Metric Thread Tolerance 6H and 6g Explained

On a metric thread, the tolerance class is the number and letter after the size, such as 6H or 6g. The number is the tolerance grade and the letter is the tolerance position. A capital letter is used for an internal thread and a lowercase letter for an external thread.

6H for internal threads

6H is the most common class for nuts and tapped holes. The number 6 is the medium tolerance grade, and H is the position that starts exactly at the basic size.

6g for external threads

6g is the most common class for bolts and studs. The number 6 is the same medium grade, and g is a position that leaves a small allowance below the basic size, so the external thread can assemble with a 6H internal thread.

Other classes

Lower numbers mean a tighter tolerance and higher numbers a looser one, for example 5H against 7H. The class is set by the drawing, and the gauge has to be made for that exact class.

How to order

Give the thread as diameter, pitch and class, for example M10 × 1.5 6H, on our quote page.