Machinery's Handbook, 31st Edition
Dryseal Pipe Threads 2097 For more complete specifications for production and acceptance of Dryseal pipe threads, see ANSI/ASME B1.20.3 (Inch) and ANSI/ASME B1.20.4 (Withdrawn) (Metric Translation), and for gaging and inspection, see ANSI/ASME B1.20.5 (Inch) and ANSI/ ASME B1.20.6M (Withdrawn) (Metric Translation). Designation of Dryseal Pipe Threads: The standard Dryseal pipe threads are designated by specifying in sequence nominal size, thread series symbol, and class: Examples: 1 ⁄ 8 -27 NPTF-1; 1 ⁄ 8 -27 PTF-SAE SHORT; and 3 ∕ 8 -18 NPTF-1 AFTER PLATING. Table 8. Suggested Tap Drill Sizes for Internal Dryseal Pipe Threads
L 3
L 1
Hand Engagement
Internal Thread
Col 4 Diam.
Col 3 Diam.
Taper Pipe Thread
Straight Pipe Thread
Minor Diameter
Minor Diameter At Distance
Drill Size a
Probable Drill Oversize Cut (Mean)
L 1 + L 3 From Large End
L 1 From Large End
Without Reamer
With Reamer
Drill Size a
Size
NPSF NPSI
“A” (0.234) 21 ∕ 64 (0.328) 27 ∕ 64 (0.422) 9 ∕ 16 (0.563) 11 ∕ 16 (0.688) 57 ∕ 64 (0.891) 1 1 ∕ 8 (1.125)
0.2482 0.2505 “D” (0.246) 0.3406 0.3429 “R” (0.339)
1 ∕ 16 -27 0.0038 0.2443 0.2374 “C” (0.242)
0.0044 0.3367 0.3298 “Q” (0.332)
1 ∕ 8 -27 1 ∕ 4 -18 3 ∕ 8 -18 1 ∕ 2 -14 3 ∕ 4 -14 1-11 1 ∕ 2
0.0047 0.4362 0.4258 0.0049 0.5708 0.5604 0.0051 0.7034 0.6901 0.0060 0.9127 0.8993
0.4422 0.4457 0.5776 0.5811 0.7133 0.7180 0.9238 0.9283
7 ∕ 16 (0.438) 9 ∕ 16 (0.562) 45 ∕ 64 (0.703) 29 ∕ 32 (0.906)
7 ∕ 16 (0.438) 37 ∕ 64 (0.578) 45 ∕ 64 (0.703) 59 ∕ 64 (0.922)
1.1600 1.1655 1 5 ∕ 32 (1.156)
0.0080 1.1470 1.1307 1 9 ∕ 64 (1.141)
… … … … … … … … … … … … … … …
0.0100 1.4905 1.4742 1 31 ∕ 64 (1.484) 1 15 ∕ 32 (1.469) 0.0120 1.7295 1.7132 1 23 ∕ 32 (1.719) 1 45 ∕ 64 (1.703) 0.0160 2.2024 2.1861 2 3 ∕ 16 (2.188) 2 11 ∕ 64 (2.172) 0.0180 2.6234 2.6000 2 39 ∕ 64 (2.609) 2 37 ∕ 64 (2.578) 0.0200 3.2445 3.2211 3 15 ∕ 64 (3.234) 3 13 ∕ 64 (3.203)
1 1 ∕ 4 -11 1 ∕ 2 1 1 ∕ 2 -11 1 ∕ 2
2-11 1 ∕ 2 2 1 ∕ 2 -8
3-8
a Some drill sizes listed may not be standard drills. All dimensions are given in inches.
Special Dryseal Threads.— Where design limitations, economy of material, permanent installation, or other limiting conditions prevail, consideration may be given to using a special Dryseal thread series. Dryseal Special Short Taper Pipe Thread, PTF-SPL SHORT: Threads of this series con form in all respects to PTF-SAE SHORT threads except that the full thread length has been further shortened by eliminating one thread at the small end of internal threads or one thread at the large end of external threads.
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