154. Tenon and Mortise System Design, Part 1: Standard Molded Stems

Not long ago, a friend sent me an interesting technical question that bears consideration for everyone who likes to geek about System pipes:

I’ve seen a lot of old De Luxe Systems from Peterson, spanning most of the 20th century. I’ve seen a lot fewer Standard Systems. I understand from the book that the Standard Systems never had the bone (later aluminum) chimney. Were those System Standard stems just tapered all the way down? The current version has that little stepped tenon, and for the life of me, I can’t understand what that really achieves. If it’s just about increasing the length of the stem, wouldn’t a natural taper all the way down look better? I’m just wondering if you know when Standard Systems developed that tenon thing.

There’s a lot to unpack here. One good place to begin is always at the beginning, so take a look at the Patent Standard and Premier System tenons illustration at the top, from the 1896 catalog.

While there were the four mouthpiece styles available on what we now call the Standard and Premier grades, notice that the ABC and AC are light: these are screw-in bone extensions (or “chimneys” as the old Kapps hands called them). The AB and A, on the other hand, which are dark, are extensions molded into the stem itself. The chart is meant to represent shouldered and tapered, Standard and Premier (or what we now call Standard and Premier).

I’\ll look at the screw-in Premier and De Luxe chimneys at some point in the near future. For now, let’s look at the molded extensions: why are they there? what function do they serve?



The biggest problem with any army mount is, of course, turbulence, as any good pipe artisan will tell you. I’m sure Charles Peterson knew this, which is why he designed these step-down extensions to have a conical, tapered shape that extends to, or to just below, the air hole in the stummel, as you can see in the 309 demonstrator pictured above.

Look at the photo from the 1906 catalog above. The taper isn’t as obvious as in the 1896 illustration, but that’s probably because of the length of it. That is, the Morse taper on both the A and AB, seen from a side perspective like this, is quite graduate. Much more gradual, inf act, than recent generations of mouthpieces. This would allow the tenon to fit more deeply (and hence more securely) into the mortise.

A tight fit, preventing any air to escape from the juncture between tenon and mortise, is necessary for the best performance of any army mount, and even more so of the System, which has to contend with the demands of the reservoir.

This detail from the 1937 catalog is one of the best insofar as showing the taper of the original Patent-style molded vulcanite Standard System tenon. It also shows the higher shoulders and graceful curves of the A and AB respectively as compared to those made in the later 20th and early 21st century.

And now here are some photographs documenting changes in Standard tenon design, beginning with a baseline or Patent-style mouthpiece. These photos are of an IFS (1922-37) “A” mouthpiece, and show the classic tapered step-down created by Charles Peterson:

It may have occurred to you that to create this type of taper, the mortise must be wider than the mortise on current System pipes, or a 5mm opening at the tenon end probably will be difficult to achieve. And when you look at older Systems, that’s exactly what you see: wider mortises. This shape 4, a gold-mount hallmarked to 1911, is a perfect example:

A wider mortise, in turn, makes it easier for the machinist to create the kind of 3-part stepped reservoir seen in the demonstrator reproduced, or so Brad Pohlmann, pipe artisan trained in die-and-cut machinery, informs me.

I have to ask, parenthetically, whether these older, wider mortises—which you can see on the 308 System until its demise in the late 1950s—weren’t gradually modified because their extreme width (resulting in a thin wall at the top of the mortise) sometimes caused cracks in the briar? If you’ve restored many Systems, you’ve doubtless seen cracks and sometimes even breaks in the briar below the ferrule.

Take a look now at a hand-cut stem from the Irish Free State era (it’s stamped HAND over MADE at the base of the tenon-end, just above the step down):

I include these photos to help explain the function of the tenon extension itself. First, notice the long taper. Second, it should dawn on everyone that, as my friend noted in his question at the top of the page, the cone or “chimney” is there to get the tenon away from the walls of the mortise and deeper into the reservoir, allowing air to pull down from the top of the chamber airhole to the reservoir and hence into tenon airhole.

The first change in the molded vulcanite System mouthpieces apparently occurred later on in the Éire era, as documented by this unsmoked mouthpiece which can be accurately dated to 1937–45:

If, as I believe, the tapered tenon tension creates less air turbulence and a better smoking experience than a “stepped” one—as seen above—then this change should, at least from an engineering standpoint, produce a less satisfactory smoke. It is certainly less satisfying aesthetically, since it doesn’t follow the lines of the taper in the stem. But does it, in fact, produce a less satisfactory smoking experience? Or does it simply make it possible to create a narrower mortise with correspondingly thicker wall where tenon and mortise meet?

I don’t feel like I can give you any authoritative answer, as I really can’t tell much difference, and there’s so many other variables involved: the bowl shape, the tobacco, my body chemistry, the tobacco and so forth.

I want to show one more step-down, this one from a factory P-Lip mouthpiece executed in horn, probably from the Emergency period (1938-45). Look at the severe step-down, copied from the engineering of the molded vulcanite of the same period.

While it preserves the 5mm opening and makes the narrower mortise possible, the disregard for air flow created by such a large step between extension and tenon end makes this stem, in my smoking experience, inferior to the molded mouthpieces from the period.

Molded vulcanite P-Lip mouthpieces haven’t changed in any substantial way since 1937. And that goes for the recent acrylic P-Lip stems as well, insofar as the tenon step-down is concerned:

Why Charles Peterson’s original design wasn’t continued may always be a mystery: was it to solve a potential cracking problem at the mortise? Was it just an oversight? Or perhaps a slight cost savings, or even the work of an out-sourcer who didn’t care and got away with it?


In Part 2 : Premier & De Luxe Extensions


The gold-mount Patent may still be available from
Secondhandsmokes on eBay
Photograph of 1911 gold-mount Patent courtesy Gary Malmberg

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Jorgen Jensen
Jorgen Jensen
8 months ago

Good morning, just out of bed , coffee and smoking my NAP pipe. I am not sure that I understand so much of it but I like the reading. And yes, I have some systems with cracks in the mortise………….but, no problems as I said to Carsten when he showed me one, they often look like that.

Al Jones
Al Jones
8 months ago

Fascinating! I saw that Gary had listed the 1911 gold-mount Patent pipe, alas too rich for my pocketbook, but it’s great to see it as an example in this blog entry.

8 months ago
Reply to  Mark Irwin

I’m wondering if a lot of the tapered ones would burn or melt if an ember came into the reservoir? I’ve seen some melted spots toward the end of the tenon extensions on some standard systems. I would bet that with that tapered area closer to the draft hole this would only be exaggerated?

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