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ww w.drilldoctor.com 21
Identifying Correctly Sharpened Drill Bits
(and what to do with those that aren’t!)
Correctly Sharpened Bits
The entire surface from the Cutting Edge
to the Heel will have a nely ground
surface without indentations. The Heel
will always be lower than the Cutting
Edge (positive relief).
Once you have reached spark-out (no more grinding noise at all)
take a look at your drill bit. The chisel angle should be between
1:00 and 1:30.
*Look at the bit: Hold
the bit up and look at it
with the cutting edges in
line with the horizon (or
parallel with the 9:00 and
3:00 position imagining a
clock’s face).
Now look at the chisel.
It should be between
1:00 and 1:30. 2:00 is too
far advanced, and if the
chisel gets too close to 12:00, the relief will be negative.
Too much relief will cause an oversized hole diameter and rapid bit
wear. Too little relief will limit feed rates, slowing down the drilling
operation or in extreme cases cause the drill not to perform at all.
If chisel angle looks to be about 2 o’clock, re-align bit 1-2 ticks to
the right of the 118° mark (toward the minus sign) and re-sharpen.
If chisel angle is up to about 2:30, align 2-3 ticks towards the
minus sign.
If chisel is about 12:45,
it’s at the low end of chisel & relief, re-align bit
1 tick to the left of the 118° mark (toward the plus sign) and re-sharpen.
Heel
Cutting
Edge
Chisel
Tip
9:00
3:00
1:00
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