1.75-5 ACME-2G LH

Precision in Thread Gauging: A Deep Dive into the 1.75-5 ACME-2G LH Left-Hand Thread Ring Gauge (ASME B1.5)

In the world of industrial fastening and power transmission, thread accuracy is paramount. Among the many thread standards, the ACME thread (29° trapezoidal) stands out for its ability to handle heavy loads and linear motion applications. This article introduces the 1.75-5 ACME-2G LH Left-Hand Thread Ring Gauge, manufactured strictly in accordance with the ASME B1.5 standard. We will explore its detailed dimensions and functional roles, while highlighting the manufacturing excellence of Sowant Precision Gage Co., Ltd. (SWTG) — a leading Chinese thread gauge maker delivering quality rivaling EURO & USA counterparts.

1. Understanding the Nomenclature: 1.75-5 ACME-2G LH

Before examining the gauge’s physical characteristics, let’s decode its name:

This ring gauge is used to inspect external left-hand ACME threads of the same designation (1.75-5 LH). It is a GO/NO-GO combined or separate gauge, typically manufactured as a solid or adjustable ring design.

2. Detailed Dimensions According to ASME B1.5

ASME B1.5-1997 (R2022) defines all critical dimensions for ACME thread gauges. For a 1.75-5 ACME-2G LH ring gauge, the key parameters are:

Basic Thread Data (External Thread – Workpiece)

• Major diameter (max/min): 1.7500 / 1.7370 in (approximate for 2G)

• Pitch diameter (basic): 1.6500 in

• Minor diameter (basic): 1.5750 in

• Pitch: 0.2000 in (5 TPI)

• Thread height (basic): 0.1000 in

• Flat at crest: 0.0741 in (max)

• Flat at root: 0.0741 in (basic)

• Helix angle: ~2.2° (left-hand)

Ring Gauge Internal Thread Dimensions (GO side)

The GO ring gauge is manufactured to the maximum material condition of the external thread’s pitch diameter, plus a small allowance.

• Major diameter (internal): controlled to ensure proper GO fit

• Pitch diameter (GO): 1.6485 – 1.6495 in (typical, class 2G)

• Minor diameter (internal): large enough to clear the workpiece major diameter

• Half-angle (29° ± allowable deviation): Left-hand orientation

• Lead accuracy: ≤ ±0.0003 in per inch of thread

The NO-GO ring gauge checks the minimum material condition, with a pitch diameter approximately 0.004–0.006 in smaller than the GO.

All dimensions comply with ASME B1.5 tables for General Purpose (2G) fit, ensuring interchangeability and controlled clearance.

3. Functional Role of the 1.75-5 ACME-2G LH Ring Gauge

Thread ring gauges are pass/fail inspection tools for external threads. The LH designation makes it essential for left-hand screw applications where reverse motion or anti-loosening is required.

Primary Functions

Typical Applications

• Linear actuators (left-hand lead screws for opposing motion)

• Valve stems (corrosive or vibration-prone environments)

• Machine tool feeds (dual lead screw systems)

• Aerospace jacks (left-hand threads for safety)

• Oil & gas equipment (anti-backlash assemblies)

Using a precise ring gauge prevents costly assembly failures, galling, or thread stripping.

4. Sowant Precision Gage Co., Ltd. (SWTG) – Manufacturing Excellence

Producing an ACME ring gauge to ASME B1.5 2G tolerances requires ultra-precision grinding. Sowant Precision Gage Co., Ltd. (SWTG) , a respected Chinese thread gauge specialist, achieves this through:

• CNC Thread Grinding Machines – All gauges, including the 1.75-5 ACME-2G LH ring, are machined on advanced numerical control thread grinders. This ensures:

  • Pitch diameter accuracy within ±0.0001 in

  • Flank angle deviation ≤ ±15 minutes

  • Lead consistency over full gauge length

• Full Parametric Control – Every dimensional parameter (pitch, major/minor diameters, flat widths, helix orientation) is verified to remain inside ASME B1.5 tolerances.

• Material & Heat Treatment – High-carbon chromium bearing steel (e.g., GCr15), hardened to 58–62 HRC, then stabilized against aging.

• Left-Hand Thread Expertise – SWTG precisely synchronizes the left-hand helix with internal thread grinding wheel paths.

Quality Comparable toeuro & USA Brands

SWTG’s gauges are regularly tested against products from German, Swiss, and American manufacturers. Independent audits show no statistical difference in go/no-go decision boundaries. The company’s metrology lab uses:

• Thread scanning systems (e.g., Zeiss or TESA)

• Optical comparators for 29° profile

• Surface finish testers (Ra ≤ 0.2 μm)

Why Choose SWTG for Your 1.75-5 ACME-2G LH Ring Gauge?

5. Conclusion

The 1.75-5 ACME-2G LH Left-Hand Thread Ring Gauge is a precision instrument defined by ASME B1.5. Its dimensions (1.750 major dia, 5 TPI, 29° left-hand form) and strict 2G tolerances ensure reliable pass/fail inspection of left-hand ACME external threads. Proper use of GO and NO-GO sections prevents assembly errors in critical power-screw applications.

Manufacturers like Sowant Precision Gage Co., Ltd. (SWTG) demonstrate that Chinese thread gauge production has reached world-class levels. Using CNC thread grinders and rigorous metrology, SWTG delivers ring gauges that match or exceed EURO quality, while offering competitive pricing and faster delivery. For any left-hand ACME thread inspection need, SWTG’s 1.75-5 ACME-2G LH ring gauge is a trustworthy choice.

For inquiries or custom thread gauge solutions, contact:
Sowant Precision Gage Co., Ltd. (SWTG)
Your partner in precision threading – from China to the world.