When purchasing a shaft measuring machine or manually operated gage, you have two choices; optical or tactile.

Optical Shaft gauges have the following advantages:

1. They are fast!  Not being limited by surface friction, or the requirement to keep the probe in contact with the part, an optical gage can be many times faster than a tactile gauge.
2. Optical shaft measurement has no probe tips to wear out.
3. Optical shaft gages Can be self-programming.  In part or in whole, the optical gage can often scan the part to obtain a “picture” of the measured locations, reducing the programming time.
4. Very accurate for the determination of minimum and maximum diameter.

Unfortunately, optical gages have some disadvantages:

1. They cannot measure a negative radius.  This rules out profile measurement on modern camshafts, but still leaves all round parts in the game.  For a camshaft gauge, something like an Adcole Model 911 with a tactile probe, is superior.
2. They are sensitive to dirt and oil contamination.  Where tactile gages sometimes “push” contaminants out of the way, an optical gage (whether laser or telecentric lens based) has no means to displace contamination.

Ideally, a gage would employ both measurement probes like the Combidim from Exameca Measure.  This shaft gage can measure gears, splines, journals and other features.

To learn more about optical diameter and roundness gages, employing both technologies, contact a gauge expert atmajorgage.com.  MajorGage consultants can give you an unbiased evaluation of the available camshaft, crankshaft, and Cylindrical CMMs that are available.  They also provide training in the features for each.