Figure 1 A manual-feed, portable magnetic drill is a suitable
tool for many hole-making jobs, but for heavy-duty, highly
repetitive jobs, a basic tool may be the best choice.
A guide to portable
magnetic drills
like most magnetic drills. They also have an excellent cutter size range, and because they have a quill feed, just the
cutter moves. They will operate in any place they can fit.
Their light weight also makes them a suitable choice
when the job requires moving the drill around a job site
or carrying it up a ladder.
When the job requires repetitive holes, consider
power-feed drills. They provide consistent hole-making
with less operator fatigue. Productivity also can be improved because one operator can operate two or more
drills simultaneously. While one unit is cutting, a second
can be set up. Drills that electronically optimize the feed
rate may help to extend tool life and produce higher-quality holes.
When drilling in vertical or horizontal positions,
swivel-base drills (see Figure 3) should be given strong
consideration. A swivel-base drill allows you to roughly
position the drill and activate the magnet. Then, by releasing the swivel mechanism, you can precisely position
the drill pilot over the hole’s centerpoint and lock down.
This feature will speed up alignment for precision holes.
Permanent-magnet drills are not as widely used, but
they are suitable power tools for special applications
where electric power is unavailable. However, they are extremely heavy and have limited holding power. Some permanent-magnet drills have pneumatic motors for use in
explosive atmospheres where sparks can be catastrophic.
Another type of drill uses a hydraulic motor, which
provides higher horsepower in a smaller package and is
offered with either an electro- or permanent magnet.
Some manufacturers modify existing magnetic drills
to solve unusual hole-making problems for customers.
An example is a unit that drills from the bottom up or
special fixturing for deep-hole drilling.
Learn about the different types, how to set up
for a job, and ways to keep the drill running
By Jeff Miller
hen you need to make holes and cannot
take the work to a machine, a portable magnetic drill is usually the tool of choice. Today
fabricators and contractors can choose from several
types and sizes of magnetic drills and annular cutters—
all with different features—for on-site hole-making.
Although basic portable magnetic drills are the most
popular and quite versatile, they may not be big enough
or powerful enough to handle a particular job. On the
other hand, the drills may not be small enough if you
were drilling, for example, in hard-to-reach or confined
spaces. Additionally, if you’re working on extremely hard,
rusty, scaly, or painted material, you may not be able to
do the job with basic power tools.
With so many magnetic drills and so many different
applications, a person would have difficulty covering every
scenario. However, this guide will give you some basic descriptions of the different types of tools available to fabricators and advice on how to increase productivity with
those tools.
W
Drill Types Available Today
Presenting a complete list of the various sizes and types
of portable magnetic drills available today would be im-
practical. For discussion purposes, most can be organ-
ized into general categories.
Setting up the Job
Setting up the job is basically the same no matter which
type of magnetic drill you use. Here are some helpful
hints to improve your drill’s performance and cutter life.
Obviously, the material base to be used must be ferrous metal for the electromagnet to work properly. The
material type dictates the type and grade of the cutting
tool to be used.
The first step is to make sure you have a clean, flat, and
smooth work surface that is free of chips. Make sure the
bottom of the magnet is also clean. Any foreign matter
such as chips under the magnet could rock it and decrease
its holding power, resulting in the drill rotating or shut-ting down because the safety mechanism was activated.
If the surface is not perfectly flat, such as an I-beam that
has a crown, you need to make sure the magnet is not affected. Placing the magnet to one side and not over the
crown will give better results. The use of a swivel-base
magnetic drill might help in this situation.
If the surface is heavily rusted or covered with paint,
especially epoxy, the magnet may not obtain good holding power. Special care must be taken to ensure proper
magnet adhesion. The proper, well-sharpened cutting
tool may help in this situation because it may put less
stress on the magnet while making the hole. Or this may
be a good time to step up to cobalt or carbide cutting
tools.
Using a safety chain or strap is critical in the event of
a loss of power (see Figure 4) or if the drill safety circuitry
shuts itself down because it will ensure the drill does not
fall on or injure you.
