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Tool To Measure Internal Spaces
When Lee Paxton needed to measure the interior of a set rim, he made his own measuring device. The simple tool was low cost, easy to make, and exact.

    “I needed to get an accurate measurement of an inside stepped bore on a housing I was machining,” says Paxton. “Standard measuring equipment wouldn’t work, so I made my own.”
    Paxton has a degree in mechanical engineering and worked in the aerospace industry. He started his own company with a few tools in a garage. Today, he and his staff make robotic and other high-tech equipment for some of the largest and most technologically demanding companies in the country. Solving his problem required no fancy equipment, just ingenuity.
    The problem was the “stepped bore” design. The deep interior groove to be measured was wider than the surface passage through which the measuring device had to pass. The device had to be inserted, a measurement taken, and then the device collapsed to be removed.
    Paxton’s solution was to pick up a low cost set of calipers with a digital readout. He recognized that by adding “horns” to the caliper arms, he could get an internal measurement.
    “I TIG welded short pieces of welding rod to the ends of the arms,” explains Paxton. “It didn’t matter how long they were, only that they were fixed in place and short enough to slip inside the bore.”
    Once inserted into the bore, he spread the caliper arms. When the horns touched opposite sides of the groove, he zeroed out the digital scale. He then collapsed the arms and removed them from the groove.
    “I expanded the caliper back until the scale read zero again and measured the distance from one horn to the other with another set of calipers,” explains Paxton. “I was then able to machine it down the extra few thousands of an inch needed.”
    Paxton suggests that anyone needing internal measurements, such as machining snap ring grooves, could quickly and easily make a similar device. He bought his calipers with their digital readout at Harbor Freight. Simply attach horns and measure.
    Contact: FARM SHOW Followup, Paxton Engineering, Inc., 4946 Watt Ave., North Highlands, Calif. 95660 (ph 916 344-7511; lee@paxtonengineering.com; www.paxtonengineering.com).


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2016 - Volume #40, Issue #4