 The Clarinet BBoard
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Author: PipeTobacco
Date: 2021-05-23 23:35
Hello:
Ihave replaced corks on various joints on clarinets in the past..... but used cork given to me. I am now in need of BUYING some new sheet cork..... but foolishly I did not think to measure the thickness of the cork I had previously.
In your opinion, which thickness is typically most useful for cork repairs.... 1mm, 2mm, or 3mm? I am currently wanting to recork a bass clarinet mouthpiece (Bundy, standard).... but also have a few soprano clarinets I will eventually be refurbishing too.
Advice, guidance, opinions.... all appreciated. I have been looking at rolled cork on Amazon..... but if that is not a good choice..... I would appreciate guidance in that regard as well.
PipeTobacco
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Author: Chris P
Date: 2021-05-24 00:50
1.6mm thick sheet cork is best for tenon corks and mouthpiece corks.
If the cork slots are particularly deep, you can use 2mm thick sheet cork, but it is more prone to cracking if it's very dry. You can always glue a strip of tech cork in the slot to bulk it out, then glue the 1.6mm thick cork strip onto the top of that and shape the tenon cork as normal.
As far as key corks go, you're best using something far more durable for linkages - 0.4mm thick tech cork is ideal for that. It can also be used on the speaker key, in the cut-out on the throat A key under the adjusting screw, the LH3 'sliver' key, the side F# key and the bridge key linkage. On the lower joint it can be used on the RH F/C key linkage and on the other linkages on the E/B and F#/C# if they're not pinned to the LH levers.
Where there's sliding between two linkage pieces, either coat it with graphite to make it slippery or stick a piece of self adhesive thin teflon sheet to keep the friction down to a minimum.
You can get tech cork in various thicknesses (usually in 0.5mm increments) which is excellent for the side/trill keys, the throat G# and Ab/Eb key - choose the ideal thickness and you'll not have to sand anything down. Tech cork isn't easy to sand down, but it can be trimmed with fresh razor or scalpel blades.
On open standing keys you're better using something that's not going to create noise as natural cork can be noisy in these applications, so use ultrasuede or thin felt on the thumb ring, on the throat G# stopper (or tech cork of the correct thickness), the RH ring key foot, the crow's foot, the LH F/C lever foot and the E/B key stopper - either on the LH E/B lever if it's not pinned or on the RH E/B linkage piece if the LH levers are pinned. And like tech cork, felt and ultrasuede can't be sanded down so choose the correct thickness. Thick felt and ultrasuede is best trimmed and sliced with fresh razor blades for the best finish.
But if you want to use natural cork, then 0.5mm, 1mm, 1.6mm and 2mm thick sheet cork should be suitable. Only use the requred thickness sheet cork insteas of sticking on thick cork and having to sand loads of it down leaving the key corks looking uneven.
Depending on the make or model, I only use natural cork on the throat A key stopper, using a 9.5mm waterkey cork trimmed at an angle to form a wedge shape with a sharp razor, then glued onto the underside of the key, the sides trimmed and sanded smooth, then the thickness trimmed and sanded to achieve the required venting. Vito, Normandy, Noblet and Leblanc throat A keys use a thin piece of sheet cork or tech cork as well as using thin key corks (or tech cork) throughout. And as already mentioned, use the sharpest or freshest blades to trim sheet cork for the best finish as blunt blades will only tear at it.
If the rolls of cork on Amazon are composite/reconstituted cork, then that's no good as it crumbles and compresses easily. Some makers have used it on their instruments, but it doesn't hold up well. Natural cork is best for tenon corks and not many of the synthetic alternatives that has been tried have come close to it - they either compress too much, aren't as easy to sand, turn sticky when they react with cork grease or don't bond well to the adhesive.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: PipeTobacco
Date: 2021-05-24 02:50
Oh! Thank you!!!
I was thinking of the tenon corks initially.... so 1.6 or 2 will be great!
I had not been thinking about the key corks... but now that you mentioned them.... I will get some different sizes for those too!
Again, thank you!!!!
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Author: clarnibass
Date: 2021-05-24 07:29
For tenon/mouthpiece corks the most common thicknesses to use are 1.2mm and 1.6mm (also sold as 3/64" and 1/16"). These are relatively standard thicknesses available. You could just get 1.6mm and sand any extra, but...
The thinner the cork, the easier it is to roll over the tenon, so I prefer to not use cork thicker than it has to be. Also to not unnecessarily sand a lot and waste material for no reason.
Some suppliers sell corks in 0.2mm or sometimes even 0.1mm increments, but most don't, and possibly most who have in the past stopped doing that.
I've been accused of overkill by doing this... but I measure the socket in several places and directions, measure the tenon (same), then subtract and divide by two to find the gap between them. I decide the cork thickness based on that (keep in mind the cork needs to be significantly thicker than that gap). I know a lot of people automatically use 1.6mm but I put a lot of weight on not wasting material.
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Author: Chris P
Date: 2021-05-24 12:20
I use 1.6mm thick cork as the centre of it will have very little removed when it's sanded barrel shaped - if I were to use 1.2mm thick cork, then there'd be nothing left when it's sanded to the correct shape.
I don't go for American-style tenon corks that are left completely flat and often seen with square edges as that just looks amateur.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: Tony F
Date: 2021-05-24 17:33
I prefer flat tenon corks as I think they provide more support and stability for the joint, but I bevel the edges before fitting them.
Tony F.
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Author: LFabian
Date: 2021-05-24 18:10
What Behn has done with his high end mouthpieces is to put ridges instead of cork. Is this better than using cork?
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Author: PipeTobacco
Date: 2021-05-24 22:53
LFabain:
I noticed the ridges on the Bain’s too and was wondering.
Without any first hand knowledge.... to me it seems like they would work well at least initially..... but it seems that with only a few small edges of contact that they would be more prone to air leaks as they wear and age. But, again.... that is just a guess from my perspective.
PipeTobacco
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Author: Matt74
Date: 2021-05-25 03:29
I think the Behn ones are rubber o rings.
I always bevel the cork edges well before mounting, but most of it gets sanded off.
I've tried making it thicker in the center than the edges, with a hump, but I've never managed it. I think you need a lathe (or A LOT of patience). I want to design a machine sander to sand corks to fit those wavy Buffet tenons.
I've tried measuring for thickness. My painter boss used to comment about crown trim, that "It was too long, so I took off a little, and it was still too long, so took off more, but it was STILL too long, and then I cut off a tiny sliver, and now it's way too short". His measurements were something like "12' 5 3/4" - SHORT", or "16' 2 3/8" - LONG". LOL That's how I feel about cork. I try to economize by using a thinner piece, and then find it's too small, so I have to re-do it.
- Matthew Simington
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Author: clarnibass
Date: 2021-05-25 07:35
I prefer a "tweener" shape, more similar to what Tony F described. The corners are rounded and some of the width is curved, but most or at least a significant amount is left parallel.
The main thing is that it varies depending on the gap between socket and tenon, and ignoring the rare exception of extremely small or large gap, the cork thickness of normal tenons can usually vary by up to 0.3mm or even 0.4mm-0.5mm sometimes. So keeping the same shape, you'll either use thinner/thicker cork sometimes, or you'd use the thicker cork always and sand much more.
It's possible that, depending on preference of feel and shape, different people will use a different cork thickness for the same gap, but they would still need to vary that thickness for different tenons.
To clarify, the extreme exceptions are when 1.2mm is significantly too thick or when 1.6mm is borderline thick enough or even loose, which is rare.
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Author: Chris P
Date: 2021-05-25 15:01
As far as wavy and grooved tenon slots go, the best thing to do there is machine them flat. That will provide maximum contact between the tenon slot and the underside of the cork.
Then there's the old "Yeah but grooved tenon slots have more surface area"
For the adhesive maybe, but with minimal contact with the underside of the cork strip as it's only in contact with the peaks of the grooved section and not in full contact within the grooves. And as contact adhesive is only a thin layer, there will be air gaps between each peak.
Put all those lamearse theories aside and go with what is true and what works - two flat surfaces will have maximum contact than one flat surface and one grooved or wavy surface, unless you can form perfectly meshing grooves or waves on the cork strip which is very doubtful.
In the olden days when shellac was used for everything, the grooved tenon slots did provide good keying for molten shellac to fill in the grooves and bond to the cold wood, then the cork strip sat on top of the filled in grooves, so effectively sitting on a flat surface of shellac. But those days have gone and contact adhesives require both surfaces to be bonded to be as close fitting as possible and you can't get a closer fit than two equally flat surfaces.
Even if the tenon slot is made barrel-shaped which they are on some oboes and recorders, the cork strip will conform to that and bond to it with full contact as the surface of it is usually smooth instead of grooved. With barrel-shaped tenon slots, much thinner cork can be used (1.0 to 1.2mm thick) with minimal sanding to remove any square edges and achieve a barrel-shaped tenon cork with the least amount of grief.
If I'm having to shape tenon corks by hand as my lathe isn't long enough for the joints (cors anglais or bass clarinets), then I rough trim the tenon corks to the required barrel shape with a scalpel, turning the joint with one hand with the tenon rotating and secured by the bench peg and holding the scalpel in the other which will trim it evenly to the shape you want as you're effectively acting like a lathe. Then when that's done, it only needs some light sanding to smooth out all the scalpel marks. You can use that same method to remove grooves, using a scraper or a chisel to scrape the grooves down to leave a nice flat surface for the cork strip to bond onto.
Tenon fit is far more important than anything and no amount of cork will cure sloppy fitting tenons - it will give the impression they're fitting tight, but they can still wobble regardless how thick the tenon cork is. So get those tenon rings fitting well in their respective sockets so there's no wobble, even without the tenon cork fitted. And bevel the leading edge of the sockets to reduce the cork getting torn when fitting the joints together if it's left square or has a very sharp leading edge.
All tenons should have the tenon ring at the shoulder made as wide as you feel is right as leaving that tenon ring too short will mean it may not engage in the socket and the joint will wobble. Anything less than 2mm in width is too short. And if you're of the type that likes to pull out all the joints, you want stability with all the tenons and the only way to achieve stability is to have that tenon ring made wider than most currently are.
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: Matt74
Date: 2021-05-26 12:25
Attachment: 169A81A0-BAD2-4FAF-8018-FEABE32919FA.jpeg (99k)
All:
I need suggestions. A clever person from time immemorial machined off the body side tenon “rings”on my Noblet. They didn’t just take off a thousandth or two. They’re way loose, so that the body wiggles and comes loose. One of them is parallel to the bore, but the one at the barrel is obviously tapered. I don’t have a lathe to replace the “rings” properly, but I need to fix them. I thought of cork, string, or super glue and grenadilla dust.
IDK if I can get cork on the parallel one (probably not enough room). The tapered one would be a pain to cork, but possible. I suspect using string would result in it working it’s way down the taper and into the cork (maybe string with shellac?) Grenadilla dust and super glue could get messy.
What do you think?
- Matthew Simington
Post Edited (2021-05-26 12:34)
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Author: Chris P
Date: 2021-05-26 14:52
Attachment: noblettenon.png (539k)
Adding more cork won't cure a wobbly tenon - it'll only compress. You need to use much harder materials with no give to get the best fit and ideally you need a lathe to be sure any additional material is all trued up and made even.
Superglue and wood dust is the best used to rebuild ill-fitting tenon rings so they fit well in their respective sockets, but you will have to machine them down to the correct diameter for the best fit so they fit like a sax crook tenon in its socket or flute headjoint fits in its socket even without the cork fitted. Tenon corks are only providing an airtight seal plus some outward pressure in the socket to ensure the joints remain held together - they don't make the tenon fit in the socket as that's the job of the tenon rings.
The only other option is to skim the remainders of the tenon rings down and sleeve the tenon with plastic or metal to form the new tenon rings, again making them as close a fit with the socket as is possible - plastic and metal tenon rings won't bind up solid in the sockets whereas wood will when things swell up. And when fitting metal tenon caps, make sure the leading edge is slightly rounded off so it won't gouge out the socket.
And when remaking the tenon rings, make the one by the tenon shoulder longer than it was previously for a much better and secure fit in the socket as they're often made too short and only just engage in the socket. See attachment (fingers crossed it will attach!).
Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.
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Author: Matt74
Date: 2021-05-26 21:45
Thanks, Chris. I really need a lathe.
I think I can manage dust and superglue, but it will take some patience.
- Matthew Simington
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