A wrench is a hand tool, often having fixed
or adjustable jaws, used for gripping, turning, fastening, tightening,
twisting or loosening objects such as nuts, bolts or pipes and pipe
fittings. A wrench is mainly used to hold and turn nuts, bolts, caps,
screws, plugs and various threaded parts. Top quality wrenches are
forged from fine-grade tool steel or chromium-vanadium steel alloy,
machined to close tolerances and hardened and tempered for long service
life. Wrenches come in Metric sizes or American Standard Inch. There are
also many special designed wrenches that can be applied to only a few
selected jobs or parts. Since most imported products are made to metric
specifications, a set of metric wrenches has become a must in many home
workshops. A wrench is also known by the name spanner. In fact , spanner
is the standard term in British English.
Classification of wrenches/ spanners
Wrenches are available in various shapes and sizes and are of two
- Pipe wrenches: They are used in plumbing for gripping
round or cylindrical things.
- General use wrenches: They are used on bolts and nuts
that have flat, parallel surfaces, like for example square or
Accordingly, there are two categories of wrenches:
Types of wrenches/ spanners
- Adjustable wrenches: As the name suggests, the adjustable
wrenches can work on a whole range of nut sizes as they can be
adjustable to different sized pipes, nuts and bolts.
- Fixed wrenches: Fixed wrenches are those wrenches which
fit single, specific sizes.
Depending on whether the wrench is fixed or adjustable, there are
different types of wrenches used for different purposes. The following
table will give us an idea about the various types of wrenches with
their uses and features.
Some other types of spanners
- Open-end wrench or open-ended spanner: This wrench has a
U-shaped opening which is used to grip two opposite faces of the nut
or bolt . It also comes double-ended, with a different-sized opening
at each end.
- Combination wrench or Combination spanner: A double-ended
wrench with one end being like an open-end wrench and the other end
like a box-end wrench. Both ends usually fit the same size of bolt.
They are made in metric and standard sizes.
- Ring spanner or box-end wrench: It has an enclosed or
ring shaped opening that grips the faces of the bolt or nut. The
ring opening can be either of a six-point, eight point or
twelve-point opening for use with bolts, nuts heads with a hexagonal
shape or any other shape. Ring spanners are also double-ended.
- Flare-nut wrench or tube wrench, or line wrench: They are
almost same as box end wrench and are used for gripping the nuts on
the ends of tubes. They have narrow opening to allow the wrench to
fit over the tube. They are preferred than open ended wrench because
they allow for maximum contact on plumbing nuts, which are made of
softer metals and more prone to damage from open-ended wrenches.
- Adjustable wrench or adjustable spanner: Used for
tightening or loosening nuts and bolts, having moveable lower jaw to
adjust wrench size, depending on the size of the nuts or bolts.
There are three main types of adjustable wrenches. Monkey
wrench with adjustable end wrench with a straight handle and
smooth jaws. Crescent wrench has adjustable jaws
set at a 30 degree angle from the handle. Pipe wrench
also belongs to adjustable wrench.
- Socket wrench: They are like closed end wrenches but they
are cylindrical in shape. They can easily fit over a nut in a
recessed hole which is otherwise inaccessible with open or closed
- Torque wrench: A type of socket wrench, it has a built-in
spring-loaded indicator which displays how much torque is being
applied. In other words it shows how hard the nut is being
- Nut drivers: A type of socket wrenches that can be
permanently fixed to a screwdriver-type handle.
- Allen Wrench: A L-shaped wrench made from hexagonal wire
stock of different sizes, and are used to turn bolt heads or screws
designed with a hexagonal recess to receive the wrench.
- Chain Wrench: Chain wrenches are designed for easy use in
extra-close quarters such as on round, square or irregular shapes.
- Ratchet wrenches: They are available in 1/4" 3/8"
and ½" drive sizes and are used with socket wrenches. They
are available with a round or teardrop-shaped head, and contain a
reversing mechanism to facilitate tightening or loosening of
- Tap spanner: A double ended wrench, with cranked jaws, it
is also known as basin wrench and used to tighten basin and bath
taps nuts in the areas where an ordinary spanner would have
insufficient turning space.
- Open ended: 'C' spanner The open ended spanner is the
most common type and may have a single or double end. The head has
its jaws offset by about 15 degrees from the run of the shaft. This
is to ensure that the spanner can be turned over to engage different
flats of a nut when working in confined spaces.
- Obstruction Spanner: Obstruction spanner, another version
of open ended spanner is designed for use in confined spaces. It has
one head set at anything up to 90 degrees to the shaft, and the
shaft may have a slight curve.
- Ring Spanner: The ring spanner usually has a completely
enclosed head, and may have six or 12 flats. A 12 flat spanner
engages upon the corners of the nut and can engage both hexagon and
square bolts. A six flat spanner is normally shaped to fit against
all 6 sides of hexagon nuts, this ensures a very tight fit and can
allow considerable force to be applied. Ring spanners are stronger
than the open ended type, but they need access to fit them over the
- Offset Ring Spanner: The most useful ring spanners have
offset heads, allowing the spanner to connect with nuts in awkward
places and to give room for your hand to move without hitting the
- Bulldog Spanner: In this pattern, a worm screw is located
close to the opening jaw, which has a rack engaged with the screw,
making the spanner very easy to adjust with the finger and thumb of
the holding hand.
Wrenches are considered to be one of the most useful and often used
hand tools, used for holding and turning all types of threaded parts
like bolts, nuts. A good quality wrench is designed in such a way so
as to keep excessive torque from stripping or damaging the nut or
bolt. A good quality wrench helps in keeping leverage and the load
in balance. So before buying a wrench, you should be aware of the
job that is to be done. Whichever job you are using a wrench for, it
is advisable to choose a size that exactly fits the fastener. If the
wrench is too big, it can destroy the outside of the nut. In such a
case, box or socket type wrenches are safer than open ended
wrenches. Individual sized wrenches are always safer as well as
stronger than adjustable wrenches.