I've been trying to find a conversion table for Ts joints. I want to get some 29/42 glass stoppers but the site only gives numbers, e.g., "No. 27". I
would have thought that this information would be easy to find but I've been searching quite a bit and haven't yet found it.
Thanks for any help.Neil - 25-9-2011 at 03:55
Is the joint you are trying to stopper standard taper?
If so you need to find a standard taper 29/42 stopper which is a size that occasionally comes up on Ebay.
the numbered sizes use a different taper and will not fit to a standard taper joint.
The numbered joints are used for things like volumetric flasks and sep funnels. The other ST joints are for glassware.
24/40 is the most common, but 29/42 is good for larger flasks. Get a reducing adapter, very useful.ScienceHideout - 26-9-2011 at 12:28
I reccoment ST 19/22. Love it!Dr.Bob - 26-9-2011 at 12:32
I have a few 29/42 glass stoppers, how many are you looking for? I could sell you a few for about $2 each plus shipping.
And I agree with Neil that a glass stopper with a single number will not fit correctly. There are probably a few people selling them on Ebay as
well, but it is a less common size that 24/40, 19/22 or 14/20.
Bob
Endimion17 - 27-9-2011 at 05:23
As usual, there is an European ISO standard and an US standard (what idiot came up with the idea to make 2 standards?), but they can usually be used
together and differ in the length of the taper only.
The other number can be simply ignored for most applications, except when you're trying to do something really important and you've got a box full of
both standards. But that's happens almost never.
Because of that, and the fact my glassware is all European ISO, I use the typical "NBxx" notation, where NB means the same thing as NS in German
language - nominal bore or normal bore, or normal schliff kern if I'm correct.
NB19 is a very good one and AFAIK the most common of all at college laboratories. Other than that, NB14, NB24 and NB29 are used. Other tapers are
rare. 14, 19 and 24 are the best ones for home experiments, though NB14 is usually reserved for thermometers and alike.
I've got some NB29 flasks so a reducing adapter would be handy. Luckily, I know a good flameworker that does his job well so that won't be a problem.
Except for the money. Money is always a problem.
Does anyone of you have any experience with those barb protrusions used to mount steel springs? They seem to be a much cheaper option instead of Keck
clips, but I'm not sure if clips can be mounted on a joint supplied with barbs.
[Edited on 27-9-2011 by Endimion17]Mildronate - 27-9-2011 at 22:06
I use 14 and 29, 19 and 45 rare. My favorite is 29 Dr.Bob - 28-9-2011 at 09:50
Does anyone of you have any experience with those barb protrusions used to mount steel springs? They seem to be a much cheaper option instead of Keck
clips, but I'm not sure if clips can be mounted on a joint supplied with barbs.
I have used the glassware with barbs and haven't found that to be the best solution for several reasons:
1) the barbs break off easily and leave sharp edges that cut you
2) the springs are small and easily lost, my fingers are clumsy
3) you cannot rotate joints easily with barbs
4) barbed glassware cost more
5) keck clamps give before apparatus blows up in the case of overpressurization.
6) Keck clamps and steel clips are cheap in the long run.
Bobjock88 - 17-10-2013 at 12:52
What are the advantages and disadvantages of different joint sizes in combination with different vessel sizes. I find the joint sizes baffling.
Last link is an extreme example of a small vessel with a large joint.
What size is used for what. Is there a discussion/writeup somewhere on the net about this?Dr.Bob - 18-10-2013 at 12:09
Large joint flask are normally used where one wants to stir with a mechanical paddle stirrer, and the better ones are too big to fit through a 24/40
jointed neck on a flask. There are also other reasons to use them for larger flasks, just due to the larger area, which allows faster distillations,
etc, as vapor flow is proportional to diameter of the neck.
On a separate note: People still need to understand that a ST22 or ST 27 glass stopper size and taper angle is NOT the same as the 14/20, 19/22,
24/40, or 29/42 type joints on flasks and other items. So a TS#14 stopper will NOT fit into a 14/20 joint, and a TS#19 stopper will not work in a
19/22 joint, etc. So please be careful when describing the stopper or joint size to use both numbers if they are there.
But with two number type sized joints, all joints of the same first number have the same taper, and will fit into each other, thus a 19/22 male end
will fit into a 19/38 female joint just fine, just not reach all the way in.
