zxguesser OP , vor 5 Tagen

Here's a photo of the improvised thread cutting machine I used to cut the printing spindle. Shown with a spare spindle in the "chuck".

The cutter is a bit of 4mm drill shank with something approximating a cutting geometry ground onto the end with a rotary tool. It is spring loaded into the work, with a depth stop on the rear to set the maximum depth of cut.

Turning the handle rotates and translates the workpiece in the correct relationship to generate the thread pitch, and the starting position was repeatedly reset to remove all but the double-helix needed.

Also a bonus photo showing the print mechanism more clearly, and the final print quality achieved 😀

The printing mechanism of the Meccano Hellschreiber machine, with the ink roller raised to show the print element. The paper tape contains the message "hello to everyone from Hackaday".