Testing the action
If you've read the page in the Glossary about the
action then you'll know just what a complex thing it is. You'll
also be aware that any problems associated with the action tend to be
somewhat expensive to fix.
But perhaps you have a brand new instrument, and so you naturally assume
that there can't possibly be any problems with the action - or perhaps
your instrument isn't so new, but because all the keys seem to go up and
down it's probably a fair bet that all is well. Unfortunately, neither
scenario is any guarantee that all is well with the action. Most woodwind
instruments will exhibit some signs of wear in the action after a few
years of use - and it's entirely possible to find brand new instruments
that show signs of wear in the action...though this will be down to poor
manufacturing rather than proper wear and tear. In some cases, particularly
with cheap instruments, it can be quite severe.
It's relatively easy to check for wear or defects in the action - all
you really need is a finger and a thumb, and a basic understanding of
how the mechanism works. I can (hopefully) provide the latter, and you
might find it useful to have your instrument handy as you read through
Study the picture below, which shows the two common types of pivot/key
combinations; a rod or hinge screw mounted key and a point or pivot screw
mounted key. Note that in the case of the rod screw, it passes through
the key via its barrel, and in the case of the point screw the key is
mounted on (typically) a pair of screws at each end of the key barrel.
The two pivot types wear in slightly different ways. Rod screws may
rub along their entire length, thus wearing the entire barrel of the key.
Point screws only contact on the ends of the barrel, so the wear is confined
here (much cheaper to sort out too).
Find a rod screw key first; for sax players you can do no better than
your low F key, clarinettists grab your speaker keys and flautists stand
by your G keys.
The diagram above shows the three types of wear commonly
found on keys that are pivoted on rod screws.
Now, pinch the key as near to its centre on the key barrel
as you can - and try to move it from side to side...left to right, as
Is there any movement? Does the key have room to move between the pillars?
Sure, there will be some movement, but it ought not to be much
more than a tiny fraction. If there is much more than this then you have
longitudinal wear - i.e. the ends of the key barrel have been worn away.
Now grab the key cup and try rocking the key from side to side again with
a slightly circular motion. What you're testing for here is end play...which
means the bore of the key barrel is worn at its ends. Again, there will
be a little play there...but not much.
Lastly, grab the cup and push/pull it against the pivot. Not too hard
mind - there should be no play at all. If the key moves then that indicates
lateral wear along the length of the key barrel. It could also mean wear
in the pillars.
Try some other keys...sax players head for the top B key, clarinettists
head for the low F, flautists for the thumb keys.
let's have a go at the point screw keys.
Sax players have to start with the Bis B key (the one with the small pearl,
below the top B key), clarinettists with the low E and flautists with
the low D (though I'll come back to flutes in a moment...with even more
bad news). This time you need to test each end of the key barrel. Pick
an end, grip the key wherever you can and give it a wobble...left to right,
back and forth, round and round. Any movement? Try the other end of the
key, same tests.
Point screw wear can sometimes be hidden. The diagram above shows that
wear can take place both inside the barrel and on the end - but it's often
the case that the barrel wears inside and not on the ends...so that although
the key seems to sit snugly between its two pillars, it can still show
movement due to internal wear in the barrel.
Flutes are a slightly different matter - some of the keys are joined
together to form what's known as a 'compound key'. This means that two
or more keys are pivoted on a rod...which is then pivoted itself on points.
Typically there are three such keys on a flute...the C/A key, the right
hand stack (low F to D) and the trill keys. You need to be a little bit
careful when testing these compound keys for wear as what might seem to
be free play on, say, the F key may well be free play at the point screw
at the D key. Once you've wiggled the keys about a bit you'll start to
notice the difference.
Let's just scare the sax players a little bit more - try the low B/Bb
key, don't forget to wobble the keys at both ends.
By doing these simple tests all over your instrument you'll gain a rough
idea as to the (excuse the pun) state of play. This is just a guide though,
you might perhaps feel that a little wobble is insignificant when in fact
it could be quite a problem. And that problem is that whenever a key is
pressed down it tries to take the path of least resistance. With a well
maintained action the keys have no choice but to go where they're meant
to go...straight down onto the tone hole. Chuck in a bit of wear on the
pivots and a key will try to take up this free play as soon as it can.
This might be at the beginning of its stroke or at the end.
If it does so at the beginning then the action will feel clunky, and you
cannot expect that key to reliably bring down any others it is connected
to (and they might be worn too...thus doubling the effect). If it occurs
at the end of the stroke as the pad hits the tone hole then it will lift
slightly, creating a leak...usually at the back of the pad, nearest the
pivot, where it can't be seen.
All is not lost - this free play can be removed (though with varying
degrees of difficulty). Rod screw keys can have the key barrels 'swedged'
(pronounced swayged, as in wages). This is done using a special tool that
compresses the key barrel - and let me tell you, it can be hard going.
Point screws are much easier, the pillars are reamed out a fraction to
allow the screws to reach further into the pillar. If necessary, beefier
screws can be fitted and the holes in the key barrels can be re-bored
too if required
Those instruments that have those nasty parallel point screws fitted will
have built-in free play from the off...but it's a simple matter to change
these for proper point screws.
There are still other methods. Some point screws have no shoulder (see
and need only be screwed in further. Some rod screw keys have little or
no key barrel to compress, so they may require filling in and re-boring,
or an oversized rod screw (always a pain, as you have to do the pillars
too - and any other keys that sit on the same pivot).
Some repairers take up end to end play with little teeny washers. This
works a treat...for longitudinal play, but the tragedy is that this kind
of play is nowhere near as bad as lateral play, which washers do b****r
all to correct. They also look rather ugly.
I should imagine that some of you are wondering why you can't just take
a screwdriver to your instrument and tighten all the point screws
up yourself. Well, you can - but depending on the type of screw
(shouldered or cylindrical) you'll either make no difference at
all and possibly bust the head of the screw finding out, or you'll
lock the action up solid. With plastic bodied clarinets in particular
you might find that all goes swimmingly well - but when you next
take the instrument out of the case the action has locked solid
because the body has cooled and contracted.
For more information on the action, take a look at Matt
Stohrer's excellent article on key fitting, which discusses
in detail the techniques used to correct free play in the action.