31
GB
GENERAL GUIDELINES FOR DRILLING
Always centre punch the position for drilling. A centre punch is
a pointed tool that marks the material to be drilled with a small
indent. It stops the drill bit moving from the desired position.
Always start by drilling a small pilot hole and gradually
progress in drill diameter. When drilling metal, lubricate the
drill tip with oil.
NEVER cool with water or water based lubricant otherwise an
electric shock could occur. DO NOT use oil when drilling copper
or brass. Care should be taken when drilling copper and brass
as the drill bit will be prone to jamming.
Small diameter drills require a higher speed and as the drill
diameter increases the slower the speed required.
The following drilling speed chart is a guide only and only covers
the more common materials, drill diameters and speeds.
Drilling Speed Chart (Guide Only)
Material to be drilled
D
E
F
G
H
I
C
Drill Speed (RPM)
3
2500
2500
2500
2500
2500
2500
4
2500
2500
2500
2500
2500
2500
5
1750
2500
2500
2500
2500
2500
6
1750
2500
2500
2500
2500
2500
7
1250
1750
2500
2500
2500
2500
8
1250
1750
2500
2500
2500
2500
9
900
1250
1750
2500
2500
2500
10
900
1250
1750
1750
2500
2500
11
600
900
1250
1750
1750
2500
12
600
900
1250
1250
1750
1750
13
600
600
900
1250
1250
1750
C Drill Dia mm
D Steel
E
Cast Iron
F
Gun Metal
G Aluminium
H Plastics
I
Wood