| 摘要 |
<p>Sharpening means comprising abrading means (31, 39, 34) providing a rotatable cyclindrical abrading surface (34), means (32, 33) to support a twist drill to be sharpened with its axis (X2-X2) intersecting a rectilinear generatrix of said surface (34) at an ''approach'' angle of generally half the point angle of the drill (4), and means (45, 51, 52, 55, 56) to vary said ''approach'' angle upon angular movement of the drill (4) about its axis. Preferably the sharpening means comprises a drill holder (33) to hold a drill to be sharpened, a carrier (35) for supporting the holder for angular movement about the drill axis (X2-X2), means mounting the carrier (35) on a support for angular movement relative to the support about an axis (Z-Z) orthogonally intersecting the drill axis (X2-X2), and cam means (51/52, 56) associated with said drill holder (33) such that said angular movement of the carrier-supported drill holder (33) can effect, via said cam means (51/52, 56), a said relative angular movement of said carrier (35) thereby to vary said ''approach'' angle and enable a requisite ''relief'' for a land of the drill to be provided.</p> |
