MIL-DTL-917F(SH)
3.2.24.11.1 Lockwashers. The following are the preferred, acceptable, and prohibited types of lockwashers
(see 3.2.24.9):
a.
Preferred type Split ring (helical spring) lockwashers.
b. Acceptable type External-tooth lockwashers, preferred for electrical connections, shall be in accordance
with MS35335 tin-brass, copper alloy 425 washers (see 3.12.2.8). Toothed lockwashers may be used where the
weight of the part does not exceed 2 ounces per screw such as a terminal block.
c.
Acceptable type Internal-tooth lockwashers.
External-tooth lockwashers shall be used in order to bite through protective coatings of aluminum parts if they
are to be grounded or electrically bonded through the fastening device. Internal-tooth lockwashers shall be used
instead of external-tooth where warranted for appearance or other special conditions. Where internal-tooth
lockwashers are used, the size of the washer and diameter of the bolt hole shall be so that the teeth make satisfactory
contact.
d.
Prohibited type Serrated lockwashers.
e.
Prohibited type Star lockwashers.
f.
Prohibited type Belleville lockwashers.
g.
Prohibited type Wave lockwashers.
Use of other lockwashers shall obtain NAVSEA approval.
3.2.24.11.2 Flat washers. Flat washers shall be used for the following applications:
a. Between screw heads and soft materials, unless a washer head screw, or similar type that provides a bearing
surface equivalent to the bearing surface of the appropriate flat washer, is being used.
b.
Between a nut or lockwasher and a soft material.
c. Where lockwashers are used for securing a soft material, a flat washer shall be provided to prevent marring
or chipping of the material and the applied protective coating, except in areas where an electrical ground is required.
d. Except where it conflicts with EMI considerations, a flat washer shall be used between an organically
finished material and lockwashers, bolt and screw heads, or nuts. A flat washer shall not be installed between two
soft materials that are current carrying conductors.
3.2.24.12 Lockwire and safety cable. Lockwire (also called safety wire) or safety cable may be used on any
appropriate fasteners (see 3.2.24.8), but any one joint must use one or the other, but not both, in the same joint.
a. Lockwire shall comply with and be installed in accordance with NASM33540. The wire material must
conform to NASM20995, except that aluminum and copper lockwire are not permitted.
b.
Safety cable shall comply with and be installed in accordance with SAE-AS567 and SAE-AS4536.
3.2.24.13 Liquid locking adhesives. Liquid locking adhesives should be of the anaerobic single component
type in accordance with ASTM D5363.
3.2.24.14 Prohibited locking devices. The following locking devices shall not be used:
a.
Nut and jam nut
b.
Clip-on types of nuts
c.
Single-thread engaging nuts formed by stamping a thread-engaging impression in a flat piece of metal
d.
Setscrews
26
For Parts Inquires submit RFQ to Parts Hangar, Inc.
© Copyright 2015 Integrated Publishing, Inc.
A Service Disabled Veteran Owned Small Business