What are calipers?
Calipers are a ruled scale, dial, or digital method to measure dimensions of an object via two adjustable jaws.
Inside calipers measure the internal size of an object, and outside calipers measure the external size of an object. For example, inside calipers may be utilized to measure the inside of a cylindrical ring gage, while outside calipers could be used to measure the diameter of a master disc.
There is a fixed, main scale with a sliding readout that moves across the main scale. This sliding readout is typically moved with a thumb slider and can be set in place via a set screw.
The three main types of calipers are vernier, dial, and digital. They are comprised of four main parts: the outside jaws, the inside jaws, the main scale, and the measurement method.
How are calipers used?
For our purposes here, we will focus on dial and digital calipers.
First, you must zero your caliper. For dial calipers, you use the thumb slider and close the caliper jaws fully using the thumb slider until no light can pass through where they meet. If the dial does not read zero, loosen the lock screw, turn the dial face until the needle points to zero, and tighten the lock screw. For digital calipers, again, close the caliper jaws fully using the thumb slider until no light can pass through where they meet. If zero is not displayed on the digital readout, press the zero button on the digital readout. You have successfully zeroed your dial or digital calipers.
Next, we will discuss an outside measurement. Open the outside caliper jaws via the thumb slider so that the opening is slightly larger than the outer edges of the object you are measuring. Place the outside caliper jaws on either side of the object and close the outside caliper jaws in on the object using the thumb slider. Be careful! You do not want to over tighten the caliper jaws. They should fit snugly around the item without causing damage to the item under test or the outside caliper jaws themselves.