GB651162A - Improvements in or relating to drill grinding jigs - Google Patents

Abstract

651,162. Grinding twist drills. READING, H. C. June 24, 1948, No. 16992. [Class 60] A drill-grinding jig provided with a drill guide 35, Fig. 5, pivotally mounted about an axis 30, Fig. 1, has means for adjusting the guide together with the axis towards and away from the grinding face 12 and means for adjusting the drill guide independently of the axis 30 in a direction having components along the drill axis and in a direction normal to and intersecting both the axis 30 and the drill axis. The drill guide is bolted to a slide 33 which can be locked in position on a slideway 32 integral with and inclined to an arm 28. The latter has two centres 24 which are received in conical depressions at the top of a column 22 forming part of a slide 21 adjustable along a rectilinear slideway 19. One of the centres 24 is in threaded-engagement with the arm 28 and may be adjusted by means of a nut 31, while both centres lie on the axis 30. The slideway 19 forms part of a table which can be angularly adjusted about a pivot 11 the axis of which is midway across the face 12 and tangential to it. The table is graduated at 16 to facilitate adjustment and provided with clamping means. The drill guide 35 is of V crosssection, Fig. 6, and supports a slide bar 50 on which are adjustably mounted a second guide 52 of similar shape to the guide 35 and a calibrated adjustable abutment 55 by which the drill may be fed along the guide. The drill is clamped on the guide by a lever 37 having a cam-faced portion 42 which is engaged by a nose 41 on a lever 38 provided. with a thumb-piece 40 and the drill is located angularly with respect to the guide by a platform 49. The faces of the drill guide are disposed at unequal angles to the vertical so that an increase in the size of drill produces a displacement of the drill axis towards the right as viewed in Fig. 6. The drill size also determines the position of the slides 21 and 33 along their slideways and each slide is set by placing the drill shank between two inclined abutments, one of which is supported by the slide and the other by the slideway. These adjustments may alternatively be made by the use of calibrated scales. When all of the adjustments have been effected to produce the correct relationship between the drill and the grinding face, the arm 28 is given a swinging movement by means of a handle 29 in order to produce a facet with the required clearance at the drill point. The base of the jig, which is mounted on a slide arranged to be traversed parallel to the grinding wheel axis, carries a diamond for trueing.