How to Counterbore For Screws
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Counterboring is increasing the diameter of part of a hole.
When the clearance hole for a wood screw is counterbored to
receive the screw head, it is necessary to increase the depth
of the clearance and pilot holes an amount equal to the length
of the counterbore. The size of the counterbore is made large
enough to accommodate the entire head of the screw below the
surface of the stock. Counterboring may be done before clearance
and pilot holes are drilled. However, since counterbores usually
have removable pilots, such drilling may be done last.
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Counterboring of screw holes is used: a) to allow the root
of the screw to enter the stock to be joined when the thickness
of the stock counterbored is greater than the length of the
screw. b) to cover the screw head with a wood plug. The plug
may be required for concealment, protection, or decoration.