GB632437A - Improvements in drill grinding - Google Patents

Abstract

632,437. Grinding drills. HOGFORS, H. F. B. Feb. 5, 1947, No. 3460. Convention date, Feb. 8, 1946. [Class 60] [Also in Group XXII] In a method of grinding twist drills, the drill 38 is fixed in a holder 37, which is carried in a device 15 so that it can be turned round the axis of the drill, and is first ground with a flat clearance plane 2a nearest the cutting edge 1a and another flat plane 4a inclining at a greater angle b than the clearance plane, whereupon the holder 37 is, without other movement, turned half a revolution, and the. other cutting edge 1b is ground in like manner. A swinging arm 14, carrying the holder 37, slides on a rod 9 and is initially set at the angle d of the cutting- edge to be ground by aligning a gauging plate 18 with the face 12 of the grinding wheel 2. A plate 19 on the underside of the arm 14 engages a follower 20 carried on an arm 21 pivoted to a slotted link 24 which is held against a stud 27 by a spring 28. By turning the arm 14 until the opposite end of the slot abuts the stud 27, the arm is positioned at the angle of the plane 4a. In operation, a cutting-edge of the drill is aligned with a plane 10 formed on the end of the rod 9 and which is, itself, initially set by aligning a perpendicular plane 11 with the grinding face 12. The drill is traversed past the wheel 2 bv hand and the necessary cut is applied by a cam 39, being measured by a scale on a knob 43. The arm 14 is then turned to grind the second plane. To grind the opposite cutting edge, the drill is rotated 180 degrees, gauged by a spring plunger 33. The arm 14 and rod 9 are swung about a pivot 3 for removing the drill. The slotted link 24 may carry stops to vary the angles of the planes 2a, 4a, and the arm 14 may be formed in two parts to permit variation of the drill-point angle d.