Starrett 120AZ-9 Dial Calliper, Stainless Steel, White Face, 0-9" Range, +/-0.001" Accuracy, 0.001" Resolution

• Precise dial graduations of 0.001" with one revolution equivalent to 0.100"
• Thumb-operated fine adjustment roll for one-handed use
• Lock screw holds the sliding jaw in position, to ensure a consistent measurement
• Rack teeth point down to keep foreign matter from clogging the gear
• Knife-edge contacts for inside and outside measurements

The Starrett dial calliper 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 callipers 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 calliper 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 calliper, unlike many callipers 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 calliper 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 calliper operation.