Torque Driver for Calibrating Belt Tension

Torque driver for setting correct tension on 6mm belt on 3d printers. It is designed to limit torque- hence pulling force, on an M3 screw. Tension is calibrated using a fixed weight (1.25kg). The weight is based on the figure described in Lost in Tech's video https://www.youtube.com/watch?v=zoKmmT0a7jk

If you wish to tension the belt via the idler pulley, double the weight in calibrating the driver.

Demo video

Belt tensioner used is available here 

Build Guide.pdf included

Assembly video

Hardware required: 

• Spring from a retractable ball pen (clicky pen)  4.5 mm diameter x 20 mm long (relaxed)
• Steel ball x 2- 6.35 mm or 1/4 inch diameter.  Soft air 6mm BB pellets can also be used although the sound will be softer.
• M3 Allen Socket head screw - 25mm or longer with full thread
• M3 nut
• For calibration piece, M3 Allen socket head screw 25mm or longer, flat washer and nut.