0.5" × 12 TPI BUTT (pull type) External Thread Specifications

0.5-12 BUTT-2A · 0.5000-12 BUTT-2A

ASMESTD: ASME B1.9SOURCE: Table 3, Tables 1, 2, 5TYPE: External (bolt/screw)CLASS: 2AFLANKS 7° / 45°ROOT: roundTable 1 combination

Thread profile

0.5-12 BUTT-2A: solid = maximum material, dotted = minimum material, dashed = basic profile before the allowance. Flanks 7° (pressure) and 45° (clearance) from the radial line, 52° thread angle; drawn to scale.

Limits of size, class 2A

Dimension	Basic	Max	Min	Tolerance
Major diameter dCrest of the male thread, max = D − G	0.5000	0.4956	0.4889	0.0067
Pitch diameter EMax = D − h − G	0.4500	0.4456	0.4389	0.0067
Minor diameter KsRoot of the male thread; min is a reference value	0.4000	0.3851	0.3716ref.	0.0135ref.
Allowance GSpace below basic size; equals the Class 3 PD tolerance (Sec. 7)		0.0044
Root radius rRound root, male (Fig. 1a)		0.005951	0.002975
Thread engagement heh − G/2 at max, less the PD tolerance at min		0.047800	0.041100

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 female thread, limits of size, class 2B

Dimension	Basic	Max	Min	Tolerance
Major diameter DnRoot of the female thread, min = D + 0.12542p; max for reference	0.5000	0.5240ref.	0.5105
Pitch diameter EMin = D − h	0.4500	0.4567	0.4500	0.0067
Minor diameter KnCrest of the female thread, min = D − 2h	0.4000	0.4067	0.4000	0.0067
Root radius rRound root, female (Fig. 1a)		0.005951	0.002975

Lead, flank angle and length of engagement

Lead + flank variation limit Σ: 0.00670 inPitch diameter equivalent of lead and flank errors together (Class 2: the PD tolerance; Class 3: half)
Lead variation alone ±δl: 0.00376 inAllowable lead error if there is no flank error
45° flank angle variation alone ±δα: 4.232 °Half-angle error of the clearance flank
7° flank angle variation alone ±δα: 8.933 °Half-angle error of the pressure flank

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

Male thread 0.5-12 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: 0.4456 in
NOT GO pitch diameter limit: 0.4389 in
NOT GO truncated crest diameter: 0.4097 in
Setting plug truncated major diameter: 0.4789 in
Best-size wire: 0.04512 · C = 0.06822 in, C
Maximum wire: 0.05119 · C = 0.08738 in, C

Female thread 0.5-12 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: 0.4500 in
NOT GO pitch diameter limit: 0.4567 in
NOT GO truncated crest diameter: 0.4859 in
Plain gage tolerance: 0.00010 in
Root relief width GO: 0.013917 in
Root relief width NOT GO: 0.020833 in

Notes

Table 5 prints allowance 0.0044 for 12 TPI, from 0.5 thru 0.7; the Sec. 7 formula (= Class 3 PD tolerance) gives 0.0045. Printed value kept. Class 2: no taper/roundness requirement (para. 6.6.1).
allowance printed 0.0044 (Table 5), formula 0.0045

Mates

0.5-12 BUTT-2A screws into a thread of the same standard at the same size and pitch. The standard mating internal thread is class 2B. 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

→ 0.5" × 16 TPI → 0.5" × 20 TPI → 0.625" × 12 TPI → 0.5" × 12 TPI internal

All values for 0.5-12 BUTT-2Aevery column of the workbook row

All values of the workbook row 0.5-12 BUTT-2A
Designation	0.5-12 BUTT-2A
Decimal designation	0.5000-12 BUTT-2A
Threads per inch	12
Thread form	BUTT
Series (Table 1)	BUTT
Series name	Pull type, rounded root (default)
External / internal	External
Class	2A
Nominal size (in.)	0.5
Pitch P (in.)	0.08333333
Basic major dia D (in.)	0.5000
Size category	Table 1 combination
Source table	Table 3, Tables 1, 2, 5
Printed page	4, 5, 6, 10
Major dia max (in.)	0.4956
Major dia min (in.)	0.4889
Major dia tolerance (in.)	0.0067
Major dia status	Toleranced: D - G (max), minus the PD tolerance (min) (paras. 6.2, 7)
Allowance G (in.; internal: mating external value, reference)	0.0044
Tolerance range (Tables 3-5)	From 0.5 thru 0.7
Range over (in.)	0.5
Range thru (in.)	0.7
Range mean dia for formula (in.)	0.600
Length of engagement Le = 10P (in.)	0.8333
Basic pitch dia E = D - h (in.)	0.4500
Pitch dia max (in.)	0.4456
Pitch dia min (in.)	0.4389
PD tolerance (in.)	0.0067
Basic minor dia K = D - 2h (in.)	0.4000
Minor dia max (in.)	0.3851
Minor dia min (in.)	0.3716
Minor dia tolerance (in.)	0.0135
Minor dia status	Max = D - 1.32542P - G; min is reference only = min PD - 0.80803P (para. 6.3, Sec. 4)
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.)	0.047800
Engagement height he min (in.)	0.041100
Lead + flank PD-equivalent limit (in.)	0.00670
Lead variation alone ± (in.)	0.00376
45° flank variation alone ± (deg)	4.232
7° flank variation alone ± (deg)	8.933
Lead angle at basic PD (deg)	3.3735
Lead angle (deg min)	3° 22′
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	Pull type (external thread pulls): 45° clearance flank leads, 7° load 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.)	0.495600
Sweep cut: tip diameter (in.)	0.385100
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
W gage: pitch tolerance (in.)	0.00020
W gage: 7° flank tolerance (min)	10
W gage: 45° flank tolerance (min)	6
W gage: major/minor tolerance (in.)	0.0006
W gage: PD tolerance (in.)	0.00020
W gage: PD equivalent of pitch/flank tol. (in.)	0.0006
Z plain gage tolerance (in.)	0.00010
GO gage PD limit (in.)	0.4456
NOT GO gage PD limit (in.)	0.4389
NOT GO crest/minor truncated dia (in.)	0.4097
Setting plug truncated major dia (in.)	0.4789
Root relief width GO (0.167P) (in.)	0.013917
Root relief width NOT GO (0.25P) (in.)	0.020833
Best-size wire (in.)	0.04512
Measurement constant C, best wire (in.)	0.06822
Maximum wire (in.)	0.05119
Measurement constant C, max wire (in.)	0.08738
Check against formulas	allowance printed 0.0044 (Table 5), formula 0.0045
Notes	Table 5 prints allowance 0.0044 for 12 TPI, from 0.5 thru 0.7; the Sec. 7 formula (= Class 3 PD tolerance) gives 0.0045. Printed value kept. 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.