This calculator is based on the VDI 2230 guideline. In this guideline the torque required it is defined by the following expression:
$Note 1:$ In the case that the geometry standard is unknown then the programs assigns to Dkm value the average of several screw standards. It is not so significant in the end result.
$Note 2:$ In the case of do not know the constact surfaces material the calculator will assign a friction coefficient of 0,1 (($\mu$) is 0,1)
Another function is to help to check the maintainability. If you introduce the screw standard and thread size you will have the link to the recommended 3D models tools in order to check the required space to apply torque and to remove the screw. This will help to check that the design is easy to mantain and prevent future redesign process during the assembly. You only have to insert the tool in your 3D model and you will see that the bolt head clearance for the wrench, spanner or socket is enough.
1) Enter thread diameter nominal value in section Thread Size. Click on info button for more info
2) In section Head Size and Type either select one fastener ISO with the "Select Standard for Type" option or enter manually the type and whether the fastener is socket or not in the right part of the page, once you have selected Custom option.
3) Enter strength class of the fastener. Click on info button for more info
4) In section Coefficient of Friction either select one lubrication condition (faster and surface combination) with the "Select Friction condition" option or enter manually or let the default value in the right part of the page, once you have selected Unknown option.
5) Click on button calculate, and the calculated torque will appear below.
This values are automatically loaded based on iso and metric thread size, what at the same time give us the head and the shape needed for calculation.