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Table 4.3 - The basic bolt sizes of normal accuracy are resulted in table 4.3.

Nominal thread Pitch of a thread S H D* R D l 0 c
diameter d n , mm coarse fine no more not less
16 2.0 1.5 24 10 27.7 1.2 26.5 36 2
18 2.5 1.5 27 12 31.2 1.6 29.9 42 2.5
20 2.5 1.5 30 13 34.6 2.2 33.3 46 2.5
22 2.5 1.5 32 14 37.0 2.2 35.0 50 2.5
24 3.0 2.0 36 15 41.6 2.2 39.6 54 3

The parameter D* determines the reference diameter of a circle described round a hexagon,
and the parameter of D regulates actual low-limit size hexagon diagonal for the real roller stock.

4.4.2 NUTS

Nuts are generally made in the form of hexagonal or square prism. Besides this, cylindrical
and other forms are also used to suit the particular requirements. They have internal threads and
hold the part by giving the tightening effect on the bolt.
The form of the external surface, the type of execution and the accuracy of manufacturing are
determined for the standardized nuts. Three types of a nut are shown in fig.4.17. A metrical thread
with coarse and fine pitches is used in standard nuts. Standard hexahedral nuts of different height
are widely used.

Figure 4.17 – Hexagonal nut.
The example of the conventional denotation of a nut (type 1), normal accuracy with the
diameter of a metrical thread 12 mm, a coarse pitch, tolerance zone 7Н, the strength class 5 and the
coverage 02 (cadmium with chromating) 9 mkm thick:
Nut M12-7H. 5.029 State Standard 5915:2008.
The basic parameters of nuts are resulted in table 4.4.

Table 4.4
Nominal thread Pitch of thread
diameter coarse fine S H D* D с
d n, mm
16 2.0 1.5 24 13 27.7 26.5 2
18 2.5 1.5 27 15 31.2 29.9 2.5
20 2.5 1.5 30 16 34.6 33.3 2.5
22 2.5 1.5 32 18 37.0 35.0 2.5
24 3.0 2.0 36 19 41.6 39.6 3

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