2.75" × 4 TPI BUTT (pull type) External Thread Specifications

2.75-4 BUTT-2A · 2.7500-4 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

2.75-4 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	2.7500	2.7423	2.7307	0.0116
Pitch diameter EMax = D − h − G	2.6000	2.5923	2.5807	0.0116
Minor diameter KsRoot of the male thread; min is a reference value	2.4500	2.4109	2.3787ref.	0.0322ref.
Allowance GSpace below basic size; equals the Class 3 PD tolerance (Sec. 7)		0.0077
Root radius rRound root, male (Fig. 1a)		0.017853	0.008925
Thread engagement heh − G/2 at max, less the PD tolerance at min		0.146150	0.134550

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	2.7500	2.8136ref.	2.7814
Pitch diameter EMin = D − h	2.6000	2.6116	2.6000	0.0116
Minor diameter KnCrest of the female thread, min = D − 2h	2.4500	2.4616	2.4500	0.0116
Root radius rRound root, female (Fig. 1a)		0.017853	0.008925

Lead, flank angle and length of engagement

Lead + flank variation limit Σ: 0.01160 inPitch diameter equivalent of lead and flank errors together (Class 2: the PD tolerance; Class 3: half)
Lead variation alone ±δl: 0.00651 inAllowable lead error if there is no flank error
45° flank angle variation alone ±δα: 2.442 °Half-angle error of the clearance flank
7° flank angle variation alone ±δα: 5.156 °Half-angle error of the pressure flank

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

Male thread 2.75-4 BUTT-2A

Gage pitch tolerance (W): 0.00030 in
Gage 7° flank angle tolerance: 5 min
Gage 45° flank angle tolerance: 4 min
Gage major / minor tolerance: 0.0009 in
Gage pitch diameter tolerance: 0.00025 in
PD equivalent of pitch and flank tolerance: 0.0010 in
GO pitch diameter limit: 2.5923 in
NOT GO pitch diameter limit: 2.5807 in
NOT GO truncated crest diameter: 2.4932 in
Setting plug truncated major diameter: 2.6923 in
Best-size wire: 0.13537 · C = 0.20469 in, C
Maximum wire: 0.15358 · C = 0.26217 in, C

Female thread 2.75-4 BUTT-2B

Gage pitch tolerance (X): 0.00040 in
Gage flank angle tolerance: 5 min
Gage major / minor tolerance: 0.0009 in
Gage pitch diameter tolerance: 0.00050 in
PD equivalent of pitch and flank tolerance: 0.0013 in
GO pitch diameter limit: 2.6000 in
NOT GO pitch diameter limit: 2.6116 in
NOT GO truncated crest diameter: 2.6991 in
Plain gage tolerance: 0.00016 in
Root relief width GO: 0.041750 in
Root relief width NOT GO: 0.062500 in

Notes

Class 2: no taper/roundness requirement (para. 6.6.1).

Mates

2.75-4 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

→ 2.75" × 10 TPI → 2.75" × 12 TPI → 2.75" × 16 TPI → 2.75" × 5 TPI → 2.75" × 6 TPI → 2.75" × 8 TPI → 2.5" × 8 TPI → 3" × 10 TPI → 2.75" × 4 TPI internal

All values for 2.75-4 BUTT-2Aevery column of the workbook row

All values of the workbook row 2.75-4 BUTT-2A
Designation	2.75-4 BUTT-2A
Decimal designation	2.7500-4 BUTT-2A
Threads per inch	4
Thread form	BUTT
Series (Table 1)	BUTT
Series name	Pull type, rounded root (default)
External / internal	External
Class	2A
Nominal size (in.)	2.75
Pitch P (in.)	0.25000000
Basic major dia D (in.)	2.7500
Size category	Table 1 combination
Source table	Table 3, Tables 1, 2, 5
Printed page	4, 5, 6, 10
Major dia max (in.)	2.7423
Major dia min (in.)	2.7307
Major dia tolerance (in.)	0.0116
Major dia status	Toleranced: D - G (max), minus the PD tolerance (min) (paras. 6.2, 7)
Allowance G (in.; internal: mating external value, reference)	0.0077
Tolerance range (Tables 3-5)	Over 2.5 thru 4
Range over (in.)	2.5
Range thru (in.)	4.0
Range mean dia for formula (in.)	3.250
Length of engagement Le = 10P (in.)	2.5000
Basic pitch dia E = D - h (in.)	2.6000
Pitch dia max (in.)	2.5923
Pitch dia min (in.)	2.5807
PD tolerance (in.)	0.0116
Basic minor dia K = D - 2h (in.)	2.4500
Minor dia max (in.)	2.4109
Minor dia min (in.)	2.3787
Minor dia tolerance (in.)	0.0322
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.)	0.017853
Root radius min (in.)	0.008925
Root truncation s max (in.)	0.020650
Root truncation s min (in.)	0.010325
Engagement height he max (in.)	0.146150
Engagement height he min (in.)	0.134550
Lead + flank PD-equivalent limit (in.)	0.01160
Lead variation alone ± (in.)	0.00651
45° flank variation alone ± (deg)	2.442
7° flank variation alone ± (deg)	5.156
Lead angle at basic PD (deg)	1.7531
Lead angle (deg min)	1° 45′
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.)	0.222660
Basic thread engagement height h (in.)	0.150000
Thread height hs = hn (in.)	0.165678
Crest truncation f (in.)	0.036330
Crest width F (in.)	0.040790
Sweep cut: start diameter (in.)	2.742300
Sweep cut: tip diameter (in.)	2.410900
Sweep cut: depth (in.)	0.165678
Sweep cut: profile width at start diameter (in.)	0.209210
Sweep cut: tip width (root flat S max or radius r max) (in.)	0.017853
Constant c = 0.80803P (in.)	0.202008
PD tolerance component 0.00854√P (in.)	0.004270
W gage: pitch tolerance (in.)	0.00030
W gage: 7° flank tolerance (min)	5
W gage: 45° flank tolerance (min)	4
W gage: major/minor tolerance (in.)	0.0009
W gage: PD tolerance (in.)	0.00025
W gage: PD equivalent of pitch/flank tol. (in.)	0.0010
Z plain gage tolerance (in.)	0.00020
GO gage PD limit (in.)	2.5923
NOT GO gage PD limit (in.)	2.5807
NOT GO crest/minor truncated dia (in.)	2.4932
Setting plug truncated major dia (in.)	2.6923
Root relief width GO (0.167P) (in.)	0.041750
Root relief width NOT GO (0.25P) (in.)	0.062500
Best-size wire (in.)	0.13537
Measurement constant C, best wire (in.)	0.20469
Maximum wire (in.)	0.15358
Measurement constant C, max wire (in.)	0.26217
Check against formulas	OK
Notes	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.