Machinery's Handbook, 31st Edition
SOCKET SET SCREWS
1831
British Standard Hexagon Socket Set Screws.—Metric Series BS 4168:Parts 2, 3, 4, and 5:1994
90 to 120°
90 to 120°
45°**
≈45°**
t
t
≈120°
d f
d z
d f
d z
d
d
2 P Max. Incomplete Thread
2 P Max. Incomplete Thread
l
l
FLAT POINT
CUP POINT
90 to 120°
≈45°**
Slight Radius
t
d f
d p
A slight rounding or countersink at the mouth of the socket is permissible s
z
d
2 P Max. Incomplete Thread
l
DOG POINT 90 to 120°*
t
Cone Angle 90 or 120°***
d
d f
d t
2 P Max. Incomplete Thread
l CONE POINT
ALTERNATE CONE POINT (M6 AND LARGER) *The 120 ° angle is mandatory for short-length screws shown in the Standard. Short-length screws are those whose length is, approximately, equal to the diameter of the screw. **The 45 ° angle applies only to that portion of the point below the root diameter, df , of the thread. ***The cone angle applies only to the portion of the point below the root diameter, df , of the thread and shall be 120 ° for certain short lengths listed in the Standard. All other lengths have a 90 ° cone angle. †The popular length ranges of these set screws are listed in Table 3 . These lengths have been selected from the following nominal lengths: 2, 2.5, 3, 4, 6, 8, 10, 12, 16, 20, 25, 30, 35, 40, 45, 50, 55, and 60 millimeters. Holding Power of Set Screws.— While the amount of power a set screw of given size will transmit without slipping (when used for holding a pulley, gear, or other part from turning relative to a shaft) varies somewhat according to the physical properties of both set screw and shaft and other variable factors, experiments have shown that the safe holding force in pounds for different diameters of set screws should be approximately as follows: For 1 ∕ 4 -inch (6.35 mm) diameter set screws the safe holding force is 100 pounds (445 N), for 3 ∕ 8 -inch (9.5 mm) diameter set screws the safe holding force is 250 pounds (1112 N), for
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