Coun"ter*bore` (-b?r`), n.

1.

A flat-bottomed cylindrical enlargement of the mouth of a hole, usually of slight depth, as for receiving a cylindrical screw head.

2.

A kind of pin drill with the cutting edge or edges normal to the axis; -- used for enlarging a hole, or for forming a flat-bottomed recess at its mouth.

 

© Webster 1913.


Coun`ter*bore" (koun`t?r-b?r"), v. t.

To form a counterbore in, by boring, turning, or drilling; to enlarge, as a hole, by means of a counterbore.

 

© Webster 1913.

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