Hardware Structural Analysis
Preferred Torque Callouts
The information contained herein is based
on 50% ultimate tensile strength of series 300 CRES@80 KSI and A286 CRES@160
KSI, published tensile area for each screw size and pitch, and Shigley's
5T/D relationship. Here's a link to another
user friendly torque chart.
Screw Size Torque +/- 10 %
300 Series CRES A286 CRES
(@80 KSI) (@ 160 KSI)
#0(.060) -80UNF 14.0 in-oz --------
#1(.073) -72UNF --------- 26.0 in-oz
#2(.086) -56UNC 2.5 in-lb 5.1 in-lb
#4(.112) -40UNC 5.4 in-lb 10.8 in-lb
#6(.138) -32UNC 10.0 in-lb 20.1 in-lb
#8(.164) -32UNC 18.4 in-lb 36.7 in-lb
#10(.190) -32UNF 30.4 in-lb 60.8 in-lb
*1/4(.250) -20UNC 63.6 in-lb 127.0 in-lb
1/4(.250) -28UNC 72.8 in-lb 146.0 in-lb
*5/16(.312)-18UNC 131.0 in-lb 262.0 in-lb
5/16(.312)-24UNF 145.0 in-lb 290.0 in-lb
*3/8(.375) -16UNC 232.0 in-lb 465.0 in-lb
3/8(.375) -24UNF 263.0 in-lb 527.0 in-lb
* non preferred pitch sizes.
If your using self-locking
screws and/or nuts you should add, "above prevailing torque", to your torque
note. Example: TORQUE 5.4 PLUS OR MINUS .6 IN LBS, ABOVE PREVAILING TORQUE. See
Figure 1 below, for some simple calculations relating to this.
Optimum Lug Design Utilizes the E/D Relationship
Normally, 1 1/2 D is adequate structurally. See
Figure 2, below.
