| 摘要 |
1,251,156. Making trepanning tool or saw. E. D. HOUGEN. 30 Jan., 1969 [6 May, 1968], No. 5700/69. Headings B3A and B3C. [Also in Division B5] A hole saw or trepanning tool comprises a sheet steel strip 20, Fig. 2, rolled into cylindrical shape and having a series of successive teeth 32 extending circumferentially around one edge thereof, the teeth being ground such as to present cutting edges at the apices of the teeth, which edges are inclined to a plan perpendicular to the axis of the saw so that they extend axially further at the outer periphery of the saw then at the inner periphery. The strip is rolled so that its ends abut and is press fitted into a cyanide hardened mild steel cup 18 secured to an arbor 16. The press fitting causes the cup and strip to flare outwardly slightly so that the cylindrical shape is slightly tapered to provide a clearance when cutting. Prior to fitting in the cup, the teeth are cut by a punch and die 46, 48, Fig. 8, the punch moving outerwardly. Every other tooth over less than half the circumference is set inwardly by a tool 83. The teeth are ground to have an inclined cutting edge by a grinding wheel 52, Fig. 11, the saw is provided with a piercing tool 36, a drill or a tapered centring tool which may be formed with an enlarged part to assist in removing the cut piece of a workpiece from within the tool. The cup is formed with holes and vanes 116 which serve to guide lubricant to the saw. In an alternative embodiment, a sponge 124, Fig. 17, is retained within the blade by a plate 126 supported by rods 128. In use, the sponge is saturated with lubricant and compressed as the saw into the workpiece. The lower edge of the cup may be serrated to effect clearing of the surface adjacent the edge of the cut hole or be chamfered so as not to damage the surface. |
