Stem tenon... Tapered or straight?????

[Butch_Y]

Just wondering how you pros do it. To date, I have tried making both straight insert (which I don't care for) and a tapered insert. I really like the taper fit as it acts no different than the Morse Taper being used on tooling. You can insert the stem almost all the way to the end and then push it tight and it grips firmly all the way around and almost the entire length of the taper depending on how well you can shape the join.

Is there a set way to make your tenon/mortise join?

[ToddJohnson]

Just wondering how you pros do it. To date, I have tried making both straight insert (which I don't care for) and a tapered insert. I really like the taper fit as it acts no different than the Morse Taper being used on tooling. You can insert the stem almost all the way to the end and then push it tight and it grips firmly all the way around and almost the entire length of the taper depending on how well you can shape the join.

Is there a set way to make your tenon/mortise join?

Butch,

What you describe is called a millitary tenon, but it requires a correspondingly tapered mortise. The advantage to this is, as you say, the ease of insertion and removal, without any real need for precision. The downside is that you can easily crack a shank. That's why you'll see most shanks that incorporate military tenons employ a metal ring that reinforces the shank. The ring just slides into a sleeve in the face of the shank created by a sort of hole saw. This way the shank will never crack.

Standard straight tenons are, by far, more common, but require a great deal of precision. They also have a tendency to break easily or cause a shank to crack of the pipe is dropped etc. Delrin tenons can solve the problem of the tenon breaking, but are more likely to crack a shank if the pipe is jarred or torqued significantly. That's why some decry the use of Delrin tenons; it removes the sort of weak point that, in a stress situation, keeps the pipe from failing (i.e. the shank from cracking). In other words, it's much easier to replace a stem or insert a new tenon than it is to repair a cracked shank. Alright, that's a very long-winded answer to a simple question, so I'll go back to work now.

Todd

[bvartist]

I'm more of a semi-accomplished newbie than a pro, but I'll add my 2c anyway! :thumb:

I use straight mortise and tenon because its easier to do with the tools and machinery I have. I would think hand cutting a tapered tenon with hand tools would be very time consuming and require exacting precision. But thats my opinion! Also, I would think a tapered mortise and tenon would be more difficult on some pipe shapes. Especially ones that have a flush shank/stem junction. However, I don't think there is one right or wrong way to do it. Just one may be better depending on what tools and equipment is available.

Just my 2 cents!

David

[KurtHuhn]

Military stems have merits, for all the reasons Todd described. However, they're holy hell to do right unless you have the right bits and cutters. I get the feeling, however, that you're an old-school machinist and may have access to that tooling, or the ability to make them yourself.

But, as David said, they're not appropriate for all pipes. Stems that you want to fit flush can't use a military stem since it's not ever going stay fitting just the way you initially make it. As you know, the nature of the material pretty much rules it out.

[mahaffy]

That said, however, Butch, I have to admit that I kind-a like the military style, too. Seems t'me, though, that the taper must vary according to the diameter of the join. (I recall reading that somewhere --- maybe in my old green "Machinist's Handbook" back when Hector was a pup.) If so, what's the proper angle for a pipe-size Morse taper?