Maker’s toolbox: Hand drills
TUTORIAL
DRILL BITS
Not all bits are created equal, and getting a drill to do
what you want often comes down to putting the right bit
in it. There’s a mind-bending array of different bits on the
market, including the simple and general-purpose twist bit
and specialist bits for ceramic and glass. A few of the most
popular are:Twist
This is the most basic drill bit. It’s simply a rod with a
twisted groove along its length and a sharpened point. It’s
the original drill bit, but still versatile and can be used on a
variety of materials, including wood and metal.Brad Point
The classic wood drill bit has a spur on the end that ensures
that the drill bit goes in exactly where you want it to.Spade
A wide, flat drill bit for making large holes in wood. This drill
bit can be a bit rough, so you can get a cleaner finish by
drilling from both sides and meeting in the middle.Forstner
These bits drill wide, flat-bottomed holes in wood that are
neater than those created by spade drill bits. However,
these can require a bit more force to create the hole.Step
A single drill bit to create a wide range of hole sizes. Conical
step drill bits can be pushed into sheet metal as far as
necessary to create exactly the size hole you need.Hole saw
A central drill bit guides a circular saw blade into the wood.
This bit is capable of creating large holes in wood, but has
to drill all the way through.Diamond
Coated in diamond dust, these bits can get through glass or
ceramic, but they need water to keep them cool.Masonry
Designed for use with hammer drills, masonry bits are
designed to chisel out the material.Screwdrivers
These bits turn the drill into a power screwdriver. The
potential problem here is that drills are far more powerful
and faster than screwdrivers, so you need to be able to
control both of these to make a drill work as a screwdriver.
Usually, the clutch can limit the power of the drill, and you
should be able to limit the speed with the trigger. It’s best to
start with a much lower power than you think you need, as
it’s easy to strip screws.As well as the general shape of the bit, the material
it’s made from can have a big impact in how it works, and
this generally comes down to the toughness of the metal.
High-speed steel (HSS), cobalt steel, tungsten carbide, and
titanium nitride can all be used to make bits. You often find
that you get what you pay for. Cheap bits will quickly blunt,
while bits from a reputable manufacturer will last years, if
treated properly.However, if you know you’re only going to need to
drill softer materials, the lower voltage drills can be
significantly lighter and smaller.WHAT’S UP CHUCK
Drills hold bits in chucks, which are essentially circular
vices that fasten three points together to hold the
bit firmly and centrally. Almost all chucks follow this
basic design, but some require a key to operate, while
some can be operated by hand. It’s a little easier to use
key-less chucks as there’s no risk of losing the key, but
don’t always grip as firmly on the bit.
Not all chucks are the same size. Generally, in
drills for hobbyists, you’ll get a chuck either 10 mm or
13 mm, and this is the maximum diameter shaft that
you can fit in. In general, you’ll find 10 mm chucks in
less powerful drills that simply don’t have the torque
to spin the large bits. This limit is only on the shaft
size, and doesn’t necessarily relate to the size of the
hole created.
Although drills are almost always used for the
same function (to make a hole in something), theirability to make a wide range of holes in a wide range
of materials is due to the wide range of bits available
(see ‘Drill Bits’ above).UNDER TEST
Finding the right drill is really about understanding what
you need it for. A drill for woodwork may need to be
small and light, while for more general DIY usage, the
hammer function might be important. You might need
to be able to use it all day (and so have a cord or a large
battery), or just for a few holes at a time. In general,
you can get any one feature (size, weight, power, etc.)
on a fairly cheap drill, but the more general-purpose
you need your drill to be, the more it will cost.Finding the right drill
is really about
understanding what
you need it for”
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