Inspection standard for bolt go and stop gauges

David Dai

sales

Ningbo Zhongli Bolts Manufacturing Co., Ltd. founded in 2003, is a professional manufacturer of high-strength fasteners in different specifications for various models, which is covering an area of about 10,000 square meters, registered capital of 1500,000 RMB, with the total annual productivity of 8,000 tons per year. The company has set up several sales branches in different provinces in China. Meanwhile, the company's products are exported to Europe, USA, Middle East, Africa, Southeast Asia and other regions.

In the field of mechanical manufacturing, the safety and reliability of bolt connections directly depend on the thread accuracy. According to statistics, approximately 15% of mechanical failures are caused by fastener issues. As a core means of thread quality control, the accuracy of no-go gauge inspection standards directly affects the product's lifespan and safety.

The core standard system for check and go gauge testing

1. Comparison of international standard differences

ISO 1502: It strictly stipulates that the stop gauge should not be screwed in more than 2 teeth and is applicable to threads with a total number of teeth ≥3. Insertion is prohibited when the number of teeth is no more than 3.

ANSI/ASME B1.2 (American Standard) : Allows the stop gauge to be screwed in with 3 threads, applicable to uniform imperial threads, and distinguishes tolerance grades 1A/2A/3A.

JIS B052 (Japanese Standard) : Consistent with ISO 1502, it reflects the strict requirements for thread accuracy in the Asian market.

2. Key Points of Chinese National Standards

GB/T 197-2003: It stipulates that the general gauge should be smoothly screwed in within 10 seconds, and the stop gauge should not be screwed in more than 2 turns (teeth).

GB/T 1483.1-2008: Detailed inspection of lamp cap threads, emphasizing the surface roughness (Ra≤0.8μm) and anti-corrosion treatment of go and stop gauges.

The golden rule in practical testing

1. Operating norms

Screw-in force control: Axial force 2-5N to avoid misjudgment caused by tilting.

Environmental adaptability: For Marine bolts, the thickness of the coating (20-30μm) needs to be tested.

2. Judgment logic

The pass gauge is too small → The thread is too small (rework is required); The stop gauge passes → The thread is too large (needs to be scrapped).

Special case: The torque coefficient of high-strength bolts needs to be simultaneously tested (for example, 0.110-0.150 for grade 8.8 M20 bolts).

Technological evolution and industry application

1. Material and process innovation

Material of the no-go gauge: CrWMn alloy steel (hardness HRC58-62) is preferred, and it undergoes quenching and tempering treatment to ensure stability.

The trend of intelligent inspection: AOI (Automatic Optical Inspection) systems are gradually replacing manual labor, enhancing efficiency.

2. Full life cycle management

Calibration cycle: Calibrate every 3 to 6 months in accordance with JJG 34-2008. For frequent use, the interval should be shortened.

Failure analysis: Combining metallographic microscopy with ultrasonic flaw detection to trace the root cause of thread defects.

Conclusion: The Safety Philosophy Behind Standards

From aerospace to automotive manufacturing, the inspection standards for bolt go and stop gauges are the invisible cornerstones of industrial civilization. With the deepening of global trade, the convergence of ISO and ANSI standards has become a trend, but enterprises' pursuit of the limit of precision has never ceased. Mastering the standard details essentially stems from a sense of awe towards life and equipment.