Thread Failure in Aluminum Casting

[Pedee68]

What the common failure modes for an aluminum casting where threads fail during assembly of bolt. The failure is stripped threads causing the bolt to not engage during assembly. Casting is A304 alloy with threads for M5 bolt. The torque value is 5.5 Nm.

Looking for areas to investigate either the casting, bolt or torque process.

 

[GregLocock]

Inadequate thread engagement

Galling

Clumsy operators

Poor tapping technique

 

[MintJulep]

Off hand, that seems like a pretty high torque for tapped threads in a relatively weak grade aluminum casting.

Look at the stress in the female threads. Consider all the variability associated with torque-controlled tightening.

 

[mfgenggear]

OP
Threads in aluminum is not good practice.
Inserts are a better option.
If the threads seize it will strip out easily.
Over torque strip out.
Cross thread strip out
And more.

 

[JohnRBaker]

I agree, a threaded insert would seem to be the best way to go.

 

[waross]

https://www.stanleyengineeredfastening.com/en/brands/Optia/heli-coil

Heli-Coil®​

The Heli-Coil® portfolio of wire threaded inserts includes offerings of a variety of configurations whether it be plating, material, locking, or non-locking variants that make it fully adaptable and configurable for industries spanning automotive, industrial, aerospace, and defense. There is a strong industry trend toward the lightweighting of materials, yet achieving structural integrity of bolted or fastened joints. Heli-Coil® by nature of its design is an ideal solution to be incorporated as part of these assemblies.

https://www.boellhoff.com/ca-en/products/special-fasteners/helicoil-thread-inserts-for-metals/

 

[waross]

AI Overview
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The German company Böllhoff Grouphas owned the Heli-Coil trademark since October 1, 2021. Böllhoff acquired the trademark from Stanley Engineered Fastening.



The Heli-Coil thread insert was originally patented in the United States in 1938. Josef Böllhoff licensed the production and sale of Heli-Coil thread inserts in 1954.