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How to distinguish between metric thread and inch thread


The outer diameter of the metric thread is in millimeters, such as 6, 8, 10, 12, 18, 20 mm, etc. The pitch is also in millimeters, such as 0.5, 0.75, 1, 1.5, 2, 3, etc.
The outer diameter of the inch thread is in inches, (each inch equals 25.4 mm) such as 3/16, 5/8, 1/4, 1/2, etc. Therefore, the reading of the outer diameter with a metric caliper often has irregular decimals. .
Inch pitch is expressed by the number of teeth per inch. Set the caliper at 25.4 mm, align one ruler tip with the thread tip, and the other ruler tip should be inch thread if the thread tip is aligned, and metric thread if the thread is not aligned.
When measuring the pitch, it is best to print the tip of the thread on the white chalk. The mark on the chalk is relatively clear and easy to measure. To measure the metric thread pitch, you should measure a length, such as 10, 15, 20, millimeters, etc., count how many threads it contains, and calculate the pitch in inches. The thread specification is an inch thread, such as: G1". Use the metric unit mm The metric thread is specified for the thread specification, such as M30.
The imperial system is determined by how many teeth there are in one inch (24.5 cm), generally 55 degrees. The metric system is the pitch of the pitch determined by the distance between the two tooth tips, usually 60 degrees.


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