How to Measure the Pins on a Halogen Bulb

Place the large jaws or the “outside diameter” jsaws of your dial calipers around one pin and take a reading on the dial calipers. Inspect the vertical lines on the main scale of the caliper, which is printed on the long bar the dial slides on. The scale is numbered 1 through 10 to denote increments of 0.1 inch. The dial is labeled 1 though 100 to denote increments of 0.001 inch. The main scale will read "0" since you are measuring the diameter of a small pin. Look at the number on the dial, because it is the important number. This tells you the diameter of the pin. As an example, if the dial reads 50, the diameter of the pin is 0.5-inch.

Place the smaller jaws between the two pins and then spread the jaws outward until the jaws just touch the pins. Take a reading on the dial caliper.

Add the reading you obtained in Step 1 to the reading you obtained in Step 2. The reading in Step 1 gave you the distance between the inside edges of the pins. Adding the diameter of the pins from the reading obtained in Step 2 tells you the actual distance between the center of each pin. As an example, if one pin measures .05 inch and the space between both pins measures 0.5 inch, the actual distance between the center of each pin is 0.55 inch.