 The Clarinet BBoard
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Author: eddiec ★2017
Date: 2017-05-08 09:13
I acquired an instrument where, on one key, about a half inch long, the hinge rod seems to be too large for the tube. I don't know how it got to this state, but judging by the marring on the rod, someone had to work hard to get it out. Its a Patricola from around 1996.
The tube and rod seem reasonably straight; the rod is just too big.
The rod had some high spots from marring, so I turned it some to take those off. It still didn't fit, so I turned it some more and it goes most of the way through now, but it may take a lot more turning to get it all the way. It is down to 1.84 mm.
Most of the rods seem to be about 1.88 mm / 0.074". This seems to be an odd size. I pulled a rod off a Selmer Signet and measured it at 1.92 mm / 0.075" - reasonably close to a #48 drill. This mainly matters if I end up having to fabricate a new rod. (Other measurements for those looking for reference info: the threads seem to be 1.7mm OD, 1.39 mm ID, 0.35mm pitch).
My caliber can't directly measure the key tube's diameter accurately, but I can say that the exit diameter is about 0.05 mm smaller than the entry.. I would think they should be the same. Maybe this is a semi-finished replacement key, or was re-plated, in either case expecting some finishing work.
I could keep turning down the rod, but it may end up with too much play at the post. Or I could drill out the tube with the smallest size bit that has some "bite" to it, or possibly file it with a tiny round file, but I'm not sure that would achieve a good round hole.
Or at last resort, hire someone who knows what they are doing. Somehow, my natural instinct is to avoid taking power tools to keywork.
Any advice? Thanks!
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Author: Tony F
Date: 2017-05-08 09:34
I'd suspect a buildup of crud or corrosion in the tube, or perhaps distortion. No way should the bore vary along the length of the tube. I suggest you buy a set of broaches from Ferrees or Votaw and open the tube up to constant diameter. They cost very little and are always useful to have.
Tony F.
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Author: clarnibass
Date: 2017-05-08 15:38
Turning a small diameter like that, probably unsupported (or is it?), diameter will definitely not be even. I guess your lathe may be accurate, you could use a tiny collet, turn a little and then pull it out just slightly more each time... but in general this is not done by turning.
I'm not sure if that clarinet is also a Selmer Signet and even if it is, clarinets from a different time can be different even if they are the same model. If it is not a Signet then matching rod screw diameters is just a coincidence.
Check if the rod screw and/or hinge tube are not bent. Sometimes there's an actual bend but sometimes it's a small spot that is pushed in. Check the rod from both sides. Sometimes there's a burr or a small bent at the opening of the tube which can cause that.
It's more common to just sand rod screws from rust, etc.
You can clean the tube even with a small file or a broach. Try with very little force, so it just cleans it from whatever can't get out using e.g. a degreader rather than really filing the tube itself, though filing and broaching are good ways (among others) to fit hinge tubes.
You can get a close fit that is slightly tight or loose, then swedge and sand/lap them for a good fit.
It's hard to know what the real problem is, but just turning the screw to fit into a warped/bent/etc. tube... it's better than not being able to use the clarinet if that's the only other option.
>> No way should the bore vary along the length of the tube. I suggest you buy a set of broaches from Ferrees or Votaw and open the tube up to constant diameter. <<
If you are talking about the jewelers broaches then those are tapered
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Author: Steven Ocone
Date: 2017-05-08 16:43
The rods are probably all the same. If another rod fits then the rod you have is wrong or is damaged. If the other rods get stuck you have a bent hinge tube.
I keep as many sizes of drill rod as I can find to use as stock for new rods. .075" rod is a standard size but there can be a lot of variation.
Steve Ocone
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Author: eddiec ★2017
Date: 2017-05-08 17:20
The other rods on the instrument don't even begin to enter this tube, from either end. There must be a story here, but I may not want to know it.
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Author: Chris P
Date: 2017-05-08 20:14
While it may be a generalisation, Italian built woodwinds aren't perfect by any stretch of the imagination, so always expect the worst and you won't be disappointed.
I had the opposite problem with some Orsi instruments - the rod screws were far too narrow for the (cast) key barrels.
European woodwinds tend to use metric rod screws in 0.1mm increments, so you'd have a minimum of 1.9mm to 2.5mm and all sizes in between on clarinets.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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