The Starrett dial caliper has sharp black graduations every 0.100" on the no-glare, satin-finished stainless steel bar, and graduations on the dial every 0.001". One full revolution of the dial is equivalent to 0.100". These calipers have knife-edge contacts for measuring both inside dimensions (ID) and outside dimensions (OD). The knife-edge contacts can be used to scribe parallel lines on the workpiece. This caliper can be used with one hand through operating the fine adjustment roll with the thumb. The lock screw locks the dial bezel and holds the sliding jaw in position. The depth rod is integrated into the rack of the caliper, unlike many calipers which offer a detachable depth rod, or none at all.
The hardened stainless steel components, including the bar, measuring surfaces, rack, gears, and depth rod, offer corrosion resistance, increased accuracy, and long life. Positive split gear anti-backlash control offers increased accuracy over standard gear configurations. Backlash is the amount of clearance between mated gear teeth in the caliper controls, which prevents the gear teeth from jamming. It is undesirable to have much backlash due to the lack of precision offered by the increased amount of play between gears. Certain gear designs can minimize or eliminate backlash; split gear systems actually split the gear into two gears, each half as thick as the original gear. One of these gears is then fixed to the shaft while the other gear is allowed to turn. The free-turning gear is connected to coil springs that rotate it until all of the backlash in the control system has been eliminated. The rack teeth point down to keep foreign matter from clogging the gear operations. This prevents measurement errors where metal chips could interfere with proper caliper operation.
Calipers measure the distance between two opposing sides of an object. They make inside, outside, depth, or step measurements, according to their type. Calipers are commonly used in architecture, metalworking, mechanical engineering, and machining. The simplest calipers have two legs to mark the two points and require a ruler to take the measurement. More complex calipers use two sets of jaws instead of legs and have up to two graduated scales. Vernier, dial, and digital calipers give direct and accurate readings and are functionally identical, having a calibrated scale with a fixed jaw, and another jaw with a movable pointer that slides along the scale. The vernier caliper has a scale sliding parallel to the main scale for an additional, fractional reading to improve measurement precision. The dial caliper has a circular dial with a pointer on a toothed gear rack replacing the second vernier scale. As with the vernier, this second measurement is added to the reading from the main scale to obtain the result. The digital caliper takes a differential by zeroing the display at any point along the slide, with an LCD that displays a single value in English and/or metric units.
The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company was founded in 1880 and is headquartered in Athol, MA.