There are two main types of screws used on woodwind instruments to secure
the keys in place; one is the rod or hinge screw and the other is the
point or pivot screw.
This article deals with point screws and discusses how they work and the
various pros and cons of the different types you're likely to see.
screws allow for keys to be securely mounted to the body of the instrument
whilst still allowing them to move in an appropriate fashion. Typically
you'll find them used on long single keys where a rod screw would be impractical
or undesirable. In most cases a point screw can be recognised by its large
head (usually much larger than that of rod screws), though a more reliable
way of spotting them is to look at the pillars at each end of a key -
if you can see a screw head with a slot in it in each pillar then it's
very likely the key is pivoted on such screws.
Here we see a typical setup in which a pillar is fitted with a point
screw, which in turn supports a key barrel. Attached to the barrel would
be various key arms or key cups.
This diagram represent the best-case scenario; the slotted head of the
point screw fits flush into the pillar (so there are no edges sticking
out on which to catch your fingers) and the tapered point of the screw
exactly fits a corresponding hole in the pillar.
There is a very tiny gap between the end of the key barrel and the opposing
face of the pillar. This keeps friction to a minimum and by preventing
the key barrel from rubbing against the pillar also reduces wear to both
When suitably lubricated, this arrangement allows the key to rotate quite
freely and smoothly, and because everything is a snug fit there's no free
play in the mechanism. The key cannot move in any other fashion.
Point screw types:
are the six most common types of point screws in use.
They're divided into two sections; proper points and parallel points.
From the top down we have:
1: Proper point screw - the 'King' of point screws, its tapered
point allows for it to be adjusted to take up wear and tear.
2: Shoulderless point screw - essentially the same, but without
a head. We'll see how useful this feature is later.
3: Elliptical point screw - a relative newcomer, but because
of the ever-increasing diameter of the tip, still a proper point screw.
4: Parallel point screw - also known as a cylindrical point
screw. It has no taper, though is sometimes seen with a slight point.
5: Pseudo or bullet point screw - looks like a proper point,
but isn't as it has a cylindrical section on the tip.
6: Spear-headed point screw - another newcomer, but effectively
just a combination of the above two screws.
The parts of the screw are broken down as follows:
The head - the largest diameter of the screw, which also
houses the slot...where the screwdriver goes.
The thread - the section that screws into the pillar.
The tip - the 'business' end of the screw, which sits inside the
Screws can vary in size - small ones would be found on flutes, oboes
and clarinets - larger ones on saxophones.
These too will vary in size, shape and design - the threads will be different
between manufacturers, the diameter and thickness of the heads vary, the
length of the tips too.
This is an important consideration - if you happen to lose a screw (they
do sometimes drop out of their own accord) you can't just bung any old
thing back in the pillar as there's a very slim chance that it will fit...or
even if it appears to fit, it very probably won't be of the correct dimensions.
Forcing a screw with a different thread into a pillar may damage the pillar
- and if the screw gets so tight that it breaks you'll end up with a hefty
bill for putting it right. It's not uncommon to find that someone has
gone to all the trouble of forcing an incorrect point screw into a pillar
(and thus 'crossing' the thread) only to find that the tip is too small
for the job.
Incidentally, if you do happen to lose a point screw (and it happens
to the best of us from time to time) poke a matchstick into the pillar.
It's strictly a temporary measure, but it'll get you through a gig or
The pros and cons:
referred the the proper point screw as the 'King' of screws earlier, and
On the left is a diagram of what happens to the setup shown in the opening
diagram after the instrument has seen a good few years use.
The pillar and screw haven't moved - but now there's a noticeable gap
between the tip of the point screw and the key barrel. This will mean
that the barrel is able to wobble on its pivot screws, and when that happens
it leads to a rattly action that feels sloppy and imprecise. It also means
that any key cups and arms attached to the barrel won't move with as much
accuracy - so a pad might leak or a connection with another key won't
be spot on (this can lead to what's known as a regulation leak...a leak
caused by the mechanism rather than a pad).
It also means that any lubrication between the screw tip and the barrel
will get pumped out...and grit can get in, so the wear gets ever worse.
You can see too that the gap between the pillar's face and the key barrel
has increased because the point screw can no longer hold the barrel off
- so it can now rub against the pillar and wear itself down.
Here's the clever thing though - because the tip of the screw is a proper
taper, if there were a means of allowing it to push deeper into the key
barrel it would once again fit snugly and all would be well.
And there is such a means - by reaming the pillar. This simply involves
removing a small amount of metal from the head end of the pillar, which
then allows the screw to be driven further into the pillar...thus pushing
the tip further out from the face. The section of the pillar that would
be removed is indicated in red. The actual amount removed would be far
smaller than shown, and such a job would need doing maybe two or three
times in an instrument's life - assuming it was kept well lubricated inbetween-times.
This is half of the job known as tightening the action - the other half
being that which deals with free play on keys mounted on rod screws.
a slight variation on the theme.
In this instance the barrel has been drilled out with a cylindrical hole.
This is far more likely to to be the case than finding a barrel that's
been properly reamed with a tapered hole to match the screw tip. It's
a lot harder to get a tapered hole exactly right - one tiny fraction too
big and the key will never sit snugly...and the manufacturer would have
to throw it away and start again. Very costly indeed.
That's why I said 'in an ideal world', because this diagram shows what
you're more likely to encounter.
It's our good old proper point screw again, but note how almost all of
the tip is sitting in air.
The part of the tip that's actually in contact with the barrel is marked
in red. As with most of these diagrams it's slightly exaggerated in order
to make it clearer, so you could reasonably expect rather more of the
tip to be doing some work.
I've shown the point of contact as being near the base of the tip, but
it could quite easily be near the end of the tip. It doesn't really matter
that much (although you might have realised that there won't be much more
room for adjustment with this particular setup) as long as there's a single
point of contact that holds the key barrel snugly.
The variations on the proper point screw (the elliptical and the shoulderless)
deal with the wear in exactly the same way - though because the shoulderless
screw has no head it does not require the pillar to be reamed...you simply
screw it in further. This is a simple and efficient way of dealing with
wear but it does, however, require a means of locking the screw in place
- and this can be in the form of a small grub screw, a lock-nut, a nylon
insert or a drop of threadlocking fluid.
So this explains how and why proper point screws work, and what makes
them such a desirable feature. Let's look now at why the parallel types
fare less well.
you can see it's much the same setup as the proper point screw.
The diagram show the 'ideal world' scenario, with the cylindrical tip
of the screw nestling snugly inside the key barrel, which has been drilled
so as to perfectly accommodate it.
Unfortunately it seldom works out that way. What's more likely to be the
case is that the hole extends some way into the barrel - as marked by
the dotted lines.
When this occurs it allows for the barrel to move back and forth along
the screw tip - so the only thing preventing it from doing so is having
the ends of the key barrel rub up against the pillar face.
We already know that's not a good idea as it adds friction and leads to
wear...and when that happens it leads to yet more wear.
However, as long as the diameter of the hole in the barrel is a close
fit to that of the screw tip the key will at least be unable to wobble.
This means that the setup is unlikely to lead to regulation problems but
could, just about, lead to slight leaks in pads. At least until the hole
wears...and then it all gets a bit nasty.
here it is, a classic example of wear in a key pivoted on a parallel point
As per the wear with a proper point screw, you can see that the key barrel
has worn around the diameter of the hole, so the tip is now floating in
When this happened with the proper point screw setup it was able to be
taken up by means of driving the whole screw deeper into the pillar. But
that's not going to work here.
If we assume this diagram accurately represents the state of wear in
a typical key barrel you can see that driving the screw in deeper would
allow for the end of the tip to meet the bottom of the hole. But that
wouldn't be of much use - the best that it would do would be to prevent
the ends of the barrel rubbing against the pillar face...the key would
still wobble. Besides, as we saw just above, the hole is often very much
It should be quite clear then that's there's very little that can be
done to take up the wear.
Well, there is one method - which involves swedging (pronounced sway-jing)
the key barrel. This technique compresses the barrel and thus decreases
the size of the hole. It's a technique that's used to take up the wear
in keys mounted on rod screws. It's hard work, and therefore expensive,
and it often leaves visible marks on the key barrels.
It's also the case that it's not always possible to swedge a key barrel.
The one shown in the diagram is conveniently bare, but many of them will
have a key arm attached at precisely the place where you'd need to swedge
In such cases rather more drastic measures are called for - such as filling
up the hole with silver-solder and re-drilling it.
the same problem, but this time with a pseudo or bullet point screw.
Remember, the definition of a parallel point screw is that its tip doesn't
get increasingly larger in diameter - so the pseudo point screw is prone
to exactly the same problems as the cylindrical type.
It does, however, have a slight advantage - it has a tapered tip. In
effect it's half a proper point screw.
The diagram show the screw fitted to a barrel that has some wear - note
the gap above and below the tip - but the coloured sections are where
it gets interesting.
The green section represents that portion of the key barrel that the end
of the tip is in contact with. As long as this remains the case this type
of screw will function as a proper point screw...i.e. perfectly well.
When it wears it can be driven further into the pillar...but only as far
as the green portion extends. Once it gets much beyond this you will have
driven the head of the screw so far into the pillar that there won't be
much thread left in it - and that's not at all good.
At this point the tip enters the red section...and with the end now floating
in free space the screw reverts to being nothing more than a fancy cylindrical
screw...with all the disadvantages that come with it.
The spear-headed point screw would work in exactly the same fashion...though
why anyone would go to all the trouble of making such a screw I have no
idea - it seems utterly (and I've been waiting for this bit) pointless.
All this assumes that the hole in the key isn't already too deep - and
unfortunately it usually is. The easy way to check this is to remove the
point screw from the pillar and poke the tip into the hole in the barrel.
If the screw goes in right up to the thread then the hole is too deep.
As it happens, this is one way in which parallel point screws can be 'botched'
to take up free play...they're driven into the pillar until the threaded
portion of the screw comes out from the pillar face - the barrel then
rubs up against the thread, giving the appearance of being nice and snug.
And it is, but only for as long as it takes the rough thread to chew away
the metal of the barrel...which won't take very long at all.
fascinating variation is this system found on modern Selmer saxophones.
These instruments use a unique method to automatically adjust for any
wear in the action by means of a sprung cylinder inserted into the bore
of the key barrel.
As the tip of the screw wears away the contact point in the cylinder,
the spring pushes the cylinder forward to close the gap (obviously this
wear happens at an extremely slow rate). This ensures that the business
end of the pseudo point screw is always in contact with the key barrel
- and this means that you should never need to ream the pillars to take
up wear in the action.
Sounds ideal, but there are one or two drawbacks.
Because the system requires that there's a bit of a gap between the end
of the key barrel and pillar face (otherwise the sprung cylinder would
simply butt up against the pillar and you'd be back to square one once
the point screw tip starts to wear the barrel), and because there's a
spring in the barrel...or one at each end actually...you can never adjust
the action so that it's really tight.
By tight I don't mean stiff...but if you've ever wiggled a key properly
fitted between two proper point screws you'll know exactly what I mean.
The key can move up and down freely but there's no lateral movement.
The other drawback is that it's possible for the cylinder to wear in
the key barrel...and then you're in trouble.
Technically speaking you can replace the cylinder...but if the barrel's
worn then there's little point. It could get very messy!
In the review section you'll often see comments like "I was disappointed
to find pseudo point screws had been used..." and perhaps this article
explains why I feel that way about them. Wear and tear is part of a woodwind
instrument's life, and if you've coughed up well into four figures for
a nice sax or clarinet etc. it's a bit disheartening to find that, sooner
or later, you're going to run into problems when it comes to tightening
The worst of it is, the part that's responsible for the problem isn't
even replaceable. Putting a new point screw in when a key has worn isn't
going to change anything - you'd have to change the key itself.
There is an option though - changing the type of point screw fitted.
In theory you could take out the pseudo or parallel points screws and
replace them with proper points - but this upgrade rather relies on being
able to find point screws of a suitable size and shape. It's tricky, admittedly,
but not always impossible. If all else fails there's always the option
of having them custom made. This won't be a particularly cheap option,
but it will be a one-time fix and you'll be able to have the wear and
tear in the keywork adjusted out for at least as long as your playing