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I did complete Bb clarinet overhauls in the past. Now I have to do a few more after about 8 years break in that area.

I never understood how the proper joint cork thickness should be selected. The rule of thumb advice found everywhere is to use 1.2 mm thickness. I took it for granted right from the start and never put any more thought into it.

However - I always wondered why I had to sand down quite a lot of that 1.2 mm cork to fit the joints even very tightly.
I just measured the OD/ID of the three joints on a HR 1960's Pedler clarinet and the measurements are as follows:

- Bell joint: OD = 25.5 mm ; ID = 26.8 mm ; difference = 1.3 mm
- Middle joint: OD = 21.0 mm ; ID = 22.4 mm ; difference = 1.4 mm
- Barrel joint: OD = 22.6 mm ; ID = 24.4 mm ; difference = 1.8 mm

Out of the above I see it makes sense to use the 'standard' 1.2 mm cork thickness only for the barrel joint.
For the other 2 it looks like maybe 1.0 mm cork will do well?

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Oh, my! - Gordon - you are everywhere and it's GREAT!!!
While typing in my message I recalled that I previously saw some relevant advice on the clarinet forum and I just found it. Yes, it's Gordon with his typically helpful advice at the bottom of that thread:

http://test.woodwind.org/clarinet/BBoard/read.html?f=1&i=59455&t=59414

I would probably have to remove my entire message now but I'll leave it here for a cross-reference. Maybe someone will find it helpful.
Gordon - thank you as usually!
 

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So, according to the Gordons 'rough guide' I see that I can either get away with the standard 1.2 mm cork which I always did or use 1.0 and 1.3 corks but 1.3 may not be easily found. The 1.2 mm cork will definitely require some sanding for 2 tight fitting joints and theoretically should be a little loose for the barrel joint but something tells me that the 1.2 mm cork will fit fine even for the latter because the barrel is a short part of the clarinet and it should not experience any side wiggling which sometimes happens at the middle joint when too much cork is sanded off in the process of fitting the joints.
 

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1.2 mm or 1/16" is typically used, but in some situations where a barrel especially is a tighter than usual fit, I've gone with 3/64". There's NO automatic fit, no matter what cork thickness is used. Sanding (with a bench peg) is always needed to assure proper fit. Also notice the general thickness of the cork that's removed from the tenon(s). Why start with 1/16" when it's going to be sanded down to half its thickness? Common sense rules.
 

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3/64" (1.2 mm) is my "go to for center and bell joints. For the tenon where the barrel fits, it depends a lot on the barrel being used since they vary in opening diameter. That said, I have good success using techniques I was taught by my mentor with whom I apprenticed for 7 years.

- sand the cork to a barrel shape that is thicker in the center than on the sides.
- after sanding the cork to a very snug fit, melt some paraffin wax on the surface and iron it in using a hot pad slick
- use cork grease very sparingly and only when needed letting the paraffin do the lubricating
 

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Check the thickness of the old cork, consider that it's significantly compressed.

I heard that some people automatically use a certain thickness, but I found that it varies too much (even on the same model) to ever use a thickness without checking.

I usually measure the socket and the tenon, subtract and divide by two, to find the gap between them. Then I decide what cork thickness to use, also based on being familiar with how "stretchy" the cork is (it can vary).

Another thing to consider is that different joints don't require the same firmness. The bell only needs to not fall off and is a longer joint than the others. The middle is the most critical and is often the shortest, so you might want a tighter fit for it.

In the case you mentioned, the middle joint gap is 0.7mm, so 1.2mm cork might definitely be ok, assuming the edges are slightly rounded anyway. You might need to sand it a little bit, or not at all, depending on the cork.

Unlike saxclese, I prefer a cork with rounded/tapered ends as opposed to barrel shape (at least most of the time) and also prefer only cork grease and don't like paraffin wax (or some other waxes I've seen used for this).
 

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I also melt paraffin wax on the corks (both for clarinet tenons and saxophone necks). I find it gives long lasting "lubrication" and somewhat lowers the need to constantly slobber with cork grease.
It's always very interesting and informative for me to read different approaches/techniques by others who do repair.
 

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Discussion Starter #7
All good replies! Thank you.

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Another thing to consider is that different joints don't require the same firmness. The bell only needs to not fall off and is a longer joint than the others. The middle is the most critical and is often the shortest, so you might want a tighter fit for it.

In the case you mentioned, the middle joint gap is 0.7mm, so 1.2mm cork might definitely be ok, assuming the edges are slightly rounded anyway. You might need to sand it a little bit, or not at all, depending on the cork.
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Good point clarni! A very good point indeed.
 

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I don't like wax because it changes more in temperatures. I just saw an extreme case when someone was using a harder wax which actually came with the clarinet (said something like "cork wax") specifically to grease the tenon corks. It was very difficult to assemble, but once assembling and rotating a couple of times, it was borderline too easy. A bit more and it was definitely like a loose tenon cork. The wax hardening in colder temp made it hard to assemble and the slight rubbing was "melting" it.

Paraffin is the best wax for that and is not anywhere near as bad as that, but it still happens to a small degree. With good grease and tenon fit, only very little cork grease is necessary. Amount of grease or how tight the fit is can also vary a bit depending on the player.
 

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Check the thickness of the old cork, consider that it's significantly compressed.

In the case you mentioned, the middle joint gap is 0.7mm, so 1.2mm cork might definitely be ok, assuming the edges are slightly rounded anyway. You might need to sand it a little bit, or not at all, depending on the cork.

Unlike saxclese, I prefer a cork with rounded/tapered ends as opposed to barrel shape (at least most of the time) and also prefer only cork grease and don't like paraffin wax (or some other waxes I've seen used for this).
I don't think we are that far apart on the shape. I install the cork and then taper both ends. I call it a "barrel shape" because it is thicker in the center than at the ends and that's what my teacher called it. Of course the farther the taper extends the "rounder" the shape becomes. Please don't dismiss the use of paraffin wax because you had a bad experience with a wax-like product. I have been using it on sax neck corks for over 20 years both on my own saxes and customer neck re-corks. It really works. It extends the life of the cork and eliminates the need to constantly apply cork grease.
 

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This video shows pretty much exactly how I apply paraffin wax to both saxophone neck corks as well as clarinet/oboe tenon corks. Start at 27:44:


-For what it's worth...
 

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I don't think we are that far apart on the shape. I install the cork and then taper both ends. I call it a "barrel shape" because it is thicker in the center than at the ends and that's what my teacher called it. Of course the farther the taper extends the "rounder" the shape becomes.
I've mostly seen it described as barrel shape when it is rounded (usually on a lathe) to really resemble the shape of a barrel so that's what I thought you meant.

Please don't dismiss the use of paraffin wax because you had a bad experience with a wax-like product. I have been using it on sax neck corks for over 20 years both on my own saxes and customer neck re-corks. It really works. It extends the life of the cork and eliminates the need to constantly apply cork grease.
Just to clarify, I've tried paraffin. I just gave the example of a different wax to show a more extreme case where there was a serious problem. It happens to a much smaller degree with paraffin, but enough that I prefer not to use it. I haven't found a need to constantly apply cork grease when not using paraffin wax, so no need to eliminate :)
 

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3/64" is the most common size used, but 1/16" is common as well, and every now and then even thicker cork is required. I only cut the slightest bevel on the leading the edge. The reason I do this is to avoid damage of the cork during assembly, also the more surface area making contact, the less prone to wobble the joint becomes. I melt on the wax, then work the parts together and clean off the excess from the tenon and receiver. To do this requires a tighter dry fit,as the wax will help to compress the cork more initially than when only grease is used. The wax seals the cork, which helps keep grease from penetrating the cork and dissolving the contact cement, and it reduces the amount of grease needed to assemble the instrument. The compression increases the density of the cork, that along with a more cylindrical profile make for a much more stable joint. Since the compression is done up front, there is less chance of it compressing more after a short period of use and becoming loose prematurely, since there is less grease used there is less of a mess made in the case. I have done it both ways, and still do at a customers request, but prefer sealing the cork with canning wax, and only making a very slight bevel to the leading edge. I have done so for about the last 25 years now, and my most discriminating customers love it, so I will probably continue.
 
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