Helicoil alternative for stripped TA threads?

[peejay4A]

I stumbled across this today. It seems that the smallest Imperial size is 5/16 UNF though.

 

 

https://www.youtube.com/watch?v=UFhzMRmbeCI

[Don H.]

I don't know that offering, but everything I've bought from Würth over the years has been terrific. One of those companies, like 3M, that I take to the bank when they put their name on something.

[stillp]

They go down to 1/4 UNF.

http://www.threadrepairkits.co.uk/timesert%20kits%20for%20sale.htm

 

Pete

[AlanT]

You'll be wanting Mickeystuds for this:

https://flic.kr/p/qTYD2x

 

3/8 UNC one end, 5/16in UNF on the other.

[Stanpartmanpartwolf]

Avoid these things like the plague in safety-critical areas- the inserts only lock in by a few threads at the base.

Never use Time-Serts in trailing arms, 5/16" UNC Helicoils every time.

[AlanT]

Not quite. The original thread is 5/16in UNF. You could fit 5/16in UNF Helicoil.

 

This would mean you drilled out 5/16in clearance. plus a little bit actually, to suit a Helicoil tap.

 

But 5/16 is the tapping size for a 3/8in UNC.

 

Thats why I made the studs with 3/8in one end and 5/16in the other. This isn't convenient from a manufacturing point of view because of the extra ops and the need to waste a bit of stock.

[Matt]

Avoid these things like the plague in safety-critical areas- the inserts only lock in by a few threads at the base.

Never use Time-Serts in trailing arms, 5/16" UNC Helicoils every time.

I agree these only lock on the final few threads at the base but that's how they lock in. How does a helicoil lock in??

[RogerH]

Hi Matt,

the Helicoil is quite clever. The coil is inserted for the full depth of the thread.

When the bolt is inserted into the helicoil and is torqued to whatever level the bolt thread pulls upwards and the angle of the thread (60 degree's or so) pushes the insert outwards into the parent material.

The coil is stainless steel and quite strong.

 

Where an over torqued bolt would pull out of an ali casting thread it would not pull out of the same sized helicoil thread.

 

Thus the 5/16UNF trailing arm stud holes, if fitted with helicoils would be more than strong enough - no need for UNC or 3/8 studs. Honest gov.

 

Roger

Edited August 1, 2015 by RogerH

[Matt]

Hi Roger,

 

Thanks for the explanation, my question was in relation to the statement on the Timesert locking only on the last few threads as in fact the Helicoil doesn't lock in at all it relies on the bolt pulling it up against the thread.

 

I've used both and both have their place, I personally don't like Helicoils where you are removing the bolt on a regular basis as they do tend to come out, Timesert doesn't. On a side note Wurth don't actual own or produce these they just distribute under their banner in many countries.

 

Matt

[Motorsport Mickey]

"Removing bolts on a regular basis" that's just what you won't be doing on the hub fitments for trailing arms.

 

If you are paranoid you'll do it once a year, the rest of us...every couple of years tops to regrease bearings, the Helicoils will be fine (as long as they don't break through the wall thickness of the retaining cast blocks and trailing arm wall) that's where the 3/8th UNC studs with 5/16th UNF hub dimensions come in.

They have the strengths of the larger Helicoil outer diameter but they use a 16 thou on dia smaller dimension to do it, hence less chance of breaking through the wall thickness and no chance at all of the UNC thread form coming loose because it's in the parent metal of the trailing arm...my choice.

 

Mick Richards

[Matt]

"Removing bolts on a regular basis" that's just what you won't be doing on the hub fitments for trailing arms.

If you are paranoid you'll do it once a year, the rest of us...every couple of years tops to regrease bearings, the Helicoils will be fine (as long as they don't break through the wall thickness of the retaining cast blocks and trailing arm wall) that's where the 3/8th UNC studs with 5/16th UNF hub dimensions come in.

They have the strengths of the larger Helicoil outer diameter but they use a 16 thou on dia smaller dimension to do it, hence less chance of breaking through the wall thickness and no chance at all of the UNC thread form coming loose because it's in the parent metal of the trailing arm...my choice.

Mick Richards

Mick,

 

Totally agree, never mentioned I'd want to remove them more than once every 3-4 years just that if you are using Helicoils on a bolt you remove regularly ???? I never implied that it would work or come lose just that they can and do tend to come out with bolts. Having sold both I've seen my fair share.

 

Helicoils are well and truly capable of the job on trailing arms and most other stripped threads, it's all about choice and application.

 

 

Matt

Edited August 1, 2015 by Matt

[RogerH]

Hi Matt,

just to clarify. The helicoil doesn't lock in place due to the coil being pulled up against the parent metal thread - it is forced outwards and becomes truly stuck.

 

As you say there is always the chance it may unscrew - you could simply replace with a new helicoil.

 

Another benefit of the helicoil compared to the other fixings is that they can be stacked on each other to re-thread deep holes.

 

Roger

[stargazergs]

Hi all

 

I agree with Roger, I've been using helicoils of all sizes for industrial repairs across many applications and materials for many years.

 

For those who have never used them before I've only ever had two maybe three fail over the years and is mainly due to not fully tapping the bore to be helicoiled, bottoming out on a blind bore or not adjusting the sliding stop on the inserting tool or maintaining pressure against the helicoil when inserting which stops you expanding the helicoil on insertion. It's also very tempting to twist off the tab but this only burrs the helicoil thread and causes the bolt or stud to sieze on extraction as the sharp end of the twisted off helicoil digs into the stud or bolt. If your kit does'nt come with a punch just use a suitable parallel punch and with a sharp crack punch out the tab and the helicoil will work every time. To remove an installed helicoil all you need is a pick/scriber and a pair of pointed nose pliars. Use the pick to catch the end of the helicoil thread and pull it out of the parent thread and grip with the pliars and pull to remove using a circular action as you unwind the helicoil off the the parent thread.

 

I've tried the early tubular thread inserts with varied success but I've not tried the wurth time sert and would be interested in how they perform in the field.

 

Gavin

[ctc77965o]

As a further vote for helicoils in alloy, all the alloy threads on 60s/70s/80s Rolls Royce cars were helicoiled from New. The helicoil instructions form part of the workshop manual.

[Motorsport Mickey]

Rolls Royce also used the Helicoils in their Eagle range of Truck engines for cylinder head retention, upwards of 450HP.

 

Mick Richards

[tim hunt]

+1 for Helicoils. I inserted all the threads on the TAs on my 4A in 1979 having found that some studs had apparently been

Araldited in place by the PO!

 

Have had no further problems in 36 years despite the hub assemblies having been off several times over the years. It's nice to be able with confidence repeatedly to apply the factory torque of 12-14 lbs ft to the nuts retaining the brake back plate to the TA.

 

Tim