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I've recently noticed that a good few of my pipes have a button that is concave on the end. What I mean is that the end where the slit is cut is often curved inwards. After thinking about it, it seems all wrong. If the idea of the last 1/2 inch of the stem is to spread the smoke out across the tongue, wouldn't a concave button end work against this? Essentially "holding onto" the outside edges of the smoke stream longer than the center and thereby making the shape of the smoke stream less "fan shaped?"

It seems to me that the best way to encourage this fan shaped smoke stream would be exactly the opposite: a convex button.

What are your thoughts?

I have no idea about spreading out the smoke, but I like the look and feel of this type of bit. A few of my Dunhills have bits like this, and as I recall one of my Pete's has it also.

I like the "mouth feel", so I've sanded the bits on my last few pipes like that also, using sandpaper wrapped around a pill bottle.

I think it is purely aesthetic. To do it I use a 1 1/2 in dowel rod with a piece of 220 sandpaper taped to it. I put that between the centers of my lathe and press the end of the stem against it.

You make an interesting point but I do not think it has that much of an effect.

Probably not a huge effect, but I bet it does have some effect.

As a quick point of clarification, the description I gave as to how to cut the slit results in exactly what random is talking about: a WIDE OPEN draw. Just wanted to clarify that the term "slit" does not necessarily imply a tight draw.

As to concave buttons, that is an issue of comfort in the mouth aesthetics. Dunhill claims (if I am not mistaken) that they do it to their bits so the stem is out of the tongues way when held in the teeth. Personally, I've never really had a stem that was uncomfortable on my tongue while held in my teeth. I do my stems that way because I like how it looks. As for the smoke spreading out, I don't think that is much of a concern. The curve is usually relatively minor, and a properly cut slit should do its job even with such a curve.

Tyler

Pooka,

I have had a bit of physics and fluid mechanics myself, and you are correct that a smaller orifice will require more pressure, assuming a constant volume and temperature. (Velocity is also a factor, and should not be neglected in the conversation.) Ultimately though, cross-sectional area is the most important factor, and a slit can provide the same flow as a round opening. Of course the trick is to make an appropriately sized slit.

You point is exactly right Pooka, and that is why I argue that many good pipes are ruined in the last 1" of their construction. A well drilled stummel can easily have its smoking properties hijacked by a poorly done slit. The only answer is not larger diameter hole at the end of the stem though. It is one answer, but not the only one. A well done slit has the same effect.

Tyler

My engineering skills are much more suspect, I assure you! Mine were acquire from flakey professors at Texas Tech University, where I acquired a degree in Chemical Engineering.

Tyler

have to differ with you on this. With a Peterson P Lip IMO you get more "taste" as the smoke stream comes up against a "closed end" then is forced thru the opening up to the roof of the mouth. There it spreads out all "around" your mouth.

As they say "every man to his own taste as the man said when he kissed a cow"

Pooka wrote: Also, I get MUCH better range of taste from a wide hole than, say a Peterson type "special" thingy or a regular old stem. It really "thins the stuff, I think."

I'll steal Random's old quote, though, "I know nothing......."

Cool discussion guys! And Tyler, your points really drove the idea of how important the last inch is home. Too cool.

BTW, I've had no engineering expirience, but I did play one on TV.

Well, I am not sure I have a clear mental picture of a concave stem. I know my preference is for a 'trumpet' or flared stem (think mouth of a blunderbuss), and I have tuned quite a few of my pipes to have this kind of bit. It may be psycholigical, it may be reality, but I much prefer this type of opening to slot bits. The only thing I don't like about them is the incredible amount of sanding and polishing I feel compelled to do once the shaping is done.

Great discussion.

Best,

Nick

Welcome, got 1 member of the family there with you and another on the way. Luck from a old Vet:

ngp4 wrote:Well, I am not sure I have a clear mental picture of a concave stem. I know my preference is for a 'trumpet' or flared stem (think mouth of a blunderbuss), and I have tuned quite a few of my pipes to have this kind of bit. It may be psycholigical, it may be reality, but I much prefer this type of opening to slot bits. The only thing I don't like about them is the incredible amount of sanding and polishing I feel compelled to do once the shaping is done.

Great discussion.

Best,

Nick