GB1435725A - Grinding attachments - Google Patents

Abstract

1435725 Sharpening saw blades ROBERT BOSCH GmbH 21 Sept 1973 [23 Sept 1972] 44410/73 Heading B3D [Also in Division B5] An attachment 1 for fitting to a grinding stand 3 for sharpening a saw blade 29 comprises means 28 for locating the blade for pivotal movement about its axis, and a stop pin 20 for limiting the pivoted movement by engagement with the gap between adjacent teeth, the pin being arranged on a bolt 16 slidable in a guide bore 15 located to extend substantially tangenially to the periphery of the blade, nuts 17, 18 screwed on to the ends of the bolt limiting the sliding movement thereof. The saw blade has large teeth 35 the rear of which are of convexly arcuate configuration 36 centred on the axis of the black and merge tangentially by way of concavely circular regions 37 with the rake of the chisel-like tips of the teeth. The attachment has a horizontal arm 2 having a blot 5 secured by a wing blot 6 in a bore in the grinding stand 3, which may be an accessory for a hand drill having an electric drive motor. The arm is formed as a guide 7 for slidably supporting a bracket 11 which can be secured in position by a wing bolt 9. The bracket is formed with a tube-like member 14 which provides the guide bore 15 at an angle of approximately. 75 degrees to the bracket 11. The bolt 16 is slidable in the bore to an extent determined by the adjustable units 17, 18 and carries the stop pin 20 which extends through a slot 19 in the member 14 into a gap between adjacent teeth of the saw. A holding bar 21 is slidable in bearings 23, 24 in the bracket 11 and an extension 12 thereof and is urged by a spring 25 towards the stand 3 by an amount determined by a nut 27. A clamping device 28 is secured by a wing bolt 30 to the bar and a clamping member 32 is rotatably supported on the device 28 for receiving the saw blade which is clamped on the member by a knob 33. In use, the saw blade is clamped on the member 32 which is slipped on to the pivot 28<SP>1</SP> of the device 28. The rear 36 of a tooth is pressed against the grinding disc 4 and the device 28 is fixed on the bar by the wing bolt 30. The pin 20 engages the gap between adjacent teeth and the nuts 17, 18 are adjusted so that the wheel can grind the convex portion 36 and the region 37 up to the tip of the tooth. With the grinding wheel running, nut 27 is adjusted to advance the blade into the wheel for grinding a tooth, the bar 21 then being retracted against the spring 25 to effect indexing of the blade.