Some critical fastener characteristics must be inspected using the Optical Comparator. These features include under head fillets, thread root radii, flat head and point angles. Additionally, Optical Comparators are very useful in measuring special features such as groove depths & widths, shoulder lengths, distance for first full thread to the head and chamfer diameters. The Optical Comparator is probably the most versatile instrument available for fastener measuring. There are very few fastener features which it cannot measure.
Optical Comparators use two types of illumination. When using profile illumination, the comparator’s light shines past the part and casts a shadow on the comparator’s screen, showing only the outline. When using surface illumination, the surface of the part is shown on the comparator’s screen. This allows measurement of characteristics such as chamfer diameters and letter sizes.
There are two models available.
- Model OC-121E has a 12″ screen and digital scale readout capable of measuring lengths and heights to .0005″ resolution.
- Model OC-1400 has a 14″ screen and computerized digital readout capable of calculating angles, radii and measuring lengths and heights to .0001″ resolution.
Both models can measure in either inches of millimeters.