The worldwide metric screw thread, with the same 60 degree profile as the Unified thread but sized in millimeters. A designation gives nominal diameter and pitch, M12 x 1.75, and when the pitch is left off the coarse pitch is implied, so M12 means M12 x 1.75; fine pitches such as M12 x 1.25 must be written out. Tolerance class 6g for external and 6H for internal threads is the general-purpose fit, playing the role 2A and 2B play in inch threads.
Print just calls an M10 ISO metric thread, so that's one-and-a-half pitch, if they wanted fine they'd have written M10 by one and a quarter.
M8 x 1.25 and M8 x 1.0 look identical in a bin, so put a pitch gauge on before a nut gets forced on and ruins both.
Also heard as
- metric thread
- M thread
Related terms
Pitch
The distance from one thread crest to the next, measured parallel to the screw axis.
Thread class
A number-and-letter grade, such as 2A or 3B, that sets how much tolerance and allowance an inch thread has.
UNC
Unified National Coarse: the standard coarse inch thread series, such as 1/4-20, 3/8-16 and 1/2-13.
Property class
The metric strength grade of a bolt or nut, stamped on the head as a number such as 8.8, 10.9 or 12.9.