clean-up and the job is done!

Posted: Wed Jun 24, 2009 2:44 pm
by Roady
Most excellent writeup, John.

I haven't had the good fortune to need this on my bike but I'm happy the info is now available.

Suggesting this for ShopTalk.

Posted: Wed Jun 24, 2009 2:46 pm
by CYBORG
VERY WELL DONE. who makes the kit you used. haven't seen those install tools before.

Posted: Wed Jun 24, 2009 6:11 pm
by FirstYearDeek
In the states, you can find them at Fastenal.

-Deek

Posted: Wed Jun 24, 2009 6:27 pm
by sunnbobb
Excellent tutorial!

Posted: Wed Jun 24, 2009 6:39 pm
by sodbuster
Another way to keep the drill bit straight is to use a drill bushing. I made a small fixture to drill two holes into the frame when I mounted my saddle bag brackets. The hole for the bushing was done on a drill press and bushing loctited into place. Drill to bushing I.D. is very close fit and keeps the drill bit straight .... ;)

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Posted: Wed Jun 24, 2009 7:34 pm
by Whiskerfish
Excellent presentation John. It will be a great addition to ShopTalk.

Posted: Wed Jun 24, 2009 10:15 pm
by sodbuster
Oops .... Sorry John, but I should have acknowledged the fact on how well your tutorial was before I added any comments .. :oops:

Great execution and good use of pictures. An inspiration to others on how to make an excellent "How To" post. tumb2

Posted: Thu Jun 25, 2009 11:46 am
by ElPiloto
Well done.

I have 2 suggestions. After cleaning the shavings out of the hole with grease on a probe, I always rinse the grease out with lacquer thinner or acetone before putting the Helicoil in with LocTite.

Also, I have found that heavy duty aluminum foil and masking tape are easier to work with to cover exposed engine parts.

Posted: Thu Jun 25, 2009 12:05 pm
by Old Fogey
ElPiloto wrote:Well done.

I have 2 suggestions. After cleaning the shavings out of the hole with grease on a probe, I always rinse the grease out with lacquer thinner or acetone before putting the Helicoil in with LocTite.

Also, I have found that heavy duty aluminum foil and masking tape are easier to work with to cover exposed engine parts.
Good suggestions EP!

Yeah, I should really have degreased the holes as you say. Even a blast with aerosol carb cleaner will usually do the trick.

And using foil also eliminates the risk of the cloth getting caught up in the drill.

UK supplier for thread repair - KWIKFAST

Posted: Wed Jul 15, 2009 7:42 am
by Bufobufo
I had most of my carb float bowl screws pulled, the last mech must have been heavy handed. I bought an M4 kit the same as shown in Old Fogeys excellent write up from Kwikfast, called ArmaCoil. Go for the Eco kit if you dont want a fancy box.
Make sure you order more inserts as you will need them and their postage charges hurt!
www.qwikfast.co.uk/catalogue/

And look after than drill, mine has escaped to live with all the others and will take ages to find again.

Re: STRIPPED THREAD RENEWAL

Posted: Sun Jan 13, 2013 2:19 pm
by Bobalou
Excellent write up. Hope your around! I do realize this isn't a current post but I thought it is worth the comments. Actually splains well eenuff to make me feel I know how! Good job.
:crosso action1 anim-cheers1

Re: STRIPPED THREAD RENEWAL

Posted: Wed Jan 16, 2013 6:54 pm
by Old Fogey
Bobalou wrote:Excellent write up. Hope your around! I do realize this isn't a current post but I thought it is worth the comments. Actually splains well eenuff to make me feel I know how! Good job.
:crosso action1 anim-cheers1
Thank you! Yeah, still very much a round! But I'm trying to loose the weight! :-D

Re: STRIPPED THREAD RENEWAL

Posted: Thu Jan 17, 2013 12:24 am
by ericheath
Great tutorial, and now to strip this thread, John, what exhaust header do you have on the Wing in the tutorial? I have not seen that on a Wing.

Re: STRIPPED THREAD RENEWAL

Posted: Thu Jan 17, 2013 2:08 am
by Old Fogey
ericheath wrote:Great tutorial, and now to strip this thread, John, what exhaust header do you have on the Wing in the tutorial? I have not seen that on a Wing.
Motad stainless system. You can see it better here.

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