INSTALLATION WIRING SYSTEMS ENCLOSURES - Pearson Schools

Chapter 4: Installation of wiring systems and enclosures
A hole saw should be used for cutting large holes in metal. Hole saws, or
tank cutters as they are sometimes called, are metal cylinders with teeth cut
into the open end. The saw is then screwed onto a mandrill. The mandrill is
also fitted with a twist bit which drills a pilot hole into the workpiece and
which anchors the saw while cutting takes place.
Drilling wood
Wood can be drilled using a metal twist bit, but there are a range of
specialist wood bits available. These are spade-shaped with a sharp pilot
point. Care must be taken when using these types of drill bit because they
can become jammed and cause the drill itself to twist round.
If no power is available, a brace-and-bit is used for drilling wood.
This is shaped like a crank shaft and fitted with auger bits (much like
twist drills). A brace-and-bit is usually fitted with a ratchet handle so
that it can be used in a confined space where the crank cannot be
rotated fully.
Activity 4.1
Carry out a visual safety inspection on a selection of tools. Demonstrate this to your
tutor. Explain what you are looking for, e.g. damaged handle, blunt edges, damaged
leads and plugs on power tools.
Figure 4.13: Wood bit
Tool Check for: Optimum performance PPE and other safety
advice
Electric drill
Table 4.17: Using electric drills safely
• Damaged lead and plug
• Damaged insulation and casing on the drill
• Free movement of the chuck
• Chuck grips the drill bit securely
INSTALLING WIRING SYSTEMS
Select materials from drawings
• For battery drills, keep batteries
fully charged a nd always keep a
spare charged battery.
• Only use sharp drill bits.
1st Proof
The main diagram the electrician will work to is the scaled layout drawing,
often called a plan. From this the electrician can count up the amount of
accessories and items of equipment needed for the job. Cable lengths can also
be calculated using the scale and likely cable routes shown on the drawing.
Figure 4.12: Metal bit and hole saw
• Eye protection
• Gloves
• Ear protection
• Secure the workpiece.
Progress check 4.6
1 What type of drill bit is used
for drilling a small hole in
metal?
2 What is a pilot drill?
3 What tool can be used for
drilling wood if no power is
available?
Chapter
4
177
Unit
GH8
Marking out
Before starting actual installation work, the job has to be marked out. The
drawing is used to show where all accessories and items of electrical equipment
are to be fitted. It is important to install all equipment in the correct position.
If a socket or switch is not placed where it should be it could end up hidden
behind a cupboard or radiator. When marking out, the position of accessories,
equipment and cable drops are drawn on to the wall with a pencil or chalk.
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