How to gauge wire? Many people complained that the gauge was not accurate for wire,they made a mistake on how to measure wire.Pls follow the instruction bellow: 1.Pls measure the metal part of the wire,do not include the isulator part,we mean do not include rubber,because the SWG is just about the metal part of wire. Pls do not use the round hole to measure wire .You have to use the slot to gauge wire or metal. We pls look at picture we supply in the picture, we explain how to correct use the gauge & This fractional drill gauge is a useful guide for identifying drill bit sizes and has 28 measuring holes for determining twist drill sizes from 1/16" to 1/2" in 1/64" increments. The tool shows drill sizes in both inches and decimal equivalents. Etched graduations are filled in black to give high contrast and will not wear off this drill gauge. The gauge measures 2-3/8 inch x 6-3/4 inch overall and is made from stainless steel to prevent rust.