Page 35 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS ELECTRICIAN - CITS

The handle shown in Fig 2 is called a pistol grip handle.

The parts of an electric hand machine are shown in Fig 2.

Fig 1 Fig 2

Precautions to be observed : Make sure the holes are properly located and punched with a centre punch.
Be sure the drill is properly centred in the chuck by turning (rotating).
Be sure the work is mounted properly in a holding device such as a vice or `G’ clamp.

Check the centering of the drill after the point has just started in the metal. Relocate the hole with a centre punch,
if necessary. Feed the drill with a light, even pressure.
Types of Electric Drilling Machines: Some of the electric drilling machines are listed here.

• The sensitive bench dilling mchine
• The pillar drilling machine
• The radial arm drilling machine. (Radial drilling machine)
(As you are not likely to use the column and radial type of drilling machines now, only the sensitive and pillar type
machines are explained here.)
Sensitive bench driling machine: The simplest type of sensitive bench drilling machine is shown in the (Fig 3)
with its various parts marked. This machine is used for light duty work. (Fig 3)

This machine is capable of drilling holes up to 12.5mm diameter. The drills are fitted in the chuck or directly in the
tapered hole of the machine spindle.
The pillar drilling machine: This is an enlarged version of the sensitive bench drilling machine. These drilling
machines are mounted on the floor and are driven by more powerful electric motors. They are used for heavy
duty work. Pillar drilling machines are available in different sizes. Large machines are provided with a rack and
pinion mechanism for moving the table for setting the work.

22 PB

CITS : Power - Electrician & Wireman - Lesson 1- 4