## 5. Calculations for the selection of rivets

If on the working drawing no details on the rivet are indicated, the following has to be taken into consideration:

The diameter of the rivet shank shall be at least one quarter of the thickness of all plates to be riveted - formula:

D = diameter of the rivet shank
s = thickness of all plates to be riveted (clamping length)

Figure 22 - Riveted joint:

1 - Diameter of the rivet shank
2 - Length of the rivet shank
3 - Allowance
4 - Clamping length

The length of the rivet shank has to be calculated on the basis of the thickness of all plates to be riveted:

The rivet shank must be longer than the thickness of all plates to be riveted by the measure of the "allowance" - formula:
 L = S + z
L = length of the rivet shank
S = thickness of all plates to be riveted
Z = allowance
The allowance depends on the kind of rivet and on the field of application:

- Button closing heads in steel construction;

For rivets of diameters of the rivet shank up to 20 mm -

 Z = 1.5 x D

For rivets of diameters of the rivet shank of more than 20 mm -

 Z = 1.6 x D

- Button closing heads in boiler construction:

For rivets of rivet shank diameters up to 20 mm -

 Z = 1.7 x D

For rivets of rivet shank diameters of more than 20 mm -

 Z = 1.8 x D

- Countersunk closing heads in general:

 Z = 0.5 x D
Rivets which are too long must be cut - the right length of the rivet shank is the precondition of the quality of the closing head.

Calculating example:

A button head rivet shall be calculated in order to connect two plates of 4 mm in thickness in steel construction:

1. Diameter of the rivet shank:

 D = 2 mm selected: 3 mm

2. Length of the rivet shank:

 L = S + Z Z = 1.5 x D = 1.5 x 3 mm Z = 4.5 mm L = 8 mm + 4.5 mm L = 12.5 mm selected: 12 mm

Result: A rivet with the designation button head rivet 3 x 12 can be used for the intended connection.

Exercise:

A countersunk riveting of three 5 mm thick plates shall be made What rivet can be used for this purpose?
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