Differences in Interior Stem Design

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Mar 7, 2013
Everything Sas said.

Smoother is better, the fewer sharp zig-zags the better (unless designed for deliberate condensation & entrapment, Pete System style), and smoke stream compression via venturi actually works, but is doesn't cause much improvement with standard-size pipes.

I'm sure of the latter because I tested it.

Re-cut the tenon-end of an antique mondo-venturi stem (the airway opening at the base is about 3/8") to fit a modern pipe, and lit 'er up. Yes indeed, it concentrates flavor quite noticeably.

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The same "cone-ification" thing done to a normal size pipe's airway with a tapered reamer isn't really noticeable, though.

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Can't Leave
Mar 16, 2024
Shuswap, British Columbia
This pipe is a Polo, which I understand is or was Vauen’s seconds line. I bought it as new old stock and never smoked.

As you can see, this channel is even more extreme than the V-shaped one. It is the only channel like it I’ve ever seen. The draw on this is exceptionally open and effortless for a 9mm filter pipe. I never realized how large the channel was until I sent a pipe cleaner through after the first smoke.

I have wondered why I haven’t seen more pipe stems with huge channels like this or how this was even made. Maybe they stopped doing this because it was a lot of work and so many people just bit right through the mouthpiece. I’ve never had that problem with any pipe but it looks like it would be chomped down pretty easily by people who have that issue.
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Jun 20, 2019
The Big Rock Candy Mountains
@sasquatch and @georged, with respect to the idea that smoother is better, how does Dunhill assure that its dri-tubes always go the same depth into the stem? Does it drill a stop-step inside the stem? Or am I mistaken in my assumption that the stem is drilled to allow the tube to go in a standard depth?


The Bard Of Barlings
Jun 15, 2013
Southern Oregon
This discussion piqued my curiosity about how Barling handled their early slots and from the examples I just looked at from 1907, 1908, 1912, 1920, and so on, they all have a deep funnel, between 3/8 and 1/2 inch. They continued this when they developed the modern thin flat bite zone, the design for which they registered in 1930.

My preference is for funnels to spread out the smoke.


Jun 4, 2021
Tasmania, Australia
Very informative thread. Being a Castello fanboy I will have a look into the cut of their bits but it seems square rather than fantail like and no taper just 4mm (minimum) I'm guessing all the way through.


Jul 16, 2012
So, lot's of questions.

Why don't we do "bigger is better" and make every pipe stem a McDonald's milkshake straw in diameter... answer is, you can make a lot of smoke and that's not the same thing as "smoking a pipe". Overheated tobacco tastes bad, burnt briar isn't good, if you have a huge airway, you have less control of the burn. Could it be done? I guess, but it doesn't FIX anything that isn't broken after say, 5/32" or so, 4mm roughly. Go to 5mm. Okay. Go to six, you'll see the pipe smokes differently. Go to 8, 10, 20 mm, and it's just... not the same game. Smoke a cigar for that.

The early dunhill tubes had a ridge on them, a stopping flange for fit. This is in fact what the Dunhill "Group Number" started as, a tube number, literally the size of the tube for the pipe in your hand. This is no longer the case and new ones are fitted inside the stem with a double drilling (I believe - anyone show a new one?).

The Castello: yes, castello's mostly smoke great. But. That proto-slot, because it's so square-cut, is a low-pressure zone, prone to condensing. Look at one after a few smokes.

Look at all the crud building up!

So I mean, now we're at the sort of root level secret-society stuff in terms of pipe building.

How do you analyze where your pipe is working poorly? Just open it up, look for where the crud is building up, and that's.... that's it. That's all there is to it. Make the pipe right and it doesn't gunk up like this. Castello gets away with it at the very end of the mouthpiece, but if this is occurring in the middle of the smoke stream, probably the pipe is not smoking well.