Caliper measuring tools are comparators, used for transferring a dimension from one place to another. Calipers can be set from a sample of work, from a ruler or from a micrometer.
Most accurate setting can be obtained from a sample piece of work. Quite accurate results can be obtained by setting calipers from micrometer. The caliper legs should move smoothly but not too easily.
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- Outside calipers (Bow calipers, egg calipers)
Outside calipers are used to measure the external size of an object. To adjust a caliper to the work, open the legs wider than the work and then bring them down to the work.
- Setting to required dimensions
- Inside calipers (Straight calipers)
Inside calipers are available in the same size range as outside calipers. They have straight legs, turned out at the top and are used to take inside measurements.
Setting to required dimensions
To adjust a caliper to a scale dimension, one leg of the caliper should be held firmly against one end of the scale and the other leg adjusted to the desired dimension.
Spring joint calipers
The spring joint calipers have legs pivoted on a roller and the legs are tensioned by means of a strong bow spring. The adjustment for measuring is made by opening and closing the legs by means of an adjusting nut.
Transfer calipers are used for measuring chamfered grooves or flanges. A screw attaches a small auxiliary leaf to one of the caliper legs. The measurement is made as with ordinary calipers. The leaf is locked to the leg. The legs may be opened or closed as needed to clear the obstruction. The legs are then brought back and locked to the leaf, restoring them to the original setting.
Inside/outside calipers (Combination calipers)
Odd leg calipers (hermaphrodite calipers, Jenny calipers)
Odd leg calipers are used to draw lines parallel to an edge. They consist of one caliper leg and an leg with an adjustable scriber point. Odd leg calipers can also be used to lay out the center of round stock.