b'Center Stage Diagram of a centerless grinding configurationpoor surface finish and incorrect geometry. A work rest generally has an angled working surface, which plays a vital role in the efficiency of the process. As the angle becomesGrinding wheel Part Regulating wheelsteeper, the rounding action of the process is enhanced.These three components can be configured in several ways to allow a part to sit on the centerline of the wheels, above center or below cen- C. TateWork restter. Most setups place a part above center of the wheels. The angle of the work rest surface height above center and the tangency of the reg-ulating wheel and grinding wheel to a workpiece create a unique geo-metric arrangement that allows thetook 33 seconds, and we held thethroughthemachine.End-feed centerless process to efficientlydiameter to a 0.0127 mm (0.0005")grinding is used ordinarily to pro-generate round parts. tolerance and produced roundnessduce tapered parts.within 0.0051 mm (0.0002").Types of Centerless Grinding In-feed centerless grinding, alsoAdvantagesThrough-feedgrindingistheknown as plunge grinding, is con- Centerlessgrindingcanre-most popular form of centerlessducted by placing a part on theplace turning when parts have high grinding. Through-feed grindingwork rest and radially feeding thelength-to-diameter ratios, fine finish is performed by traversing a partpart into the grinding wheel withrequirements and close tolerances. from one side of the machine to thethe regulating wheel. In-feed grind- The process works well when finish-other, between the grinding wheeling is used when a part has oneing thin-walled components that are and regulating wheel, without stop- portion that is larger than another.difficult to clamp. Centerless grind-ping. Axial feed is created by dress- Crush form dressing imparts the de- ing can be used to rough bar stock ing a regulating wheel and tipping itsired shape into the grinding wheel.before other machining operations at an angle relative to the blade andThis method is used to create com- so material arrives clean, round and grinding wheel, normally about 3.plex forms or generate multiple di- straight. Bars for Swiss machines This combination of factors pulls aameters at one time. In-feed grind- often are ground before use.workpiece across the work rest anding is efficient at generating smallThere are many benefits with cen-between the grinding wheel andparts with close tolerances. terless grinding, but most shops regulating wheel. Through-feedEnd-feedgrindingisaccom- do not have enough work to sup-grinding is very productive. At aplished by feeding a part into aport the purchase of a centerless previous employer where we mademachine, much like through-feedgrinder, nor do they have people power steering gears, we wouldgrinding. With end-feed grinding,with the skills needed to efficiently grind 0.305 mm (0.012") from a 31.75a part runs axially like with through- set it up. (A fair amount of magic mm-dia. (1.25") steel bar that wasfeed, but an end stop prevents thegoes into getting good parts from 914 mm (36") long. The full processpart from traversing all the waya centerless grinder.) Fortunately, many job shops specialize in center-less grinding. Recognizing center-about the authorless applications and finding a good Christopher Tate is engineering manager of advancedjob shop to grind parts can reduce manufacturing engineering and machining at the Savannah,aggravation with tough jobs, lower Georgia, facility of Mitsubishi Hitachi Power Systems Ameri- costs, improve margins and make a cas Inc., Lake Mary, Florida. Contact him at chris23tate@ company more competitive in the gmail.com. market.CTE56JULY 2020CenterlessGrinding.indd 56 6/16/20 2:30 PM'