nut factor

huangyhg

nut factor
sirs,
does anyone know of a reliable source of information for the "nut factor" or coefficient of friction between silver plated bolts and an austenitic stainless steel part?  closest references i have been able to find are on the order of 0.4, between silver and steel.(details of materials unspecified)
mikemkc
i checked my references and no luck.  try the gear people since they use silver as a anti-gaulling coating for steel.
try mil-hdbk-60, 1990,
a 鈥渘ut factor鈥?answer may be more than adequate for your application.  however, depending on the degree of accuracy/certainty you need to establish your fastener tension values, approach "nut factor" usage with great caution.  the reported ranges, and the ranges of those ranges, vary widely from publication to publication.  almost all of these lists (the responsible, enlightened ones) will emphasize their "reference" nature, and contain strong cautions regarding their use in a particular application without empirical verification (torque/tension testing).   
a good discussion of nut factor, including some of its limitations and variables, can be found at
good catch, kenneth.  i should have clarified my post as follows.
thanks for the kind words vonlueke.  i guess i should have clarified as follows:
i was unable to see how (using mil-hdbk-60, 1990, sect. 100.5, p. 26, eq. 100.5) one could calculate a "nut factor" (even if mu1 = mu2 is assumed) with the information given.  the mil-hdbk-60 torque/tension equation(s) contain(s) variables that i didn't see anywhere in the thread: "l" or lead of the thread helix in inches; either the fastener nominal ("d") or pitch ("d2") diameter; and (if not assumed) the "washer," or "bearing face", diameter ("b").
my fault, kenneth, and good point.  i was too cryptic and didn't fully state my derivation and assumptions, as follows.  using mil-hdbk-60, eq. 100.5 (shigley eq. 8-19 gives almost exactly the same answer), and using the assumptions stated on the cited page numbers, namely dw = 1.5d and mu2 = mu1, where dw = washer face od and d = bolt nominal diameter, then for mu1 = 0.14 from the cited table (no wax), the mean k value for typical bolt sizes (4 to 12.7 mm), metric and imperial, coarse and fine-pitch, is mean1 = 0.185, with standard deviation s = 0.0032.  this is mean of 17 bolt sizes and pitches analyzed.
similarly, for all bolts (d = 1.6 to 38 mm), metric and imperial, coarse and fine-pitch, 76 bolt sizes and pitches analyzed, the mean value is mean2 = 0.183.  i of course placed more emphasis on the most commonly used bolt sizes (for posted ae or me application), and therefore reported mean1, not mean2.
as an example, evaluating eq. 100.5 for m8 x 1.25 mm bolt, for dw = 1.5d and mu1 = mu2 = 0.14, gives k = (0.1989 + 0.5810 + 0.7000)/8.00 = 0.1850.  of course the engineer must understand that using theoretical equations and typical values from the cited references merely gives an estimate, and that if a more accurate answer is needed, one should measure the installed fastener with a micrometer and compute torque coefficient k = t*l/(e*a*delta*d), per shigley, p. 345, para. 2, to test specific combinations and lubricants, where t = installation torque, l = bolt grip length, e = bolt modulus of elasticity, a = bolt cross-sectional area, and delta = measured bolt elongation in units of length.
any insight into how much of that wax typically comes on say an ms21043-4 nut, and what it typically lowers the above mu1 value to, assuming say an nas1004 bolt?  thanks.