[R-390] R390/URR and R390A/URR clamp screw torque

[Jim Whartenby]

NASA torque spec covering different thread materials from aluminum to stainless steel.  Several hundred pages which should hopefully satisfy everyone!

https://ntrs.nasa.gov/api/citations/20170003491/downloads/20170003491.pdf

Jim


Logic is a systematic method of coming to the wrong conclusion with confidence.  Murphy 

    On Friday, July 24, 2026 at 02:58:04 PM CDT, Perry Sandeen via R-390 <r-390 at mailman.qth.net> wrote:   

 List,
I was trained on the R390A in USAF tech school in 1963. There was no training or information given about clamp torque.
However list member Glen Scott who has done total remand (including complete panel restoration) of the R390A for years as a living, posted on this list his experience.  It involved using a torque screwdriver and the value he found optimum for no slippage or clamp  breakage.
I don't remember when it was posted so if someone would re-posit it, it should provide the necessary information needed.
73,
Perry KM6FQV


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