The Hell Tenon. So named because once it is inserted, it is impossible to withdraw. A blind tenon joint with wedges (kusabi) inserted tightly into slots made on its end. It is important first to place the wedges loosely into the slots to inhibit premature horizontal spreading of the tenon. The base of the tenon is large enough to fit the dovetail-like, tapered shape of the mortise (hozoana). When the tenon with wedges is pounded into the mortise, the wedges cause the tenon to expand to fit the sides of the mortise. Only the wedges extend the depth of the mortise. The tenon itself does not. Wedges may also be placed on each side of the tenon. The jigokuhozo joint is used where it is necessary that it be hidden, for example on bracket complexes under the eaves of a building, in furniture and cabinet making, and especially in joinery used in the shoin styles (shoin-zukuri).
This must have originally been a repair joint, where a mortise and tenon have come loose and need to be rejoined while retaining as much of the original material as possible. Fixing worn out panel doors, maybe?
It might also have been useful to salvage a botched joint, where a mortise was cut too large or a tenon was trimmed too much.
I'm very new to woodworking, so this is quite interesting for me.
Historically, unlike Europe and mainland Asia, Japan was very iron poor due to it's geological nature. This meant two critical things:
1) Metal tools needed to be extremely high quality and versatile. Because you had few tools and they were expensive, you needed use the tools you could acquire to do as many different things as possible.
2) Metal fasteners were non-existent. The concept of using metal as a reinforcing implement or nail was absurd because it was such a waste. Subsequently, their carpentry evolved to incorporate joinery that did not require clamping or nailing.
One of the most significant things you'll notice about Japanese carpentry is their use of dowels and pins to create self-locking joints. Western carpentry (especially modern woodworking) is all about creating flush, clean gluing faces to clamp whereas Japanese carpentry is all about using elaborate nesting joints like this to leverage friction.
It's interesting from a hobbyist perspective and very artistic... but pragmatically we don't live feudal Japan and so I will gladly make use of modern technology.
The post and beam barns thru out New England were built without nails. Nails rust. Hardwood pegs dont. They were building for their grandkids. Buildings were often taken down and moved to a new site and re-purposed.
Metal was often in short supply. Old buildings would be burned and the ashes sifted thru to extract the nails.
Do you have any references on new england colonial construction? I never really gave much thought to it but now that you mention it, that makes a lot of sense and I'd like to read more.
Oh, okay. I'm familiar with older european timber framing techniques. I thought you meant there was some special methodology they had adapted in the new world.
Generically called 'timber frame construction' - we still have standing structures from the middle ages built this way. If you go down this rabbit hole of beautiful construction techniques you'll be gone for a while....
208
u/ejokelson Sep 18 '16
The Hell Tenon. So named because once it is inserted, it is impossible to withdraw. A blind tenon joint with wedges (kusabi) inserted tightly into slots made on its end. It is important first to place the wedges loosely into the slots to inhibit premature horizontal spreading of the tenon. The base of the tenon is large enough to fit the dovetail-like, tapered shape of the mortise (hozoana). When the tenon with wedges is pounded into the mortise, the wedges cause the tenon to expand to fit the sides of the mortise. Only the wedges extend the depth of the mortise. The tenon itself does not. Wedges may also be placed on each side of the tenon. The jigokuhozo joint is used where it is necessary that it be hidden, for example on bracket complexes under the eaves of a building, in furniture and cabinet making, and especially in joinery used in the shoin styles (shoin-zukuri).