NPSM Straight Pipe Thread Gage Pitch Diameters

Size
GO Plug Gage Class 2B
NO GO Plug Gage Class 2B
GO Ring Gage Class 2A
NO GO Ring Gage Class 2A
1/8-27
.3736"
.3783"
.3725"
.3689"
1/4-18
.4916"
.4974"
.4903"
.4859"
3/8-18
.6270"
.6329"
.6256"
.6211"
1/2-14
.7784"
.7851"
.7769"
.7718"
3/4-14
.9889"
.9958"
.9873"
.9820"
1-11 1/2
1.2386"
1.2462"
1.2369"
1.2311"
1 1/4-11 1/2
1.5834"
1.5912"
1.5816"
1.5756"
1 1/2-11 1/2
1.8223"
1.8302"
1.8205"
1.8144"
2-11 1/2
2.2963"
2.3044"
2.2944"
2.2882"
2 1/2-8
2.7622"
2.7720"
2.7600"
2.7526"
3-8
3.3885"
3.3984"
3.3862"
3.3786"

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