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Parallel shank drills as the name suggests
have a parallel shank and are held in the
drilling machine using a three jaw self
centring chuck.
These types of drill range from 0.5mm to
13mm diameter in 0.5mm increments as
standard.
Sizes in between at 0.1mm increments are
available for tapping dills and special
applications but are more expensive.
The chuck is fixed in to the spindle of the
machine using a Morse taper.
When fitting drills in to the chuck it is
essential that the chuck only grips on the
shank of the drill and the correct chuck
key is used
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Drills larger than 13mm diameter
are manufactured with a taper shank
as seen opposite.
These types of drills are fitted
directly in to the spindle of the
drilling machine as opposed to in a
chuck.
The drill is held in place by means of
friction between the taper on the
shank and the taper in the spindle.
This means much larger drills can be
used without the risk of them
slipping due to the larger area in
contact with the machine.
The tang on the top is purely to
remove the drill from the machine
not to secure it in place.
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Taper shank drills are available as standard in
0.5 mm increments up to around 50mm
diameter.
The tapered shank (Morse Taper) on the drill
is available in a range of sizes depending on
drill size these being MT1, MT2, MT3 and
MT4.
The Taper in the spindle of drilling machines
also varies depending on the size of the
machine usually MT2, MT3, MT4 or MT5.
To enable fitting of different size drills in
different machines Morse Taper Sleeves and
Adaptors are available, these come in various
sizes e.g. MT1-MT2, MT2-MT3 etc. Allowing
you to step up or down depending on the
spindle size and the drill being used.
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To fit the chuck or taper shank drill in to the
machine the taper is inserted into the spindle
with the tang rotated to line up with the slot
as shown opposite.
The drill is then secured into the spindle
using one of the following methods.
Tapping the drill into the spindle lightly using
a soft faced mallet
Placing a piece of wood on the table and
rotating the spindle handle until the drill
lowers and touches the wood then applying
light pressure to push the drill securely into
place.
In both cases only minimal force is required as
the power is transmitted by friction between
the two tapered components.
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To remove the taper shank drill
or chuck, the spindle is rotated
by hand until the slot lines up
with the slot on side casing.
A drill drift is then inserted into
the slot and tapped with a
hammer as shown.
This ejects the drill from the
machine and the drill drift can
then be removed.
When ejecting the drill or chuck
from the machine it is essential
to hold it at the same time to
prevent it falling on the floor
which can cause damage.
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It is important that the angle point
and the length of the of the cutting
edges (lips) are ground accurately
and equally to avoid problems when
drilling holes.
This can be checked when
sharpening using a drill angle gauge
as shown opposite
If the angles are different it can cause
the drill to chatter and drill a hole
that is out of shape, a bit like a 50p
piece.
If the edges are of different lengths it
can cause hole to be drilled over size
as shown.
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When drilling holes it is essential the
location is accurate, to achieve this we
start the hole using a centre drill. Due
to its small point the centre drill can
be located accurately in the centre
punch mark; also it provides a good
lead for the correct size drill
 When drilling larger holes it is
necessary to use a pilot drill to remove
some of the material first. Trying to
take too much material out at once
will make the process more difficult,
and may cause damage due to
overheating of the drill and material
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When several items are to be
assembled together Countersink
screws or cap head screws, are often
used and these need to sit down flush
with the component.
To achieve this we use countersinks
bits top right or counter boring drills
bottom right.
When counter boring you need to
ensure that the pilot hole is the correct
size for the shank of the tool.
When using these tools it is essential
that the speed of the drill is slowed
down or the tool will overheat and
become blunt very quickly.
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Drilling holes is reasonably
accurate but some holes need to
be perfect or have a much better
surface finish than that achieved
by drilling.
To achieve this a Reamer is
used.
Reamers are of similar shape to
drills but have more flutes and
no point, they also run slower,
around a third of the speed of
drills.
Reamers come with either a
spiral flute or a straight flute as
shown, they also come in hand
version or machine versions
Hand Reamer
Machine Reamer
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Machine reamers are used in
the same way as drills by
inserting them in a drilling
machine as shown
Using a Machine Reamer
Hand reamers are used by
placing them in a tap wrench
as shown and rotating them by
hand
When reaming a hole you need
to drill a pilot hole roughly half
a millimetre smaller than the
finished size and then open it
up using the reamer.
Using a Hand Reamer