Обший каталог Yamawa 2016 - 2017 - страница 786

Length of engagement

■Length of engagement

Thread tolerance class is chosen in consideration of "engagement classification" and "engagement length". To realize the stable tapping, it is necessary to fully understand the relation between these factors and to choose the suitable tolerance class.

On "engagement calssification : middle", the tolerance class 6H is almost always chosen for standard internal threads. However, in case of "engagement length : L", tolerance class 7H can also be chosen.

On M12x1.75, the tolerance of 7H is 25% (50μm) larger than that of 6H. And this widens the selection range of the tolerance class for taps to customer's advantage.

M12x1.75

6H Pitch diameter : 10.863 ~ 11.063mm (tolerance 0.200 mm)

7H Pitch diameter : 10.863 ~ 11.113mm (tolerance 0.250 mm)

1) Engagement classification

classification application fine precise screw threads with a little allowance middle standard screw threads used for machines, apparatuses and constructions bodies screw threads used for construction and building installation, and screw threads for coarse which threading operation is very difficult such as threading of hot rolled steel bars.

2) Classification of engagement length

symbol classification limit size engagement length

thread

3) Selection rule of internal threads and external threads external

Selection rule of the tolerance class of internal threads

thread

tolerance position H engagement length

S N L

engagement classification fine

4H 5H 6H

middle

P : pitch

Selection rule of the tolerance class of external threads

tolerance position h g

engagement length

S N L S N L

engagement classification

S L S L