GB153135A - Improvements in lathes or turning machines particularly adapted for use in forming curved surfaces - Google Patents

Abstract

153,135. Tanner, W. S. Aug. 26, 1919. Lathes.-A lathe particularly suitable for forming lens-grinding tools is adapted to cut either convex, concave, or toric surfaces. Figs. 1 and 2 show the setting for cutting a concave surface. The upper bed 1 carries a slidable headstock 3 while a lower bed 2 supports a radius-post 7 and the saddle 4 having a cross-slide 5 and a revoluble tool-post 6, which is connected by an adjustable link 8 to the radius-post. The tool-post has a base 15 sliding in bevelled guides on a revoluble table 14, and its upper part has a tool clamp 21 and micrometer adjustment 22. The exact overhang of the cutting- tool is determined by a vernier device, Fig. 4, attached to the head of the tool-post. This distance added to the reading of a scale 29 on the link gives the radius of the tool being cut. The positions of the radiuspost and saddle are set by hand, but modifications are described having longitudinally-placed screws to effect these adjustments. The cut is made by transverse feed of the tool by means of a screw 11, and the headstock may be adjusted to put on cut instead of resetting the radiuspost. For cutting tools of small radius, the link may be dispensed with, the base 15 clamped to its table, and the tool-post rotated by means of an eccentrically-mounted worm 17. For cutting convex surfaces, the headstock is moved to the right-hand end of its bed and the radius-post to the left-hand end, or alternatively separate radiusposts may be provided for convex and concave work. For cutting toric surfaces, a cylindrical face is first formed and mounted in a headstock with its axis transverse to the bed. The superposed spherical surface is then turned as described. Modifications of spherical surfaces mav be cut by means of a guide or former preferably clamped to the bed 2 and bearing against a roller on the arm 8, the clamps 28 being left loose.