Modifying Twist Drills for Wood
A
WORN-OUT TWIST DRILLcan be modified to perform much
better in wood. First grind the tip flat. Then, using a cone-
shaped stone in a hobby grinder or the rounded-over corner of an
abrasive wheel, grind two hollows—one on each side of the center.
The hollows form a center spur and two outer spurs. Be sure to bevel
the hollows so that the back side of the flutes will clear the wood.
In use, the center spur holds the bit stable and keeps it from wan-
dering. The outer spurs cut the wood’s fibers in advance of the cutting
edge to give straight, clean holes.
—STANLEYF. KAYES,Richmond,Va.
CHAPTER FIVETwist drill
as sharpened
for metal- Grind flat. 2. Grind flutes.
Grind flutes with corner of grind-
stone or with cone-shaped stone.