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Heli coils

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Heli coils

Postby gizmo » Mon May 06, 2024 10:43 am

Are the top two threads on a horncasting deep enough to fit a Heli coil.
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Re: Heli coils

Postby Toddy » Mon May 06, 2024 11:54 am

gizmo wrote:Are the top two threads on a horncasting deep enough to fit a Heli coil.


Yes you can get different length helicoils though
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Re: Heli coils

Postby gizmo » Mon May 06, 2024 3:13 pm

Toddy wrote:
gizmo wrote:Are the top two threads on a horncasting deep enough to fit a Heli coil.


Yes you can get different length helicoils though
Nice one Thanks Toddy. Just ordered some.
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Re: Heli coils

Postby LambrettaMarky » Tue May 07, 2024 10:09 am

Something I tend to do nowadays with any helicoil and especially so when they're into ally, is to soak the helicoil in thread lock (Green, so a strong one) & then run a tap through it when it's had time to dry.

Should last pretty much forever then.

You can also stack them so having shorter ones is generally a good idea as shortening a longer helicoil can leave a sharp edge at the top.
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Re: Heli coils

Postby hullygully » Wed May 08, 2024 10:41 am

Toddy wrote:
gizmo wrote:Are the top two threads on a horncasting deep enough to fit a Heli coil.


Yes you can get different length helicoils though
+1
just done mine with a 5mm long M5 8-)
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Re: Heli coils

Postby Fast n Furious » Wed May 08, 2024 8:40 pm

LambrettaMarky wrote:Something I tend to do nowadays with any helicoil and especially so when they're into ally, is to soak the helicoil in thread lock (Green, so a strong one) & then run a tap through it when it's had time to dry.

Should last pretty much forever then.

You can also stack them so having shorter ones is generally a good idea as shortening a longer helicoil can leave a sharp edge at the top.

Need to be a bit careful about running a tap down the inside of a Helicoil.
You've got 2 very hard materials here. The tap can snatch and bind to the Helicoil usually resulting in dissapointment.
I prefer to use a standard soft screw and run it in and out with some Toothpaste to bed the thread. Sounds a bit unconventional but it works.
if you need to shorten a Helicoil,then I find the slitting disc on a Dremmel works best. Deburring the cut afterwards is paramount. ;)
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Re: Heli coils

Postby LambrettaMarky » Fri May 10, 2024 9:47 pm

We all have our ways. I have found that Helicoils just need a clean through & alignment once inserted which is where the tap has helped me over the years. You're not removing material with the tap, as like you say they are HARD...
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Re: Heli coils

Postby Storkfoot » Sat Nov 07, 2026 8:32 pm

I have just used an 1.25 pitch M8 Helicoil (well, a cheap Chinese version actually) through steel of about 10mm. It seems to have taken pretty well albeit that it is not at 90 degrees precisely.

I have never done one before. My question is related to not using any loctite. In fact, the coil is probably infused with cutting fluid.

The thread won’t be constantly tightened up and released but neither will it not be used.

Does that sound okay to leave as is?
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Re: Heli coils

Postby dickie » Mon Nov 09, 2026 8:04 am

I'd be perfectly happy with that. As long as the parent material is thicker than the helicoil is long, it's got as much hold as it can get. 20mm steel won't be any better than 10mm.
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Re: Heli coils

Postby LambrettaMarky » Mon Nov 09, 2026 12:50 pm

Storkfoot wrote:I have just used an 1.25 pitch M8 Helicoil (well, a cheap Chinese version actually) through steel of about 10mm. It seems to have taken pretty well albeit that it is not at 90 degrees precisely.

I have never done one before. My question is related to not using any loctite. In fact, the coil is probably infused with cutting fluid.

The thread won’t be constantly tightened up and released but neither will it not be used.

Does that sound okay to leave as is?



Paul - the worst that can happen is the helicoil can pull out which is fairly unlikely.. if that does happen then try the loctite trick, failing that leave it be..

Cheers

Mark
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