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Author: Subject: ISO standard taper joints

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[*] posted on 4-12-2011 at 09:56
ISO standard taper joints

I understand what 24/29 and stuff like that means but I often see different codes such as B24. Firstly what does B mean? I notice that sites selling glassware often put B24 along with 24/29 joints in the items name. For example "Quickfit RB Flask 24/29 B24" or "RB Flask 14/23 B14". I see that the B number is the diameter of the joint but what does B represent?

[Edited on 4-12-2011 by JibbyDee]
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National Hazard

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[*] posted on 4-12-2011 at 19:59

Not giving you a answer here but don't think it means anything. Only place I've ever seen the "B" branding is on Quickfit glassware, though some other companies may have joined in on that branding.
I've always thought the "B" had something to do with the fact that Bibby produced most of the Quickfit glassware I've seen, the "B" from Bibby, though I have nothing to back it up.

Had/may still have this table on all the different taper/joint sizes which is standarized and no mention of the "Bxx" sizes were listed. Only real difference between the different sizings is that the Americans prefer longer tapers, as 29(mm)/42(mm) to european 29/32( also both in mm). Also it appears they dont use to much of the 19mm tapers, mostly 14 and 24 (base this on ebay listings and catalogs), which is a shame since I really adore the 19mm taper sized glassware, just big enough and small enough for mostly everything. For micro stuff I have a Kontes taperless set, which is held together by butyl rubber and is about max 2mL on the RB flasks with a internal tube diameter of about 4.5-5mm.

Enough of my ramblings, as an "answer" I think the "B" branding is just something to relieve the customers from thinking too much, e.g. as all Quickfit B14 fits all B14 from the same company, and as such I wouldn't put too much thought into it..

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National Hazard

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[*] posted on 4-12-2011 at 20:13

I think it was put there by the Illuminati in their efforts to take over the world... That is probably not it... but i was looking around the internet and it seemed that the marking was usually on European websites, so it could just be how the Europeans label it.

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International Hazard

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[*] posted on 4-12-2011 at 21:59

The B actually means something, and refers to the length of the joint. A B29 (29/32) is longer than a C29 (29/24). I presume A29, A19 and so on also exist, having longer joints than the standard B. Where this labeling originated or what it actually means (I.e. could someone actually tell me the dimensions of a C19 or A32 joint?) I have no idea about. But yes, it seems to be a European phenomenon, specifically British. The Germans (homeland of Schott) and Czechs (homeland of Simax) don't make use of the A/B/C-labeling.

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Bon Vivant

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[*] posted on 14-12-2011 at 10:24

They're EU (UK) joints.

I'm in England, and the process glassware (the bits connected together for a reflux, distillation, addition etc) is B10, B14, B19, B24, B29 etc.

I also own a fair quantity of US glass and the tapers go together fine. There seem to be bigger problems between manufacturers than there are between US / EU glass as a standard (e.g. regardless of where you are, badly ground sockets are badly ground whether they were originally intended for US or EU glass, they will fit each just as poorly).

The only difference between them is the length, and it's not a lot. It's also not true that US glass is universally longer than EU glass.

A UK B24 is 24 by 29.

A US 24 is 24 by 40.


A UK B14 is 14 by 23.

Whereas a US 14 is 14 by 20.

It really doesn't matter most of the time. I mix the two together frequently and have not encountered a single problem on the lengths. They are both the same actual gradient (taper).

There are other lettered sizes, e.g. C, which are used for the tops on volumetric flasks and such. The letters are a way of grouping common sizes together. Whether or not QuickFit were the first to start using it I don't know, but it is not solely QuickFit who do.

The precise reasoning behind using the odd sizes for things like volumetric flasks has so far eluded me, but I would expect it to be related to the strict standardization of volumetric glass.

[Edited on 15-12-2011 by peach]

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