Modern Machine Shop

MAY 2018

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BETTER PRODUCTION MMS MAY 2018 98 mmsonline.com CENTERLESS GRINDING dead centers paired with a "drive dog" clamp that transfers spindle motion to the workpiece. And in this application, grinding the smaller end sections of the shaft without a collision between wheel and fixture would have required f lipping and re-clamping the part. All told, Mr. Homer says the complexity of grinding between centers would have made the operation cost at least twice as much as centerless grinding, possibly even three times more. Although grinding between centers would have been more complicated and more expensive, it appeared to be the only option at first, Mr. Homer says. Initial plans for the Gizmotron 2.0's shaft had the end diameters terminating too close to the main diameter. "You can't grind up a shoul- der," he explains. Contoured grinding wheels—and by exten- sion, ground features—can be only as precise as the dressing tool allows, he continues, and there is a tolerance to everything. In this case, the 0.02-inch-radius edge of the diamond dressing tool was not capable of creating a corner as sharp as the turning machine. Any rounding in the pro- file of the wheel would translate directly to the profile of the shaft. Avoiding this effect required longer reliefs—longer undercuts immediately adjacent to the main diameter to ensure the rounded portions of the wheel encountered only air. With this additional empty space between sections of the shaft, grinding could proceed on all three critical diameters without fear of the wheel rolling material over the sharp-cornered shoulders created by the turning machine. Having experienced problems with bearings popping off shafts produced by other suppliers, Mr. Kipness was initially wary of any change that would reduce the size of the bearing lands. However, previous experience with similar parts FINISHES FOR IRON, STEEL & ALUMINUM FREE SAMPLE FINISHING – Send parts & we test and provide recommendations. www.birchwoodtechnologies.com TOLL FREE 1.800.328.6156 TRU TEMP ® black oxide for iron and steel. 30 minute process operates at 200 o F and creates a black magnetite finish. PRESTO BLACK ® cold blackening for iron and steel. 20 minute process operates at room temperature and creates a satin black finish. MICROLOK ® MZN zinc phosphate for iron and steel. 20 minute process operates at 140 o F and creates a matte grey finish. LUMICLAD ® black oxide for aluminum. 30 minute process operates at 200 o F and creates a satin black finish. Workholding requirements generally make between- center grinding a more complicated proposition than centerless grinding.

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