Threaded Fasteners Flashcards
pitch angle for ISO thread and Unified National Thread
60deg
meaning of 1/2-20UNF-3A-LH
1/2 - 1/2 inch nominal size 20 - 20 threads per inch (tpi) UNF - unified national fine thread series, UNC - unified national coarse thread series 3A - class 3 fit LH - left hand thread
AN, NAS & MS meaning
AN - Air force - navy standards
NAS - National aerospace standards
MS - military standards
meaning of AN 4 - 20 A
AN - air force & navy 4 - series no. and diameter (4/16" dia) dash - steel material, DD - aluminium 20 - length (20/8" = 2.5") A - shank not drilled, H - drilled head
meaning of MS 20004 - H9
MS - military standard
20004 - bolt class and dia (1/4” = 4/16” dia)
H - drilled head for safetying
9 - bolt grip length (9/16”)
meaning of NAS 14 4 - 15
NAS - national aerospace standard
14 - series number
4 - bolt diameter (4/16” dia)
15 - bolt grip length (5/16”)
range of thread showing when installing bolt
at least 1 full thread and no more than 3 threads exposed
bolt material identification
- (dash) = corrosion-resistant steel
D - 2017 Al alloy
DD - 2024 Al alloy - or + non-corrosion resistant steel
bolt head thickness purposes
thick bolt head for tension loading
thin bolt head for shear loading
What nut is used for low temp area
elastic stop nut (self locking nut)
what nut is used for high temp areas
metal locknuts (self locking nuts)
purpose of washers
adjust grip length, distribute bearing load, prevent material corrosion
maximum no. of washers used on 1 fastener
3 (1 below bolt head, 2 above nut)
which washer eliminates the need of torque wrench?
pre-load indicating washer
what bolts are used in excessive vibration or stress reversal areas?
close-tolerance bolts
