Reverse Calabash. Anyone made one? Have any tips?

[DanH]

Been getting more serious about pipemaking recently after a year of super-slow production (only 4 pipes this year).

I'm curious to try a reverse calabash for one of my next pipes, but I'm a little unsure about what to do about the mortise and tennon.

Since the bit used to drill the smoke reservoir is probably a spoon bit, that means that the sides are going to be sloped. I don't want to try to cut a sloped tennon, and I'm pretty sure that no one in their right mind would.

So, what do you do to get a round, flat area to plug the tennon into?

You could use a drill bit wider than the mouth of the reservoir and drill a flat area around the top for the tennon to sit in. But that would leave a corner in the reservoir. I suppose as long as the tennon meets the corner, that would be ok.



Am I thinking about this all wrong? Is there a better, more recommended way to do this?

[Massis]

Drill the hole with a spoon/chamber bit, but deep enough, and add a flat part by using a forstner bit just slightly oversize? Seeing as you want the inside of the reservoir to be smooth with the hollow part of your tenon, would mean to me that the outside of the tenon is wider.

Something like this:
black = shank, grey = tenon


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[wisemanpipes]

in my limited experience ive cut them 2 ways. the way you showed in the drawing. then i also cut straight walls with forsner bit that was smaller than the mortise. i would say both work fine but its easier to clean with a sloped spoon bit like cut.