Page 18 - Threading_Handbook

Recommended tolerance classes for internal Threading Position H
INTRODUCTION Medium Short Normal Long Short Normal Long
Position G
Tolerance
Class
6H
5H
4H
---
---
---
Fine
7H
7G
5G
5H
6H
6G
Coarse
8H
---
---
7H
8G
7G
Recommended Tolerance Classes for External Threading
Tolerance Position e Position f Position g Position h
Class Short Normal Long Short Normal Long Short Normal Long Short Normal Long
Fine --- --- --- --- --- --- --- 4g 5g4g 3h4h 4h 5h4h
Medium --- 6e 7e6e --- 6f --- 5g6g 6g 7g6g 5h6h 6h 7h6h
Coarse --- 8e 9e8e --- --- --- --- 8g 9g8g --- --- ---
When:
nd
st
rd
1 choice 2 choice 3 choice
** bold - most common
There are several options for thread description with accuracy class
according to the ISO standard:
Internal Threading

Major X Pitch - Tolerance Class for Tolerance Class for
Diameter Pitch Diameter Minor Diameter

M8X1.25 – 5H 6H

Major Tolerance Class for Pitch and
Diameter - Minor Diameter

M8 – 6H

External Threading

Major X Pitch - Tolerance Class for Tolerance Class for
Diameter Pitch Diameter Major Diameter

M8X1.25 – 5g 6g

Major Tolerance Class for
Diameter - Pitch and Major Diameter

M8 – 6g

18 ISCAR