Using
The Drill Press
15th in a series of articles by Barb Siddiqui
As a new or beginning woodworker, it won't take long to realize your
work would benefit from the repeatable accuracy of drilling holes with
a drill press. Both benchtop and floor models are quite serviceable, and
the choice depends more upon how much space is available in your shop,
than a preference for one over the other. Large, heavier drill presses
usually have a higher horsepower rating, and floor model drill presses
can drill holes in the endgrain of long boards more easily.
Drill presses, originally designed for metal work, become efficient woodworking
tools with the addition of a plywood or melamine-covered table, and some
kind of fence to hold the work against. This arrangement can be as simple
as a piece of 3/4" plywood lag-bolted from below the small metal
table, and a 2x4 clamped to the plywood (to counteract the torque of the
drilling action), or as elaborate as a professionally manufactured table
with embedded T-track for hold downs and a sliding fence with micro-adjustments.
Whatever your set up, it is important the workpiece is securely clamped
or held down before drilling. Many bits have a tendency to pull the workpiece
upward off the table when the operator retracts them from a hole, resulting
in the entire board's length being spun in the circular motion of the
bit. Clamp each workpiece, or secure it tightly against the fence and
downward to the table, by hand.
Before using the drill press, mount a straight piece of steel rod in
the chuck and set a small engineer's square on the table in several different
positions around it, to assure a drill bit will enter your wood vertically
at 90º to the table. Another method to test this is to bend a piece
of heavy metal coat hangar into a level 'Z' shape, with one end bent up
at 90º, a long straight section, and the other end bent down at 90º.
One end is captured by the drill chuck, and the other end set just onto
the table. Turning the drill chuck by hand sweeps the bent wire in a broad
circle, testing the levelness of your table and its orientation to a drill
bit.
One thing you want to avoid when drilling deep holes is heat build up.
It is smart to reduce the friction while drilling by occasionally lifting
the spinning bit free of the workpiece to allow chip removal, then re-inserting
it to cut deeper. Be sure your fingers are well away from the bit. Also,
never bury a drill bit below the spiral flutes of its design. They are
there to clear away compacted wood chips.
Large holes can be cut with a hole saw in softwoods, or with a fly-cutter,
but only on very slow speeds such as 200-400 rpm. If your drill press
is not capable of such slow speeds, please avoid using a fly-cutter, as
they can be quite dangerous. A router, or even a saber saw, would be preferable.
Setting depth stops can be a problem. Always test the depth of the cut
on scrap pieces before committing your good wood. If the measurements
and arithmetic cause headaches, there is a shortcut. Before setting the
fence distance to align a hole in a workpiece, put a pencil mark on the
edge of the wood at the required depth, set the wood beside your drill
bit, and lower the bit in open air to meet the pencil line. Lock your
depth stop at that point, then set up the fence distance to align for
drilling. (But it's still a good idea to test your depth in scrap lumber.)
Brad point bits have distinct spurs on the outer cutting edges of the
flutes, and are ideal for drilling wood, but they are not commonly available
in the many increments that regular metal drilling bits offer. Spade bits
work well, but leave a rougher hole compared to other bits. It is best
with any of these, to mark your hole location with a cross-hair marking
using a sharp pencil, then indent that point with an awl, so the bit will
have a starting point and not wander off -target.
Drill press tables get cut up pretty quickly, and each through-hole you
drill needs a backer board to prevent tear-out, so many people cut a replaceable
square in the surface of their plywood table. These can be offset rather
than centered under the drill chuck, so they can be lifted out and turned
to fresh wood on each of four corners, then inverted and used at each
of four corners again before being discarded as an expendable item and
making another. Any such insert should be of the same thickness, and sit
flush with, the table's surface.
Whenever you acquire a new (to you) machine, read and follow the owner's
manual. Know how to check it for alignment procedures, lubrication and
general maintenance. Be aware of any safety precautions, and then learn
by doing.
Click
on the links below to see the previous articles by Barb Siddiqui.
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