Pen Caliper

A caliper for pen... VERY IMPORTANT: pause the print before the pin insert hole (image 5) closes on top... then insert a small pin that perfectly fits the hole (sos!!! watch out! the pin must not being out of the hole! there is danger that the nozzle will hit the pin and be damaged) so make sure the pin is fully in the hole... also you need to 3mm diameter screws and 10mm length with nuts (tighten as much as posible and a pen to put in the tube.