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4 7/8-4 STUB ACME-2G

4 7/8-4 STUB ACME-2G Thread Ring gage per ASME B1.8 ,all parameters include pitch diameter/major diameter/minor diameter/lead/angel ,all of them in tolerance made in China by Sowant Precision Gage.
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4 7/8-4 STUB ACME-2G Thread Ring gage per ASME B1.8 ,all parameters include pitch diameter/major diameter/minor diameter/lead/angel ,all of them in tolerance made in China by Sowant Precision Gage.

 

A Comparative Analysis of ASME B1.8 Stub ACME and ASME B1.9 Buttress Thread Gauges

1. Introduction

ASME B1.8 Stub ACME and ASME B1.9 Buttress threads are two distinct trapezoidal thread forms standardized under American Society of Mechanical Engineers (ASME) specifications. While both are designed for power transmission and load-bearing applications, their geometries and functional priorities differ significantly. This article focuses on the ASME B1.8 Stub ACME thread gauge, detailing its features, properties, and applications, while contrasting it with the ASME B1.9 Buttress thread gauge. Additionally, we highlight Sowant Precision Gage, a leading Chinese manufacturer of thread gauges, including API oilfield gauges, and a distributor of global brands like Mitutoyo (Japan), Mahr (Germany), and INSIZE.

2. ASME B1.8 Stub ACME Thread Gauges: Features and Applications

Key Characteristics

  • Standard: ASME B1.8-1988 (revised 2021).

  • Thread Profile:

    • 29° included angle.

    • Shallow thread depth (approximately 40% of standard ACME).

    • Coarse pitch for reduced engagement depth and stress concentration.

  • Tolerance Classes: 2G (General Purpose) and 3G (Centralizing).

  • Material: High-carbon steel, carbide, or stainless steel for corrosion resistance.

  • Surface Finish: ≤0.8 μm Ra for precision measurement.

Functional Advantages

  • Optimized for high-strength applications in limited axial space.

  • Resists wear and galling due to reduced thread depth.

  • Ideal for systems requiring rapid assembly/disassembly with moderate clearance.

Applications

  • Military and aerospace equipment (e.g., artillery mechanisms).

  • Compact robotics and hydraulic systems.

  • Oil and gas valves with space constraints.

3. ASME B1.9 Buttress Thread Gauges: Overview

  • Standard: ASME B1.9-1973 (revised 2021).

  • Thread Profile:

    • Asymmetric 7° pressure flank and 45° trailing flank.

    • Designed for unidirectional axial loads (e.g., jackscrews, presses).

  • Tolerance Classes: 2G, 3G (similar to Stub ACME).

  • Applications:

    • Injection molding machines.

    • Heavy-duty lifting systems (e.g., hydraulic jacks).

    • Medical devices requiring high thrust capacity.

4. Similarities and Differences

Aspect ASME B1.8 Stub ACME ASME B1.9 Buttress
Thread Angle 29° symmetrical 7° (pressure) / 45° (trailing) asymmetrical
Load Direction Bidirectional load capacity Unidirectional axial thrust optimized
Thread Depth Shallow depth for space efficiency Deeper engagement for load distribution
Pitch Design Coarser pitch (4–12 TPI) Variable pitch, often finer for precision
Applications Space-constrained, high-stress environments Heavy axial load systems (e.g., presses)

Similarities:

  • Both are trapezoidal threads standardized under ASME.

  • Utilize 2G/3G tolerance classes for assembly flexibility.

  • Require precision gauges for quality assurance.

5. Case Study: 4 7/8-4 STUB ACME-2G Thread Ring Gauge

Specifications:

  • Major Diameter: 4.875 inches (123.825 mm).

  • Pitch: 4 TPI (6.35 mm per thread).

  • Thread Depth: 0.0866 inches (2.2 mm).

  • Tolerance Class: 2G (General Purpose).

  • Material: Hardened tool steel (HRC 60–62).

  • Surface Finish: ≤0.8 μm Ra.

  • Compliance: ASME B1.8-1988(R2021).

6. Example Specifications

20 Stub ACME-2G Thread Ring Gauges (ASME B1.8)

No. Specification Major Diameter (Inch) TPI Pitch (mm) Thread Depth (mm)
1 0.5-8 STUB ACME-2G 0.5 8 3.175 0.82
2 0.75-6 STUB ACME-2G 0.75 6 4.233 1.10
3 1-4 STUB ACME-2G 1.0 4 6.35 2.20
4 1.25-5 STUB ACME-2G 1.25 5 5.08 1.65
5 1.5-6 STUB ACME-2G 1.5 6 4.233 1.10
6 1.75-4 STUB ACME-2G 1.75 4 6.35 2.20
7 2-5 STUB ACME-2G 2.0 5 5.08 1.65
8 2.25-6 STUB ACME-2G 2.25 6 4.233 1.10
9 2.5-4 STUB ACME-2G 2.5 4 6.35 2.20
10 2.75-5 STUB ACME-2G 2.75 5 5.08 1.65
11 3-4 STUB ACME-2G 3.0 4 6.35 2.20
12 3.25-6 STUB ACME-2G 3.25 6 4.233 1.10
13 3.5-5 STUB ACME-2G 3.5 5 5.08 1.65
14 3.75-4 STUB ACME-2G 3.75 4 6.35 2.20
15 4-4 STUB ACME-2G 4.0 4 6.35 2.20
16 4.25-6 STUB ACME-2G 4.25 6 4.233 1.10
17 4.5-5 STUB ACME-2G 4.5 5 5.08 1.65
18 4.875-4 STUB ACME-2G 4.875 4 6.35 2.20
19 5-6 STUB ACME-2G 5.0 6 4.233 1.10
20 5.5-4 STUB ACME-2G 5.5 4 6.35 2.20

10 Buttress Thread Ring Gauges (ASME B1.9)

No. Specification Major Diameter (Inch) TPI Pitch (mm)
1 1-6 BUTTRESS-2G 1.0 6 4.233
2 1.5-4 BUTTRESS-2G 1.5 4 6.35
3 2-5 BUTTRESS-3G 2.0 5 5.08
4 2.5-6 BUTTRESS-2G 2.5 6 4.233
5 3-4 BUTTRESS-2G 3.0 4 6.35
6 3.5-5 BUTTRESS-2G 3.5 5 5.08
7 4-6 BUTTRESS-3G 4.0 6 4.233
8 4.5-4 BUTTRESS-2G 4.5 4 6.35
9 5-5 BUTTRESS-2G 5.0 5 5.08
10 6-4 BUTTRESS-2G 6.0 4 6.35

7. Sowant Precision Gage: Global Expertise

As a leading Chinese manufacturer, Sowant Precision Gage offers:

  • Custom Thread Gauges: Compliant with ASME B1.8, B1.9, ISO, and API standards.

  • Global Brand Distribution: Mitutoyo calipers, Mahr micrometers, and INSIZE measurement tools.

  • Quality Assurance: NIST-traceable calibration and ISO 9001 certification.

8. Conclusion

The ASME B1.8 Stub ACME thread gauge excels in space-constrained, high-stress environments, while the ASME B1.9 Buttress gauge prioritizes unidirectional thrust capacity. Sowant Precision Gage provides tailored solutions for both standards, ensuring precision and reliability across industries such as aerospace, oil and gas, and heavy machinery.

References: ASME B1.8-1988(R2021), ASME B1.9-1973(R2021), and Sowant Precision Gage technical documentation.