Plane Articles

Why Make Planes From Beech?
by Bill Clark & Larry Williams

Our choice of wood for plane making is the traditional wood, beech. It is one of the more dense of our domestic woods. If you consider beech unstable, we suppose you'd consider any dense wood unstable.

Wood for plane making requires specific properties. It needs to be of relatively uniform density, wear resistant, and have the ability to retain it's shape through dimensional changes. The iron also needs to remain firmly bedded with humidity changes. Three hundred years of commercial plane making and evolution have led to beech as the choice for planes.

Beech unlike teak, mahogany, white oak and many other dense woods is diffuse-porous. The annular rings in beech aren't more porous than other areas and it is a fine grained wood. This property makes the mouth of a plane less likely to suffer from uneven wear when a less-dense section of annular ring crosses the mouth area. Ring porous woods have little wear resistance at their growth rings because of their increased porosity.

The specific gravity of American beech at 12% moisture content is 0.64 and it weighs a heavy 45 pounds per cubic foot. As hard woods go, beech is pretty dense. A draw back of dense wood is that the more dense it is, the less dimensional stability it has with a change in moisture content. Dense woods also take proportionally longer to react to humidity changes and their reaction to those changes occur over a greater period of time.

Cell structure
To understand moisture-related dimensional change in wood you have to look at the cell structure. Most cells in the trunk of a tree are involved in one of two functions. Predominately, they move moisture and nutrients from the root system to the leaves. These cells have a tubular structure and work through capillary action. Think of them the same as when you grab a handful of straws. Wood density is a function of the diameter of the cell, cell wall thickness and the size of the central void.

Keep in mind that wood, in its natural state is wet. As woodworkers, we tend to look at things backwards and assume that wood should be dry. I'm not going to try to change that here because, from a practical stand point, it doesn't make a lot of difference when it comes to dimensional change due to moisture content.

As moisture passes through these cells, the cell walls absorb part of it. This is called bound moisture. The cell walls expand when they absorb moisture. This makes them grow slightly in length and to a much greater degree in cross section. I don't want to explain the math of this but a small change in the circumference of a circle makes a big difference in its area. We'll spare a lengthy discussion here...this is going to be long enough. If you need help understanding this, go to your local pizza joint and ask them to explain the pricing of various diameters of pizza.

Millions of wood cells reacting to absorbed water cause wood to expand more in width than in length. There would, in fact, be no difference in dimensional change between radial and tangential surfaces if it were not for another group of cells in wood. Some wood cells are oriented differently from others and these are those of the rays. Another function of the trunk of a tree is to store nutrients and/or moisture. Rays are oriented radially and their tubular structure is perpendicular to the majority of wood cells and their function is to tap into the stored nutrients and moisture of the trunk. One of the effects of this network of cells is to limit the dimensional change of the other cells. The cells of rays actually force a change in the circular shape of the vertical cells. Their shape becomes elliptical rather than circular and this forces a greater dimensional change in tangential wood surfaces than the radial. Compared to other dense woods beech has more abundant and well dispersed rays and they are generally exceptionally long in comparison.

Trees in wet or tropical areas of the world have a more consistent supply of water and have, for the most part, evolved with less ray structure than trees from drier climates. Tropical woods simply don't need to depend as much on stored moisture and nutrients and have less ray structure. This generally gives their wood a more similar tangential and radial expansion and contraction characteristics.

Advantages of beech's ray structure
For many woodworking applications a great difference in radial and tangential stability can cause problems. It can, however, be used to advantage. Plane makers have done this through history with their choice of beech. As mentioned earlier, a tight fitting wedge and firm bedding of the iron are critical in planes. Beech; when the bed, wedge abutments and wedge are made within the radial surface; offers the stability of a less dense wood while having a relatively high density. This high density naturally imparts greater wear resistance.

An example of this would be joining two perpendicular pieces of wood with a miter joint. The angles of the cuts will change as the pieces change in width but not much in length. Your miter joint will be open at the toe of the cut during humid times and open at the heel during dry times. You can limit this change by taking advantage of the increased stability of quarter-sawn wood. This same effect applies to planes. A plane wedge open at it's point will trap shavings and tend to choke. When only tight at the point the wedge will have very limited holding power. No matter how stable the sole of the plane may be, an ill fitting wedge will cause the plane to be effectively useless. A dense wood with the ability to stay relatively stable in the planes of the wedge and iron surfaces is and important consideration in making good planes. Beech, relative to density, is one of the more stable dense woods in it's radial or quarter-sawn dimension.

To accommodate this use, you must learn to deal with the increased instability on the tangential surface. For instance, plenty of clearance needs to be left for the plane width to change around the iron which has no dimensional change with humidity. The presence of so many old planes with cracked cheeks from shrinkage around the irons is evidence to how much change can be present.

Grain orientation is critical on planes. The wide bodies of bench planes require the most careful orientation. Not only for wedge fit but also for shape stability. Normal dimensional changes in wood can even cause a bench plane body to lean one direction or the other should the wood selected not be dead quarter sawn.

The abundant rays of beech offer yet other advantages to the plane maker. End grain is more wear resistant than other possible orientations. A flat sawn face of beech will be made up of about 40% rays. The ray cell orientation on a flat sawn beech face will be essentially the same as end grain. So 40% of the surface of the sole will be made up of ray cells oriented for maximum wear resistance. They are uniformly distributed through the diffuse-porous wood and increase wear resistance.

Beech's ray structure also gives it other interesting properties. Its abundant rays are particularly effective at moving moisture to ambient air. A plane made of a tropical wood is slow to react to moisture changes and this can be good. If you assume that dimensional movement is inevitable, you'll soon start looking for ways to keep shape stability while that change is taking place. This can be handled with design; We have some information on how this is done elsewhere on our web site. Shape stability is, in planes, more important than dimensional

Ocaasionally the abundant rays of beech are visible as they line up perfectly with the side of a plane. Its length and density become visible especially on the chamfers. Normally, much of the one cell thick ray structure requires significant magnification to see on flat-sawn surfaces. It's worth noting here that this delicate and difficult to plane surface is as left by a Clark & Williams smooth plane with the exception of finish a burnishing with 400 grit sand paper.

Let's get back to the speed of moisture exchange. Beech offers rapid exchange of moisture with air on both the flat sawn surfaces and end grain. A plane made of a tropical wood will change slowly. In effect, it's always moving. A plane made of beech changes rapidly and we think this is an advantage. Most of us experience two major ambient humidity changes a year. These are somewhat gradual but in our homes and shops tend to be sudden when you go from heating to cooling or the other way around. It may take up to a couple weeks for a beech plane to reach equilibrium moisture content. with seasonal changes. Planes made from more exotic woods with slower moisture exchange may not have completed their change by the time the next seasonal change happens. We think it wise to get any seasonal tuning over with and get on with work rather than deal with daily changes.

This property of beech also creates problems. It is difficult to dry without degrade because the tangential surfaces give off moisture so easily. This is so prevalent that it is nearly impossible to locate a source of thick beech today. We can't help but think early plane makers also had problems drying beech. If there was another wood that offered as good a combination of characteristics, wouldn't plane makers have gladly made a change? There are similar woods that don't have these problems in drying and they can make some good planes. These include maple, cherry, persimmon, yellow birch and pear or apple. Some are plentiful and were often used for craftsman-made planes as well as some commercially made planes but they don't equal beech for common commercial plane making use.

Finish for hand planes
This brings us to finishes. some try to stop moisture exchange with a finish. Soaking planes in finishes has been tried in the past. Some 19th century woodworkers and even dealers made a habit of soaking planes in linseed oil. Sometimes for long periods. If this treatment was effective, We'd expect to find old boxed molding planes that have endured this soaking to have their boxing complete and in good condition. What we actually find is the opposite. The old boxed planes often show the tell-tale ugly linseed oil buildup on their toes and heels tend to show more problems with boxing. Perhaps people are having better luck with new products. Only time will tell. We can say that people have, through history, tried to stop wood movement with finishes. As far as we know, it hasn't worked yet.

"Dymondwood," a high resin content/high pressure laminated product made of birch plys, is more stable in moisture changes but its thermal stability ,and other characteristics, more reflects its volume of plastic resin than its wood content. You'll find that the more foreign ingredients are added to man-made wood products, the more it will have the properties of those ingredients.

Choice of finish should reflect acceptance of the natural properties of wood. One should try to use a finish that protects the finished surfaces of the plane from the daily rigors of use but doesn't offer, as much as possible, a lot resistance to moisture movement between the air and the wood.

Laminated planes?
Laminated soles or other plane parts also limit moisture movement through the plane and increase the time for a plane body to reach EMC. An impermeable layer of adhesive in the plane body can create problems. Just the adhesive itself can add stresses. Glue chip glass, for instance, is created by glue bonding to the surface of glass and shrinking as it cures. This shrinking is strong enough to break away the existing glass surface. Adhesives simply have different properties than the wood they join. Natural internal stresses are difficult enough with out adding more problems.

Then you must look at different properties of different woods. There is the potential for movement problems with laminated soles. 'Fine Woodworking' once published instructions to make a device that displayed relative humidity through using the dissimilar properties of wood. Laminate two thin strips of different woods and use their movement to indicate RAH. This is exactly the same process as laminating a sole of different wood to a plane body. Using woods of the same species in laminations can cause problems. During our years general contracting we, for a short time, used interior doors that were made with stiles and rails that were laminated 1X material for thickness. Problems and call-backs quickly forced to quit using them and our supplier ended up discontinuing the line because of stability problems.

One may be reminded of Cecil Pierce and his experience when he ordered a video tape on plane making. In his book, Fifty Years a Planemaker and User he describes purchasing the tape hoping to find some information he'd over looked in plane making:

"...soon I was viewing a workman in a shop so sterile that it could have been a lab at the local hospital. No errant chip or shaving marred the floor or factory-made craftsman's bench. Likewise no crude tools such as chisels, rasps or mallet graced the unworn top of that bench..........It turned out the he was not going to need any hand tools, for the plane was going to be made of three pieces of wood, all precisely machined, then doweled and glued together. I had gone through and abandoned that phase half a lifetime ago.......A redeeming feature for me was that after all he used the thing (the laminated plane) conventionally - he didn't pull the plane toward him and had he used a saw, he probably wouldn't have pulled that either."

French plane makers for a time made laminated planes. Goodman's British Planemakers from 1700 , 3rd Ed states:

"The real skill in the process came in the stage when the mortise had to be marked and then sunk. If the iron was skewed this added further difficulty. French molding planemakers apparently thought this was all too difficult as their normal method was to saw the "mortise" in from the side and close it up by sticking a piece over the side. In some cases this method was taken even further and the planes were made of four pieces, a front body, a back body and two sides. Later still there was even grooving to improve the adhesion of the sides. All very well until the plane gets wet, when it divides into its constituent parts; many planes found in the foires aux puces now present three-dimensional jigsaw puzzles to the collector. This all seems to be a long way round to avoid the cutting of a mortice!"

As you can tell, we're not fans of laminated planes. Larry made a number of them 20 to 25 years ago and even sold a few. He was just never satisfied with them or the quality of laminated planes.

Choosing a plane wood and plane making technique involves some trade-offs. Properties of different woods and the anisotropic nature of wood offer a number of options. We believe earlier plane makers found the best solution when they adopted beech for their work. It seems wise to be to build on the successes and knowledge of generations of earlier plane makers.