Oil Level indicator

Oil Level Gauge

1. Meaning of “G” in the Model

This denotes a pipe thread, where “G” is the first letter of the Chinese term “Guan” (pipe). The subsequent 1/2 unit refers to inches.

Pipe thread G1/2 has an outer diameter of 20.956mm, an inner diameter of 18.632mm, a pitch of 1.814mm, and 14 threads per inch.

The national standard for pipe threads is GB/T 7307-2001.

In the imperial system: 1 inch = 25.4 mm

Pitch = 25.4 ÷ 14

2. Imperial Thread Designation Method:

Unified National Threads (UN), widely adopted in inch-based countries, comprise three series: Coarse Thread (UNC), Fine Thread (UNF), and Extra Fine Thread (UNFF), plus a Constant Pitch Thread (UN) series.

Designation format: Thread diameter - Threads per inch - Series designation - Precision grade

Example: Coarse Thread 3/8-16 UNC-2A;

Fine series 3/8-24 UNF-2A;

Extra fine series 3/8-32 UNFF-2A;

Constant pitch series 3/8-20 UN-2A.

The first digit 3/8 indicates the thread outer diameter in inches. To convert to metric units (mm), multiply by 25.4:

3/8 × 25.4 = 9.525 mm; The second and third digits (16, 24, 32, 20) denote the number of threads per inch (over a 25.4mm length). The alphabetic designations following the third digit (UNC, UNF, UNFF, UN) indicate the series, while the final two digits (2A) denote the precision grade.

3. Metric Pitch

Multiplying the inch value by 25.4 yields the metric major diameter. The pitch is the number of threads per inch divided by 25.4, resulting in the metric pitch.

4. British Standard Thread Designation Method: (e.g., 3/16-32UNF-1B)

3/16 represents the thread major diameter (outer diameter), measured in inches (1 inch = 25.4 mm).

32 indicates 32 threads per inch, specifying the pitch; UNF denotes United Fine Thread (British fine-pitch thread), while UNC denotes United Coarse Thread (British coarse-pitch thread); 1B represents the tolerance accuracy grade, with similar grades including 2A, 3A, etc.

For example: 3/16-32 means 32 threads per inch. Since 1 inch equals 25.4 mm, the pitch is 25.4/32, and the outer diameter is 25.4/16 × 3.

Example: 3/16-32 UNF

Pitch P: 25.4/32 = 0.794 Outer Diameter D: 25.4/16 × 3 = 4.7625