Loose Tenon Joinery
I am often asked why I prefer loose tenon joinery to integral tenon joinery.
My answer simply stated is that I find loose tenons, in most cases, to be faster and easier to cut. Letís say for example we are making a table. Most tables are constructed with four legs joined together with four aprons. The aprons meet the legs at right angles which means we are joining end grain to long grain thereby requiring some type of mechanical fastener. The mortise and tenon joint is one of the strongest methods for joining wood at right angles as well as a large variety of other angles. Its use dates back thousands of years and has been found in the tombs of ancient Egyptian pharaohs. The loose tenon is a variation of this joint and similar to a dowel joint only wider, thereby incorporating more side grain to side grain glue surface making it stronger than a dowel joint.
Cutting an integral tenon joint involves several set ups at the table saw to precisely cut the cheeks and shoulders on the apron stock. Much care must be taken to ensure that the shoulders have been accurately cut all the way around so that the tenon from the apron fits cleanly into the mortise in the leg with no gaps.
I find it easier to cut the aprons to length so that they cleanly butt up against the leg stock and then use a plunge router to rout a matching mortise in the aprons and legs. Once all of the mortises are routed then I will mill up the tenon stock. Having cut all of the mortises with the same router bit, I know that they are all identical in width, so to make the matching tenon stock, I will simply run everything through the planer until they fit. I am looking for a friction fit so I want them snug so that they wonít fall out if turned upside down, but not so tight that they require a hammer to drive them in.
Strength comparison is the next question. No matter what kind of joinery is used, the majority of wood workers agree that the joints need to be glued in order to stay together. The modern adhesives developed since World War II have made techniques like bent wood lamination possible and proven that a long grain to long grain glue joint is stronger than the wood itself. I have proved this many times by doing a simple test. After running two boards over the jointer, then gluing and clamping them together, I will let them set overnight. The next day I will stand on top of my workbench and slam the boards on to the concrete floor of my shop. After repeated slamming, I will find that the wood cracks before the joint breaks.
If I am dealing with a more challenging situation such as a wood that is oily or waxy or a piece of furniture that will be subjected to a harsh environment with severe fluctuations in humidity, then I will use a stronger adhesive such as epoxy or urea resin glue. I have been building furniture since 1973 and have yet to see one of these joints fail.