1/16-27 NPT NPT (taper pipe thread) External Thread Specifications

1/16-27 NPT · 0.0625-27 NPT

ASMESTD: ASME B1.20.1SOURCE: Table 2 · p. 9TYPE: External (bolt/screw)CLASS: —SERIES: NPT (taper pipe thread)TAPER 1:16
Major diameter
0.31312 – 0.30383
max – min, at the gage plane
Pitch diameter
0.28349 – 0.27887
max – min, at the gage plane
Minor diameter
0.25853 – 0.24924
max – min, at the gage plane
Pitch
0.03704
27 threads per inch

Thread profile

gage plane: hand-tight, L1 from small endthread axisD1 = 0.3131–0.3038major dia (crest)E1 = 0.28349–0.27887pitch dia, basic 0.28118K1 = 0.2585–0.2492minor dia (root)P = 0.0370460°⟂ axis30°crest flat = 0.0014–0.0041crest truncation 0.0012–0.0036root flat = 0.0014–0.0041root truncation 0.0012–0.0036H0.032075h0.029630 max0.024960 mintaper 1:16 on dia (1:32 on radius) · β = 1° 47′ 24″, included 2β = 3° 34′ 47″ · bisector ⟂ axisexternal thread (male)

External profile over three pitches at the gage plane, drawn at maximum material (sharpest crest, flattest root); hatched bands are the truncation zones. Diameters shortened.

Thread length, taper and gage planes

plane 0 · E00.27118plane 1 · E10.28118plane 2 · E20.28750pipe OD D 0.3125MALE · 1/16-27 NPTtrue scale (lengths and diameters); axis below, not drawnL1 0.1600 (4.32 thd)full thread 0.2611 (7.05 thd)V 0.1285

Lengths, taper and gage planes to scale; diameters shortened. D and K at the planes are calculated with the mean truncations.

Limits of size, class —

DimensionBasicMaxMinTolerance
Major diameter D1Crest of the external thread at the gage plane0.313120.303830.00929
Pitch diameter E1Gage plane E1: L1 from the small end (external) or at the large end of the fitting (internal); gaging tolerance converted to diameter0.281180.283490.278870.00462
Minor diameter K1Root of the external thread at the gage plane0.258530.249240.00929
Allowance esNone: taper threads are made up to interference (NPT/NPTR); NPSC uses sealant—
Crest truncation fcTable 1 (both threads)0.0035560.001222
Root truncation frTable 1 (both threads)0.0035560.001222
Crest flat FcEquivalent width of flat0.0041110.001407
Root flat FrEquivalent width of flat0.0041110.001407

Dimensions in inches. Values are those of the standard (ASME B1.20.1); calculated cells follow the standard’s formulas. Where the standard prints a value that differs from its formula, the printed value is shown with a note.

Taper, lengths and gaging

Taper, gage and sealing paras. 3, 5; Tables 1, 3

Taper on the diameter T
1 in 16 (0.75 in./ft)
Half apex angle of the pitch cone β
1.789911 °
Taper tolerance on the diameter, max / min
0.1250 / -0.0625 in/ft
Lead tolerance in the effective length ±
0.003 in
60° angle tolerance ±
2.5 °
Lead angle at the basic PD λ
2° 24′
Gaging method
L1 ring gage (external) / L1 plug gage (internal), or L1 indicating gage (para. 3.2)
Gaging tolerance
±1 turn
Gaging position
Small end of pipe flush with small end of ring
Sealing
Pressure-tight: wrench-tight with sealant (para. 1.4)

Basic pitch diameters and lengths Table 3

Pitch dia at the small end of the external thread E0
0.27118 in
Hand-tight engagement L1
0.1600 · 4.32 in, threads
Pitch dia at the hand-tight plane E1
0.28118 in
Effective external thread L2
0.2611 · 7.05 in, threads
Pitch dia at L2 E2
0.28750 in
Wrench make-up length L3
0.1111 · 3 in, threads
Pitch dia at the wrench make-up plane E3
0.26424 in
Complete external threads L5
0.1870 in
Pitch dia at L5 E5
0.28287 in
Vanish thread V
0.1285 · 3.47 in, threads
Overall external thread length L4
0.3896 in
Basic minor dia at the small end K0
0.2415 informula gives 0.2416
Change of diameter per turn
0.00231 in
Hand-tight engagement range, ± 1 turn
0.0859 – 0.2341 in
Wrench make-up interference on the PD
0.00694 in
Hand-tight plus wrench make-up length L1+L3
0.2711 in

L1 plug and ring gages Tables 8 and 9

Plug gage major dia at the E0 plane
0.29289 in
Plug gage major dia at the gaging notch (E1)
0.30289 in
Plug gage major dia at the large end (E2)
0.30920 in
Gage pitch dia at the E0 plane
0.27118 in
Gage pitch dia at the gaging notch (E1)
0.28118 in
Gage pitch dia at the large end (E2)
0.28750 in
Ring gage minor dia at the E0 plane
0.24948 in
Ring gage minor dia at the gaging notch (E1)
0.25948 in
Thickness of the L1 ring or gage elements
0.1600 in
Working gage crest truncation
0.005185 in
Maximum standoff between plug and ring gages
0.032 in

Working gage tolerances Table 7

On the pitch diameter ±
0.0002 in
Lead, plugs / rings
0.0002 / 0.0003 in
Half angle ±, plugs / rings
15 / 20 min
Taper, plugs / rings
0.0003 / 0.0006 in
Major dia of plugs
0.0004 in
Minor dia of rings
0.0004 in
Total cumulative tolerance on the PD, plugs / rings
0.00080 / 0.00118 in

Notes

  • Table 2 Notes: L1 is also the length of the L1 ring gage and the distance from the gaging notch to the small end of the L1 plug; E1 is also the PD at the gaging notch of the L1 plug; L2 is also the threaded length of the L1 plug; L4 is a reference dimension; L5 = L2 − 2P (the next two threads are complete at the root); K0 is given for selecting tap drills (Appendix B). Gaging: ±1 turn from basic (Fig. 4 / Fig. 6); with indicating gages ±0.0625/n on diameter (paras. 3.2.1.2, 3.2.2.2). The gaging tolerance can lengthen or shorten engagement by up to two turns; gage wear reduces it further (para. 3.1.9.1). Diameter limits here are calculated at the gage plane (E1 ± 0.0625/n on PD; major and minor add the Table 1 truncation limits). The standard itself tabulates basic dimensions only. Chamfer: external threads with chamfer smaller than the minor dia are gaged from the last scratch of the chamfer cone (para. 3.2.4.1, Fig. 5); otherwise from the end of the pipe (para. 3.2.4.3).
  • K0 (col. 24): printed 0.2415, formula 0.2416 (1 in last place, rounding)

Mates

1/16-27 NPT screws into a thread of the same standard at the same size and pitch. The standard mating internal thread is class Std. Check the fit with the standard pair →

Working out the mating options…

Different pitch or a different thread family never mate; the fit check runs over both tolerance zones.

Related thread sizes

Same diameter other pitch, and neighbouring sizes

→ 1/8-27 NPT→ 1/16-27 NPT internal
All values for 1/16-27 NPTevery column of the workbook row
All values of the workbook row 1/16-27 NPT
Designation1/16-27 NPT
Decimal designation0.0625-27 NPT
Threads per inch27
Thread formTaper
SeriesNPT
Series nameAmerican National Standard Taper Pipe Thread
External / internalExternal
Class—
Nominal pipe size1/16
Pitch P (in.)0.03703704
O.D. of pipe D, basic major dia (in.)0.3125
Size category (Table 3 group)1/16, 1/8 (27 TPI)
Source tableTable 2
Printed page9
Where the diameter limits applyGage plane E1: L1 from the small end (external) or at the large end of the fitting (internal); gaging tolerance converted to diameter
Major dia max (in.)0.31312
Major dia min (in.)0.30383
Major dia tolerance (in.)0.00929
Major dia statusCalculated at the gage plane: PD limits with Table 1 truncation limits (para. 2.4)
Basic pitch dia at gage plane E1 (in.)0.28118
Pitch dia max (in.)0.28349
Pitch dia min (in.)0.27887
PD tolerance (in.)0.00462
Minor dia max (in.)0.25853
Minor dia min (in.)0.24924
Minor dia tolerance (in.)0.00929
Minor dia statusCalculated at the gage plane: PD limits with Table 1 truncation limits (para. 2.4)
Allowance sourceNone: taper threads are made up to interference (NPT/NPTR); NPSC uses sealant
Root radius max (in.)not given in the standard
Root radius min (in.)not given in the standard
Lead tolerance ± in effective length (in.)0.003
60° angle tolerance ± (deg)2.5
Taper tolerance max (in./ft)0.1250
Taper tolerance min (in./ft)-0.0625
Lead / angle / taper sourceTable 3, p. 10
Lead angle at basic PD (deg)2.400879
Lead angle (deg min)2° 24′
Tensile stress area As (sq in.)not given in the standard
Thread angle (deg)60
Flank angle (deg)30
Sharp V height H (in.)0.0320750
Thread height h max (in.)0.02963
Thread height h min (in.)0.02496
Crest truncation min (in.)0.001222
Crest truncation max (in.)0.003556
Root truncation min (in.)0.001222
Root truncation max (in.)0.003556
Crest flat min (in.)0.001407
Crest flat max (in.)0.004111
Root flat min (in.)0.001407
Root flat max (in.)0.004111
Sweep cut: start diameter (in.)0.30081
Sweep cut: tip diameter (in.)0.24155
Sweep cut: depth (in.)0.029630
Sweep cut: profile width at start diameter (in.)0.035630
Sweep cut: tip flat (in.)0.001407
Sweep cut: start diameter isMajor dia at the small end (E0 plane), basic position; the blank is a 1:16 cone
Taper half-angle β (deg)1.789911
Taper on diameter1 in 16 (0.75 in./ft)
E0 pitch dia at small end (in.)0.27118
L1 hand-tight engagement (in.)0.1600
L1 (threads)4.32
E1 pitch dia at hand-tight plane (in.)0.28118
L2 effective thread, external (in.)0.2611
L2 (threads)7.05
E2 pitch dia at L2 plane (in.)0.28750
L2 − L1 (in.)0.1011
L2 − L1 (threads)2.73
L3 wrench make-up, internal (in.)0.1111
L3 (threads)3
E3 pitch dia at wrench make-up plane (in.)0.26424
V vanish thread (in.)0.1285
V (threads)3.47
L4 overall external thread length, reference (in.)0.3896
L5 complete external threads (in.)0.1870
E5 pitch dia at L5 plane (in.)0.28287
Height of thread h, Table 2 col. 22 (in.)0.02963
Change in dia per turn 0.0625/n (in.)0.00231
K0 basic minor dia at small end (in.)0.2415
E0 by formula D − (0.05D + 1.1)P0.27118
E1 by formula E0 + 0.0625·L10.28118
L2 by formula (0.80D + 6.8)P0.2611
E2 by formula E0 + 0.0625·L20.28750
E3 by formula E0 − 0.0625·L30.26424
L5 by formula L2 − 2P0.1870
E5 by formula E0 + 0.0625·L50.28287
V by formula 3.47P0.1285
L4 by formula L2 + V0.3896
K0 by formula E0 − 0.8P0.2416
Gaging methodL1 ring gage (external) / L1 plug gage (internal), or L1 indicating gage (para. 3.2)
Gaging tolerance (turns)±1 turn
Gaging limit large (turns)1
Gaging limit small (turns)1
Basic gaging positionSmall end of pipe flush with small end of ring
Hand-tight engagement min, ±1 turn both parts (in.)0.0859
Hand-tight engagement max, ±1 turn both parts (in.)0.2341
Wrench make-up interference on PD, basic L3/16 (in.)0.00694
Hand-tight + wrench make-up length L1 + L3 (in.)0.2711
SealingPressure-tight: wrench-tight with sealant (para. 1.4)
Gage: plug major dia at E0 plane (in.)0.29289
Gage: plug major dia at E1 gaging notch (in.)0.30289
Gage: plug major dia at E2 large end (in.)0.30920
Gage: pitch dia at E0 plane (in.)0.27118
Gage: pitch dia at E1 gaging notch (in.)0.28118
Gage: pitch dia at E2 large end (in.)0.28750
Gage: ring minor dia at E0 plane (in.)0.24948
Gage: ring minor dia at E1 gaging notch (in.)0.25948
Gage: thickness of L1 ring or gage elements (in.)0.1600
Gage: working gage crest truncation (in.)0.005185
Gage: root must clear 0.0381P width (in.)0.001411
Gage: plug major at E0 by formula E0 + (H − 2·trunc)0.29289
Working gage tol. on PD ± (in.)0.0002
Working gage tol. lead, plugs (in.)0.0002
Working gage tol. lead, rings (in.)0.0003
Working gage tol. half angle, plugs ± (min)15
Working gage tol. half angle, rings ± (min)20
Working gage tol. taper, plugs + (in.)0.0003
Working gage tol. taper, rings − (in.)0.0006
Working gage tol. major dia, plugs − (in.)0.0004
Working gage tol. minor dia, rings + (in.)0.0004
Working gage total cumulative tol. on PD, plugs (in.)0.00080
Working gage total cumulative tol. on PD, rings (in.)0.00118
Max standoff between plug and ring gages (in.)0.032
Check against formulasK0 (col. 24): printed 0.2415, formula 0.2416 (1 in last place, rounding)
NotesTable 2 Notes: L1 is also the length of the L1 ring gage and the distance from the gaging notch to the small end of the L1 plug; E1 is also the PD at the gaging notch of the L1 plug; L2 is also the threaded length of the L1 plug; L4 is a reference dimension; L5 = L2 − 2P (the next two threads are complete at the root); K0 is given for selecting tap drills (Appendix B). Gaging: ±1 turn from basic (Fig. 4 / Fig. 6); with indicating gages ±0.0625/n on diameter (paras. 3.2.1.2, 3.2.2.2). The gaging tolerance can lengthen or shorten engagement by up to two turns; gage wear reduces it further (para. 3.1.9.1). Diameter limits here are calculated at the gage plane (E1 ± 0.0625/n on PD; major and minor add the Table 1 truncation limits). The standard itself tabulates basic dimensions only. Chamfer: external threads with chamfer smaller than the minor dia are gaged from the last scratch of the chamfer cone (para. 3.2.4.1, Fig. 5); otherwise from the end of the pipe (para. 3.2.4.3).
Lookup key1/16-27 NPT · External

Related tools

ASME B1.20.1: Pipe Threads, General Purpose, Inch. Source: workbook data (2026-10-11). Confirm against your licensed copy of the standard before use.