1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result
Choose the joint type that mostly corresponds to your design.
Enter data about the screw and let the tool calculate output values such as clamping force, static and dynamic strength, etc.
Enter data about the screw and desired assembly methods.
Inspection
Print or review your results.

Screw joint design and assembly

With this simple tool you can design the screw joint for your application and in addition get help with choosing a suitable assembly method.

The input values from your last session are automatically stored in a cookie.
Click 'Reset values' to delete your last input.

Screw joint design and assembly

With this simple tool you can design the screw joint for your application and in addition get help with choosing a suitable assembly method.

The input values from your last session are automatically stored in a cookie.
Click 'Reset values' to delete your last input.

1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result


High strength joint

High strength joints are metric threaded joints with screws of property class 8.8 or 10.9. Also includes thread forming screws with a thread.

Low strength joint

Low strength joints are non-metric threaded joints with self-tapping and in most cases case hardened screws made for plastic or sheet metal applications.

1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result
Your use of any information on this website is entirely at your own risk, for which we shall not be liable. The calculated output/results are approximate.
1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result


Choose a joint type from the examples below by clicking on one of the images.

Examples high strength joints

Standard static high strength joint

Transport loading bracket

Standard static high strength joint. Transport loading bracket.

Classified static high strength joint

Safety belt

Classified static high strength joint. Safety belt attachment.

Standard dynamic high strength joint

Connecting rod - standard dynamic high strength joint Chassis joint

Standard dynamic high strength joints. For example, a connectiong rod or chassis joint.

Classified dynamic high strength joint

Wheel screw joint

Classified dynamic high strength joint. Wheel screw joint.

Examples low strength joints

Low strength joint screws

Low strength joint screws

Low strength joint screws, used in sheet metal and plastic application.

1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result
Your use of any information on this website is entirely at your own risk, for which we shall not be liable. The calculated output/results are approximate.
1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result

High strength joint

Input data

2.1 Screw

Screw head

Assembly friction

The assembly friction consists of two parts:

  1. The friction between screw head and the part to be assembled (the base) during tightening
  2. The friction between the external and internal thread during tightening.
Together they substitute the resultant assembly friction and together with the assembly torque give the initial clamping force of the joint.

Enter the preferred friction coefficient in the text box to change the default friction coefficient.
To access the min-max friction coefficient values for different materials, click 'Friction coeff. matrix'

Assembly head friction

Enter the preferred friction coefficient in the text box. To access the min-max friction coefficient values for different materials, click 'Friction coeff. matrix'.

±

Assembly thread friction

Enter the preferred friction coefficient in the text box. To access the min-max friction coefficient values for different materials, click 'Friction coeff. matrix'.

±

2.2 Clamped part

Clamping length


Minimum clamping length

The clamping length is the distance between the Head/flange of the fastener and the first thread in engagement.

To avoid subsequent problems the clamping length must be at least 1 times d (1d) for all joints and at least 2 times d (2d) for dynamic high strength joints. In addition to this the threaded part within the clamping length must for yield point tightened joints be at least 1.5d to accommodate for the plastic deformation of the screw.

 TorqueYield point
Static0.5dNA
Dynamic1d2d

Material

Material and/or surface of clamped part.

Minimum interface friction

Some values seen by the Swedish Fasteners Network (www.sfnskruv.se)

  Powder painted steel Water painted steel ED coated steel Uncoated steel Uncoated aluminium
Powder painted steel 0.05        
Water painted steel 0.07 0.08      
ED coated steel 0.10 0.08 0.10   0.13
Uncoated steel 0.06     0.13  
Uncoated aluminium 0.06     0.13 0.17

2.3 Internal thread part, e.g. nut

Choose material and hardness in order to determine the minimal thread engagement.

2.4 Screw joint information


Calculate loss in clamping force

Results calculation

NOTE!

If the contact pressure will be higher than the ones given in the table below there will be some indentation of the assembled part, under the screw head.

Max recommended contact pressure
Assembled part hardness (HB)Max contact pressure (MPa)
50180
70250
90320
110380
130460
160560
190660
210740
240840
270950

Dynamic axial strength

With the state of the art limit of 45MPa as max external load amplitude to avoid fatigue for normal electroplated or dip spin applied screws in property class 8.8 or 10.9, the max external dynamic load amplitude (in kN) of the joint has been calculated based upon a stiffness ratio of 2, meaning the base to have double the fastener stiffness. A steel base is normally at least three times stiffer than the fastener but a base made of aluminium can sometimes be just two times stiffer than the fastener due to the lower modulus of elasticity of aluminium (E = 70GPa for aluminium and E = 205GPa for steel).

max amplitude
max amplitude
1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result
Your use of any information on this website is entirely at your own risk, for which we shall not be liable. The calculated output/results are approximate.
1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result

Low strength joint

Please read this document about Low strength joint design: Low strength joints guidelines

1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result
Your use of any information on this website is entirely at your own risk, for which we shall not be liable. The calculated output/results are approximate.
1
Joint type
2
Design
3
Assembly
4
Inspection
5
Result

Input data

3.1 Screw joint

3.2 Assembly method

Clamping length


Minimum clamping length

The clamping length is the distance between the Head/flange of the fastener and the first thread in engagement.

To avoid subsequent problems the clamping length must be at least 1 times d (1d) for all joints and at least 2 times d (2d) for dynamic high strength joints. In addition to this the threaded part within the clamping length must for yield point tightened joints be at least 1.5d to accommodate for the plastic deformation of the screw.

 TorqueYield point
Static0.5dNA
Dynamic1d2d

Results - assembly methods graph

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