Scratching Tool acc. to van Laar, Model 426

A ball-shaped hard metal pin with a tip diameter of 0.5 mm is mounted stably in a ballpoint pen-shaped holder made of anodised hard aluminium. This handy design ensures that the device can be guided stably during the scribing/scratching process. The stability of the ball tip is tested in a continual endurance test: A cylinder made of machining steel of approx. 100-mm diameter is scratched by a scribing needle at approx. 20 cm/s and with a load of 50 N on a rotary table. After a distance of 18000 cm, no damage to the ball end should be detected.