Levelling rolled toneholes
The no-filing method of tonehole levelling
I had an email recently from a regular correspondent
who, for one reason and another, was thinking about having a go
at sorting out the warped toneholes on a Buescher/Martin tenor
(yep, you read that right). He's an experienced engineer - and
had it been a regular horn with plain drawn toneholes I reckon
(with a few hints and tips) he'd have been more than capable of
making a decent job of it. However, the toneholes are soldered-on
- and someone's been at them already - which means that as far
as tonehole levelling jobs go, it's likely to be about as bad
I did the decent thing and wrote back with predictions of doom
and disaster, end-of-world scenarios, a whole new dimension of
arsedness and the very real possibility of ruining a rather rare
horn. Fortunately he knows me well enough to realise that when
I say "Noooooo...don't do it!" I really, really mean
As luck would have it I had a client in with a Keilwerth
SX90R who'd commissioned me to inspect and sort out any tonehole
anomalies - so I thought I'd take the opportunity to run up an
article detailing the procedure I use for levelling toneholes
that can't (or at least shouldn't be) filed.
It'll kill three birds with one stone; it'll likely put off any
DIY repairers who fancy giving it a go (once they realise how
hard it is), it'll hopefully provide some interesting reading
for all the sax buffs out there...and maybe it'll give up-and-coming
repairers something to think about.
a shot of what we have to deal with. There are noticeable warps
on all the toneholes, but for the purposes of this article I'm going
to tackle the low F, E and D.
Why not just show the levelling process on a single tonehole? Well,
here's the thing - if you're going to have straight at the tonehole
with a file then sure, you can deal with each one in isolation.
However, this means relying on the file to remove metal - which,
for the sake of best practice, is something that's best avoided
where at all possible. In the case of the Keilwerth it's essential
due to the pseudo rolls fitted to the rims - and the same would
be true of a traditionally rolled tonehole, such as those you might
find on an old Conn.
When you can't or don't want to use a file you have to resort to
other methods of levelling the toneholes, and that means manipulating
the base of the hole until the rim levels out. It's an effective
if rather time-consuming technique, but it can't really be applied
to a tonehole in isolation because any manipulation of the body
tube is going to have a knock-on effect to the adjacent tonehole(s).
This means that you have to deal with the toneholes in pairs or,
for my preference, trios.
Before we get started it's vitally important
to clean the rims of the toneholes. Any debris or gunk on them will
affect the reading when the flat standards are placed on them. A
light wipe over with some 1200 grit carborundum paper followed by
a wipe with a spot of cigarette lighter fluid will do the job nicely.
With the rims nice and clean the first order of business is to examine
the batch of toneholes with a set of flat standards and note where
the peaks and troughs are. If I'm lucky I'll find that they correspond
- so that if I'm having to push the bore down to level off a peak
on one tonehole, there'll be a similarly positioned peak on the
next tonehole up or down the line...which will benefit from the
change in the bore.
it doesn't always work out that way, and as you can see here I have
the low D tonehole showing a peak that nearly corresponds to the
apex of the body tube. To make things clearer I'm going to use clock
positions to describe the various peaks and troughs, with the rear
of the tonehole (nearest the rod or hinge screw) being the 12 o'clock
spot - and I'd describe this peak as being at the 4 o'clock position.
It's usually the case that the peaks and troughs come in pairs on
roughly opposite sides, and in this instance there's a similar peak
at the 8 o'clock position.
Now look at the 3 o'clock position on the E tonehole.
I'm out of luck because there's a trough in it. I'm going to have
to lower the body tube at the low D's 8 o'clock position and raise
it at the E's 3 o'clock - which means that each operation will have
an adverse effect on the adjacent tonehole.
This is precisely why you can't deal with each tonehole in isolation
- it's going to be an exercise in give and take as I creep up to
a point where the trough on the E and the peak on the D find their
There will be much swearing.
The trick is not to try to aim for precision too
early in the game. No doubt other repairers have their favourite
way of doing this, but I like to work on reducing the overall size
of the warps so that the required adjustments become ever more finer.
The smaller the adjustment needed, the less likely it is to have
an effect on the adjacent hole. Once the pair (or trio) of holes
are at this point, they can effectively be tackled in isolation.
However, it's a bit of a constantly moving target because until
you get to either end of the body tube there's always going to be
an adjacent tonehole - so there's a lot of back and forth going
decided to start with the low D, and here you can see me tapping
down the 4 'o clock peak. I'm using plastic (Delrin) rod and hitting
it with a mallet rather than using a mallet directly onto the tonehole
rim. The rod provides a far greater degree of control, which is
important in terms of regulating the 'spread' of the impact and
the alignment with the tonehole wall. Get either of these wrong
and you could end up creating more warps than you remove, and you
might bend the tonehole wall (which would ruin your day). It's a
fairly large rod - as the adjustments become finer I'll use smaller
and smaller ones to tap down the peaks.
when I say tapping I mean just that. It's not too much of a concern
on this horn because the tonehole rims are solid, but on a properly
rolled tonehole the roll is likely to be hollow...and thus far more
susceptible to being damaged by a careless impact. It's all about
gentle persuasion, firm but considered coaxing and constant checking.
Here's the result of the first tap, and you can
see that the warp has shifted slightly and changed the tonehole's
'table' (its state of evenness). As it changes it also changes the
decisions you make as to where next to manipulate the tonehole,
and if you're not careful it's easy to find yourself undoing the
adjustment you just made because it now looks like the right thing
This is largely where the 'feel' aspect of the job comes into play;
there's a certain amount of making it worse before it gets better,
so to speak - and part of the skill is in having a plan of action,
and knowing when to ditch it when a potentially more promising plan
happy with how the first tap turned out, so the next step is to
repeat the process at the 8 o'clock spot. The top shot is what it
looks like now - and the lower is what it looks like after a tap.
There's a huge difference in the table - so much so that the front
of the tonehole is now almost level, but note that very slight increase
in the length of the trough at the 9 o'clock position. This is pretty
much par for the course and I'm none too worried about it because
it'll almost certainly change again when I start working on the
But even at this stage we've made a significant improvement to the
tonehole. The gaps have gone from being a tad over a thou deep to
around about just under a half a thou. If I were to pop the key
back on now, I could easily tweak the pad to accommodate a gap that
small...and it'd be a fairly reliable seal.
it at least it would be if it wasn't for a dirty great trough at
the rear of the tonehole.
It's a biggie, and because it's at the rear it's sitting on top
of rather a lot of metal. This is going to make it a bit of a challenge,
but on the plus side I can be pretty sure that while any changes
I make here are bound to have an impact on the table, they're rather
less likely to have a knock-on effect to the E tonehole.
I'm going to leave it for now though, because the work needed on
the E is bound to affect the D - and I may well come back to this
trough later to find that it's shrunk a little (well, I can hope).
On to the E then - and the big question is, is
it a trough at 3 o'clock or a peak at 5 (and 1) o'clock? I have
to make a judgement call on it, and by examining the table all the
way round I reckon that I should treat it as a trough.
need a different tool for this job because we want to raise the
body tube rather than knock it down. You could use a dent bar down
the bore of the horn, but it's a bit crude and it doesn't really
lend itself to quick adjustments and inspections - so I'm going
to use a burnisher and a spreader. The burnisher is used as a lever
while the spreader provides a fulcrum point for it and spreads the
load out over the opposite side of the tonehole. This helps to minimise
any unwanted deformation of the tonehole - though it's impossible
to eliminate it altogether (unless you reach for a file).
not sure whether you can buy such tools, but they're quite easy
to make. At its simplest the burnisher/lever is just a bit of round
bar that's been slightly flattened at the ends, bent over at one
end and then polished to a smooth finish (this is very important).
Any old steel will do - you could even use brass at a pinch - and
it's useful to have a range of sizes.
The spreaders are also easy to make...if you have a lathe. Delrin's
the best choice of material, but any stiff plastic will do. You
can even use wood...but you might find you need to make them rather
thicker to prevent them splitting. There's an inner diameter that
sits inside the tonehole, which prevents the spreader from being
pushed off the rim, and an outer diameter that sits over the rim...and
then the whole thing is sawn off at the 3/4 point and a rounded
notch is ground dead centre (the hole in the centre of the large
spreader is just what was already in the bit of plastic offcut I
made the thing from). Again, you'll need a range of sizes but there's
no requirement for them to be a snug fit - and if you don't have
a lathe you could always try glueing a couple of bits of shaped
the tool in use on the E tonehole. I've positioned the lever dead
centre of the trough, and because it's quite a wide one I've pulled
the lever out so that the flatter part of the end sits beneath it.
The spreader is pushed back against the opposite wall of the tonehole,
and you can see that the downward force from the lever is going
to be spread over at least half the circumference of the rim.
Just as with the tapping down, the force applied is quite gentle.
You can perhaps see from my grip on the lever that I'm looking to
tease the trough up rather than yank at it.
Make no mistake, no matter how gentle you are the spreader will
still have an effect on the table - but it'll be a great deal less
than the effect of the lever on the trough.
the result of my levering, and I reckon it looks like I made the
right call this time. The trough has all but gone and the width
of the peak has increased so that the table now presents a shallow
trough at the 7 o'clock spot...some of which will be down to the
action of the spreader at the 9 o'clock position (i.e. directly
opposite the portion of the tonehole that was being lifted). I'm
pleased with how this turned out, and as the tonehole looks pretty
good from 8 o'clock round to 12 I think it'll pay to lift this trough
so far so good - the front of the tonehole looks pretty even, but
have a close look at the 3 o'clock position. The trough I just pulled
out has deepened again, so I'll need to return to it and give it
another tweak...which'll probably throw the front of the tonehole
out again. But not by as much as before, and that's the point. Little
by little I'll even the anomalies out. There's still some business
at the rear of the hole to deal with, but I reckon it's good enough
to allow me to go back to the low D and see what I can do about
bringing it closer to spec. I'm also interested in seeing what effect
the work on the E tonehole has had on it.
The sax gods have smiled down upon me, because
all I can see is a slight extension of the shallow trough that was
there before I started work on the E. I'll deal with that in a moment,
after I've sorted out that trough at the rear because it's deep
enough to affect the whole table when it's pulled up - but from
here on in the adjustments get smaller and smaller.
the E and D close to level I can think about finishing up on the
D and moving along to F to make a start on the coarse adjustments.
This is a tricky one because not only does it have toneholes either
side of it, it has one below it (the side F#). Nasty.
And I wouldn't mind betting you're thinking "Wow, that wasn't
so hard! What's all the fuss about?". Here's the thing - what
you see above is the entrée...the starter... the amuse bouche.
Getting out the major peaks and troughs is pretty easy - it's dealing
with the finer levelling that's really punishing.
Essentially it's the same process as described above, though the
adjustments are smaller and follow in rapid succession - and there's
a lot of tail chasing as the table gets closer to level. There are
also an increasing number of judgement calls to be made - and you
can't expect all of them to go as planned.
here's the result of all that pushing and pulling. I've left the
F in its original state for comparison, but the E and the D are
now even across the table. For me the result is the warm glow of
a job well done, along with a certain amount of relief that it all
went reasonably to plan...though once I start working on that F
hole, the E is going to be thrown out of whack - and I'm not much
looking forward to tackling the G tonehole...because it's always
a tricky little bugger.
As you can see, it's a vast improvement over the opening shot of
this article - and when I've finished the job the result for the
player will be a noticeable boost in the depth of tone across the
range, increased response and stability and a great deal less finger
pressure required in order to get the low notes to speak. And it'll
stay that way for far longer when the pads start to harden up with
If you were able to look closely enough at the toneholes you'd see
one or two faint spots of light. If you could be bothered to measure
the gaps you'd probably find they were just a few tenths of a thou.
This is as close as it's realistically possible to get with what
is, in reality, quite a crude method of levelling - but it's well
within the long term tolerance of a pad seat. If you wanted to go
the extra few yards you'd have to 'dress' the tonehole by running
a very fine grade slipstone over them (or a flat disc with 1200
grit carborundum glued to it). If I were fitting new and firm pads
to this horn I'd probably go for it, but as I'll be using the existing
pads (which aren't all that firm) I really don't feel it would be
worth the bother.
It all takes a heck of a lot of time and demands,
shall we say, a certain degree of experience...and a lot of care.
All of which ends up on the invoice as a rather unimpressive "Level
off x toneholes".