A rolling blog of everyday life on and around the workbench

14/01/2023: 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...

Given 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.

Replacing 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 tapers.

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.

In 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 damaged.

Having 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.

Here's 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 'dual fit'.

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.