Making trains run more smoothly is only one of the missions of Progress Rail Services (Albertville, Alabama) and its 27 U.S., Canadian and Mexican operations. The company is a supplier of rail, rail anchors and track work components as well as signal devices, rail car repair facilities and other railway products and services.

Fitting the wheels onto axles is another matter, especially when the tonnage required to force the wheel securely on to the axles is somewhere between 90 and 160 tons. Therefore, high precision in measuring wheel bore diameters during machining so that the wheels can be fitted perfectly to an axle is critical to the successful and smooth performance of train wheels. According to Mike Russell, quality assurance manager at Progress Rail’s Jackson, South Carolina, plant, comparing the new and old ways of measuring bore diameters has shown a ten-fold increase in accuracy with the newest instrument acquired by the company.

“The optimum fit between the axle and the wheel bore is critical, and it’s really necessary to hold a total tolerance of 0.002 inch on the wheel bore,” he says. “We formerly used a ‘stick’ micrometer for measuring these wheel bores, and it wasn’t very reliable. But we’ve begun using a new Bowers electronic pistol grip bore gage from Fred V. Fowler Company (Newton, Massachusetts) to get highly accurate readings.

“In studies of gage repeatability and reproducibility (GR&R) with the old ‘stick’ gage, we showed 159 percent or no better than 1.59 times the tolerance. This meant it was impossible to hold the 0.002-inch tolerance effectively. Most manufacturers like ourselves look for a 30 percent GR&R and prefer it to be nearer to 10 percent, if possible. With the Bowers gage, we achieved a 15 percent result,” Mr. Russell says.

Progress Rail Services uses Fowler’s Bowers bore gage to measure the bore diameter of a railroad wheel for precise fitting onto the axle. (Inset) Squaring the collar on a rail wheel to measure the bore accurately with a Bowers bore gage has helped to cut the “misfit” rate.

The company’s previous experience in fitting wheels to axles had shown a “misfit” rate of 1 percent, but during August’s first half, Mr. Russell said the rate had dropped to 0.65 percent. Further, using the new gage has eliminated the factor of operator fatigue. Such fatigue contributes to unreliability in meeting Progress Rail Services’ quality standards. In time per measurement, the difference is the current 5-second rate versus 30 seconds. “When we worked before,” he adds, “three different operators gave us three different readings. Now, they’re all on target, and we have greater confidence in our methods.”

The importance of the low misfit rate, according to Mr. Russell, has to do with the standards set by the Association of American Railroads (AAR), the national arbiter. When a wheel is mounted, it must meet either the minimum or maximum tonnage requirements stipulated by AAR. “That’s why our goal is not to have any misfits,” he says.

To enable the gage to provide optimum results, Fowler supplied the company with special spherical anvils to accommodate the intentionally rough surface finish in the wheel bores. “This enables the operator to place the gage into the component by resting the squaring collar on the wheel face and obtain an instant reading by simply releasing the trigger of the pistol,” explains Denis Newton of Fowler. “The spherical profile on the anvils takes care of any misalignment of the gage and the axis of the bore.”

The Bowers XT Holematic pistol grip bore gage, sold exclusively by Fred V. Fowler in the United States, allows a measurement range of ¼ inch to 8 inches without the need to change anvils. It has two preset memories, self-centering heads and an RS-232-C output. Providing constant measuring pressure, it has tungsten carbide measuring faces on all three-point heads from 5 inches (12.5 mm). Extensions are available for deep measuring.

Progress Rail Services is now in the process of switching from its 1994 ISO 9000 certification to 2000 standards, and it expects to receive that certification soon. Mr. Russell is recommending that the other company wheel shops in California, Texas, Indiana, Kentucky, Nebraska, South Carolina and Canada go over to the new bore gage. “It takes variability out, assures accuracy and is easy to use,” Mr. Russell says. “Training time is minimal.”