In 2003, United States Patent 6,609,308 was awarded to Q-Mark for drilled silicon nitride balls.
What is silicon nitride?
Silicon nitride is an extremely hard hybrid ceramic (Si3N4) with a very low coefficient of friction. Silicon nitride takes a polished finish well. It is used in high-speed spindle bearings and aircraft flap actuators in order to provide longer service life in demanding applications.
Why are silicon nitride styli better than ruby styli?
When ruby balls contact soft materials - aluminum, for example - they tend to accumulate tiny bits of the material on the ball. Over time, this build-up of metal on the ball can result in measurement errors. When this occurs, the stylus must be discarded.
When ruby balls are used on hard or abrasive materials, they can develop flat spots caused by wear. When the ball develops a flat spot, the stylus should be discarded.
Silicon nitride has a significantly lower coefficent of friction than ruby. It's extremely hard, too - about 78 Rc. Thererfore, silicon nitride balls exhibit less wear and don't tend to accumulate material on their surface like ruby balls. Our clients report up to 5 times longer tool life in demanding applications using silicon nitride balls instead of ruby.
Q-Mark offers hundreds of styli with silicon nitride balls. We can put a silicon nitride ball on any stylus with a ball 1 mm diameter and larger.