| 摘要 |
<p>A positive feed drill having a spindle drive gear train and a spindle feed gear train coupled to the drive gear train by side teeth on coupling gears mounted on the same shaft is provided with actuatable means for uncoupling the feed coupling gear from the drive coupling gear, and locking it when the spindle has been fed a predetermined extent, thereby retracting the spindle, and for unlocking the feed gear train, once the spindle is retracted, without recoupling it to the drive gear train, thereby holding the feed gear train in an idle mode until the automatic means is manually reset. Alternatively, the positive feed drill is provided with a spring between the feed coupling gear and a housing to bias the feed coupling gear against the drive coupling gear to feed the spindle forward as it drills. A positive stop prevents the spindle from feeding beyond a predetermined point, thus causing the feed coupling gear to be driven by the spindle. A slope on the faces of the side teeth engaging the drive and coupling gears in order to allow the feed coupling gear to ratchet over the drive coupling gear when the spindle feed reaches the positive stop.</p> |
