1.25" × 12 TPI PUSH-BUTT (push type) Internal Thread Specifications

1.25-12 PUSH-BUTT-2B · 1.2500-12 PUSH-BUTT-2B

ASMESTD: ASME B1.9SOURCE: Table 3, Tables 1, 2, 5TYPE: Internal (nut/tapped hole)CLASS: 2BFLANKS 7° / 45°ROOT: roundTable 1 combination (footnote a)

Thread profile

1.25-12 PUSH-BUTT-2B: solid = maximum material, dotted = minimum material. Flanks 7° (pressure) and 45° (clearance) from the radial line, 52° thread angle; drawn to scale.

Limits of size, class 2B

Dimension	Basic	Max	Min	Tolerance
Major diameter DnRoot of the female thread, min = D + 0.12542p; max for reference	1.2500	1.2744ref.	1.2605
Pitch diameter EMin = D − h	1.2000	1.2071	1.2000	0.0071
Minor diameter KnCrest of the female thread, min = D − 2h	1.1500	1.1571	1.1500	0.0071
Root radius rRound root, female (Fig. 1a)		0.005951	0.002975

Dimensions in inches. Values are those of the standard (ASME B1.9); 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.

Mating male thread, limits of size, class 2A

Dimension	Basic	Max	Min	Tolerance
Major diameter dCrest of the male thread, max = D − G	1.2500	1.2452	1.2381	0.0071
Pitch diameter EMax = D − h − G	1.2000	1.1952	1.1881	0.0071
Minor diameter KsRoot of the male thread; min is a reference value	1.1500	1.1347	1.1208ref.	0.0139ref.
Allowance GSpace below basic size; equals the Class 3 PD tolerance (Sec. 7)		0.0048
Root radius rRound root, male (Fig. 1a)		0.005951	0.002975
Thread engagement heh − G/2 at max, less the PD tolerance at min		0.047600	0.040500

Lead, flank angle and length of engagement

Lead + flank variation limit Σ: 0.00710 inPitch diameter equivalent of lead and flank errors together (Class 2: the PD tolerance; Class 3: half)
Lead variation alone ±δl: 0.00399 inAllowable lead error if there is no flank error
45° flank angle variation alone ±δα: 4.484 °Half-angle error of the clearance flank
7° flank angle variation alone ±δα: 9.467 °Half-angle error of the pressure flank

Gaging Sections 10, 11 · Tables 6, 7, 8, 11

Male thread 1.25-12 PUSH-BUTT-2A

Gage pitch tolerance (W): 0.00020 in
Gage 7° flank angle tolerance: 10 min
Gage 45° flank angle tolerance: 6 min
Gage major / minor tolerance: 0.0006 in
Gage pitch diameter tolerance: 0.00020 in
PD equivalent of pitch and flank tolerance: 0.0006 in
GO pitch diameter limit: 1.1952 in
NOT GO pitch diameter limit: 1.1881 in
NOT GO truncated crest diameter: 1.1589 in
Setting plug truncated major diameter: 1.2285 in
Best-size wire: 0.04512 · C = 0.06822 in, C
Maximum wire: 0.05119 · C = 0.08738 in, C

Female thread 1.25-12 PUSH-BUTT-2B

Gage pitch tolerance (X): 0.00030 in
Gage flank angle tolerance: 10 min
Gage major / minor tolerance: 0.0006 in
Gage pitch diameter tolerance: 0.00030 in
PD equivalent of pitch and flank tolerance: 0.0009 in
GO pitch diameter limit: 1.2000 in
NOT GO pitch diameter limit: 1.2071 in
NOT GO truncated crest diameter: 1.2363 in
Plain gage tolerance: 0.00012 in
Root relief width GO: 0.013917 in
Root relief width NOT GO: 0.020833 in

Notes

Table 1 footnote a: best-size wire measurement of PD may be incorrect (double contact on the 7° flank, lead angle over 2°); see Table 11 maximum wire. Class 2: no taper/roundness requirement (para. 6.6.1).

Mates

1.25-12 PUSH-BUTT-2B takes a thread of the same standard at the same size and pitch. The standard mating external thread is class 2A. 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

→ 1.25" × 10 TPI → 1.25" × 16 TPI → 1.25" × 6 TPI → 1.25" × 8 TPI → 1" × 16 TPI → 1.375" × 10 TPI → 1.25" × 12 TPI external

All values for 1.25-12 PUSH-BUTT-2Bevery column of the workbook row

All values of the workbook row 1.25-12 PUSH-BUTT-2B
Designation	1.25-12 PUSH-BUTT-2B
Decimal designation	1.2500-12 PUSH-BUTT-2B
Threads per inch	12
Thread form	PUSH-BUTT
Series (Table 1)	PUSH-BUTT
Series name	Push type, rounded root
External / internal	Internal
Class	2B
Nominal size (in.)	1.25
Pitch P (in.)	0.08333333
Basic major dia D (in.)	1.2500
Size category	Table 1 combination (footnote a)
Source table	Table 3, Tables 1, 2, 5
Printed page	4, 5, 6, 10
Major dia max (in.)	1.2744
Major dia min (in.)	1.2605
Major dia status	Min = D + 0.12542P (basic); max is reference only = max PD + 0.80803P (para. 6.3, Sec. 4); no tolerance specified
Allowance G (in.; internal: mating external value, reference)	0.0048
Tolerance range (Tables 3-5)	Over 1.0 thru 1.5
Range over (in.)	1.0
Range thru (in.)	1.5
Range mean dia for formula (in.)	1.250
Length of engagement Le = 10P (in.)	0.8333
Basic pitch dia E = D - h (in.)	1.2000
Pitch dia max (in.)	1.2071
Pitch dia min (in.)	1.2000
PD tolerance (in.)	0.0071
Basic minor dia K = D - 2h (in.)	1.1500
Minor dia max (in.)	1.1571
Minor dia min (in.)	1.1500
Minor dia tolerance (in.)	0.0071
Minor dia status	Toleranced: min = D - 2h (basic), max = min + PD tolerance (para. 6.2)
Root radius max (in.)	0.005951
Root radius min (in.)	0.002975
Root truncation s max (in.)	0.006883
Root truncation s min (in.)	0.003442
Engagement height he max (in.)	0.047600
Engagement height he min (in.)	0.040500
Lead + flank PD-equivalent limit (in.)	0.00710
Lead variation alone ± (in.)	0.00399
45° flank variation alone ± (deg)	4.484
7° flank variation alone ± (deg)	9.467
Lead angle at basic PD (deg)	1.2663
Lead angle (deg min)	1° 16′
Tensile stress area As (sq in.)	not given in the standard
Thread angle (deg)	52
Pressure (load) flank angle (deg)	7
Clearance flank angle (deg)	45
Flank orientation	Push type (external thread pushes): 7° load flank leads, 45° clearance flank follows (Sec. 9)
Sharp V height H (in.)	0.074220
Basic thread engagement height h (in.)	0.050000
Thread height hs = hn (in.)	0.055226
Crest truncation f (in.)	0.012110
Crest width F (in.)	0.013597
Sweep cut: start diameter (in.)	1.150000
Sweep cut: tip diameter (in.)	1.260500
Sweep cut: depth (in.)	0.055226
Sweep cut: profile width at start diameter (in.)	0.069737
Sweep cut: tip width (root flat S max or radius r max) (in.)	0.005951
Constant c = 0.80803P (in.)	0.067336
PD tolerance component 0.00854√P (in.)	0.002465
X gage: pitch tolerance (in.)	0.00030
X gage: flank angle tolerance (min)	10
X gage: major/minor tolerance (in.)	0.0006
X gage: PD tolerance (in.)	0.00030
X gage: PD equivalent of pitch/flank tol. (in.)	0.0009
Z plain gage tolerance (in.)	0.00012
GO gage PD limit (in.)	1.2000
NOT GO gage PD limit (in.)	1.2071
NOT GO crest/minor truncated dia (in.)	1.2363
Root relief width GO (0.167P) (in.)	0.013917
Root relief width NOT GO (0.25P) (in.)	0.020833
Check against formulas	OK
Notes	Table 1 footnote a: best-size wire measurement of PD may be incorrect (double contact on the 7° flank, lead angle over 2°); see Table 11 maximum wire. Class 2: no taper/roundness requirement (para. 6.6.1).

ASME B1.9: Buttress Inch Screw Threads. Source: workbook data (2026-10-10). Confirm against your licensed copy of the standard before use.