Most coordinate measuring machines (CMMs) are sold with a stylus kit containing an assortment of ruby ball styli and associated tools. Many CMM users soon realize that the standard assortment won’t meet all of their needs. Some part features simply can’t be accessed with these kit styli. Difficult-to-measure features may include ID grooves, features located deep inside a part, part undersides, and small radii. In these cases, a custom stylus may be helpful. But, what will it look like? How long will it take to manufacture? And how much will it cost?

We call it the “back of the napkin.” A fax or email arrives with a freehand drawing of a “concept” stylus, sometimes with a sketch of the part feature it’s supposed to measure. Usually, the CMM operator is in a hurry to obtain the right probe tip for the job. Often the only thing standing in the way of successful measurement is the lack of a suitable stylus.