GB131196A - Method and Means for Producing Improved Twist-drills, Reamers, and other Boring and Cutting or Finishing Tools. - Google Patents

Abstract

131,196. Brundrett, H. Sept. 27, 1918. Milling helical surfaces; drills; reamers; chucks.-Twist drills, reamers, and the like having grooves of increasing pitch towards the base are cut with the area of the groove the same throughout but with an increasing sectional area of metal from the point to the shank, by the use of a master drill with an increasing pitch toward the shank end. The drill blank e<5> is carried by a split chuck e<4> secured to one end of the master drill a which is secured at its other end to a spindle on which is mounted, loosely, a screwed sleeve g between ball bearings on the spindle. A sliding bearing g<3> receives one end of the screwed sleeve which is adapted to be rotated by a worm wheel g<2> and a pivoted worm h<2>, Fig. 11. Axial and rotational motion is given to the master drill bv the screwed sleeve and bushes h<1> and by spring-controlled balls d in a fixed adjustable support e<3> respectively. The spiral grooves may be made of uniform depth or of gradually decreasing depth, and for this purpose the cutter spindle i<1> is mounted in a bearing pivoted at j, Fig. 14, an offset j<1> of the bearing holding a micrometer screw k, Fig. 20, which abuts against a lever m carrying a spring pawl m' operated by a sliding bar n which controls the position of the tool with respect to the blank. The bar n has also a recess o which allows complete withdrawal of the tool from the work by means of springs on completion of the cutting and on reverse movement of the bar the pawl is tilted backwards against a spring m<3> until it enters a recess o<1> in the bar and resumes its active position against a stop on the lever m. The slide bar n is actuated through levers from the sliding bearing g<3> on the feeding sleeve g. The toolholder may be slidable instead of pivoted and the bar a may be replaced by a cam. If two grooves are to be cut, the master drill is indexed before the advance of the drill commences. In order to get uniform or an increasing area of groove as the depth of cut is decreased means are provided to present the blank to the cutter at various angles for this purpose the main slide bar c is pivoted at q and lateral motion is given to the blank in respect to the cutter by an adjustable wedge plate r<2> engaging a projection t on the sliding bearing g<3>, the projection being held up to the plate by a cord and weight r. The operations may be performed successively in three machines instead of in one.