Machinery's Handbook, 31st Edition
SPARK PLUG THREADS
2113
SAE Standard Threads for Spark Plugs SAE Standard Threads for Spark Plugs (Continued)
Major Diameter
Pitch Diameter
Minor Diameter
Size a Nom. × Pitch
Max.
Min.
Max.
Min.
Max.
Min.
Tapped Hole Threads, mm (inches)
… 18.039 … (0.7102) … 14.034 … (0.5525) … 12.000 … (0.4724) … 10.000 … (0.3937)
17.153 (0.6753) 13.297 (0.5235) 11.242 (0.4426)
17.026 (0.6703) 13.188 (0.5192) 11.188 (0.4405)
16.426 (0.6467) 12.692 (0.4997) 10.559 (0.4157)
16.266 (0.6404) 12.499 (0.4921) 10.366 (0.4081)
M18 × 1.5
M14 × 1.25
M12 × 1.25
9.500
9.350
9.153
8.917
M10 × 1.0
(0.3740)
(0.3681)
(0,3604)
(0.3511)
a M14 and M18 are preferred for new applications. In order to keep the wear on the threading tools within permissible limits, the threads in the spark plug GO (ring) gage shall be truncated to the maximum minor diameter of the spark plug, and in the tapped hole GO (plug) gage to the minimum major diameter of the tapped hole. The plain plug gage for checking the minor diameter of the tapped hole shall be the minimum specified. The thread form is that of the ISO metric (see page 2046). Reprinted with permission © 1990 Society of Automotive Engineers, Inc. Lamp Base and Electrical Fixture Threads Lamp Base and Socket Shell Threads.— The “American Standard” threads for lamp base and socket shells are sponsored by the American Society of Mechanical Engineers, the National Electrical Manufacturers’ Association and by most of the large manufacturers of products requiring rolled threads on sheet metal shells or parts, such as lamp bases, fuse plugs, attachment plugs, etc. There are five sizes, designated as the “miniature size,” the “candelabra size,” the “intermediate size,” the “medium size” and the “mogul size.” Rolled Threads for Screw Shells of Electric Sockets and Lamp Bases—American Standard P
R
D
R
R
R
b B
A a
Male or Base Screw Shells Before Assembly
Major Dia.
Minor Diam.
Radius Crest Root R
Threads per Inch
Depth of Thread D
Pitch P
Max. A
Min. a 0.370 0.460 0.645 1.031 1.545
Max. B
Min. b 0.330 0.410 0.591 0.965 1.445
Size
Miniature Candelabra Intermediate
14 10
0.07143 0.020 0.10000 0.025 0.14286 0.033 0.25000 0.050 0.11111 0.027 0.07143 0.020 0.10000 0.025 0.14286 0.033 0.25000 0.050 0.11111 0.027
0.0210 0.0312 0.0353 0.0470 0.0906 0.0210 0.0312 0.0353 0.0470 0.0906
0.375 0.465 0.651 1.037 1.555 0.476 0.664 1.053 1.577
0.335 0.415 0.597 0.971 1.455 0.426 0.610 0.987 1.477
9 7 4
Medium Mogul
Socket Screw Shells Before Assembly
Miniature Candelabra Intermediate
14 10
0.3835 0.3775 0.3435 0.3375
0.470 0.657 1.045 1.565
0.420 0.603 0.979 1.465
9 7 4
Medium Mogul
All dimensions are in inches.
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