Abstract: A very thin abrasive material on a substrate is comprised of ceramic particulates contained within a metal matrix. The particulates extend fully through the matrix from the substrate surface to the machined free surface of the abrasive. In a representative 0.38 mm abrasive the particulates are sized normally at 0.42-0.50 mm and have an aspect ratio of less than 1.9 to 1. This enables a high density of particulates, in the range 33-62 per cm.sup.2, while at the same time ensuring good bonding in that most of the particulates are fully surrounded by matrix. When the abrasive is applied to the tip of a superalloy gas turbine engine blade, about 10-50% of the matrix metal is removed after machining. This allows the machined ceramic particulates to project into space and to thus better interact with ceramic abradable seals. In the preferred practice of the invention the particulates are alumina coated silicon carbide contained in a nickel superalloy matrix.

Abstract: A single electric motor is employed to drive two, separate backup roll supporting shafts which are mounted to rotate about a common horizontal axis. A first, solid, cylindrical backup roll of relatively small diameter (less than 11/2") is secured to one end of one of said shafts for rotation beneath a first grooving roll, and a second, relatively larger diameter backup roll (greater than 11/2" and less than 2"), which is annular in configuration, is secured coaxially to one end of the other shaft for rotation thereby beneath a second grooving roll. Each grooving roll is mounted for vertical reciprocation by springs and by a hydraulic ram supplied by fluid from a separate hand pump. Means is also provided for adjustably limiting the descent of each backup roll.

Abstract: The roll comprises a solid, cylindrical, heat-treated steel rod having a threaded stud section on one end, and an externally knurled operating section on its opposite end. The stud section is adapted to thread into a bore formed in one end of the drive or work-rotating shaft of conventional roll grooving apparatus, thereby to support the operating section in the path of a conventional grooving roll which is mounted to reciprocate radially of the drive shaft between operative and inoperative positions. A circumferential groove in the operating section of the backup roll registers with a circumferential boss on the grooving roll. When one end of a piece of thin walled pipe is inserted over the operating section and the grooving roll is advanced against the pipe, the shaft is rotated and rotates the pipe so that the grooving roll forms a groove therein.