Styli and probes are slender rod-shaped stems and contact tips or points used to probe surfaces in conjunction with profilometers, scanning probe microscopes (SPMs), coordinate measuring machines (CMMs), gages and dimensional scanners. A stylus is a narrow, elongated staff that is similar in shape to a ballpoint pen. A stylus may be slightly curved so that it can be gripped easily. SPM styli or cantilevers are used to probe an image surface on an atomic scale. Profilometer styli operate on a broader scale and are drawn across a surface to measure surface roughness or waviness. Styli and probes are used for ultra-precise dimensional measurements in many different applications. A contact tip and a cantilever may be used in conjunction with measuring instruments. Dimensional gaging contact tips and probes usually consist of hard carbide or ceramic materials. Gaging probes or tips contact the workpiece to obtain measurements such as thickness, outer diameter (OD), inner diameter (ID), roundness, taper or angularity.
Styli and probes are used with other instruments and equipment. Some products are used with a scanning probe microscope (SPM), an instrument for surface topography studies. A scanning probe microscope (SPM) can also be used for height measurements. Styli and probes are used with an atomic force microscope (AFM), a high-powered instrument able to image surfaces to molecular accuracy by mechanically probing their surface contours. A coordinate measuring machine (CMM) is designed to move probes that locate point coordinates on three-dimensional (3D) structures while simultaneously integrating both the dimensional and orthogonal relationships. Coordinate measuring machine (CMMs) are used for plate work on large parts. A coordinate measuring machine (CMM) may be available in a large variety of sizes and configurations, and able to accommodate different styli and probes.
Styli and probes generally consist of a linear ball bearing assembly precisely fitted to a hardened-and-ground, non-rotating probe shaft to minimize radial play and the effects of side loading. This probe assembly results in exceptional repeatability of 0.000006 inch (0.15 µm). Probe radius is also important, as some gages require a specific radius for their application to meet an industry specification. Generally, a contact tip consists of a single piece of material, but some consist of ruby or diamond inserts swaged or glued into the tip. The material of the contact tip can affect the reading. A contact should be inspected for flats and scratches from continuous wear.
Styli and probes are designed and manufactured to meet most industry specifications. They are used in many applications. Some styli and probes are used in automotive crash tests. Others are used in the measurement of large welded assemblies. Many styli and probes adhere to the International Standards Organization (ISO) conformance guidelines.