The dial indicator came from the work of a nineteenth century watchmaker in New England. John Logan of Waltham, Massachusetts, filed a U.S. patent application on May15,1883 for what he termed as â€śan improvement in gages.â€?Its outward appearance was no different than the dial indicators of today but the pointer (indicator needle) was actuated by an internal mechanism consisting of a watch chain would around a drum (arbor). The arbor diameter determined the amplification factor of the indicator. Later, Logan developed a rack and pinion assembly that is currently in use today on most mechanical dial indicators.
The full range of applications of this device was not recognize for another 13 years when one of Loganâ€™s associates, Frank Randall, another watchmaker from E. Howard Watch CO., Boston, bought the patent rights from Logan in 1896.He then formed a partnership with Francis Stickney and began manufacturing dial indicators for general industry..
The German professor Ernst Abbe established the measuring instrument department at the Zeiss Works in 1890 and by 1904 he had developed a number of instruments, which included a dial indicator, for sale to industry. The dial indicator is still in prevalent use today and newer design have been outfitted with electronic sensors and digital readouts.
For the past 50 years, the most common tool that has been used to accurately measure shaft misalignment is the dial indicator . There are some undeniable benefits of using a dial indicator for alignment purposes:
â€˘One of the preliminary steps of alignment is to measure runout on shafts and coupling hubs to insure that eccentricity amounts are not excessive. As we have seen that, the dial indicator is the measuring tool typically used for this task and is therefore usually one of the tools that the alignment expert will bring to an alignment job. Since a dial indicator is used to measure runout, why not use it also to measure the shaft centerline positions?
â€˘The operating range of dial indicators far exceeds the range of many other types of sensors used for alignment. Dial indicators with total stem travels of 0.200 in.(5mm) are traditionally used for alignment but indicator with stem travels of 3in. or greater could also be used if the misalignment condition is moderate to severe when you first begin to â€śrough in â€ťthe machinery.
â€˘The cost of a dial indicator (around USS70 to USS110) is far less expensive than many of the other sensors used for alignment. You could purchase over 140 dial indicators for the average cost of some other alignment tools currently on the market.
â€˘Since the dial indicator is a mechanically based measurement tool, there is a direct visual indication of the measurement as you watch the needle rotate.
â€˘They are very to test for defective operation.
â€˘They are much easier to find and replace in virtually every geographical location on the globe in the event that you damage or lose the indicator.
â€˘Batteries are not needed.
â€˘The rated measurement accuracy is equivalent to the level of correction capability (i.e., shim stock cannot be purchased in thickness less than 1 mil )