I have an issue with some parts. T

[gearguy]

I have an issue with some parts. The internal thread M14 x 1.5 has been produced with an oversized tap. The pitch diameter results in a 13.71 mm (out by over .5 mm) diameter that tapers down to 13.05 mm. The external thread pitch diameter is ok. I checked a couple of parts, and the thread pullout strength for these parts is approximately 16000 lbs. I checked good parts as well, and their pull out strength was 19000 lbs. My question, is there a relationship between the pullout strength and the torque retention over time? How will this part behave after cycle loading of 50,000 cycles? 1000000 cycles? Thanks for any help.

 

[CoryPad]

It is unlikely that there is a useable correlation between pullout strength and torque retention. As far as long-term durability, I think you have a problem due to the oversized internal threads. A recent article [Engineering Failure Analysis 8 (2001) 49-56] showed problems with static properties of fasteners with non-conforming pitch dimensions, so the cyclic behavior would be even worse. My advice is do not use these suspect parts.

Cory
cpadfield@omnimetalslab.com