 The Clarinet BBoard
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Author: Micke Isotalo ★2017
Date: 2025-06-08 18:26
Attachment: Backun_Alpha_BC_Nozzle_1.jpg (585k)
Attachment: Backun_Alpha_BC_Nozzle_2.jpg (552k)
What's the function or purpose of this nozzle-like feature, seen on the attached pictures? On the long axle I could imagine an oiling nozzle (not sure though), but on the adjustment screw barrel for the neck mechanism? These are on a Backun Alpha bass, and there are several at different locations.
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Author: Chris P
Date: 2025-06-08 18:33
Grub screw by the looks of it - Conn used to use them on their saxes to keep the pivot screws locked in place (and G.R.Uebel used them too).
Both a blessing and a curse - blessing as they can keep certain screws locked in place if the threads aren't in tension and a curse if someone doesn't undo them when removing the screws, or if they haven't got the correct size Allen key or hex driver that fits them, or they've been over torqued and mash up the screw threads or dent the rod screw and kick up a burr on it.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
Post Edited (2025-06-08 18:34)
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Author: Micke Isotalo ★2017
Date: 2025-06-08 20:50
Thanks a lot Chris. Yes, a hexagonal H0.7 driver was suitable. I guess I already damaged the threads of that adjustment screw for the neck mechanism a bit, while turning it without loosening that locking screw first (at least it still turns enough for adjustments both up and down, but I can't unscrew it completely). Thanks to your advice, I at least won't continue damaging other screws. 
Equipped with proper knowledge and tools, I definitely appreciate this feature since adjustment- and other screws living their own life is definitely a curse.
Must be demanding and time consuming for the manufacturer installing these infinitesimal locking screws. Never before seen such on any other instrument. Also nice that this feature is included on the more budget friendly Alpha, and not only on the more expensive Q bass.
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Author: Bennett ★2017
Date: 2025-06-08 22:58
British Empire English GRUB screw = American English SET screw
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Author: Chris P
Date: 2025-06-09 04:04
Pearl flutes and piccolos also use 0.9mm hex head grub screws (with hollow tips) instead of knock pins when 'pinning' steels to parts of the mechanism, but that too chews up the surface of the steel and removing the pinned (or 'pinless' as Pearl call them) steels scratches up the insides of key barrels because of the burr kicked up on them.
I've been using brass M2 grub screws to bush flat spring holes, then drill them out and tap them with the appropriate size tap for the flat spring screw. Works a treat on the Eb master spring on oboes (d'amores and cors) where the flat spring screw is screwed into a hole in the wood which often strips, so I can then use a stainless steel 12BA pinning screw to secure the Eb master spring with no risk of the thread stripping.
For grub screws on woodwinds like this, brass ones would be better as they won't damage the steel screws, but they definitely need the correct size hex driver so the heads don't get mashed up. What may be a good idea may not always prove to be good in practice. I personally don't see these grub screws lasting long term when properly fitted point screws or adjusting screws with a nylon lock (think Yamaha ones which are slotted and a plastic lock fitted in the slot) are much simpler and less prone to being damaged (or causing damage).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: JMrnr
Date: 2025-06-09 09:13
On my Q Bass, there is no grub screw on the register key as shown on picture 1 of the alpha.
Post Edited (2025-06-09 09:13)
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Author: clarnibass
Date: 2025-06-09 11:13
>> Both a blessing and a curse - blessing as they can keep certain screws locked in place if the threads aren't in tension and a curse if someone doesn't undo them when removing the screws, or if they haven't got the correct size Allen key or hex driver that fits them, or they've been over torqued and mash up the screw threads or dent the rod screw and kick up a burr on it. <<
Another issue that is common with old Conns is that they are often missing. Sure it's possible to replace them but many players don't bother...
>> at least it still turns enough for adjustments both up and down, but I can't unscrew it completely <<
Set/grub screws often have a reduced diameter at the end. If not then it can eventually mushroom and cause this problem. I don't know if this is the issue with that screw but it's possible.
>> Equipped with proper knowledge and tools, I definitely appreciate this feature since adjustment- and other screws living their own life is definitely a curse. <<
If you mean screws coming out, then it's not just an advantage, there are other ways of preventing screw from becoming loose, depending on the type of screw and its use. If a screw is coming out "by itself" then it's usually a sign of some other issue.
By the way the proper tool for the very small Allen head screws is almost always a screwdriver shaped Allen "key". The small L keys are far more common, and it might seem counter intuitive, but with such small screw those can really mess up the hex even if it looks like it's completely aligned. If you only have those, then it's better to hold it with pliers so you have much more control on alignment.
>> Must be demanding and time consuming for the manufacturer installing these infinitesimal locking screws. Never before seen such on any other instrument. Also nice that this feature is included on the more budget friendly Alpha, and not only on the more expensive Q bass. <<
It's an extra step, but it is actually saving cost most of the time. For the old Conns, the pivot screws themselves were headless, with a cutout area (no threads) for the set screw to press against. This actually saves a lot of time since the posts, screws, key fitting, etc. can be made far less precise, simply relying on locking the pivot screws in their correct position. Having actual screws with heads and the fit made accurately so when fully tightened there is no play and no binding can cost more.
Only seeing it from the outside is half guessing, but since the second screw is on a post that is between two key hinges, it is likely a long rod screw with a pivot screw end, and the set screw holding it in place. If that's what it is, it's exactly a case of making it unnecessary to make it accurately. For example this is a common issue on Buffet clarinets, where completely tightening the first ring key causes the second ring key to bind.
On the neck adjustment it's different and a good idea to add a way to adjust it separately.
>> For grub screws on woodwinds like this, brass ones would be better as they won't damage the steel screws, but they definitely need the correct size hex driver so the heads don't get mashed up. <<
I think brass would be too risky even with the best tools. Also depending on how close it is to the nickel silver of the keys, and possibly more so on brass keys, it could have the issue of similar materials "bonding".
Post Edited (2025-06-10 07:12)
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Author: Micke Isotalo ★2017
Date: 2025-06-11 00:45
clarnibass, the set/grub screw of the neck mechanism adjustment screw comes out completely and easily, but it's the adjustment screw itself that I meant is stuck at the "bottom" and doesn't come out (but still turns enough for adjustments both up and down).
Also a question for you, since on my regular clarinets the rod screw for the r.h. ring keys now and then comes out "by itself". It may stay in place for even a year or two, but then suddenly during just one playing session comes out several millimeters - and sometimes even enough to cause playing issues. Once I even tried threadlock, which I messed up a bit causing other issues, so that probably wasn't the best solution. You said this usually is a sign of some other issue, so what could that be - and how should it be addressed?
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Author: Chris P
Date: 2025-06-11 03:30
That's likely down to poor fitting of the point screw on the LH2 ring key or the E/B vent on basses, so the rod screw is often left loose instead of being fully tightened which causes the LH2 ring key/E/B vent to bind up. That's easily corrected by countersinking the end of the key rod so the point screw is a good fit in it (neither binding up nor rattling about).
Another issue is if the threaded pillar the LH1 rod screw is screwed into is out of alignment or the face hasn't been fraised straight, causing the rod screw to bow when it's tightened which in turn can cause the LH1 ring key or fingerplate (and open G vent) to bind up, so backing off the rod screw will then allow the bound up keywork to work properly, but leaves the rod screw loose and prone to undoing itself. Sometimes that's dealt with by putting a taper on the shoulder of the rod screw where it meets the thread to allow it to tighten up without anything binding up.
And other issues (of which there are many) could be a bent rod screw or bent key barrel which causes friction, or a burr on the ends of the key barrels that hasn't been removed after being fraised back when fitting them between the pillars and adjacent key barrels, or a heavy, sticky oil has been used or someone's used 3-in-One oil which contains resin and turns gummy over time, or there's still polishing compound in the key barrel or the rod screw has some scratches or corrosion on it, the key barrel hasnt been reamed out and is tight in places or the rod screw can have a twist in it which you'll see where the wear spots are (forming a shiny helix on the rod screw where the high spots are).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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