Welded or heli coil?

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jedan71
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Thu Sep 25, 2014 11:22 am

My spare S3 150 block threads are all good, but in the process of cleaning it, I thought I would heli coil all the threads to prevent future issues.
As I was under the impression, from having worked in a place with metalsmiths before, that a heli coil is stronger than the original thread.

Can anyone shed some more light on this topic before I create problems?:oops:

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sean brady scooters
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Thu Sep 25, 2014 11:36 am

if it aint broken ,dont fix it as they say !
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YAMLAM
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Thu Sep 25, 2014 11:48 am

motor racing development ( Brabham racing ) used to buy hundreds of helicoils from me when i worked for an engineers merchant . I asked the buyer what they did with them, he said they used to helicoil every thread in their engines, as they were harder to strip than Ali threads. this was 35+ years ago so things may have changed
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sean brady scooters
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Thu Sep 25, 2014 12:06 pm

if you really want to do them then I would recommend "time serts"
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10 inch Terror
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Thu Sep 25, 2014 1:10 pm

sean brady scooters wrote:if you really want to do them then I would recommend "time serts"
I use these when I drill GP side casings and fit a kickstart ramp. They are very easy to use and very strong. I've also used them with good results in the stud holes where a JL or NK rear bracket fits to prevent the threads stripping.

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TheSeeker
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Thu Sep 25, 2014 1:53 pm

I've used Helicoil on chaincase studs (exhaust & normal studs) and they appear to be ok. It was V-Coil sets from eBay. Much cheaper than Wurth Time Serts which you have to buy in quite large volumes and are really expensive (see this months Scootering with an interview with Sam from LambrettaFinder.be)

Image

I read somewhere that you should not use Loctite on the coil itself as the steel of the coil will "bond" with the alloy of the case (like an alloy wheel gets stuck to the steel hub of a car). Then use Loctite on the stud.

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Ben

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monument7
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Thu Sep 25, 2014 1:59 pm

YAMLAM wrote:motor racing development ( Brabham racing ) used to buy hundreds of helicoils from me when i worked for an engineers merchant . I asked the buyer what they did with them, he said they used to helicoil every thread in their engines, as they were harder to strip than Ali threads. this was 35+ years ago so things may have changed
I would have thought this was down to the frequent stripping down of the engines more than anything else but could be wrong :roll:

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Thu Sep 25, 2014 8:19 pm

jedan71 wrote:My spare S3 150 block threads are all good, but in the process of cleaning it, I thought I would heli coil all the threads to prevent future issues.
As I was under the impression, from having worked in a place with metalsmiths before, that a heli coil is stronger than the original thread.

Can anyone shed some more light on this topic before I create problems?:oops:

there isn't a lot of metal around some of those stud holes. If you heli/perma coil them it will only make it thinner there.

Yes the coil is stronger then the aluminium but how often are you pulling the studs out? Even running bolts on the case cover is fine as long as the threads are clean with no gasket glue in them.

To coil every hole correctly (16 6mm, 4 or 5 8mm, 7 5mm, 6 7mm for the gear box) would take you at least most of the day. Providing of course you didn't run one in at an angle, break a tap or break the tool.

You're creating a lot of extra work for little return.

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Thu Sep 25, 2014 9:02 pm

Plug tap all holes clean out fit GOOD quality studs and errr forget just dont use a half inch drive to tighen 6mm nuts
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Muttley McLadd
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Thu Sep 25, 2014 9:13 pm

monument7 wrote: I would have thought this was down to the frequent stripping down of the engines more than anything else but could be wrong :roll:
Ideal for scooters then, really :)
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