shank extensions

[bscofield]

I wanna do a shank extension. Kurt H. you had that nice tulip shape with an extension... When you do an extension, with briar (cause that's what I'm working with), do you epoxy the transition piece (if you have one) to the extension AND the stem to the extension. This would in essence be just a longer stem.

But if uninterrupted air flow and what-not is so important than what about the (nearly) inevitable gaps in space with the transition pieces and the tenon on the stem?

[ToddJohnson]

But if uninterrupted air flow and what-not is so important than what about the (nearly) inevitable gaps in space with the transition pieces and the tenon on the stem?

While the theory seems to have been popularized on this board for what I would consider marketing reasons, it is simply not the case that gaps are "inevitable." You can either test fit the two pieces until the gap is nil or use a good micrometer. I have a special profile cutting tool for my lathe that cuts the exact taper on the tenon face that is present on the mortise bottom. Creating a perfect fit would be my recommendation. The other option is, I suppose, cutting the tenon with a gap, gluing everything together, and then drilling a hole through it all. I think with this method the idea is that the epoxy bridges the gap between the end of the tenon and the bottom of the mortise. I don't know what your tooling situation is, but the advantage of this method seems to be that you don't have to be very precise. If you're working with just a drill press, this might be a good route to take. Best of luck.

Todd

[ToddJohnson]

We're obviously engaged in two entirely different processes here. To me, no gap means that the carnuba on the polished tenon leaves a mark on the mortise floor when rotated. That is, for all intents and purposes, no gap. If you have some other definition whereby this actually constitutes a gap, cool. I guess mine have a mathematical gap then. It's one I have no interest in removing though. This is nothing I care to "discuss" with you either. I consider it a complete waste of my time.

I'm sure your pipes are engineered to very high standards and you should be applauded for that. Good job. Let's not get off of Ben's original question though. I'm imagine he's looking for a solution to his quandry, not a philosophical discussion about what precisely constitutes a gap.

Todd

[bscofield]

Todd, I thought you were speaking to the quandry the first time. Then I thought random was too. Then you said you didn't think random was.

OK, I have illustrated my quandry:



The gap I'm speaking of is labeled gap, and ackwardly looks like an "H" I'm confident of having no gap between the walls of my mortise and the tenon. Unless by "floor" Todd means the very end of the mortise where his "rounded" edge would touch. For my current project I've decided to create a tenon in something wth no draught hole. Packed the mortise full of epoxy, clamped it. When it's set I'll drill the airway through the entire piece and then work with a stem on the other end. I'm undecided about whether I want the the stem to be removable or not.

FYI, I understood both of your instructions well. What I'm looking into is a a LONG shank extension like the one Kurt had posted on my post of that cutty pipe (that wasn't so cutty).

[bscofield]

so then I'd end up with a three piece? stem comes out of extension that comes out of shank?

[ToddJohnson]

Well Todd, I see that you're back to your old self... make a snide offhand comment and then when it's responded to, get ugly about it. Enough.

Well, I certainly intended nothing snide or ugly. I'm trying to help Ben figure out a way to engineer the pipe he wants to make. If you would look, I think I actually ended up recommending your method because of Ben's tooling situation. I just don't want to get into it with you about tenon gaps. Please note that I ended my post by saying that I'm sure your pipes are very well engineered and you should be applauded for it. That is the most complimentary thing I know to say about your work. If you took it as sarcasm, it wasn't. You obviously work hard to make sure everything fits together quite well. I think that's great.

Todd

[Nick]

Todd,

As an aside, can you descibe the tool(s) that you use to work your tennons? It sounds interesting.

Thanks,

NJ

[ToddJohnson]

Todd,

As an aside, can you descibe the tool(s) that you use to work your tennons? It sounds interesting.

Thanks,

NJ

Hey Nick,

I have a cutting steel that is ground to an angle just a couple of degrees more accute than the angle of the mortise floor. A flat bottomed mortise only makes it more difficult to get a perfect connection (maybe this is the problem Random was speaking to above). This way, I can cut the tenon to the correct diameter with an extra 1/8" or so in length, and then trim the length off with a bit that will give it the perfect angle. This way, the tip of the tenon fits into the concavity at the floor of the mortise like a hand into a glove. I polish and wax the tenon while it's chucked in the lathe and then test fit it to the stummell. When I insert the tenon into the mortise and give it one rotation, I want to be able to see a small shiny ring in the concavity of the mortise created by the wax on the champfered edge of the tenon. If I don't, I take the stummell to my other metal lathe and remove another paper thin sliver from the face of the shank. Then I give it another go. When I see the shiny ring, and am getting no light at the stem shank joint, I'm done. It doesn't really require much fancy tooling, just a process that privelages fitting over measuring--the former being *always* more reliable.

Todd

[ToddJohnson]

Your description is relatively clear. It sounds as if the initial cut of the tapered tenon length needs to be extremely precise. But it could be that the slight difference in angle lessens the need for precision.

The first cut needs to be fairly precise I guess. I think different definitions of "precise" are operative for us, but yes, I try to make the first cut exact. I do this by taking the shank end of the drill bit, inserting it into the mortise and sliding a hard rubber grommet flat against the shank. I then remove the bit and use it to transfer the length from the shank of the bit to the tenon by scribing a line on the tenon just beyond the length I need. I then come in with the cutting tool and cut the tenon to length--that is I just remove the scribed line. Nine times out of ten it bottoms out in the mortise on the first try.

Is there some conformance-forcing going on between the end of the tenon and the bottom of the mortise? By that I mean, is the relative hardness of one material shaping the softer material?

No, otherwise there would be a mark on the face of the tenon. I suppose it's possible if you're forcing things, but that would be self defeating. One thing you've got to remember is that I do a lot of Danish style push stems that are not flush fitting. With these, you don't have the added difficulty of making certain you're getting a perfect fit on the mortise floor and at the shank. I use the same exact process with flush fitting stems, but this is when I sometimes have to skin a thousandth off the face of the shank.

I just want to make the best mortise/tenon fit that I can, sometimes mine come out perfect but usually just shy of perfect. If you feel that discussing it with me is a waste of your time, so be it.

Making pipes isn't about getting things "perfect." Yes, they need to be engineered excellently with everything fitting precisely, but to be honest, I'm not worried about getting things down from 1/4 of a thousandth to 1/16 of a thousandth. That would be a piece of paper sliced about 10 times. At that point I consider it silliness. It's fine if you (or others) don't, but I don't have the luxury of worrying about tens of thousandths of a centimeter on my tenon lengths. I have pipes to make.

Todd

[KurtHuhn]

I wanna do a shank extension. Kurt H. you had that nice tulip shape with an extension... When you do an extension, with briar (cause that's what I'm working with), do you epoxy the transition piece (if you have one) to the extension AND the stem to the extension. This would in essence be just a longer stem.

But if uninterrupted air flow and what-not is so important than what about the (nearly) inevitable gaps in space with the transition pieces and the tenon on the stem?

I use a much different method for shank extensions than, I assume, most folks here. In fact, none of them are even shank extensions, they're stem rrings. I don't really like doing extensions on shanks, it requires tooling I don't have, and I thin the stem rings look much nicer anyway.

But anyhow, that particular pipe (the cutty) was made with a 1/4" delrin tenon, a vulcanite rod for the bit[s] and a couple pieces of briar trimmed from the block. First, I drilled the end of the rod with a 5/32 hole for the airway (stopping short of the button). Then I drilled a 5/32 hole in the delrin. After that I cut some grooves in the delrin (so that the epoxy would hold) and inserted it into the stem.

At this point, I should mention that the length of delrin is about 4-5".

Then I take the length of briar, square it off on the disc sander, and chuck it in the lathe to drill a 1/4" hole the entire length. I also cut a vulcanite ring to serve as a "cap" on the stem.

When I've got all the parts, its simply a matter of epoxying everything together, triming the end of the tenon, and shaping it down.

Why not use two tenons? Heck, if you can get the two tenons into alignment with each other, I suppose you could do it that way, but then you have to have three holes drilled in the briar tube, two tenons with airways drilled, and you have to figure out, by the grace of some diety somewhere, to get the whole thing to line up right. It's possible if you have the right equipment, but not with the tools *I* have.