This article was first published in 2007.
People who have either a formal training in the
use of hand tools (eg they’ve done a trade apprenticeship) or who have had a
very long experience of using tools (ie they’ve learnt from their mistakes) tend
to assume that everyone knows how to use tools. I mean to say, what is there
to know about using spanners? Well, quite a lot.
It’s only when you see people who have simply no
idea of how to use hand tools that you realise the very real necessity of
learning. I remember when I taught automotive mechanics to secondary school
students. Not having a ‘trade’ background I wondered if my ignorance would soon
show, but I needed have worried. After all, it was only a few lessons into the
term that I saw a student using an adjustable shifter to try to remove head
bolts... (And for those that wonder at the significance: head bolts are amongst
the most tightly torqued of any bolts in a car... you need a well-fitting socket
and a long lever to undo them.)
Knowing how to use tools has two major advantages.
(1) You’re more likely to readily achieve success; (2) You’re less likely to
damage the equipment you’re working on. And those two points are related:
round-off the head of a nut you’re trying to undo with the wrong tool and/or
technique and you’ll find success terribly elusive...
Undoing and Doing-Up Nuts and Bolts
The two proper ways of undoing (and doing-up) nuts
and bolts are with spanners and sockets. Aside from the different sizes,
spanners come in two basic types: ring and open-ended. Both ring spanners and
sockets can be either 6 or 12 point. The number of ‘points’ refers to the number
of flats on the inside of the ring spanner or socket.
A 6-point design has a hexagonal shape...
... a 12-point design has twice as many internal
Six-point sockets and spanners are usually cheaper
and are less likely to slip (ie round-off the nut or bolt) but they have a major
disadvantage in that they cannot be applied at as many rotational angles. In
other words, a 6-point ring spanner may not be able to be fitted on the nut or
bolt as the length of the spanner may foul something. In the same location, a 12
point spanner will fit.
Absolutely vital in successfully working with nuts
and bolts is to know the correct hierarchy of use. In other words, which of the
available tools should be the first preference?
Number 1 Choice – Socket
The first choice in doing up (or undoing) a nut or
a bolt should be a socket. If the nut or bolt needs to be torqued to a high
value, a 6 point socket should be used. (In normal circumstances, either a 6
point or 12 point socket is fine.) The socket should be equipped with as short
an extension bar as possible - preferably with none. (This to avoid applying a
force that tries to lever the socket off the nut or bolt as it is being turned.)
The socket can be turned by a ratchet handle, a sliding T-handle or even, for
low torque values, a screwdriver-type handle.
The only exception to picking a socket as the
first choice is if there’s plenty of room and the nut or bolt is likely to be so
tight that a lever needs to be added to the tool. In that case, use a ring
Number 2 Choice – Ring
The second choice of tool for doing-up or undoing
a nut or a bolt should be a ring spanner. Where space above the nut or bolt will
not allow a socket and ratchet handle to be used, a ring spanner is appropriate.
Again, if the nut or bolt needs to be torqued to a high value, a 6 point ring
spanner should be used.
Number 3 Choice – Open-Ended
Open-ended spanners are simply great tools... for
rounding off nuts and bolts. Very few open-ended spanners have sufficient
strength to undo nuts and bolts that have been adequately torqued. Similarly,
very few open-ended spanners have sufficient strength to adequate torque-up nuts
and bolts. Open-ended spanners should therefore only be used when there is
inadequate space around the nut or bolt to permit either a socket or ring
spanner to fit – and that’s a pretty unusual situation.
However, open-ended spanners are very useful in
undoing nuts and bolts that have been ‘cracked’ (ie the initial tightening
torque undone) but which are sticky on the threads. For example, a Nyloc nut
should be cracked with a socket or ring spanner and then, if it’s easier, can be
undone completely with an open-ended spanner.
Number 4 Choice – Adjustable
An adjustable wrench or spanner is even more
likely than an open-ended spanner to wreck the head of the nut or bolt. After
all, it’s just an open-ended spanner with a built-in adjustment mechanism that
allows the jaws to spring even further apart... Adjustable wrenches should never
be normally used on nuts and bolts. Only in an emergency, where no suitably
sized spanner or socket exists, should an adjustable wrench be used.
(Not the) Number 5 Choice –
Pliers should never be used to do-up or undo nuts
and bolts. It’s as simple as that. The only reason I ever use pliers on a nut or
a bolt is if it has already been rounded and it’s impossible to use a spanner or
socket. If you ever see anyone using pliers on a nut or a bolt, they simply
aren’t much of a workman (workperson – gender not implied).
Tips and Tricks
‘Cracking’ Nuts or Bolts
Most nuts and bolts which have been torqued-up are
pretty tight. Applying gradual force by a ring spanner or socket will often
leave you frustrated and sore – the nut or bolt simply doesn’t want to ‘give’.
The trick is to ‘crack’ the torque with a sudden, high force.
On smaller buts and bolts (those on which you’d
use an 8 or 10mm spanner), hitting the end of the spanner with your cupped hand
will often crack the torque. On larger nuts and bolts, using a rubber mallet
will perform the same trick.
On really big bolts, like those used on suspension
components, pushing hard with your foot will often crack them. Now kicking a
spanner doesn’t sound very good workshop practice, but if you’re got the car
securely on stands and you’re already under the car, you can apply with your
foot a lot of force in a direction that won’t cause the spanner to be levered
Angled Extension Bars
Extension bars for socket sets are available with
bevelled edges, allowing the extension bar to be out of line with the socket.
These are sometimes called wobble extension bars and in some situations, they
can be an absolute Godsend. These bars can be bought separately: they’re
something you should have in your tool box.
Hi Torque Bolts/Nuts
If the bolt or nut that you’ve taken off was very
highly torqued, think about why the manufacturer (or whoever previously did up
the fitting!) made it so tight. If there is an important reason that it should
be tight, consider applying a Loctite or equivalent locking compound. In many
cases, using a locking compound means you won’t have to go ballistic on the
torque (which saves potential thread stripping or nut rounding) and the fastener
will be more secure than before.
Anything involving bearings (plain, roller,
needle), important gaskets (eg head gasket) or castellated nuts (ie a split pin
goes through the end) should have the bolts torqued as described in a workshop
manual. That might mean applying a certain peak torque (as measured by a torque
wrench) or by a certain angle of rotation.
Direction of Rotation
Pretty well anyone who has even picked up a
spanner knows that you turn it clockwise to do the fastener up and
anti-clockwise to undo it. But two points. Firstly, these directions are
reversed if the fastener is upside-down (and only the other day I saw a mechanic
of 30 years’ experience get this wrong!), and this convention applies only to
right-hand threads. Some special threads are backwards - eg on specific gas
cylinders, some fittings associated with rotating shafts and some tie-rod ends.
If the object you’re working on has in held in
place with multiple fasteners, never tighten one fastener to full torque before
doing up the rest. Instead, torque them up evenly, working your way back and
forth across the object. This applies to wheel nuts, cylinder head bolts, tappet
cover bolts – anywhere there’re multiple fasteners used to hold something in
place. And the reason? You want the object to ‘bed down’ evenly, not end up
cocked on one side.
In most cases, fasteners don’t need to be
mega-tight. It’s one of the most common mistakes a beginner makes - assuming
that every fastener has to be as tight as they can make it. In fact, most
fasteners can be “nipped up”. This means tightening the fastener to the point
where it starts to resist tightening, and then applying a relatively small but
sudden shock to the end of the spanner or socket handle. Sump plugs, for
example, should be nipped up – tight enough that they’ll never fall out but not
nearly tight enough that the thread will be stripped. On the other hand,
suspension and brake nuts and bolts should be quite a lot tighter than being
just nipped up.
If a long time ago someone had told me about the
concepts of 6 point and 12 point sockets, the hierarchy of tools to use when
doing-up nuts and bolts, cracking nuts, and the idea of nipping up, I’d have
spent a lot more time over the years enjoying my work on cars – rather than
staring sullenly at rounded-off bolts...