counterbore
/ˈkaʊntərˌbɔr/
verb
- To cut a counterbore into a hole or surface.
- You need to counterbore these holes before assembling the frame.
- The technician counterbored the holes to fit the special bolts.
- He learned how to counterbore accurately using a drill press.
noun
- A cylindrical recess cut into a hole to allow the head of a bolt or screw to sit flush with or below the surface.
- The drawing specified a counterbore for each of the mounting holes.
- The machinist used a counterbore to create a recess for the bolt head.
- Make sure the counterbore is deep enough so the screw sits below the surface.