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DRILLING WOOD
In addition to the instructions listed under GENERAL DRlLLlNG, the following
also apply:
1. When using twist drills in wood, they should be withdrawn from the hole
frequently to clear chips built up in flutes to avoid overheating and burning
work.
2. If a backing block is used to keep back of work from splintering, it should
be clamped securely in place. If a backing block is not used with spade bits
or hole saws, ease up pressure as soon as bit point breaks through work, and
complete the hole from the opposite side.
DRILLING METAL
In addition to the instructions listed under GENERAL DRlLLlNG, the following
also apply:
1. Use only good quality sharp high speed steel twist bits when drilling
metal.
2. Start drilling with slow speed and gradually increase speed as drill cuts.
The harder the material, the slower the speed required. The softer the material,
the faster the speed.
3. When drilling a large hole, it is easier to first drill a smaller hole and then
enlarge it to the required size.
4. The use of a lubricant, such as oil, on the drill point helps keep the bit
cool, increases drilling action and prolongs drill bit life.
DRIVING WOOD SCREWS
1. Drill pilot and shank clearance holes. See following chart.
Shank
Drill
SUGGESTED HOLE SIZES
FOR WOOD SCREWS
Shank Drill
Pilot Drill Diameter
Screw Clearance Soft Hard
Size Diameter Wood Wood
#6
9
/64 (.140)
1
/16 (.062)
7
/64 (.109)
#8
11
/64 (.172)
5
/64 (.078)
1
/8 (.125)
#10
3
/16 (.187)
3
/32 (.094)
9
/64 (.140)
#12
7
/32 (.218)
7
/64 (.109)
5
/32 (.156)
Pilot
Drill
IT’S A
SCREWDRIVER
Fig. 8
900470 - 11-30-00.QXD 9/25/02 11:10 AM Page 11