Grinding wheels used for the industrial shaping and polishing of metal are synthetic versions of ancient grindstones quarried from natural materials like sandstone. Composed of natural or artificial abrasive particles set in a matrix of bonding material, grinding wheels in progressively finer grades remove waste material from rough castings and both shape and sharpen the cutting edges of steel tools.
When Franklin Norton and his cousin Frederick Hancock opened their pottery business in Worcester, Mass., in 1858, their fledgling company focused on redware and stoneware pottery and expanded eventually into the manufacture of diverse items such as jugs, beer bottles and spittoons. In 1873 an employee, Sven Pulson, invented a kiln-fired grinding wheel shaped from a mixture of emery powder, clay and water. Frank Norton patented the concept and began production of Pulson's grinding wheels.
Although Pulson's grinding wheels surpassed the quality of the industry standard wheels of the day, which were built of wood embedded with emery particles, company politics initially prevented success. Opposed by his cousin Frederick, who soon retired, Frank Norton sold his interests in the business in 1885 and returned to the potter's trade. Five years earlier, Pulson had retired and turned over wheel making to his brother-in-law John Jeppson. Jeppson and his partners purchased the company, the Norton product name and the product patent and continued the business.
Pulson's revolutionary idea was based on the adhesive, not the abrasive. Rather than presenting a durable face prone to clogging, Pulson's wheels gradually eroded as they were used, constantly presenting a fresh cutting surface. Pulson's grinding wheels could be manufactured rather than quarried, resulting in a tool that was both cheaper and more efficient. By the late 1880s the grinding wheel was considered an essential fixture in every modern machine shop.
In the 1890s emery wheels were overshadowed by the introduction of silicon carbide and aluminum oxide composites. All three abrasives are still in use, but emery is now used more often for polishing than for grinding and shaping. New abrasives and bonding agents constantly emerge, and manufactured industrial diamond wheels are now in common use. Cutoff wheels of high strength composites reinforced with fiberglass now extend the use of grinding wheels to cutting machines such as circular saws.
Although Norton Grinding Company remains the largest manufacturer of abrasives in the world, many recent patents in the industry have been filed by inventors from both Japan and Taiwan. A shift by the steel industry to continuous casting has reduced the demand for special purpose industrial grinding wheels. Older aluminum oxide wheels have been surpassed in quality by polycrystalline cubic boron nitride and diamond, but vitrified bond grinding wheels still hold a viable place in today's market.
- Photo Credit Millstone by kevinrosseel at http://www.morguefile.com/archive/display/185512
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