Example designation
M6 x 1-6g
- M
- Metric M profile.
- 6
- Nominal major diameter of 6 mm.
- 1
- Pitch of 1 mm.
- 6g
- Grade 6 at position g for this external thread.
A grade and a position do different jobs
The grade sets the tolerance width. The position locates that tolerance relative to the basic profile. Lowercase positions apply to external threads; uppercase positions apply to internal threads.
Pitch and diameter grades
Choose the pitch-diameter grade separately from the external major-diameter or internal minor-diameter grade. A single grade in a designation can cover both; different selections require the complete combined designation.
When the drawing calls for MJ
MJ changes the root and mating-clearance requirements. The nominal diameter and pitch can match an M thread while the permitted profile differs, so start with the correct M or MJ selection.