I’m getting more in depth into artisan pipes now, so I’m paying more attention to the details and I was wondering what is the average diameter of a draft hole? Does it follow logic that if you make it slightly bigger the draw is looser?
Good question, I believe its 5/32 but I am nowhere near an expert. Id like to know what a good diameter would be for a slightly tighter draw.. would it be 9/64? Id like to know as I am considering having some custom pipes made. A pipemaker I am not! Following this one for details... ::
Rick Newcombe, author of In Search of Pipe Dreams, is a huge proponent of an open draft hole. Wider than what most recommend. I just had a a couple commissioned pieces drilled to his specs and I can attest that it makes a huge difference.
5/32" is the "standard American" airway at this point. Newcombe's spec is closer to 11/64 and that works fine, especially for bigger pipes. Lots of older British pipes are drill at 9/64 or even 1/8". I find this pretty small for functionality.
Of course, the airway size is... almost irrelevant... compared to how the stem controls the flow.
One artisan carver mentioned at the West Coast Pipe Show in a discussion that the draft hole should be uniform in shank and tennon. Someone said how they open up the draft hole in the shank and that’s when the carver said in their opinion you should take the same bit to the tennon and match it for a better draw.
There are many ways to skin this cat. The standard sort of "American Artisan" thought on airway construction is "constant-volume". No bumps, no plenum space, just a perfectly smooth ride through the pipe, so no condensation points. Newcombe's physics setup is a little more in line with Bernoulli's laws (pressure of a moving gas is lower, the faster the gas moves). So you have a smaller airway out where the smoke is more likely to condense (the cold end of the stem), opening up in a larger (more turbulent) slot for final distribution to the tongue.
Both are fine.
It's science, but ... not rocket science.