General Pipe Threads
American National General Pipe Threads (USCTI Table 357)
Crest and root limits for American National Standard External and Internal Taper Pipe Thread (NPT)
Height Pipe Thread Max (inch)
H
Height Sharp V Thread (inch)
Equivalent Width of Flat (inch)
Truncation (inch)
Threads Per Inch
The limits specified above are intended to serve as a guide for establishing limits for the thread elements of taps, dies, and thread chasers. These limits may be required on the product. For complete specifications see latest edition of USE Standard B2.1. The Military Aeronautical Specification MIL-P- 7105 agrees with all values given in this table. Max. 27 0.03208 0.02963 0.0012 0.0036 0.0014 0.0041 18 0.04811 0.04444 0.0018 0.0049 0.0021 0.0057 14 0.06186 0.05714 0.0024 0.0056 0.0027 0.0064 11 1/2 0.07531 0.06957 0.0029 0.0063 0.0033 0.0073 8 0.10825 0.10000 0.0041 0.0078 0.0048 0.0090 H h Min Max. Min.
h
Dryseal American National Standard Pipe Threads
Crest and root limits for Dryseal American National Standard External and Internal Pipe Threads (NPTF)
Height Sharp V Thread (inch)
Truncation (inch)
Equivalent Width of Flat (inch)
Threads Per Inch
H
Min Max.
Min.
Max.
Crest Root Crest Root Crest Root Crest Root Crest Root
0.0017 0.0035 0.0020 0.0040 0.0035 0.0052 0.0040 0.0060 0.0026 0.0043 0.0030 0.0050 0.0043 0.0061 0.0050 0.0070 0.0026 0.0043 0.0030 0.0050 0.0043 0.0061 0.0050 0.0070 0.0035 0.0052 0.0040 0.0060 0.0052 0.0078 0.0060 0.0090 0.0052 0.0069 0.0060 0.0080 0.0069 0.0095 0.0080 0.0110
27
0.03208
18
0.04811
14
0.06186
11 1/2
0.07531
8
0.10825
The major diameter of standard taper pipe plug gages and the minor diameter of standard taper pipe ring gages used for gaging dryseal threads will be truncated .20p minimum to .25p maximum for all pitches.
Threading Technical
780
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