Turning and grinding operations using traditional live centers require center holes that are concentric with the workpiece. However, center holes for shafts and other parts to be turned or ground are sometimes mistakenly drilled slightly off-center. In addition, reworking parts might cause their center holes to no longer be concentric with the machined surfaces. Holes that are drastically off center can cause an expensive workpiece to be scrapped.
Riten Industries offers a solution to this problem with its Adjusta-Point radial compensating live center. This device is equipped with four external adjusting screws that can move the point as much as 0.030 inch in any direction. Machine operators use an indicator to check the part’s concentricity while rotating it and then adjust the screws to compensate for the off-center holes.
The Adjusta-Point is currently available in 3, 4 and 5 Morse tapers—additional tapers are available on request, as are customizations such as longer center points and even female centers. It can be rotated at a maximum of 3,000 rpm and accommodates workpiece weights ranging from 1,500 to 4,500 pounds. The bearing design utilizes a large bore, precision, double-row angular contact ball bearing that is manufactured from low carbon steel and case hardened. The point and taper shank are manufactured from 52100 ball bearing steel and through-hardened to provide the strength and durability required in a live center.
Mitchell Kirby, Riten vice president of manufacturing, says that more than 40 percent of the company’s live centers are special designs to meet the end user’s exact specifications. However, Riten saw an increase in demand for this type of adjustable live center leading it to create a stock catalog item ready for immediate shipment. In addition, Adjusta-Point live centers can be repaired for less than half the cost of a new unit. This total reconditioning of the entire live center includes inspection of the shell for damage and regrinding of the taper shank, as needed. The bearings, seals and spindle are replaced and the live center is recalibrated to its original accuracy. It is then returned to the customer with a new factory warranty.