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End grain. A simple concept, but slightly more difficult to master what it represents in the world of woodworking. We have talked about this on one or two of the other blog posts.

To describe it in the simplest terms, a piece of wood can be thought of structurally as a collection of straws. The two broadest surfaces and the two sides, assuming that we are talking about a rectangular solid or a board, are the sides of the straws and are referred to as flat grain, while the two ends of the board, the open ends of the straws, are referred to as end grain.

End grain and flat grain have very different properties and must be seen and dealt with in very different ways. From a woodworker’s and designer’s point of view, the most important fact is that wood moves- expands and contracts- so little along its length, (the same directions as the straws run) that movement there is safely ignored. However, wood DOES move across the board, or across the ends of the straws. The fact that boards move differently on different faces of a board seems to cause great consternation among woodworkers, but there are very time-proven methods for allowing the wood to continue to move in harmony for centuries to come.

One of the main characteristics of the end grain in a piece of wood, is that being similar to a straw, it soaks things up much more easily than flat grain. More water. More oil. More finish. But, perhaps most consequentially, glue. The result of that is end grain is not generally your friend when it comes to gluing pieces of wood together. When you are gluing two boards up edge to edge, as in say a tabletop, the grain is flat (or side) and the wood stays on or near the surface. When the glue cures the two pieces are chemically bonded and are actually stronger at that joint, assuming well prepared gluing surfaces. The problem with gluing where one or both surfaces are those straws, the end grain, soaks up much more of the glue and therefore the chemical bond is relatively much weaker.

The solution? Joinery. The entire purpose of joinery is to join two pieces of wood together in a way that provides the maximum amount of strength. There are two ways to do that. The second, is to create some kind of mechanical bond such as dovetails or a myriad of the extraordinarily complicated but beautiful joints employed in Japanese joinery where there are pins and wedges used to lock pieces together. But the first method is the most easily attainable and that is to form a chemical bond using one of many types of mastics, or glue.  The way to overcome the shortcoming here, that the end grain will suck the glue out of the joint, is to create a way of increasing flat grain to flat grain mating surfaces. That can be done in countless ways such as dovetails, half laps, splined miters, finger joints, and for me, a furnituremaker, not so much a cabinetmaker, the most important of all, the mortise-and-tenon.

Very commonly used for example, where a horizontal stretcher connects to a chair or table leg. To a casual observer, it looks as though the stretcher, ( or apron), is simply butting into the leg. But we already know that the end grain of the stretcher will not afford much strength: we cut a rectangular hollow, called a mortise (think mouth) into the leg. Then, when the tenon (think tongue) is cut on the end of the stretcher and is coated with glue and slid into the mortise you have a pair of cheeks- the flat grain surfaces- mating and providing a strong glue/chemical bond. And voila! A strong joint.

Another way in which end grain is very different than the other four (flat grain) surfaces of a piece of wood is its hardness. Press down on the sides of that bundle of straws and you can collapse them very easily. Press down on the ends of those straws and they have remarkable resistance. That is why vertical support members in a building are constructed with the grain running vertically. 

One of the effects of this is it is much harder to plane or sand end grain than it is flat grain. Planes have been specially modified to deal with this problem by lowering the angle of the plane iron. ( Named, not surprisingly, a low angle plane.) An absolutely essential piece in any woodworker’s tool kit. And here’s a nice trick to remember: unless the end grain is precisely perpendicular to the length of the board, there is usually one direction to plane end grain that is a bit easier. This is most simply found by experimenting in different directions. Some woodworkers who are not as familiar with their hand planes as they could be might resort to sanding, but as most of you know by now, I consider that a vastly inferior and more inaccurate way to work wood. A tool that is very underrated and highly effective on end grain is a simple ( sharp- not the old rusty one in your Dad’s toolbox) flat file. Try it, you’ll be amazed how easy it is to get a polished finish on the end grain.

End grain is, indeed, a different animal than flat grain in a piece of wood. It comes with some difficulties, such as needing to be extra careful when working it so that there is no blowout. But it can also be quite beautiful and placed where it can be a wonderful design feature. Look at some furniture pieces with through tenons. You can also go to YouTube and search for end grain cutting boards.

Become good friends with end grain. It is worth it, and every piece of wood has it. You’ll see

October 6, 2019 By Jonathan Cohen Woodworking Share: