Page 677 - Mastik®

Recom. min. lengths of engaged thread in Length of engaged thread
cutted internal threads on components.

from information provided by manufacturer’s,

based on trail values M6 to M16
Where screws have to be screwed into tightening up there is no need to worry given to achieving the required minimum
internal threads and where full load-bear- about any resulting enlargement which length of engaged thread, in order to en-
ing capacity is required, then minimum might mean that the threads would not sure adequate durability of the screwed
lengths of engaged thread have to be grip. On the other hand, in many cases connection.
defined which depend on the strength of the internal threads on the components The following recommended values have
the material from which the component are less strong than standard nuts of the been determined from practical trials.
is made. same strength class for the screws which
There is normally less flexibility com- are being used.
pared with standard nuts, so that when This means that special attention must be

Recommended minimum length of engaged thread without
Component material with incised countersinking for the strength class of the screw
internal thread 8.8 10.9 12.9
tolerance 6 g / 6 H
coarse thread fine thread coarse thread fine thread coarse thread
Rm in N/mm 2
S 235 (St37-2) > 360 1,0 · d 1,25 · d 1,4 · d
1,25 · d 1,4 · d
2C15 N (C15) (ferrite / perlite structure) [1,5 · d] 1) [1,8 · d] 1) [2,1 · d] 1)
E 285 (St50-2)
> 500 0,9 · d 1,0 · d 1,2 · d
S 355 (St52-3) 1,0 · d 1,2 · d
(ferrite / perlite structure) [1,3 · d] 1) [1,6 · d] 1 [1,8 · d] 1)
2C35 N (C35 N)
C45 V
35Cr4 V > 800 0,8 · d 0,9 · d 1,0 · d
0,8 · d 0,9 · d
34CrMo 4 V (heat-treated sturcture) [0,9 · d] 1) [1,1 · d] 1) [1,2 · d] 1)
42CrMo 4 V
1,0 · d 1,25 · d 1,4 · d
GJL 250 (GG-25) > 220 1,25 · d 1,4 · d
[1,3 · d] 1) [1,6 · d] 1) [1,8 · d]
Al 99,5 > 180 2,0 · d 2,5 · d
AlMg3 F18 > 180 2 · d [3 · d] 1) 2 · d [3 · d] 1)
AlMgSi1 F32 > 330 1,4 · d 1,4 · d 1,6 · d 2,0 · d
AlMg4,5Mn F28 > 330 1,4 · d 1,4 · d 1,6 · d 2,0 · d
AluMg1 F40 1 > 550 1,1 · d
AlZn MgCu 0,5 F50 > 550 1,0 · d
GMgAl9 Zn1 > 230 1,4 · d 1,4 · d 1,6 · d 2,0 · d

1) Values in brackets are based on the formula from VDI 2230 (theoretical values)

Tables for the approximate values of minimum length of engagement with thread tolerances of 6g/6H require a sufficient wall thickness
for the nut thread.
For exact values a calculation according to VDI2230 are required.
The minimum length of engagement means effective sufficient overlapping of the threads without countersink at the construction unit
and without thread run out at the bolt end.

For lengths of engaged thread above 1.5 d, external or internal threads at the extreme tolerance limits can lead to the
screw becoming jammed.
ISO 965-1 defines the grades of tolerance for external and internal threads; compliance with these will ensure a
problem-free assembly of the screwed fastening.