Metals Used In Making Planes

The Stuff Of Metal

When it comes to the materials that can be used in planemaking it can sometimes become quite easy to “lose the plot”. This is especially true when you consider the vast array of metals available – both ferrous and nonferrous. In this article I concentrate mainly on metals used for making the bodies of hand planes, rather than the range of steels available for making blades – that deserves to be an article in itself!

Put simply, ferrous metals are those which contain iron such as cast iron, wrought iron, tungsten carbide, stellite and all the various kinds of steel. Nonferrous metals for obvious reasons contain either no iron, or very small amounts of it. These include metals such as copper, brass, aluminium, tin and bronze. There are many more metals in this group but generally speaking we will not come across them except maybe in some alloys.

The many types of metals available makes it all the more important to identify and understand the various attributes and/or shortfalls of a particular metal. Many potential makers looking for supplies may come across different metals in demolition yards or scrap merchants. For a few dollars they can come away with some very useful bits and pieces with which they can make planes. Here is where the trouble can start. While it might be easy enough for most people to distinguish a piece of steel from a piece of brass, it is not such a simple task to identify ordinary carbon steel from high speed steel, or brass from gunmetal. Is this information really necessary? It can be, after all – there’s no point in spending all morning making a plane iron, if only to discover that it wont hold an edge because it’s carbon content is too low. This is why it is important to know at least some information about the various metals and materials you may come across in your planemaking endeavours.

Before we look at some of the metals you’re likely to encounter there is yet another avenue we must consider for sourcing material. While scrap yards and second hand dealers may be one way to obtain metals for planemaking there is another option. New material can be purchased from manufacturers or metal stockists, where information can be given as to the exact contents and properties of various metals. Of course this will cost more than metals bought from the scrap merchants, but at least you’ll save time by not having to identify a particular piece to determine it’s suitability to the job at hand. You will also find that there is a good range of sizes and profiles at these places to suit virtually all of your planemaking needs.

Glossary Of Metal Terms

Brittleness — The ability to fracture easily with little or no deformation. Opposite of toughness.

Ductility — The ability to be easily moulded or shaped without fracturing. Capable of being drawn out into wire beyond the materials’ elastic limit.

Elasticity — The ability to be deformed from an original shape by an outside force, then returned to that original shape without permanent deformation when the force is removed.

Fusibility — The degree to which a substance is fusible. The capability of a material to be converted from a solid to a fluid state by heat. By definition all metals are fusible.

Hardness — The state or quality of being hard. Able to resist wear and abrasion. The ability to resist penetration and scratching.

Malleability — Capable of being extended or shaped by hammering or by pressure from rollers. Deformed by compressive forces rather than tensile forces.

Softness — Easily penetrated, divided or altered in shape. Able to be scratched and deformed. Easily worked. Opposite of hardness.

Strength — The ability to withstand stress without breaking. Stress is defined by Tensile Force (stretching), Compressive Force (crushing), Shear Force (sliding) and Torsional Force (twisting).

Toughness — The ability to resist shock. Opposite of brittle.

Ferrous Metals

Cast Iron — Cast iron is an alloy of iron which typically contains around 4 % of carbon. It may also contain small amounts of phosphorous, silicon, sulphur and manganese. Cast iron can be readily melted and poured into moulds to form different shapes or castings. There are two types of cast iron. White – in which the carbon content (at around about 6.5 %) has changed the crystalline structure to become cementite. This produces a much harder and more durable cast iron, but also one that is very brittle, although it can be annealed to produce malleable iron. The other, more common, type of cast iron is grey – where the carbon content consists mainly of graphite with smaller traces of perlite. This makes it much less brittle than the white and much better suited to planemaking. It should be noted that both white and grey cast iron have limited tensile strength and poor resistance to shock. For identification purposes, both types get their respective names from the way they look when fractured.

Wrought Iron — Wrought iron, in appearance, has a very grainy or styrated look to it which is produced by the layering method by which it is forged. Its low carbon content makes wrought iron ductile and quite easy to work, yet at the same time it remains quite tough. As in the case with cast iron, wrought iron may contain very small amounts of phosphorus, silicon, sulphur and manganese. Wrought iron also retains a certain amount of slag in it’s makeup which, when worked, help to produce it’s characteristic grainy look. It is less susceptible to rust than mild steel – which has since replaced it as a material. Many older British and European planes – especially mitre planes – have been made from wrought iron.

Malleable Iron — Malleable iron, like wrought iron, is not often seen today, but last century many manufacturers of high quality planes offered malleable iron as a cheaper alternative to their dovetailed steel planes. As stated previously, malleable iron is essentially white cast iron which has been modified by heat treatment. This annealing process is carefully controlled and can last for several days. The resulting crystalline structure makes the iron more ductile than it would normally be. Planes made from malleable iron were more expensive than planes made from ordinary cast iron, but they were also a great deal stronger and tougher. It is also interesting to note that some of the Norris planes available in malleable iron at the turn of the century, appear in catalogues as annealed iron in latter years.

Cast Steel — Cast steel will not be encountered in demolition yards or scrap merchants and it will certainly not be found at the local metal stockist. Why then am I even mentioning it? The reason why is that the term “cast steel” is often stamped on many pre – existing plane blades (and chisels) from the last century up until about World War II. This was to distinguish the more highly regarded and better quality “cast iron” cutters – which were made from crucible iron and cast into flat bars before being rolled out and shaped into cutters – from the more primitive method of blade manufacture. This older method involved impregnating the wrought iron with carbon in a charcoal furnace which resulted in what was known as “blister steel”.

Mild Steel — Mild steel has a low carbon content, typically between 0.15 % to 0.3 %. This makes it unsuitable for plane blades as it cannot be sufficiently hardened enough to maintain a keen edge. It is, however, extremely useful for making plane bodies and adjuster mechanisms due to the ease of which it can be worked. It is both malleable and ductile and can be welded, brazed, forged, bent and machined with little effort. Although it cannot be hardened throughout, mild steel can be given a harder outside “skin” though a process known as “case hardening”. This helps to resist wear while at the same time retains toughness and shock resistance due to its softer core. This can be very useful for adjuster parts.

Mild steel is available in a large range of forms – from sheets and strips to bars, flats, rounds and profiles, which makes it one of the most versatile materials for planemaking.

Medium Carbon Steel — Medium carbon steel contains between 0.30 % and 0.55 % carbon content. This steel can be hardened, but not enough to maintain a keen edge suitable for plane blades. It is useful for making adjuster mechanisms, as it is much stronger than mild steel. Medium carbon steels are used in the manufacture of hammer heads, pliers, cold chisels and clamps.

High Carbon Steel — High carbon steel is blade making steel! With a carbon content of between 0.55 % and 1.5 % it can be heat treated to increase its hardness and overall strength, and tempered to improve its toughness. Most of the older plane blades were made from high carbon steel, including the previously mentioned “cast steel” blades. Some of the very best cutters were made by welding or laminating a harder piece of steel at the cutting edge to a softer backing piece. This resulted in a cutter that was not only strong and hard, but one that was tough as well, with a good resistance to shock. This process was known as “steeling”.

Special Steels — There have been many “new” types of steel developed and introduced in the last sixty or so years. Metals such as chromium, manganese, vanadium, nickel, tungsten and molybdenum have been alloyed with iron to improve its working properties. Many of these metals are known as “tool steels”. Tool steels may contain either a high percentage of carbon, a high alloy content or a combination of both. An example of this is the introduction of chrome – vanadium steel for use in car suspension springs, as well as spanners and wrenches, screwdriver blades, crow bars and anything else which requires a hard, yet flexible material. The chromium increases toughness and hardness and helps to prevent corrosion, while the vanadium improves the toughness and elasticity of the steel and gives it a finer grain. The company of Vaughan and Bushnell used vanadium steel blades in their range of Stanley pattern planes, as did some other makers.

Metals such as molybdenum also increase hardness and allow the steel to remain tough – even at high temperatures.

Manganese adds strength and toughness and is used for items that must withstand shock and hard wear.

When nickel is added to steel it imparts toughness and strength as well as improving its resistance to shock – useful attributes in the manufacture of armour plate for which it is used extensively. Like chromium, nickel also helps to prevent corrosion.

Tungsten is used for making High Speed Steels, where it helps to allow the material to hold an edge at very high temperatures, as in the case of metal turning or wood turning tools and drill bits. Tungsten is also an extremely hard metal and its addition to steel can improve the grain structure of the overall material. As much as 24 % of tungsten can be found in tungsten steel, although typically it ranges from between 5 % to 15 %. The British planemaking firm Record has used a tungsten vanadium steel for some of their plane blades.

Stainless steels contain Nickel and Chromium, which help to reduce the process of corrosion. There are several types of stainless steel – and nearly all of them can be difficult to cut and work. For this reason alone I wouldn’t recommend them for planemaking generally – although I have seen some very fine examples of block planes cast in stainless steel.

Nonferrous Metals

Copper — Copper by itself is really too soft for planemaking, but when alloyed with metals such as tin or zinc however, it becomes very useful indeed. Copper is the base metal for brass and bronze alloys. As a material it is soft and ductile, and has a low tensile strength. It can become easily work-hardened, but is just as easily annealed.

Brass — Brass is an alloy of Copper and Zinc. Typically the most common form of brass consists of 66.6 % copper to 33.3 % zinc, but the proportions can vary depending on the end use of the alloy. Red brass may contain up to 86 % copper, the remaining 14 % consisting of zinc along with tin, lead and small amounts of other metals. Tin is added to make the alloy harder, while lead improves its resistance to corrosion.

Other metals such as manganese can be added to increase the toughness and tensile strength of brass, as well as improve the machinability. This alloy is sometimes known as manganese bronze, and can typically contain 55 % copper, 38 % zinc, 3.5 % manganese, 1 % aluminium, 1 % iron, 1 % tin and 0.25 % lead. Manganese bronze is one of the alloys used by the Lie – Nielsen company for their reproduction Stanley planes.

Aluminum, when added to brass, increases the strength and hardness as well as the corrosion resistance of the alloy.

Metals such as nickel, phosphorus, iron, sulphur and antimony may also be found in brass, but the alloy must contain at least 50 % of copper to be called brass.

Available in a large range of profiles, and in various gradings from soft to hard, brass is an ideal material for planemaking as it is easily worked both by hand and machine.

It is interesting to note that Mathieson of Glasgow offered brass lever caps and screws as a “second quality” alternative to gunmetal. These were sold as after market items and came complete with wrought steel rivets.

Bronze — Bronze is an alloy of copper and tin. Like brass, the properties of bronze can vary dramatically depending on the presence and proportions of various other metals within the alloy. Typical additives to bronze include zinc, aluminium, silicon, phosphorus, lead, iron, manganese and nickel.

Gunmetal — Gunmetal is the traditional nonferrous metal used by most of the great planemakers of the past. Nearly all of the lever caps and screws found on old infill planes are made from gunmetal, and many makers even cast whole plane bodies from this alloy for their “up market” models. Gunmetal planes were typically about 1 1/2 times heavier than their steel counterparts. The admiralty specification for gunmetal consists of 88 % copper, 10 % tin and 2 % zinc.

In certain circumstances where it is subjected to heavy loads and severe working conditions – as in the case of some heavy duty bushings – 2 % lead may be substituted for the zinc. This is known as leaded gun metal.

Gunmetal is not so readily available nowadays, as many of the newer bronzes have since taken over its mantle for one reason or another. Some of these alloys are still regarded as gunmetal, though for obvious reasons they’re not quite the same. If you can find it however, gunmetal is excellent for making the plane parts described above, as it is stronger and much harder wearing than brass.

Phosphor Bronze — Phosphor bronze can have up to 90 % copper, 9.5 % tin and 0.5 % phosphorus. Nickel, lead, zinc and other impurities may also be present. It casts cleanly and has good machinability properties, which makes it ideal for lever caps, screws etc. Phosphor bronze is readily available in sheets, bars, flats, rounds and profiles.

Aluminium Bronze — Aluminum bronze consists of 90 % copper and up to 10 % aluminium. It may also contain small amounts of iron and tin. This alloy has considerable strength and is equal to manganese bronze in hardness. It works well by hand or machine and makes fine and detailed castings.

Silicon Bronze — Makes very detailed castings. A ideal bronze for casting smaller planes and plane parts. Makers of violin planes such as Ibex use silicon bronze for their castings.

Aluminum — Aluminum in its pure state is soft and weak. Its strength can be increased however by adding other metals such as copper, manganese, zinc and magnesium. These aluminum alloys have excellent resistance to corrosion. They are easily worked and come in a wide variety of shapes and sizes.

Although companies such as Stanley used aluminum occasionally for planemaking, it is not a material associated with metal infill planes. If, however, you desire the look and feel of a traditional infill plane without the weight, then some of the harder grades of aluminium may be worth considering.