Torquing 300 Series Stainless Steel Bolts

[owlscreech]

The standard torque equation is T=KFD where T = torque, K is the "nut factor," determined experimentally, F is the force (LBS, N) and D = the nominal bolt diameter.

Does anyone have any data/experience with the value of K for 300 series bolt material, e.g., A193-B8? As received values (dry) are in the neighborhood of 0.3. But what is the value when you add a lubricant?

Thanks

 

[MintJulep]

Somewhere in the neighborhood of 0.17 to 0.20 would be considered a "generally accepted" value.

However, as you noted, this should be determined experimentaly for your particular application and lubricant.

Of course, if your application is important you should consider something better than torque control for controlling fastener preload.

 

[Cockroach]

Correct MintJulep, 0.20 although Mark's lists 0.15.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[GregLocock]

If the friction is doing you a favour, use 0.15. If it is working against you, use 0.3. That's steel on steel, not rusted, etc.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[owlscreech]

MintJulep, Cockroach, GregLolock ...Thanks for info. Basically what I thought.