VDI thread

The VDI thread is a historical thread type that was only used for a short period. It was developed by German engineer Karl Delisle (1827-1909), a strong advocate for standardizing threads. He presented his proposal for a new thread standard to the Verein Deutscher Ingenieure (VDI) in 1888, and the thread became known as the VDI thread. However, it was short-lived, being replaced by the SI thread in 1898, only ten years after its introduction. It is therefore unlikely to encounter VDI threads even in restoration projects. However, we can manufacture custom dies and taps for this standard upon request.

The VDI thread is a metric thread, with all dimensions in mm. Notably, it has a flank angle of 53° 8′, shared with the contemporaneous Löwenherz thread.

The thread designation for the VDI thread combines the external diameter and pitch, typically denoted as VDI, e.g., 8 x 1.20 VDI.

The table below for the VDI thread includes the external diameter, pitch, and core hole diameter, necessary for creating a correct pre-drilled hole when cutting a VDI thread. The table also includes the wrench size required for tightening or loosening screws and nuts with VDI thread.