blog of everyday life on and around the workbench
If you're a regular reader of The Black Museum you may have seen
a recent entry which detailed a truly
terrible bodge job - namely someone's attempt to fit a Conn
'Chu Berry' alto crook to a TJ RAW. Such mods aren't uncommon -
there are lots of players out there using Selmer crooks on Yamaha
horns, and vice versa - but it's usually the case that anyone who
want to experiment with such a mod takes the crook to their repairer
and has them fit it properly. Job done.
In this case the owner of the RAW had a 'friend' do the job, which
resulted in perhaps the worst botch-job I've ever seen - and the
horn was duly sent to me to put it right. So I thought I'd detail
the process in the Benchlife Blog...
that someone had taken a file to the inside of the RAW's crook receiver
and the Conn's tenon sleeve, both of these parts had been rendered
useless and would have to be replaced - as would the body octave
key pip...which had caught the tail end of the file. No problem
getting replacement parts for the RAW, a quick email to TJ and the
bits I needed were duly put on order. Took a month or so to get
them, but items like this aren't generally held as spares because
they generally don't get damaged.
the Conn's tenon sleeve was a very different matter, and a new one
would have to be made from stock brass. It's not an especially difficult
job as a rule, but the Conn's tenon sleeve has a tapered bore -
which makes it a rather more complex job. So the first order of
business was to make up a mandrel which could be used to set the
lathe topslide when it came to boring out the sleeve.
In order to do this the sleeve had to be unsoldered from the crook
then mounted on a piece of brass tube that had been trued up in
the lathe - with the idea of getting the sleeve to run as true as
possible. It took some doing - but once mounted I was able to run
a dial test indicator up the bore and determine the correct angle
of the topslide...which is the part of the lathe you use for turning
The problem with this method is that the sleeve
may well have been expanded in the past, which means that getting
a truly accurate reading is going to be all but impossible. So the
idea is to get close enough and then make up a test piece which
can be adjusted on the fly to give an average fit. This is done
by coating the mandrel in marking blue and then fitting it to the
sleeve - making adjustments to the taper to get the very best fit.
this shot you can see that the mandrel is a good fit at each end
(where the marking blue has rubbed off) but the untouched blue in
the centre indicates that the sleeve is slightly 'barrelled'. A
few adjustments were made to reduce the width of that centre portion
and then the setting on the topslide was used to reproduce this
taper on a mandrel.
In fact two mandrels were made - one in steel, to serve as a reference
for future jobs, and a 'working mandrel' in brass. Only takes a
little extra time to make two, and it saves getting the reference
turned a stock piece of brass tube down to the required outside
diameter to fit the replacement receiver, the next job was to turn
the internal taper. With the working mandrel centred on the part,
the dial test indicator was used to set the topslide to cut internally.
I could have cut the taper 'in reverse' - but it's easier if you
can use the mandrel to check the work as you go...and to set the
length of the sleeve.
Here's the completed sleeve (below). Well, almost
completed. I could have used a larger piece of stock and incorporated
the mounting socket (arrowed) - but that would waste a lot of material
(and it's not cheap these days) and I rather wanted to keep as much
of the original metal as possible.
Besides, it's a simple enough job to cut the sleeve out of the socket
and silver solder the new one in place.
You might notice that the outside diameter of the new sleeve is
slightly larger than that of the original (by looking at the wall
thickness of the sleeve). This is deliberate. The owner of the RAW
wants to use the Chu crook on it - but by making it fit the stock
receiver rather than modifying the receiver to fit a Conn crook,
the job is that much cheaper...and it gives the player the option
of going back to using the RAW crook should they wish to do so -
or in the event that the modification fails to have the results
they expect. It also means that there won't be any problems should
they ever wish to sell the RAW.
the finished crook. With the new receiver and body octave pip fitted
to the RAW I only have to adjust the fit of the crook. This has
to be done very carefully because I didn't have the horn's crook.
If I adjust the internal diameter of the receiver it may well be
the case that the original crook will be too loose a fit. Just to
be on the safe side I used my own RAW crook to keep an eye on the
The big question is, of course, does it actually
work...and how does it sound?
Well I'm at least happy to report that it does indeed work. I'd
expected to run into any number of tuning problems but was quite
surprised to find that it was actually pretty good. There's perhaps
a little bit of flaring at the top and the bottom, but nothing that
can't easily be steered by the player.
In terms of tone the Conn crook is noticeably
brighter (which was another surprise) and a little more free-blowing
than the RAW.
I wouldn't say the results were dramatic - in fact it rather got
me wondering whether the whole exercise was worth it in the first
place...but it may well be the case that spending some time with
the crook will tease out more nuances over time.
But when all is said and done I'm at least pleased to have restored
the RAW's dignity, and released it from the bodger's miserable clutches.