| 摘要 |
Anti-chatter guides for a spade drill which are perpendicular to the side faces of the spade blade and which have an end to end dimension (diameter) wholly forwardly of the rear portion of the blade corresponding to the width of the blade so as to engage the wall of the hole drilled by the blade thus to prevent chatter of the spade drill during drilling and after the cutting edges break through the workpiece. In one form of the invention, the guides constitute a portion of the clamping means by which the spade blade is mounted in the slotted end of a holder, and in another form of the invention, the guides are on the blade itself forwardly of the holder.
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