Heli-Coil question

I was looking at another thread about tapping aluminum, and this thought popped into my head that I had never really considered before.

Is a Heli-Coil as strong as a threaded hole without the insert? I was always under the assumption that they were ok, if anything they add durability. I'm curious to know the HAMBers' thoughts on this.

I try to use studs in aluminum wherever possible, especially in places like headers and valve covers, where bolts are constantly in and out.

 

Done properly, a Heli-Coil is stronger because it is larger than the bolt or stud, therefore it has more contact area with the part it's in.

 

As noted above, a Heli-Coil is stronger and that is by a wide margin. They were developed for the radial aircraft engines when the HP and RPM started climbing...the engines would pull every fastener out with alarming regularity.

 

Don't know what your part is but do a search on Timesert. They use a STI tap just like a Helicoil but are solid inserts. They are far better IMO.

 

"As noted above, a Heli-Coil is stronger and that is by a wide margin. They were developed for the radial aircraft engines when the HP and RPM started climbing...the engines would pull every fastener out with alarming regularity. "

I served my machinist apprenticeship at NAS Alameda Back in the days of R3350 Radial engines. the 3350 stands for HP. used lots of Helicoils.
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Helicoils are better than inserts where the boss in the parent material is small in diameter, like in many aluminum castings. The inserts are bigger, resulting in too much metal removal. Other than that case, the inserts are of course stronger, but how much strength do you need? The original threads were almost adequate, obviously, and the Helicoil improves on that many times over, and are easily installed and readily available.

 

TomWar....Actually the "3350"in the engine designation indicates the cubic inch displacement, not the HP.













'

 

Yup, your correction is....well, correct.
3350 cu. in. and LOUD!!
SWEET!!
Jets are for kids

 

Not 3350hp but 3800hp

 

I don't know that a heli coil is stronger than a cut thread or not. It depends a lot on the type of aluminum if the threads were cut properly etc.

A lot of guys use them as have I. I try not to use one where the bolt will be in and out a lot. If at all possible I use a Keen-Sert (I think that is a tradmark) it is a solid insert as opposed to the spring like heli coil. Threaded inside and out. The down side is that it cannot be used where you don't have a lot of meat to work with.

I have a pair of aluminum heads that came from the factory with Keen-Serts in the spark plug holes. Te are not steel inserts cast in. I called the company and asked them to be sure. Yes indeed that can be replaced if stripped.