All about Measuring Tools
Learn the fundamentals of tape measures, rules, and other measuring devices.
Accurate measurements are the foundation of just about anything produced in a shop. Measuring devices are just as varied as the objects they are designed to measure, good for extremely small distances as well as very large ones.
• Legibility and type of graduations
• Durability of materials
• Length or capacity
Retractable steel tapes are a measuring staple for woodworkers as well as carpenters. A spring-loaded metal tape with a hook at one end can be locked in one position with a lever or button on the tape housing. When the lock is released, the spring retracts the tape. Hooks loosely riveted to the tape blade can move slightly so the tape can be used for inside as well as outside measurements.
Tapes are available in a variety of lengths, but the most useful sizes for woodworkers range from 12 ft. to 25 ft. or 30 ft. Longer tapes typically have wider, stiffer blades, giving them more unsupported reach and a longer life. There also are various blade markings to choose from, including over-sized numbers for older or weak eyes, tapes with both English and metric markings, and tapes that locate the center of a layout. Fractional divisions are usually 1/16 in. or 1/32 in. Coatings, such as nylon or Mylar, prolong the life of the blade.
Straight rules are more useful and more accurate bench tools. Made from aluminum, steel or stainless steel, rulers have printed or etched markings in increments ranging from 1/8 in. to 1/32 in. (some have sections with finer increments, 1/64 in. or even 1/100 in.). Some combine English and metric markings, while others are meant to find the center of a layout. Another type of straight rule is the 6-ft. or 8-ft. wooden folding rule; some come with a slide-out brass extension for taking accurate inside measurements.
Other measuring devices
Calipers are used for very precise measurements of small objects. Vernier, electronic, and dial calipers typically have a capacity of 6 in. They are available with plastic, metal, or fiberglass reinforced plastic bodies and can measure both inside and outside dimensions. Dial indicators, mounted to a frame or base, measure even smaller distances and are used for setting up and checking machinery.