Modern Machine Shop

AUG 2018

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MMS AUGUST 2018 34 QUALITY GAGING TIPS Measurement Tools AUTHOR | George Schuetz Director of Precision Gages, Mahr Inc. which can show up as degraded accuracy, hyster- esis and/or repeatability. Measurements at this end of the spectrum would normally be reserved for an electronic amplifier with high-performance electronics. However, there may still be reasons to prefer a mechanical measurement tool. Typical examples include budgetary restrictions and avoiding the need to cable a hand gage to a transducer for applications requiring portability. Thus, the dial comparator solves the inherent mechanical problems of the geared dial indicator but at less cost than the electronic amplifier and probe. Here is how this can be accomplished: • Travel of the spindle in a dial comparator is guided by a precision ball guide. This not only eliminates friction, but also provides strong axial stiffness and reduces side play. This assures results in a near one-to-one translation of the motion to indicator movement. • A shock-proofing system isolates the spin- dle from the shock created by the banging of the gears during rapid movement. This also reduces magnification errors by reducing the number of required gears. • Jeweled components maximize sensitivity and accuracy in the movement of gears and levers, while built-in calibration adjustment enables fine-tuning for even the most minute errors. • All of these features ensure the highest accu- racy, but the dial comparator still retains all those features that make dial indicators practical and easy to use. These include: a built-in, lockable, fine adjustment control; adjustable tolerance markers; and very fast response indicator hand. The bottom line: A dial comparator has five to 10 times better resolution and accuracy than a dial indicator without a significant increase in price. The electronic amplifier has about 10 times better resolution and accuracy than the dial comparator, but at a higher price and a greater risk of problems associated with having too much resolution for the gaging being used. So, where range is not a con- cern, the comparator offers the best resolution and accuracy value. If you need high performance on a budget that is a little tight, the dial comparator could be the solution. See how Hexagon is producing quality at Booth E-5202 or visit I PRODUCE QUALITY

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