Steel Threaded insert to housing with internal fastener

[WelshEngineer87]

Hi All,
I have a question regarding using threaded steel inserts into an aluminum housing.

If you have a steel threaded insert which is bolted into an aluminum housing from what i understand this is ok.
However if you then want to tighten a bolt inside an internal thread within the steel insert to hold a part, does this work?

Tightening torque insert to housing = 35Nm
Tightening torque bolt to insert = 22Nm.

I have attached an image to try help explain my question.

Thanks

 

[IRstuff]

?? I don't get it; how is that different than its normal use?



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[TugboatEng]

I would suggest using a thread adhesive on the insert in this case. The grip length is very short.

 

[desertfox]

Hi WelshEngineer87

That looks perfectly fine to me, provided the bolt tension that holds two parts together doesn’t exceed the threaded insert pull out force from the aluminium there should be no problem.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[Jboggs]

The thread inserts I am familiar with (Helicoil, Keenserts, etc.) do not have that flange at the top. I would call that flanged configuration a threaded bushing. I'm not really confident that would work very well.

In my experience, thread inserts are normally used in aluminum for one of two reasons: either the fastener will be repeatedly removed and reinstalled, or it is a critical, high torque connection.

Helicoil (

https://www.stanleyengineeredfastening.com/brands/optia/heli-coil)

inserts are "screwed in" but do not remain in place because a high torque is applied to lock them in place. Rather their shape and the force of compression from installation locks them into place.

Keenserts utilise “keys” which, when installed, give additional positive mechanical lock against rotation and vibration.

Use one of these two options and you should be good.

 

[Tmoose]

Is the bolted part actually clamped against the insert's flange as shown in the sketch?
The details of the insert's external thread runout at the flange, the perpendicularity of the flange's underside, and the hole tapped in the aluminum require close attention.
They all have the potential to cause serious mischief and heart ache. Jamming, fastener loosening and even failure and bolted part distortion come to mind.

I love and trust Helicoils.
But if the specialized flange is not needed, sometimes a mechanically locking insert like a KeenSert is better.