countersunk, internal wrenching, and hex head styles.
MS bolts come in internal wrenching and hex head
styles. Head markings indicate the material of which
standard bolts are made. Head markings may indicate if
the bolt is classified as a close-tolerance bolt. See figure
5-3. Additional information, such as bolt diameter, bolt
length, and grip length, may be obtained from the bolt
part number.
SCREWS
The most common threaded fastener used in
aircraft construction is the screw. The three most used
types are the machine screw, structural screw, and the
self-tapping screw, as shown in figure 5-4. Figure 5-4
also shows the three head slots—straight, Phillips, and
Reed and Prince.
Structural Screws
Structural screws are used for assembly of
structural parts, as are structural bolts. They are made
of alloy steel and are properly heat-treated. Structural
screws have a definite grip length and the same shear
and tensile strengths as the equivalent size bolt. They
differ from structural bolts only in the type of head.
5-3
ANF0503
COUNTERSUNK HEAD BOLT
INTERNAL WRENCHING BOLT
DRILLED HEX HEAD BOLT
CLEVIS BOLT
EYEBOLT
CLOSE
TOLERANCE
(STEEL OR
ALUMINUM
ALLOY)
ALUMINUM
ALLOY
(62,000 P.S.I.)
CORROSION
RESISTANT
STEEL
(125,000 P.S.I.)
STEEL
125,000 P.S.I)
STEEL
(150,000 P.S.I.)
HEAD MARKINGS
Figure 5-3.—Types of bolts and bolt head markings.
ANF0504
MACHINE SCREW
STRUCTURAL SCREW
SELF-TAPPING
SCREW
PHILLIPS HEAD
REED AND
PRICE HEAD
Figure 5-4.—Screws.
