Page 74 - 05. Subyek Teknik Mesin - Automobile Mechanical and Electrical Systems Automotive Technology Vehicle Maintenance and Repair (Vehicle Maintenance Repr Nv2) by Tom Denton

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Figure 1.82 Three common types of fi le. (Source: Glenn McKechnie, Wikipedia)

Figure 1.83 Cutting edges and fl utes of a drill bit

1.6.4 Drilling

Drilling is a cutting process that uses a drill bit to cut or enlarge a hole in a solid
material. The drill bit cuts by applying pressure and rotation to the workpiece,
which forms chips at the cutting edge ( Fig. 1.83 ). The fl utes remove these chips.
In use, drill bits have a tendency to ‘walk’ if not held very steadily. This can be
minimized by keeping the drill perpendicular to the work surface. This walking or
slipping across the surface can be prevented by making a centring mark before
drilling. This is most often done by centre punching. If a large hole is needed,
then centre drilling with a smaller bit may be necessary.
Drill bits used for metalworking will also work in wood. However, they tend to
chip or break the wood, particularly at the exit of the hole. Some materials such
as plastics have a tendency to heat up during the drilling process. This heat can
make the material expand, resulting in a hole that is smaller than the drill
bit used.

1.6.5 Cutting

A hacksaw is a fi ne-tooth saw with a blade under tension in a frame. Hand-held
hacksaws consist of a metal arch with a handle, usually a pistol grip, with pins