A rolling blog of everyday life
on and around the workbench
01/09/2017: Had a
54 tenor come in for some work recently, and as part of my 'tweakery'
package I upgraded the low C/Eb rod screw.
I've mentioned this curious feature before, in my review of the
Ref. 54 alto,
and noted that there are a number of things that are less than ideal
about it - so I figured it'd make an interesting article to discuss
it in more detail and have a look at the process of replacing it.
There are a number of ways the low C/Eb keys can
be mounted on a horn. On vintage horns you're more likely to find
that both keys are mounted on a single shaft - a plain old rod screw.
On even older horns you might find that the keys are mounted individually
on their own rods screws - but the modern trend is to mount the
keys individually on point screws.
This last method makes the most sense; these two keys often get
knocked, and it's far easier to deal with a bent key that's mounted
on point screws than one that's mounted on a (now bent) rod. It's
also a lot easier to deal with wear and tear on point screw mounted
keys - and while I wouldn't say that these two keys wear any faster
than any of the other keys, the effects of it seem to have more
of an impact. Even a slight bit of free play on the low C key can
throw up a leak...and this'll have a noticeable impact on the stability
of your subtone bell notes.
few years ago Selmer came up with the idea of using sprung inserts
in the point screw key barrels, the idea being that the insert (a
tube with a spring on one end) would sit in the key barrel and exert
a constant force against the point screws that are holding the key
It's a nifty idea on paper, but in practice I find it leaves the
action feeling slightly 'approximate' - because there's always a
degree of end play in the system due to the action of the springs.
Contrast this with standard point screws, where (ideally) the key
is held snugly in place - not so tightly that the normal up and
down action of the key is hindered, but tight enough to ensure the
key cannot move in any other plane.
You could argue that point screw keys are prone to wear, and that
once they do so they'll wobble about - and that the sprung system
takes care of this wear automatically. And this is true - but it
does so at the expense of precision...which means you never have
a truly tight action, nor the sense of feel that comes with it.
Swings and roundabouts, as ever.
then they went a step further and incorporated a spring in a rod
screw - and I really can't see why on earth they did it.
Here's the rod screw in question, alongside the low C key. It's
essentially the same system - the split pivot rod is mounted on
a pair of point screws and has a spring in the middle to provide
a constant force against the screws.
There are a couple of potential issues that trouble me about this
design - the first of which is that by splitting the rod in two
and fitting a spring in the middle, you reduce the stiffness of
the rod. These are large keys, and the low C in particular tends
to suffer with quite a bit of flex in use (which is why many horns
feature double key cup arms on this key). What this means is that
an otherwise perfectly set pad can be made to leak by virtue of
the player being a bit heavy-handed. The harder you press the key,
the more the metal tries to flex - and this typically results in
a portion of the pad lifting away from the tonehole. You could say
"Then don't press so hard!" - but when the going gets
hard and fast we all have a natural tendency to press harder. It's
just one of those things. So anything that can be done to increase
the stiffness of the keys is a welcome addition - and anything that
reduces it...well, not so much.
second issue is perhaps slightly more off the wall.
Take a look at the rod screw - notice that it's not straight. This
is its 'resting state'. When you fit it to the horn, it gets worse.
You can see that the bend is now rather more pronounced because
the spring is under compression. With a bit of very careful jiggling
you can get the screw to sit straight - you just have to find the
point where the force is in balance. It's like that old trick of
squeezing a coiled spring between your fingers without it flying
off across the room.
When the keys are fitted they hold the rod in equilibrium - but
it's not a particularly stable state, and it rather depends on the
integrity of the spring. If it's got a bend or a kink in it, the
rod will never sit straight. This means there's a sideways force
acting on the key barrels, and when you couple that with the motion
of the keys you end up with friction...and friction means wear,
eventually. In some cases you might even notice a grating sound
as the keys are pressed - which means that one of the rods is rotating,
or the spring has bulged and is rubbing against the key barrel.
I think sprung pivots are a questionable-enough
feature on the point screws, and a completely silly one on the low
C/Eb - and my standard tweak is to replace the rod with a solid
one. This adds stiffness to the mechanism and does away with the
potential for friction from an off-centre rod screw.
And it's a simple upgrade - all that's needed is a length of rod
of the right diameter with holes in each end to accommodate the
are a few things to consider, though. The point screws are bullet-headed,
which means that only the tip of the point is tapered - the remainder
of the screw is cylindrical...which means the hole in the rod has
to be drilled very precisely (or the rod will wobble). You also
don't want to drill the hole out too deep, otherwise the tip of
the screw will be floating in air and won't have any scope for future
One way around this is to drill a stepped hole - a smaller pilot
hole to accommodate the tapered tip, and a larger one to take the
main shaft. This'll work fine, but it's a lot of fiddling about
and will require some very accurate drilling. A better bet is to
use a profiled reamer that will cut a hole that perfectly matches
the size and shape of the tip.
These are easy enough to make; a length of silver steel turned to
size, profiled to match the shape of the screw tip and then heat
treated to harden and temper the tool (so that it doesn't wear out
halfway through the job). It takes as much time to make such a tool
as it does to faff about precision-drilling a pair of stepped holes...and
once you're done, the tool can go into a drawer ready for the next
It might all sound like Nth-degree mechanical
twiddlery, but the upgrade makes a noticeable improvement to the
performance of the lower notes. They're far more stable and centred
- and much more consistent over a wider range of playing styles.
And the very best of it is that it's a completely reversible mod.
If you don't like the results, you simple pop the new rod screw
out and refit the old one.
I always put the old ones into a sealed bag and throw them in the
accessory compartment of the case, where - as far as I've seen -
they remain for all time.