581,015. Honing &c. machines. BURGESS, A. F. (Barnes Drill Co.). Feb. 23, 1944, No. 3363. [Class 60] In a honing &c. machine, the feed of the tool to the work is controlled by two members, one of which is movable at a rate proportional to the desired feed, whilst the other is movable at a rate proportional to the actual feed, the members thus maintaining a predetermined relationship only whilst the actual feed equals the desired feed ; a change in that relationship, in response to a lag in the actual rate of feed, for example, due to glazing of the abrasive elements of the hone, causes the operation of means effective to regulate the power-actuated means for feeding the tool. The machine, described as a multi-spindle cylinder honing machine, comprises a head carrying the spindles 5 of hones 7, the head being reciprocated by a piston 8 in a cylinder 9 by fluid from a pump P under control of a reversing valve RV ; the tools are rotated through a shaft and spiral gearing. The abrasive elements 12 of the hones are fed outwardly by push-rods 14 shifted by a rock-shaft 15 formed with eccentric portions 16 engaging the rods and rocked by a piston 20 movable in a cylinder 21 and actuating a rack 23 which engages a segmental gear 25 having a hub 26 keyed to the shaft 15. Fluid is supplied to the cylinder 21 by a pump P<1> and to ensure rapid initial expansion of the hones, an accumulator A is provided, whilst a valve RV<1> directs fluid to either end of the cylinder and connects the non-operative end thereof to exhaust. In the normal operation of the machine, the pressure of the fluid is controlled by a relief valve VN in the discharge line of pump P<1>; if the abrasive elements become glazed, and the cutting action reduced accordingly, the pressure is raised temporarily by the use of a cut-off valve CV which shuts off the fluid from the valve VN, whilst an auxiliary relief valve VH set for a higher pressure becomes operative. This operation is effected by a control device CD comprising a radial arm 30 on the hub 26 which moves at a rate in accordance with the actual rate of expansion of the hone, and a block 31 which moves at a rate in accordance with the desired rate of expansion. The arm 30 has therein a spring-pressed plunger engaging the block 31 which is formed at one side with a surface 38 inclined to the path of the block and engaged by the plunger, the block being moved downwardly during operation of the machine. At the commencement of an operative cycle, the piston 20 rocks the gear 30 to move the plunger to engage the surface 38 of block 31 and then to compress its spring and move the plunger to its limit ; the abrasive elements of the hone then contact the work under normal operating pressure. As the piston 20 moves so also does the block 31 so that the arm 30 is allowed to move at a rate for normal hone expansion; this continues until the actual rate of expansion is retarded by glazing, when the arm 30 will move more slowlv and the surface 38 will recede from the member 30, the plunger then moving forwardly under action of its spring and so actuating the device CD to close valve CV momentarily. The hone then operates under increased pressure until glazing is removed, when normal operation again is resumed. The block 31 is moved by a piston 40 in a cylinder 41 formed with the cylinder 21 in a block 43 provided with ducts 44, 45 ; the rate of movement of the member 31 is controlled by a needle valve 46. The control device CD comprises a switch S in a housing carried by the hub 26 and having an actuator engaged by the bolt of the plunger ; the switch controls the position of the valve CN through a circuit including a timer T which periodically closes a switch T<1> in circuit with a relay R<1>, adapted to close a switch R<11> to energize a solenoid SOL which closes the valve CV, the valve returning to normal position upon opening of the switch T<1>. The operation of the machine is controlled generally by the electrical circuits and fluid-operated mechanism shown, the working cycle being terminated at the end of a predetermined interval measured by the rate of movement of the member 31 ; this member at its lowest position engages an actuator 58 to close a limit switch LS<2> to start a timer T', which after an interval closes switch T1<1> to energize a relay R<6>, thus energizing a solenoid SOL<3> to move a control rod 55 into a position to allow the head 6 to be retracted fully, the limit switch LS then being opened to release a relay R<3> to terminate the working cycle.