574,042. Grinding valve seats. DEHN, F. B. (Hall Mfg. Co.). Dec. 24, 1943, No. 21661. [Class 60] An eccentric valve seat grinder has the grinding-disc carried by an outer spindle surrounding a shaft mounted on a pilot carried by the valve guide, the spindle being driven at high speed and the shaft at low speed, and the spindle and shaft each being made in two sections coupled so as to allow the grinding-disc to accommodate itself to a seat not truly aligned to the pilot. The pilot 4 is mounted in the guide 3 associated with the valve seat 2, which may be flat or tapered, and the shaft A embodies an upper section 6 and lower section 7, and the spindle B an upper section 8 and a lower section 9 mounted respectively on the shaft sections 6, 7. The section 6 is journalled in a stationary part 10, and has at its lower end a concentric bore 12 in which is threaded a tubular plug 16 flanged to carry a drive coupling member 17 driven by a key 17a. The member 17 has a flange threaded into a sleeve 18 and locked by a nut 20 ; the lower end of the sleeve 18 has an inner flange 19, the sleeve receiving an Oldham coupling connecting shafts 6, 7. The coupling member is in the form of a ring 23 with alternately disposed lugs on opposite sides engaging slots in the ends of the member 17 and a member 21 secured on the upper end of the shaft 7 and locked by a nut 22 ; this enables the shaft sections to tilt relatively to each other and also to have their axes out of register. The adjacent ends of the shaft sections 6, 7 are spaced by a half-spherical member 26 seating in a spherical face of a ring 27 mounted on the section 7 ; a flat disc member 28 seating at one side in a concentric recess in the member 17 engages with its opposite side on the flat surface of the member 26. The section 7 has threaded therein a bushing 30, projecting upwardly to enter and centre a lock washer 31 having spurs entering notches in the lock-nut 22, the ring 27 resting on the washer. The bushing 30 is threaded internally to receive a stem 34, having flattened sides to coact with the washer 31 to prevent turning thereof, and extending through members 26, 28 ; a link 35 engages the stem and is pressed upwardly in the section 6 by a spring 37, which thus holds the joint parts in close contact. The drive section 8 of spindle B is mounted on .shaft section 6 by ball bearings 45, 46, and the section 9 is mounted on section 7 on ball bearings 50, 51 and is threaded to receive the hub 55 of the grinding-wheel 5. The sections have flanges 56, 57 respectively provided with drive pins 58, 59 connected by springs 60, whereby a yielding drive, also allowing for tilting or adjusting movement between the spindle sections, is provided ; a positive drive is provided for by means of pins 61 projecting from the flange 56 and entering sockets 62 in flange 57, the sockets being of larger cross-section than the pins, so that positive drive does not occur until the pins have moved to engage the socket walls. In order to provide the eccentric grinding action, the shaft section 7 has the portion 40 of its bore, which receives the'pilot, disposed with its axis b at a slight angle to the axis a of the section 7, the axes intersecting at the centre c of the spherical members 26, 27, the grinding- wheel thus being tilted slightly, so that when driven, at high speed, by a gear 65, its point of contact with the seat 2 is moved slowly around the seat by-the slow rotation of the shaft 6, 7. In a modification, a cylindrical sleeve having an inclined bore is mounted in the shaft section 7, the inclined bore engaging the pilot. Specification 501,338 is referred to.