Identify the Procedures for Operating Portable Drills

Topic 6 – Identify the Procedures for Operating Portable Drills

The Portable Electric (AC) Drill

An essential portable power tool, the electric drill has many uses. Drills are sized according to their chuck capacity. The most common sizes are 3/8”, 1/2″, and 3/4″. This size is the maximum diameter bit the drill can accept. In corded drills, the drill speed is fixed to the size of the chuck. The larger the chuck, the slower the drilling speed (slower speeds are required to remove large amounts of material). Some drills come with varying speeds; it is important to use the proper speed depending on the task.

Types of Bits

There are 6 primary types of boring bits that carpenters use, some with their own variations:

– Auger Bits: a bit with an aggressive cut, used for rough drilling of deep holes in wood only, primarily through framing. Comes in single and double twist (solid centre), single twist with hollow centre, and is also equipped with a self-feeding screw tip.

Figure 1: (from left to right) brad point bit, carbide tipped bit, twist drill bit, auger bit, and spade bit

enough to drill through masonry and concrete. They

are most often used with a hammer drill.

*When drilling for accuracy, it may be necessary to use an awl or centerpunch

to prevent the bit from wandering from its center point.

Cordless Electric (DC) Drills

Now the industry standard for the majority of operations, the cordless drill is a must-have for any carpenter. The typical size of a regular cordless drill is 3/8”, which limits its ability to accept larger bits. For any bit larger than 3/8”, a reduced shank drill bit is required. Much like the corded drill, it comes with variable speeds which are chosen based on the job performed (remember: larger bit, slower speed). The drills are also equipped with a clutch which allows the drill to disengage after reaching a predetermined torque resistance. This is especially useful when doing delicate work or working with brittle materials.

Many cordless drill sets are equipped with an impact driver, which has become the most popular tool when it comes to fastening materials as it is capable of producing 3 times as much torque as a regular drill and can turn twice as fast. It is, however, limited to what jobs it can effectively do. As the hammering impact action can damage bits, it is only recommended to be used to drive in fasteners and not for drilling/boring.

Review Questions

1. How is the size of a portable electric drill designated?
2. How does the size of the drill bit effect the drilling speed?
3. What is the relationship between the material being drilled and the shape of the drill bit point?
4. How can a bit be prevented from “wandering” from its center point?
5. Describe two ways to drill to a predetermined depth.
6. True or False:

1. A very blunt drill point is used for drilling wood.
2. Most bits have a feed screw and tang.
3. The harder the material, the higher the drilling speed.

7. Describe the relationship between speed and torque on cordless drills.
8. Describe the function of the clutch on cordless drills.