33
Cap Screw Pilot Drill
Counterbore
Size
Size (mm) Diameter (mm)
M 3
3.4
6
M 3.5
3.9
6.5
M 4
4.5
8
M 5
5.5
10
M 6
6.6
11
M 8
9
15
M 10
11
18
M 12
14
20
Speeds & Feeds
The speeds and feeds for counterbores are approximately 80% to
85% of those for drills as given on page 11.
The counterbore diameter given in the above table is used for this
calculation.
RE-SHARPENING
Counterbores are re-sharpened only by grinding the front cutting
edges, maintaining the original relief angle of 6°- 8°.
