A standard terminology is an important part of any craft or discipline. If you are going to be certified as a master electrician, you have to know the difference between a wire nut and a split bolt. More importantly, you have to be able to describe why you should use one over the other. Woodworking has its own craft terminology and there are many resources, dictionaries, and glossaries. In general, we are pretty clear on what is what although there are certainly some variations among us. I think we can live with "rebates" and "rabbets". Maybe even with "slip feather" and "veneer spline". However, when I see an expert making a "tusk-wedged tenon" when they are actually making a keyed through tenon — well, things have just gone too far.

Before you think I am the curmudgeonly fussbudget trying to show my smarts let me explain why I am bringing this to your attention. There are at least two reasons we should be careful with our words. First, there is the risk of creating confusion within the craft. If there are not clear definitions, it is hard to teach skills, share tips, and work together. What would happen in this world if "Raise the blade" wasn't clearly understood in the shop? (Depends on whether you are using a table saw or a radial arm saw!)

Second, and perhaps more importantly, the confusion over tusked tenons shows that woodworkers are missing out on appreciating the very important distinction of this unique joint. If you don't see the difference between a tusked tenon and a through-tenon, you really don't understand the fundamental mechanics of joinery.

The tusked tenon developed in timber-framed house construction to connect joists into main beams or girders. In this application, the carpenter is trying to make sure the side member (the joist) can transfer its load to the main beam without excessively reducing the strength of the main beam. In "Historic American Timber Joinery: A Graphic Guide", Jack Sobon provides a clear discussion of how the joist-girder joint evolved from simple tenon to strengthened tusked tenons. Joseph Moxon, in his "Mechanick's Exercises" (1703) defines the term tusk as a bevel shoulder and describes its use to reinforce the "tennant" of a "joyst." This definition is refined in later works with perhaps the clearest description provided in 1880 by James Newland in his book, "The Carpenter and Joiner's Assistant":


"In framing the binding-joists into the girders, it is necessary to effect a compromise between two evils; for the tenon is stronger the nearer it is to the lower side of the joist or binder on which it is formed, and the mortise weakens the beam or girder the least when it is near the upper side thereof; this is, when it is above the neutral axis. A contrivance, therefore, called a 'tusk tenon,' is used, which is seen in sections Figure 3, Nos. 2 and 4 [Plate 42]. The tenon a is a little above the middle of the joist; but its efficiency is increased by the tusk b, which relieves it of its bearing, and the shoulder above the tenon is cut back obliquely; and thus, without unduly weakening the girder, a great depth of bearing is obtained for the joist. It is necessary to take great care in fitting the bearing parts to the corresponding parts of the mortise. The tenon a should be equal to one-sixth of the depth of the girder; and, according to the best practice, it should be inserted at one-third the depth of the girder from the lower side."

In both Moxon and Newlands, the tusk tenon is described in chapters dedicated to carpentry, not joinery. The key principle of the tusk tenon joint is that the sloping tusk creates much greater shear strength for the joist-girder connection — what Newlands calls a "great depth of bearing." It actually has nothing to do with whether the tenon is through, keyed, pegged, or wedged. The reason that the tusk slopes (which really complicates making the joint) is to minimize the reduction in the cross-sectional area of the girder caused by the mortise.

When you think about this you begin to comprehend that the tusked tenon is a highly-refined evolution of this critical timberframe connection. How many joists broke at the tenon before carpenters figured out what was going on? If you read some of the old texts about carpentry it is clear they were thinking about floor loading, springiness, and joint failure. Moxon describes the need for strong bearing members, "lest the whole floor dance." The design of the tusk tenon shows a deep understanding of mechanics and static loading stresses. Do we really appreciate joint loading with that level of knowledge when we design a chair stretcher connection?

To be fair to anyone that is calling a keyed through tenon a tusk tenon, there are good authorities that have confused the term. William Fairham's book "Woodwork Joints" (1921) starts out with the proper description of tusked tenons, but then he shows an Arts and Crafts-style through keyed tenon as an alternative "tusk tenon and wedge." This has been repeated and compounded by many other popular articles and references since then. Today some people point to the through tenon itself and call it the "tusk tenon", as if a tenon sticking out of the piece defines tusk. Other people point to the key and call that the "tusk." Maybe because the key is kind of pointy? I have also noticed a general tendency for people (online video presenters for example), to be kind of sloppy in their terminology when describing all the variations of tenon joints. What is the difference between a wedge, a key, or a peg? Is it a haunched tenon or a stopped shoulder tenon? Does it really matter?

Bob Meeson (2016), an English archaeologist, recently made the case for architectural historians to be more precise in their discussion of framing joints, particularly the tusked tenon. His paper highlights an important element of the whole discussion — this is an exchange of language and ideas between crafts. Tusk tenons were born in carpentry and are being re-interpreted into cabinetmaking. Woodworkers like the term, but don't really understand or apply the concept in the sense of its original intent. Something is getting lost in the translation. Maybe at the end of the day we can disagree about what to call some of the elements of our craft. However what really matters is whether we understand and appreciate the foundational principles that are described by those pesky words. Shear strength in a tenon joint is what the tusk tenon is all about.

References

Fairham, W. 1921. Woodwork joints. How they are set out, How made, and Where used. Lippincott and Co. Philadelphia. 214 p.

Goss, W.F.M. 1901. Bench work in wood. Ginn and Co. Boston, MA. 161 p. (see p. 139)

Meeson, B. 2016. What's in a name? The use of tusk tenons and face-pegged through tenons in England. Vernacular Architecture, 47(1):61-68

Moxon, J. 1703. Mechanick Exercises: Or the Doctrine of Handy-works. Midwinter and Leigh. London. 352 p.

Newlands, J. 1880. The carpenter and joiner's assistant. Blackie. London. 254 p.

Sobon, J.A. 2002. Historic American timber joinery. A graphic guide. Timber Framers Guild. Becket, MA. 54 p.

Bob Rummer lives in Lawrence, Kansas and is a part-time woodworker. He can be reached directly via email at rummersohne@gmail.com. You can see his shop and some of his work at www.JRummerSons.com.

Return to the Wood News Online front page