Re: SS thread strength

From: <Christopher>
Date: Sat Feb 03 2007 - 00:27:00 EST

On Feb 2, 2007, at 11:44 AM, jeffrey woolf wrote:

> Can anyone provide reference for the strength of stainless steel
> threads?

You do stainless thread strength calculations the same way you do alloy and carbon steel threads. Tensile stress based on the stress area; shear stress based on the minimum area. I use ASME Section III rules for linear supports which works out to be substantially the same as the AISC allowables for bolting. The allowable tensile stress is UTS/3.33 and the allowable shear stress is 0.62UTS/5 (= UTS/8). These design margins are 60% of the margins for ferritic steel. Combined shear and tension is assessed using an elliptical rule-- SQRT [(ft/Ft)^2 + (fv/Fv)^2] < 1. You can find fomulas for the stress and root areas in Machinery's Handbook.

These rules come from Section III Div 1 NF3324.6 but they're substantially the same as the AISC rules which only cover ferritic steel. In fact the AISC tabular values are different but only because AISC uses different reference areas for stress calculations.

Stainless threads frequently have galling problems--don't try to match equal grades and anti-seize compounds are a must. Be careful to choose the proper compound for your service.

Christopher Wright P.E. |"They couldn't hit an elephant at <a href="/group/PipingDesign/post?postID=YP3m_vksDz8H9d2k4DU9RvJ70c--XP2YY9gGJdcRvxf25KsDd5bWioW-UtKtFxKFmG29hSmOcPjd">chrisw@skypoint.com</a> | this distance" (last words of Gen.

.......................................| John Sedgwick, Spotsylvania

1864)
<a href="http://www.skypoint.com/~chrisw/">http://www.skypoint.com/~chrisw/</a> Received on Sat Feb 03 00:27:00 2007