Table 1. Permutations of tested bolt configurations  i Min Max Test \ Bolt / Inserthut Lubrication Tightenvia Samples Cycles / :KiK  ' Bolthead / 9 10 I .18 I .56  i 10 10 I .14 \ .18  i 10 I 10 , .08 , .18 ....................................................... i  ........................................ ................................................................ .............................................................................. ..................................................... ........... j ................................................. i... ........................... .......................... + 4 i + i ............................................................. i ................................................................................. 4 ......................................... ..+ ..................... .i ......................................... + ............................ * ..............  Case 1-1 ~ A286 ' Helicoil I Threads only  Case 1-2 ' A286 , Helicoil  Case2-1 MP35N / Nut ; Threads only  Case2-2 1 MP35N I Nut i Threads only  Case2-3 I MP35N Nut I surfaces of bolt i  Case3-1 , Inconel718 ' Nut I surfaces of nut I  Case3-2 I Inconel718 I Nut I surfaces of nut i  I Threads and faying ' l Bolthead ~ 5 5 / .ll I .14 Case 4-1  Case 4-2 lnconel 718 Helicoil / Threads only I Bolt head / 5 I 5 1 .21 .51 j Threads and faying I Bolt head  / surfaces of bolt i .................................................... .................... ............................................ ....................... .................. ......................................................  ........................................................ ................................................................ ...................................................... ......................... ................................................ ......................... I Nut  / Bolthead I 10 / 10 .23 ; .49 i- _____. i : i 4 i i 4.  2 i i I. + 4 4  ................................................................. ............ ...... ........................... ................................................ ............................ .. ............................................ j + i i 4 4  i i .i I Threads and faying Bolt head ,  ' Threads and faying I 5 ' 10 i .10 ; .21  i Threadsandfaying Nut 141 I 5 ~ .12 .17 ...... ............................................. ........................... ..... .................................................. ................................................................ ....................... ...................................................... ....,  L- ! -. 4 i  Bolt head ~ 4 1 5 / .13 ~ .45  .............................................. ........................... .................................................. ...................... ............................................. ............................... ;---+ .../ ..i. 4 j 4 4  ..................................................... ............................................................. .......................................................................................................................................... ..................... ......................................... ........................... ........ j + ~ i. ...I 4 i  .............................................. ............................. .............. ..................................................... c 4 ................................................................. ?urfaCeS..of.~!t ..................................................... ; i i (.. lnconel 718 1 Helicoil  Test Cases 1-1 and 1-2  Test cases 1-1 and 1-2 compared the effects of lubrication on threads only with lubrication on threads and  faying surface under bolt head for the A286 bolts. Both cases were tightened at the bolt head. Data  indicates that for bolt/insert configurations, lubrication on the faying surfaces under the head of a bolt  significantly reduces the maximum nut factor and the scatter (Figure 1). After 10 cycles, the faying-surface  lubricated bolts had a &, = 0.18 and bin = 0.14, whereas the threads-only lubricated bolts had a  K,,,, = 0.56 and Lin = 0.18. Without lubrication on faying surfaces, increasing bolt cycles also significantly  increases nut factor. This is presumed to be because lack of lubrication on the faying surface induces  wear under the washer, then additional cycles exacerbates the wear increasing the nut factor (Figure 2).  Test Cases 2-1.2-2 and 2-3  Test cases 2-1 and 2-2 compare the affect of tightening the MP35N bolts via nut versus tightening via bolt  head. Both cases had lubrication on the threads only. Bolt tightened tests were significantly higher. After  10 cycles, nut-tightened nut factors were K,, = 0.18 and bin = 0.08. Bolt-tightened nut factors were  K,, = 0.49 and Gin = 0.23. This is an increase of almost 75% (Figure 3).  Test cases 2-2 and 2-3 compared the affects of lubrication on threads only with lubrication on threads and  faying surface under bolt head for the MP35N bolts. Both cases were tightened via bolt head. Data  indicates that for bolts with lubrication applied only to the threads the nut factor will be much higher than  for bolts with lubrication applied to the faying surfaces under the bolt head in addition to threads. After 10  cycles, the threads-only lubricated bolts had a K,, = 0.49 and Lin = 0.23 whereas the faying-surface  lubricated bolts had a Lax = 0.21 and Kmin = 0.1 0. This is an increase of over 100% (Figure 4).  Test Cases 3-1 and 3-2  Test cases 3-1 and 3-2 are a comparison of tightening lnconel bolts via bolt head with tightening via nut.  Both cases had lubrication added to threads and to the faying surfaces at the nut. The bolts tighten via bolt  head had similar nut factors as those tightened via nut for the first cycle, but after just 2 cycles bolt-  tightened cases had significantly higher maximum nut factors. Bolt-tightened cases produced nut factors  of K,, = 0.45 and K,,,,,, = 0.13. Nut-tightened cases produced K,, = 0.17 and Kmin = 0.12 (Figure 5).  Test Cases 4-1 and 4-2  Test cases 4-1 and 4-2 compare the affects of lubrication on threads only with lubrication on threads and  faying surface under bolt head for the lnconel bolts. Both cases were tightened via bolt head. The bolts  that had lubrication both on threads and on faying surface under bolt head had lower nut factors than  those bolts lubricated at threads only. After 5 cycles, the faying-surface lubricated bolts had a K,, = 0.14  and Kmin = 0.1 1 whereas the threads-only lubricated bolts had a K,,, = 0.51 and Kmin = 0.21 (Figure 6).  158