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Tuesday, 26 November 2013

Grinding of Drills

Grinding of Drills Points : Grinding of Drills A properly sharpened drill is very important. A drill that is not properly ground requires considerable effort to force into the metal, and it may produce an oversize hole with a rough wall. An improperly ground drill cuts slowly does poor work becomes overheated and may break. Drills that mare often used require frequent grinding to keep them in shape.
Drills can be machine or hand ground. Both methods produce satisfactory results. However, grinding drills by hand requires a great deal of practice.
Whether a drill is ground by hand or machine three things must be considered: (1) Lip clearance, (2) Length and angle of the lips (3) Location of the dead center on the central axis of the drill.
Lip clearance angle is the relief given the cutting edge of the drill so that metal behind them will not rub against the bottom of hole.
The angle and length of the lips or cutting edges must be ground equal. Then the dead center will automatically be where it belongs on the axis. The drill point gauge is used to check the angle and length of the lips.
Grinding machines made especially for drill sharpening are produced by many manufacturers. One need only follow the simple directions provided with these machines to quickly obtain properly sharpened drill points. Drill grinding attachments for utility grinders, are a low cost alternative, and generally give good drill points. The V-block holder on the attachment centers the drill and holds it in place A special lip stop and micrometer feed insures accurate grinding of both lip.

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