194 and presented elsewhere [10]. All prevailing torque features tested [10] exhibit a decrease in prevailing torque  with reu se with the larges t decrease during first reuse. The effect of seating to preload is a higher loss in  prevailing torque (e.g., 10 to 25% loss during initial use) compared to unseated results.   

In addition to tests performed to assess initial use of anaerobic adhesives to provide prevailing torque type  locking , this paper pr esents results from  tests to assess reuse.  Reuse with and with out adding additional   anaerobic adhesive are tested.  It is found in most cases that reuse with additional ad hesive performs  comparable to the initial use case. The significance of this result is that using anaerobic adhesive to provide  prevailing torque locking may have the added benefit of negligible degradation with reuse due to self -repair  with additional adhesive.  

Test Specimens and Equipment 

Tests were performed using ¼ -28 (M6x1)  threaded fasteners. Three fastener  material s were tested  including plain grade 8, yellow -zinc grade 8, and aerospace A286. Four  low to medium strength anaerobic  adhesives (Loctite 290, Loctite 222MS, Loctite 242, and Loctite 243)  were tested with each of the three  fastener  materials . Unseated assembly conditions were tested for all fastener materials  and adhesive  combinations . Five to ten samples were tested  for each combination of  fastener  material , adhesive and  assembly condition  for a total of 96 samples . Three tests were performed for  each of these samples   including 1) an initial use test, 2) a reuse with no additional adhesive, and 3) a reus e with additional  adhesive. For each of these tests, torque measurements were obtained at multiple removal angles  including  0 (i.e., breakaway), 2- 5, 90, 180, 270 and 360 degrees.    The grade 8 test fasteners have ¼ -28 UNF  (M6x1)  threads and the aerospace A286 test fas teners have  ¼-28 UNJF  (M6x1)  threads. All test nuts are hex nuts and all test washers are flat. Specifications for the  test fasteners are as follows:    1. Plain grade 8:   a. Cap screw: ¼ -28 UNF, 1.25- in length   (M6x1, 31.75 mm)   b. hex nut: ¼ -28 UNF, 0.22- in thickness    (M6x1, 5.6 mm)   c. flat washer: 0.057- in thickness   (1.45 mm)   2. Yellow -zinc plated grade 8 :   a. Cap screw: ¼ -28 UNF, 1.25- in length   (M6x1, 31.75 mm)   b. hex nut: ¼ -28 UNF, 0.22- in thickness    (M6x1, 5.6 mm)   c. flat washer: 0.081- in thickness   (2.06 mm)   3. A286  passivated (aerospace) :   a. NAS1004- 1A cap screw: ¼-28 UNJF, 0.6- in length   (M6x1, 15 mm)   b. hex nut: ¼ -28 UNJF, 0.22- in thickness    (M6x1, 5.6 mm)   c. flat washer: 0.032- in thickness   (0.81 mm)    Four types of anaerobic ad hesive were used in the tests. These were  Loctite 290, 222MS, 242 and 243.  Loctite 290 is a medium strength wicking grade which was found to consistently exceed the specification  required prevailing torque  range of 3.5- 30 in -lb (0.40- 3.4 N -m) for ¼ -28 (M6x 1) fasteners, so limited testing  was performed with this adhesive. The main characteristics  for the other three anaerobic adhesives are as  follows:  

1. Loctite 222MS is low strength and purple in color.   2. Loctite 242 is medium strength and blue in color.   3. Loctit e 243 is med ium strength and blue in color.  It has activator or primer added to provide better  curing and performance with inactive materials such as A286 stainless steel.      Dial torque wrenches were used for measuring the removal and prevailing tor que of  the threaded fasteners.  A torque wrench with a 75 in- lb (8.5 N -m) range and 1 in- lb (0.1 N -m) increments was used for prevailing  torque measurements for both seated and unseated tests.