INTRODUCTION

There existed for many years an air of mystery surrounding the selection, heat treatment and use of tool steels. Started by the secretiveness of the early makers, it has been fostered somewhat by the seemingly never-ending introduction of new grades.

Fig 1: Halcomb Steel Company, Syracuse, New York - Dreadnought tool steel advertisement - 1913.

Today the term tool steel commonly means hard steel of a quality used for making tools for cutting and other purposes. More specifically it refers to varieties of carbon and alloy steels that are particularly well-suited to be made into tools.

For the purposes of this historical survey the author has divided the tool steels into five basic types or groups: water-hardening carbon tool steels, oil hardening tool steels, shock-resisting tool steels, air hardening tool steels; and high-speed steels.

The survey also covers the non-ferrous cutting tool alloys. Although technically not steels, they are a group of tool alloys which crop up more often than may be expected. Furthermore, they are quite useful for certain purposes and operations in the metal shop.

A BRIEF OUTLINE OF HSS CLASSIFICATION

During the 1970s the American Society for Testing and Materials (the ASTM is now ASTM International) introduced a unified numbering system for steel comprising 11 main classes each designated by a letter as follows:

The current ASTM standard recognises 7 tungsten types and 21 molybdenum types of HSS. In this unified numbering system the tungsten-type HSS grades (e.g. T1, T15) are assigned numbers in the T120xx series, while molybdenum (e.g. M2, M48) and intermediate types are T113xx.

The current standard (ASTM A600) covers types T1, T2, T4, T5, T6, T8, and T15 and molybdenum-type high-speed steels M1, M2, M3, M4, M6, M7, M10, M30, M33, M34, M36, M41, M42, M43, M44, M46, M47, M48, and M62 in the form of annealed, hot-rolled bars, forgings, plate, sheet, or strip, and annealed, cold-finished bars or forgings used primarily in the fabrication of tools. Two intermediate high speed tool steels designated as M50 and M52 are also covered.

Water-Hardening Tool steels include all class W tool steels. These steels do not retain hardness well at elevated temperatures, but they do have high resistance to surface wear. Typical applications include blanking dies, files, drills, taps, countersinks, reamers, jewellery dies, and cold-striking dies.

THE HIGH SPEED STEELS (HSS)

Just what is high speed steel or HSS? Well when tool steels contain a combination of more than 7.0% tungsten, molybdenum and vanadium, along with more than 0.6% carbon, they are referred to as high speed steel. HSS is a highly-alloyed tool steel capable of maintaining hardness at elevated temperatures better than the high carbon and low alloy steels. This good hot hardness permits tools made of HSS to be used at higher cutting speeds (hence the name “High-Speed”). Since the early 1900s a wide variety of high speed steels has been and continues to be available. For the most part these steels can be divided into two basic types: Tungsten-type, designated T-grades by the AISI; and Molybdenum-type, designated M-grades by the AISI.

Fig 2: Armstrong Whitworth & Co., Manchester, U.K. - Three Celebrated Brands of HSS - 1911.

The term HSS includes all the molybdenum (M1 to M52) and tungsten (T1 to T15) class alloys.

These steels require high temperatures for hardening. The molybdenum types are usually hardened from a range of 1200°C (2200°F) to 1235°C (2250°F), the tungsten types as a rule from 1260°C (2300°F) to 1290°C (2350°F) when heat treated in an atmosphere controlled furnace. High-speed tools steels may be hardened to 62-67 HRc and maintain that hardness in service temperatures as high as 540°C (1000°F) making them very useful in high-speed machining.

Tungsten-type HSS: The tungsten steels form the oldest class and are an outgrowth of the even older Mushet steels. Their development started in the 19^th century with Robert Mushet in UK and reached a technical flowering with the work of F W Taylor and M White in the USA just as the 20th century dawned.

Robert F Mushet practiced the addition of manganese to the steel. But he didn’t stop there; he continued experimenting and sometime in 1868 eventually discovered self-hardening steel. This new steel was immediately put into the market under the name “R Mushet’s Special Steel” or "R.M.S". A typical analysis of this steel was 2.4% carbon, 5.9% tungsten, and 2.5% manganese (these were the proportions of the original R.M.S made at Coleford - the R.M.S made at Sheffield contained 0.55% chromium). Unfortunately for Mushet, the company organised to manufacture and sell his new steel did not succeed well in business. Some three years later the production of Mushet steel was taken over by Samuel Osborn & Co Ltd at the Clyde Works, Sheffield.

Fig 3: Samual Osbourne & Co., Sheffield, U.K. - Mushnet HSS advertisement - 1903.

With a better business model the wide introduction of the new steel into engineering works and its imitation under the name of air-hardening or self-hardening steel quickly followed. Clearly a substantial advance had been made in the art of cutting metals. It was now possible to turn or plane at double or triple the former speeds; and to machine pieces which were formerly just too hard for the tools available or so hard as to make the cost of operation prohibitive. But even after gaining general use in engineering works, Mushet tools were little used for increasing speeds – most usually they were only used to save frequent grindings or to permit doing jobs previously impossible.

It took a further 25 years after ‘Mushet’ or ‘self-hardening’ steel had become an established fact in engineering before the marvellous properties latent in it were clearly appreciated and the industrial world caught a glimpse of what promised to be a revolution in machine shop methods.

Frederick W Taylor had begun experimenting with Mushet and other self-hardening steels as far back as 1894. His aim was to determine which steels were best suited to special kinds of work. So shortly after taking charge of the Bethlehem steel works in 1898 he formed an association with Maunsel White and others in order to better undertake the work at hand.

Fig 4: Samual Osbourne & Co., Sheffield, U.K. - Mushnet HSS advertisement - 1912.

Before the introduction of HSS in the USA the term ‘Mushet steel’ meant self-hardening tool steels containing tungsten. These early ‘Mushet’ steels contained from 5-8% tungsten, up to 2.5% manganese, and very high carbon (1.5-2.4%) with sometimes 0.5% chromium. The Mushet steel made by Samuel Osborn & Co Ltd in 1868 and branded ‘Self-Hard’ or R.M.S. had a typical analysis of 8% tungsten, 2% carbon, and 1% manganese.

The Taylor and White experiments from 1893 to 1898 led to a new steel with less carbon. Taylor-White steel of c.1900 contained 1.85% carbon, 8% tungsten, 3.8% chromium, and 0.3% manganese. Finally, on 19 February 1901, Taylor and White received a patent for a ‘Metal-Cutting Tool and Method of Making Same’ such a tool being "specially adapted for cutting very hard metal and capable of running efficiently when cutting such metals at higher speeds and greater temperatures than has heretofore been practicable".

The investigations by Taylor and White, which culminated in the development of ‘high speed steel’, required a very large amount of money to be spent and infinite patience to be exercised. Something like 50,000 recorded tests were made, a great many more were not recorded, and close to one million pounds of steel and iron was cut into chips; the estimated total cost was almost $200,000.

Fig 5: Arthur Balfour and Co, Sheffield, U.K. - Super Capital high speed steel toolbits - 1963.

However, this was by no means the end of experiments with HSS. In 1904 the addition of vanadium was patented by the Crucible Steel Company and this led to the formulation of what is perhaps the best-known grade, the 18-4-1 steel (later known simply as T1). Cobalt in HSS was first reported in 1912 by Becker in Germany. In 1939 high-carbon high-vanadium super high-speed tool steels (M4 and Tl5) were introduced. The M40 series high-carbon high-cobalt super hard high-speed tool steels first appeared in 1961.

Material availability and costs also had an effect on the development of HSS. Due to the shortage of tungsten and the increases in its price, molybdenum bearing high speed steels were introduced in the USA around 1930.

Since first being patented by the Crucible Steel Company the composition of the T1 type with 18% W has not changed. Indeed, it remained the main type of HSS used in engineering workshops up until the 1940s. Today however only 5-10% of the HSS in Europe is of the T1 type and only about 2% in the USA.

Tungsten HSS can be divided into two general grades according to tungsten content being those with 18% and 14% tungsten. The Super HSS or Cobalt HSS are high in tungsten, but also contain considerable quantities of cobalt. They have added red hardness, but are inclined to be brittle.

Molybdenum-type HSS: Molybdenum rich HSS such as M1 has been in general use since the 1930s. It eventually gained market leadership in the USA during the 1940s. Molybdenum HSS is an outgrowth of an early attempt by the US Ordinance Department to substitute molybdenum for the costly and imported tungsten in HSS. The first Watertown Arsenal steel of 1940 contained about 0.8% carbon, 9.5% molybdenum, 4% chromium, 1.5% tungsten, and 1% vanadium. But the earliest known molybdenum “self-hardening” steel was the ‘MoSH’ steel made by the Sanderson Steel Company in 1898.

Fig 6: Latrobe Electric Steel Co., Pennsylvania, U.S. - Electrite Uranium HSS advert in American Machinist Vol 53 Number 1 - 1920.

Many types of molybdenum HSS came onto the market in the USA. For example, Motung high speed steel (M1) was patented by the Cleveland Twist Drill Company and contains 0.75% C, 8% Mo, 1.75% W, 4% Cr, and 1.25% V. The name Mo-Tung is also used by the Universal-Cyclops Steel Corporation for this steel and other trade names for it include Mogul, Tatmo, Mo-Cut, Vul-Mo, Mohican, LMW, Rex T-Mo, HM Steel, and Di-Mol. Van Lom HSS by the Vanadium-Alloys Steel Company has 1% C, 9% Mo, 4.25% Cr, and 4% V. Bethlehem 66 HSS (M2) by the Bethlehem Steel Company contains 0.8% C, 5.5% W, 5% Mo, 4% Cr and 1.75% V. More often than not the product outlasted the company that made it.

The addition of about 10% of tungsten and molybdenum in total most efficiently maximises the hardness and toughness of high speed steel and maintains these properties at the high temperatures generated when cutting metals. Molybdenum has twice the effect of tungsten in terms of red hardness, but it makes the steel more brittle and also subject to decarburisation. Standard tungsten high speed steels are therefore sometimes modified with very small amounts of molybdenum.

The old Damascus steel and Toledo steel were molybdenum steels, the molybdenum being in the original ore. Damascene steel refers to the wavy forging marks on blades and was not necessarily a molybdenum steel. But the original Wootz steel, or Indian steel, of this type contained small percentages of aluminium incorporated in some obscure manner. Wootz steel was made in the crucible, although the crucible method was not used in Europe until 1740.

Fig 7: Vascoloy-Ramet Corp(VR) - Tantung tool catalog - circa 1940.

So, what is high speed steel used for? The main use of HSS continues to be in the manufacture of various cutting tools: lathe tools, drills, taps, milling cutters, gear cutters, saw blades, etc, although usage for punches and dies is increasing. Tool steel, in particular HSS, can also be surface treated by nitriding, laser or plasma overlays of hard coatings (e.g. Stellite) as well as by chemical or physical vapour deposition of hard carbides and nitrides. This new coating technology has extended the use of HSS.

While coatings, such as TiN, TiAlN or CrAlN significantly increase tool life, they also increase tool cost. Nevertheless, most tools in the higher-end applications today are coated as the higher cost is well balanced by the greater productivity during the machining processes.

No one composition of high-speed tool steel can meet all cutting tool requirements. The general-purpose molybdenum steels such as M1, M2, and M7 and tungsten steel T1 are more commonly used than other high-speed tool steels. They have the highest toughness and good cutting ability, but they possess the lowest hot hardness and wear resistance of all the high-speed tool steels. The addition of vanadium offers the advantage of greater wear resistance and hot hardness, and steels with intermediate vanadium contents are suited for fine and roughing cuts on both hard and soft materials.

The 5% vanadium steel (T15) is especially suited for cutting hard metals and alloys or high-strength steels, and is particularly suitable for the machining of aluminium, stainless steels, austenitic alloys, and refractory metals. Wrought high-vanadium high-speed tool steels are more difficult to grind than their particle metallurgy product counterparts. 

The addition of cobalt in various amounts allows still higher hot hardness, the degree of hot hardness being proportional to the cobalt content. Although cobalt steels are more brittle than the non-cobalt types, they give better performance on hard, scaly materials that are machined with deep cuts at high speeds.

High-speed tool steels have continued to be of importance in industrial commerce for 70 to 80 years despite the inroads made by competitive cutting tool materials such as cast cobalt alloys, cemented carbides, ceramics, and cermets. The superior toughness of high speed tool steel seems to guarantee it a continuing niche in the cutting tool materials marketplace.

HSS COMPOSITION: THE EFFECT OF SOME KEY CHEMICAL ELEMENTS

The essential elements of a steel either alone or combined with the addition of other elements is what gives the steel its inherent cutting performance, red-hardness, toughness, wear-resistance, etc. It is difficult to enumerate all the wonderful qualities steel acquires when various elements are introduced in it.

Fig 8: Electrite Uranium B tool bit.

Nevertheless, here is a summary of most of the principal alloying elements and their effect on HSS.

NOTE: All percentages given are by weight

Aluminium (Al) – Aluminium is the most effective and frequently used deoxidiser in steelmaking. Small additions are used to insure small grain size. It will combine with nitrogen and form hard aluminium nitrides, which is why it is added to nitriding steels.

Boron (B) - Boron is added to unalloyed and low alloyed steels to enhance the hardness level through enhancement hardenability. Boron added to HSS, for example, containing 18%W, 4%Cr and 1%V, enhances the cutting performance, but reduces the forging qualities.

Carbon (C) - As in all tool steels, carbon is essential to the hardenability of steel. It increases tensile strength and edge retention and improves resistance to wear and abrasion. Added in isolation, it decreases toughness. Also, it is evident that, as the wearing properties and high hot hardness depend on the presence of massive amounts of complex alloy carbides, carbon is of prime importance. The usual carbon range for high speed steels is 0.65-1.5%, of which about 0.3% is dissolved in the matrix. The hardness on the finished product increases rapidly up to about 1.0% carbon. The higher carbon grades show a fairly marked fall off in ductility.

Chromium (Cr) - Added for increased wear resistance, hardness, tensile strength, and for corrosion resistance. Cr forms large, complex carbides. A steel with at least 13% chromium is typically deemed "stainless", though another definition says the steel must have at least 11.5% free chromium (as opposed to being tied up in carbides) to be considered "stainless". Adding Chromium in high amounts decreases toughness. Chromium is a carbide-former, which is why it increases wear resistance. Unfortunately, the amount of free Chromium in the steels is almost never specified. Addition of 4% chromium is made to all high speed steels with the prime purpose of promoting depth hardening. Chromium in the absence of large quantities of retained austenite sharply retards the rate of softening in these steels, but in itself does not produce a true secondary hardening peak.

Fig 9: James Neill & Co., Sheffield, U.K. - Box of Eclipse Cobalt HSS Tool Bits.

Cobalt (Co) - Increases red hardness, also allows for higher quenching temperatures (during the heat treatment procedure). Intensifies the individual effects of other elements in more complex steels. Co is not a carbide former, however adding Cobalt to the alloy allows for higher attainable hardness and higher red hot hardness. Cobalt is optional as an alloy addition, being present in only a few of the "super grades" up to about 10% maximum, although a few special steels have higher additions. The addition of cobalt can raise the hardness by as much as 60HV, depending on the specific grade of steel. Its prime purpose is to promote red hardness, however this comes at the expense of impact strength.

Lead (Pb) - Although virtually insoluble in liquid or solid steel, lead is sometimes added to carbon steels via mechanical dispersion during pouring in order to improve machinability.

Manganese (Mn) - An important element, Manganese improves grain structure and contributes to hardenability, strength, and wear resistance. Improves the steel, deoxidizes and degasifies during steel manufacture (hot working and rolling). In larger quantities, increases hardness and brittleness.

Molybdenum (Mo) - A carbide former, prevents brittleness, and maintains strength at high temperatures. Improves machinability and resistance to corrosion. Present in many High Speed steels, and air-hardening steels (e.g. A2, ATS-34) always have 1% or more Molybdenum.

Nickel (Ni) - Adds toughness. Nickel is widely believed to play a role in corrosion resistance as well, but this is probably incorrect.

Niobium (Nb) formerly Columbium (Cb) - heat treatment of the niobium-bearing steel yields fine edged carbides, which makes the steel very tough. The introduction of niobium prevents embrittlement and improves wear resistance. In small amounts, niobium can significantly increase the yield strength and, to a lesser degree, tensile strength of steels.

Tungsten (W) - formerly known as Wolfram. Strongest carbide former after Nb and then V. W increases wear resistance. When combined properly with Chromium or Molybdenum, Tungsten will turn a steel into a High-Speed steel. The M2 high-speed steel has a high amount of tungsten; around 6%.

Vanadium (V) - Contributes to wear resistance and hardenability, and as a carbide former (in fact, vanadium carbides are the hardest carbides) it contributes to wear resistance. It also refines the grain of the steel, which contributes to toughness and allows the steel to take a very sharp edge. A number of steels contain some Vanadium, whereas M2, Vascowear, and CPM 10V, S90V, S125V (in order of increasing amounts) feature very high amounts of Vanadium. This element is always present to a minimum of 1% and generally up to 2% or 3%. It can be higher in very highly alloyed grades. Vanadium forms extremely stable carbides such as VC or V₄C₃, which are virtually insoluble at normal hardening temperatures, and thus create a very effective means of limiting grain growth.

Zirconium (Zr) - the presence of zirconium compounds reduces grain coarsening, and thus permits the use of higher hardening or carburising temperatures. It produces only slight changes in the mechanical properties of quenched and tempered steels which are generally beneficial. It produces a more uniform distortion during heat treatment than other alloying elements like vanadium. In high alloys steels, it increases hardness but decreases ductility.

TYPES, BRANDS AND MAKERS

HSS is sold under a myriad of trade names in rods, bars, flats and tool shapes. For this reason it is an all-too-often occurrence to come across a piece of branded HSS and have no idea what type or grade of HSS it is or perhaps even be unsure if it is or is not HSS.

The following information was compiled in an attempt to untangle the composition and principal uses of the many brand name tool steels (HSS and carbon) as well as introduce some of the very useful non-ferrous cutting tool alloys.

But what about Chinese and Indian tools steels? Well it is a bit of a mixed bag really. Some of these ‘imports’ perform quite well, but how can a purchaser know what these are and so avoid some of the lesser quality bits?

First it may be of help to know that of the many grades of HSS made in China, two are simply referred to as “economical” HSS. These are by analysis:

W 4% Cr 4% Mo 3% V nil%

W 3% Cr 4% Mo 2% V 2%

Clearly alongside the other HSS grades listed in the tables below these “economical” HSS grades contain comparatively low levels of tungsten and molybdenum. Not sure what the carbon content is. These are probably the types of HSS used in those very ‘economical’ boxes of drill bits and in similar versions of taps and dies labelled “HSS China”.

Just the poor finish and lack of care in grinding and sharpening these tools should be enough to put you on guard. If not you may soon find out that “economical” Chinese HSS may have some performance issues. Of course you can also buy good quality Chinese HSS.

TYPE “T” Tungsten-Rich HSS

T1 (18-4-1) typical analysis (%): C 0.7; W 18; Cr 4.0; V 1.0 – this is the original 18-4-1 high speed steel introduced around 1904. Still held up as a standard general purpose tool steel. It has a balanced combination of shock resistance and abrasion resistance. It is the easiest HSS to machine. Has high red hardness.

Principal application is for cutting tools.

T2 typical analysis (%): C 0.8; W 18.0; Cr 4.0; V 2.0; Mo 0.8 – with higher carbon and vanadium content than T1 and a small molybdenum addition this steel provides a harder and more durable tool edge. Often more economical than cobalt steels it hardens without a soft skin. Not as tough as T1.

Suitable for fine edge tools such as hobs and threading dies, form tools, twist drills, reamers, broaches and milling cutters.

T3 typical analysis (%): C 1.0; W 18.0; Cr 4.0; V 3.0; Mo 0.7 – the triple vanadium and high carbon content of this steel provide the highest wear resistance of any tool steel. It is suitable for cutting hard wrought metals or castings, material that work hardens and soft gummy materials where wear resistance is a major factor.

T4 typical analysis (%): C 0.75; W 18.0; Cr 4.0; V 1.0; Co 5.0; Mo 0.8 – the addition of 5% cobalt to T1 increases cutting ability at high temperatures, making this steel suitable for hogging cuts where high heats develop. Should be used where tools are well supported, not subject to shock and ground all over after hardening.

Generally used for cutting tools, broaches and cold extrusion punches.

T5 typical analysis (%): C 0.8; W 18.5; Cr 4.0; V 1.75; Co 8.0; Mo 0.8 – the ultimate in HSS for heavy duty cutting. Has a combination of red hardness and toughness that results in outstanding performance. Recommended for heavy duty lathe, planer and boring tools. Especially adapted for cutting hard, gritty material such as cast iron or steel, also heat treated alloy steels. Best used in tools that are well-supported and not subject to excessive shock or chattering. Cutting speeds can be about 25% faster than T1 with higher tool life.

T6 typical analysis (%): C 0.8; W 20.0; Cr 4.0; V 2.0; Co 12.0; Mo 0.8 – a high cobalt steel having the highest red hardness of any tool steel. Wear resistance is better than the lower cobalt steels.

Suitable for heavy-duty lathe and planer tools.

T7 typical analysis (%): C 0.7; W 14.0; Cr 4.0; V 2.0 – lowered tungsten content gives increased toughness with less wear resistance.

Suitable for intermittent cutting and for sand castings, hard alloys or gritty materials.

T8 typical analysis (%): C 0.8; W 14.0; Cr 4.0; V 2.0; Co 5.0; Mo 0.8 – wear resistance exceeded only by T3 combined with good red hardness make this steel suitable for severe cutting operations, especially stainless steels. It has also given good results on hard die blocks, manganese steel castings and chilled cast iron.

T9 typical analysis (%): C 1.25; W 18.5; Cr 4.0; V 4.0; Mo 0.75 – a high vanadium steel for extremely abrasive conditions. Runs best at high speeds with light cuts.

T12 typical analysis (%): C 1.0; W 14.0; Cr 4.0; V 3.0; Mo 0.75 – a tough high speed steel designed for high resistance to impact. Suitable for variable cutting, such as turning through scale and broaching.

T15 typical analysis (%): C 1.5; W 13.0; Cr 4.25; V 5.0; Co 5.0 - a tungsten super high speed steel containing high vanadium for excellent abrasion resistance and cobalt for good red hardness. Ideal for cutting difficult to machine materials where high frictional heat is present. Typical applications include broaches, milling cutters, spade drills, taps, end mills, shaper cutters.

T15 Powder Metallurgy (PM) is a tungsten high-speed steel designed for use in machining operations requiring heavy cuts, high speeds and feeds. Its primary use is in applications requiring the machining of high-hardness heat-treated materials such as high temperature alloys. The high carbon, vanadium, and cobalt contents contribute to good wear resistance, hot hardness and good hardness capabilities. T15 PM is produced by the powder metallurgy process which has resulted in improved quality from the standpoint of structural uniformity, response to heat treatment and grindability. These factors, along with increased toughness, are increased usage in the industry because of its recognized superior cutting ability.

Typical applications include roaches, chasers, form tools, heavy duty cutting tools, high production blades, milling cutters, reamers, and taps.

TYPE “M” Molybdenum-Rich HSS

M1 typical analysis (%): C 0.8; W 1.5; Cr 4.0; V 1.0; Mo 8.25 – the high-molybdenum, low-tungsten HSS which is typically used is for cutting tools of all kinds. It has good cutting ability except for heavy-duty continuous cutting operations where the ultimate in red hardness is required.

Due to its high molybdenum content M1 is susceptible to decarburisation at high temperatures, consequently in heat treating and heating for forging and annealing care must be used to prevent decarburisation.

Both toughness and wear resistance are slightly better than T1.

M2 typical analysis (%): C 0.8; W 6.0; Cr 4.0; V 2.0; Mo 5.0 - a tungsten molybdenum, general purpose grade which offers balanced shock-resistance and high toughness combined with good cutting powers. Suited for general machining of carbon, alloy and tool steel types. Offers good heat and abrasion characteristics. Standard machining operations can be carried out with M2 high speed steel tool bits. Bits are supplied hardened to approximately 62 to 66HRc.

M2 is by far the most popular high speed steel replacing T1 in most applications because of its superior properties and relative economy in general purpose cutting and non-cutting applications. A higher carbon content and balanced analysis produce properties applicable to all general-purpose high-speed uses. It has a wider heat-treating range than most of the molybdenum high-speed steels, coupled with a resistance to decarburization that is characteristic of tungsten types. M2 offers an excellent combination of red hardness, toughness, and wear resistance.

Typical applications include gear cutters, broaches, boring tools, chasers, drills, end mills, form tools, hobs, lathe and planer tools, punches, taps, reamers, and saws.

M3 typical analysis (%): C 1.0; W 6.0; Cr 4.0; V 2.75; Mo 5.0 and M3 (Class 1) typical analysis (%): C 1.05; W 6.25; Cr 4.0; V 2.5; Mo 5.7 and M3 (Class 2) typical analysis (%): C 1.2; W 5.6; Cr 4.0; V 3.25; Mo 5.5 – contains carbon and vanadium levels that are intermediate between those of M2 and M4. This gives the steel a fine balance of wear resistance and grindability and provides superior resistance to abrasion and edge breakdown. This makes M3 high speed steel a superb tool material for form tools and roll turning. Increased tool life will also be experienced in the machining of heat-treated sections, castings and similar hard materials.

M3 was developed after extensive studies of the effect of increased carbon and vanadium contents on the intermediate molybdenum-tungsten high-speed steels. The analysis was tried and proven on practically all high-speed steel applications. M3 offers the unusual combination of extremely high-edge strength at high hardness levels. With few exceptions, best life is accomplished with a minimum hardness of 65.5 Rockwell C. Experience indicates that the chemical balance achieved in M3 results in optimum combination of cutting ability, abrasion resistance, edge strength, red hardness, and long service life. M3 is more readily machined and offers less grinding resistance than higher vanadium types.

Typical applications include drills, taps, end mills, reamers, counterbores, broaches, hobs, form tools, lathe and planer tools, checking tools, milling cutters, slitting saws, punches, drawing dies, and wood working knives.

M4 typical analysis (%): C 1.3; W 5.5; Cr 4.0; V 4.0; Mo 4.75 - a high-vanadium special purpose high speed steel exhibiting better wear resistance and toughness than M2 and M3 in cold work punches, die inserts and cutting applications involving high speed and light cuts. Used for cutting tools of all types for machining operations.

M4 Powder Metallurgy (PM) a member of the molybdenum-tungsten family of high-speed steels, is a special purpose grade which utilizes its higher carbon and vanadium contents to develop excellent abrasion resistance. Produced conventionally, M4 is difficult to machine in the annealed condition and grind in the hardened condition. M4 PM is produced by the powder metallurgy process and allows an addition of 0.06 to 0.08 sulphur which provides a uniform dispersion of small sulphides throughout the structure and enhances machinability. Coupled with finer carbides and structural uniformity, better grindability is also achieved. These factors, along with increased toughness, are ideally suited for heavy-duty cold-work applications.

Typical applications include blades, broaches, chasers, die inserts, form tools, lathe and planer tools, milling cutters, punches, reamers, slitter knives, spade drills, and taps.

M6 typical analysis (%): C 0.8; W 4.0; Cr 4.0; V 1.5; Co 12.0; Mo 5.0 – has high red hardness and properties similar to T6. Suitable for cutting hard materials and heat-treated forgings. Operates at higher speeds and feeds than regular high speed steels.

Suitable for cutting hard materials and heat-treated castings. Operates at higher speeds and feeds than regular high speed steels.

M7 typical analysis (%): C 1.0; W 1.75; Cr 3.75; V 2.0; Mo 8.75 - widely used for cutting tools in machining operations. Exhibits good abrasion resistance because of its carbon and vanadium contents. It is an excellent choice for premium tools which require an outstanding balance of red hardness, edge toughness, and wear resistance. It is especially suited for machining semi-hard, heat-treated steel at about 300-350 Brinell hardness.

M8 typical analysis (%): C 0.8; W 5.0; Cr 4.0; V 1.5; Mo 5.0; Nb 1.25 – a niobium (formerly known as columbium) bearing high speed steel with unusually high wear resistance. For general-purpose cutting. Resists decarburisation in hardening.

M10 typical analysis (%): C 0.85; Cr 4.0; V 2.0; Mo 8.0 – one of the high-molybdenum types of HSS it contains chrome and vanadium but is tungsten-free. A general purpose HSS employed in tooling applications requiring excellent wear and cutting capabilities including punches, taps, drills, broaches, lathe tools, shaper tools, planer tools, etc. May also be used for boring tools, countersinks and reamers.

Due to its high molybdenum content M10 is susceptible to decarburisation at high temperatures, consequently in heat treating and heating for forging and annealing care must be used to prevent decarburisation.

M15 typical analysis (%): C 1.5; W 6.5; Cr 4.0; V 5.0; Co 5.0; Mo 3.5 -

M20 typical analysis (%): C 0.6; W 4.0; Cr 5.0; V 1.25; Co 2.5; Mo 8.0; Boron 0.25 – an economical HSS suitable for taps, threading dies, form tools and broaches.

M30 typical analysis (%): C 0.8; W 2.0; Cr 4.0; V 1.25; Co 5.0; Mo 8.0 – high red hardness and wear resistance with loss of toughness. Recommended for turning chilled iron, locomotive tyres, and heat-treated forgings and castings. Subject to decarburisation.

M33 typical analysis (%): C 0.9; W 1.75; Cr 3.75; V 1.0; Co 8.25; Mo 9.25 - typically used for cutting tools of all kinds.

M34 typical analysis (%): C 0.9; W 2.0; Cr 4.0; V 2.0; Co 8.0; Mo 8.0 -

M35 typical analysis (%): C 0.9; W 6.0; Cr 4.0; V 2.0; Co 5.0; Mo 5.0 - used in conditions where the demand for hot hardness is important. It is also a good quality wear resistant grade for cold work applications. Commonly used for cutting tools including broaches, milling cutters, reamers, end mills and saw blades. Also known as “5% Cobalt HSS” M35 is a development of M2 and contains 5% cobalt which gives improved hardness, wear resistance and red hardness. It may be used when cutting higher strength materials. M35 is also known as HSSE or HSS-E.

M36 typical analysis (%): C 0.9; W 6.0; Cr 4.0; V 2.0; Co 8.0; Mo 5.0 – developed for heavy duty cutting where the maximum of red hardness is required.

M38A typical analysis (%): C 1.5; W 6.5; Cr 4.5; V 4.75; Co 5.0; Mo 5.0 – similar to M36 but with only 5% cobalt and increased vanadium for better wear resistance.

TYPE “M” Molybdenum Ultra-Hard HSS

M40 typical analysis (%): C 0.6; W 2.0; Cr 4.0; V 2.0; Co 8.0; Mo 5.0; Boron 0.5 – more highly alloyed than M20 this steel has wear resistance said to be several times that of other high speed steels. Suitable for heat-treated steel, cast iron, brass, plastics, and other abrasive materials.

M41 typical analysis (%): C 1.15; W 6.25; Cr 4.25; V 2.0; Co 5.0; Mo 3.75 - a Molybdenum ultra-hard HSS whose primary application is as cutting tools for machining operations.

M42 typical analysis (%): C 1.1; W 1.5; Cr 3.75; V 1.15; Co 8.0; Mo 9.5 - a molybdenum-cobalt grade with a high hardness (up to 70 Rockwell C) and superior hot hardness offering excellent cutting performance and excellent wear resistance. As an 8% cobalt high speed steel type M42 tool bits are suited for tougher materials such as work hardening types. They offer increased tool life with retention of the cutting edge. M42 tool bits are supplied hardened to approximately 65 to 68HRc. The alloy has excellent hot hardness and wear resistance and is commonly employed to machine difficult to machine materials including the superalloys.

This steel is ideal for machining higher strength materials and work hardening alloys such as stainless steels, Nimonic alloys etc. Despite its high hardness, M42 has good grindability characteristics due to lower vanadium content. The carbon content is higher than in most high-speed steels, and with this balanced composition, contributes to wear resistance and hot hardness as well as the high hardness.

Typically employed in broaches, circular and dovetail form tools, drills, end mills, lathe tools, milling cutters, punches, reamers, slitting saws, and twist drills, hobs, taps, form and gear cutters, and chasers.

M43 typical analysis (%): C 1.25; W 1.75; Cr 3.75; V 2.0; Co 8.25; Mo 8.75 -

M44 typical analysis (%): C 1.2; W 5.25; Cr 4.25; V 2.25; Co 12.0; Mo 6.25 -

M46 typical analysis (%): C 1.25; W 2.0; Cr 4.0; V 3.25; Co 8.25; Mo 8.25 - primarily used for cutting tools.

M47 typical analysis (%): C 1.1; W 1.5; Cr 3.75; V 1.25; Co 5.0; Mo 9.5 -

M48 typical analysis (%): C 1.5; W 10.0; Cr 4.0; V 3.0; Co 9.0; Mo 5.25 - a tungsten type super high speed steel hardened to RC 68-69. It contains high vanadium for excellent abrasion resistance and cobalt for excellent red hardness. Ideal for special purpose cutting tools requiring super high hardness and red hardness, excellent wear resistance and good toughness.

Typical applications include milling cutters, form tools, end mills, broaches, cutting tool inserts, reamers, extrusion die inserts, cut-off tools, lathe tools, shaper tools, and taps.

M50 typical analysis (%): C 0.85; Cr 4.0; V 1.0; Mo 4.25 - most often employed in tooling applications where abrasion resistance is less important, such as woodworking tools and commercial twist drills. Considered intermediate high speed steel in view of the lower total alloy content than standard types. These leaner alloy grades normally are limited to less severe service conditions.

M51 typical analysis (%): C 1.25; W 9.5; Cr 4.0; V 3.25; Co 10.0; Mo 3.5 -

M52 typical analysis (%): C 0.9; W 1.25; Cr 4.0; V 2.0; Mo 4.25 - most often employed in tooling applications where abrasion resistance is less important, such as woodworking tools and commercial twist drills. Considered an intermediate high speed steel in view of the lower total alloy content than standard types. These leaner alloy grades normally are limited to less severe service conditions.

Suited for applications not requiring a full HSS such as body stock for carbide tipped drills and reamers, wood cutters, pipe taps, thread chasers and small drills.

M61 typical analysis (%): C 1.8; W 12.5; Cr 4.0; V 5.0; Mo 6.5 -

M62 typical analysis (%): C 1.25; W 6.25; Cr 3.75; V 2.0; Mo 10.5 -

M100A typical analysis (%): C ?; W ?; Cr ?; V ?; Mo ? -

COBALT-BASED ALLOYS: The Non-Ferrous Cutting Tools

Fig 10: Arthur Balfour and Co, Sheffield, U.K. - Balfalloy hard metal price list - circa 1940.

Non-ferrous alloys used for cutting tools are often called cutting alloys. These are distinct from alloy steels, although some may contain iron and be allied to the super high speed steels. They may have a base of nickel or cobalt and usually contain tungsten.

An early alloy of this type knows as ‘Cooperite’ contained 80% nickel, 14% tungsten, 6% zirconium (Zr) or less tungsten and some silicon and molybdenum. An English cutting alloy sold by Samuel Osborn & Co Ltd under the name SOBV cutting alloy contained high percentages of chromium, cobalt, tungsten, and iron with some vanadium and molybdenum and is really a super HSS.

Fig 11: Deloro Stellite, Birmingham, U.K. - Cutting tools advertisement - 1955.

Stellite by the Haynes Stellite Co is made in various grades for cutting tools, hard facing valves, rock bits and crusher rolls. It is typical of the non-ferrous hard metals and the cutting properties are inherent in the alloy and are NOT produced by heat treatment. Stellite contains from 40-75% cobalt, 15-35% chromium, 10-25% tungsten and about 2% carbon and small amounts of iron and molybdenum. It retains its hardness at red heat.

The use of cast-cobalt cutting tools should be considered when:

• Relatively low surface speeds cause build-up with cemented carbides;

• Machines lack the power or rigidity to use cemented carbides effectively;

• Higher production is required than is possible with high-speed tools; and

• Machining rough surfaces of castings where the surfaces contain abrasive material such as sand, oxide, slag or refractory particles.

These cutting alloys were designed to bridge the gap between HSS and cemented carbides.

Fig 12: The Haynes Stellite Company, Kokomo, Indiana, U.S. - Advertisement: Stellite Not Steel but its Master - circa 1920.

Stellite alloys possess properties somewhere between high speed steel (HSS) and carbide. They can be ground with a standard grinding wheel, though the process can be a bit slow going. They're tough and work well on interrupted cuts and on castings that would tend to chip carbide, though they're more prone to chipping than HSS.

High lubricity is another feature and that prevents welding of material on the tool tip. They cannot be annealed and thus retain their hardness and cutting ability to red heat. In general, they will operate at 2X or more the speed of HSS, but not that of carbide.

Modern cast alloy tools will be ground on all sides and look similar to HSS tooling. They resist corrosion extremely well and may stand out in used tooling for that reason. 

Don't be put off by the appearance of older cast alloy tooling; some may look like it was cast in a backyard barbecue. It will be dark in colour and have significant imperfections and poor grinding.

New cast alloy blanks may still be available from at least three manufacturers, but don't expect to get them cheap!

Stellite is used in the form of solid cast tool bits, tips, parting blades, milling blades and tipped tools. The alloy is at its best when it has plenty of work to do and it is tough enough to take interrupted cuts without chipping. It cannot be rolled or forged and is shaped by casting and subsequent grinding.

The tool bits are available in inch and metric sizes.

Stellite retains its hardness at temperatures of 700°C upwards to a much higher degree than HSS or other tool alloys.

Fig 13: ANI-VR Wesson, Florida, U.S. - Catalogue of Tantung Cutting Tool products.

The Tantung cast alloy cutting tool material is composed principally of chromium, tungsten, columbium, and carbon in a cobalt matrix. These elements combined in the proper proportions and cast in chill moulds give Tantung its most important characteristic; the ability to retain its cutting hardness at temperatures of up to 815°C (1500°F). It is neither high speed steel nor carbide.

Tantung has a high transverse rupture strength, low coefficient of friction and excellent resistance to corrosion. It is tough, readily absorbs shock and impact, and is non-magnetic; it likes to work.

As a cutting tool, it is ideal for all turning, facing, boring, milling, and cut-off applications on nearly every type of metal as well as non-metals. Tantung can be run at surface speeds of up to 450 sfpm, but performs best at speeds of 100-250 sfpm and can be used to excellent advantage on machines where speed, power, and rigidity are limited. In addition, it will not anneal or lose its cutting edge as will HSS when subjected to high-red heats generated during the cutting cycle.

Tantung G is recommended for general purpose machining of both ferrous and non-ferrous metal and general woodworking operations. For VR/Wesson catalogue items, Tantung G Hardness is quoted as 60 to 63 Rockwell C and transverse rupture strength is 300,000 psi minimum.

Typical composition of Tantung G is cited as Cobalt 35-40%; Chromium 27-32%; Tungsten 14-19%; Nickel 7%; Carbon 2-4%; and Iron 2-5%.

Fig 14: Tantung G HSS Tools.

The Carbon Tool Steels

WATER HARDENING CARBON TOOL STEELS

W1 plain carbon tool steels are made in four grades of quality: Special, Extra, Standard and Commercial. Special (Grade 1) and Extra (Grade 2) conform to rigid macroscopic, microscopic or hardenability specifications, special being the highest quality. They are suitable for tools and dies requiring steels of uniform high quality. Standard (Grade 3) and Commercial grades are not always made in electric furnaces and meet less rigid processing requirements. They are suitable for many general-purpose applications or for short-run jobs. The standard carbon range is usually 0.95 to 1.1%.

W2 is a shallow hardening tool steel. Due to its vanadium content, the grain is superior in toughness and resistance to fatigue compared to straight carbon tool steels thereby making it desirable for many types of impact tools.

W3 has higher vanadium content and this provides better toughness.

W4 (ASM composition C 0.6-1.4; Cr 0.25) - the chromium content increases the depth of hardness and reduces the danger of soft spots. A number of these steels were available in several carbon ranges.

W5 (ASM composition C 0.6-1.4; Cr 0.5) - a higher chromium content than W4 for increased depth of hardness.

W7 (ASM composition C 0.6-1.4; Cr 0.5; V 0.2) - the addition of vanadium to W5 provides more toughness because of the finer grain structure.

W8A - the molybdenum content provides deeper hardening, increased toughness and red hardness.

Carbon steels have carbon as the principal control element generally in the range of 0.85% to 1.15%. When hardened, the surface becomes intensely hard providing good wear qualities. Tools made from carbon steel can be sharpened to a keen edge with a high finish. Some special steels are made with the carbon content as low as 0.50% or as high as 1.50%.

The significant characteristic of carbon tools steels is that differential hardening results from heat treatment. This is better described as the “case” and “core” effect.

The case is a uniformly hard, outer area which is file hard in the as-quenched condition. The degree of hardness is in the range of 65-67 Rockwell C.

However, the core hardens to a lesser degree – about 40-45 Rockwell C. This core supplies support for the hard case. This also means that there is a limit to the amount of grinding or sharpening that can be done. If the hard case is ground away the cutting or wear resisting qualities are lost. But this seldom occurs in practice due to the small amount of metal removed.

The elasticity required to stand up under repeated stresses makes carbon tools steels useful in applications such as blacksmiths tools, cold chisels, hand punches, jeweller die blocks and cold forming tools. The intensely hard case which permits sharpening to a keen edge also make them valuable for tools such as knives, razors, shears and wood chisels.

These steels require a fast quench to obtain maximum hardness. Therefore, they are quenched in water or a water solution such as brine.

OIL-HARDENING TOOL STEELS

SAE composition: C 1.2; Mn 0.25; Cr 0.2; V optional; and W 0.5. This group of steels was developed for maximum safety in hardening and minimum dimensional change after heat treatment. They are preferred for tools or dies with adjacent thick and thin sections, sharp corners or numerous holes. Tools and dies made from O1 will have good wearing qualities since the tungsten and higher chromium content gives improved wear resistance over the straight manganese grades. They have better wear resistance than the water-hardening grades but are not quite so good in shock resistance. Machining properties are good and material cost is relatively low.

The addition of a substantial amount of manganese plus small amounts of chromium and tungsten permits carbon tool steel to harden in oil. The “case-core” condition of the water hardening tool steels generally disappears and these steels will harden all the way through even in relatively large sections.

O1 (SAE composition: C 0.9; Mn 1.2; Cr 0.5; V 0.2 optional; W 0.5) - is an oil-hardening, non-deforming tool steel which can be hardened at relatively low temperatures. Tools and dies made from O1 will have good wearing qualities since the tungsten and higher chromium content gives improved wear resistance over the straight manganese grades. Typical applications include bushings, forming dies, forming rolls, and gauges.

O2 (SAE composition: C 0.9; Mn 1.6; Cr 0.55 optional; V 0.2 optional; Mo 0.3 optional) – the higher manganese content gives this steel slightly better cutting ability and non-deformation properties than O1. Toughness is considerably better and is the best of any of the oil-hardening group. Suitable for blanking, forming, trimming and moulding dies, taps and threading dies, broaches and reamers.

O6 (SAE composition: C 1.45; Mn 0.75; Mo 0.25) - is an oil-hardening cold work steel which has outstanding machinability resulting from small particles of graphitic carbon uniformly distributed throughout the steel. These particles increase resistance to wear and galling in service. For an oil-hardening steel, 06 holds size well during heat treating. Typical applications include pneumatic hammers, spinning tools, punches, stamps, gauges, wear plates, and cams.

O7 (ASM composition: C 1.2; Cr 0.75; W 1.75; Mo 0.25 optional) – better cutting ability than the other oil-hardening steels except D3 with high hardness and fairly deep hardening. Suitable for taps, threading tools, drills, reamers, cutting tools for brass, and punches and dies for light stock.

SHOCK-RESISTING TOOL STEELS

S1 (SA composition: C 0.5; Mn 0.25; Cr 1.4; V 0.2; W 2.25; Mo optional) - excellent shock resistance for both hot and cold operations. Though red hardness is not as good as in the H-steels, it is better than other S-steels. Suitable for punches, chisels and pneumatic tools.

S2 (SAE composition: C 0.5; Mn 0.4; V 0.25; V optional; Mo 0.5) - this steel has the highest toughness of any tool steel. Red hardness is not as good as S1. Other characteristics are about the same as S1. Suitable for punches, hammer dies, and swaging dies.

S3 (ASM composition: C 0.5; Cr 0.75; W 1.0) - toughness is combined with fair cutting ability. Suitable for chisels, rivet sets, punches, screwdrivers and shear blades.

S4 (ASM composition: C 0.55; Mn 0.8; Cr 0.3 optional; V 0.25 optional; Mo optional) - this is the basic silicon-magnesium steel. Good toughness suitable for shear blades, chisels, punches and pneumatic tools.

S5 (SAE composition: C 0.55; Mn 0.8; Cr 0.3 optional; V 0.25 optional; Mo optional) – toughness almost as good as S2 and better red hardness than S4 because of the molybdenum content. A reduced tendency to distort or crack in heat treatment is accordingly combined with high toughness in S5. Suitable for chisels, heavy-duty punches, rivet busters, drift pins, spring collets and nail sets.

S6A – a general purpose tool steel for shock resistance where accurate temperature control is not available. Can be hardened over a wide range with satisfactory results. No tempering required.

S7 - is a general purpose air-hardening tool steel with high impact and shock resistance. It has good resistance to softening at moderately high temperatures. This combination of properties makes it suitable for many hot work and cold work applications. Excellent combination of high strength and toughness. Useful in moderate hot work as well as cold work tooling. Added size stability when air hardened. Typical applications bull riveters, concrete breakers (moll points), riveting dies, powder metal dies, notching dies, dowels, drills, drill plates, hubs, plastic mould dies, cold forming dies, blanking dies, bending dies, and master hobs.

S8A -

S9A -

S10A -

S11A – chrome-manganese. Toughness combined with ease of heat treatment and machining. Suitable for hard chisels and battering tools.

S12A – chrome-magnesium-tungsten. Toughness combined with moderate wear resistance. Suitable for forging dies and blacksmiths tools.

AIR-HARDENING TOOL STEELS

Air hardening tool steels represent an even better improvement over water hardening steels than the oil hardening types. The slower cooling in the hardening phase results in less intense strains with less distortion. While this is a notable characteristic, these steels are also more resistant to abrasion than the oil hardening types.

In general the most important element in making these steels air hardening is molybdenum. Vanadium is introduced to prevent grain coarsening.

A2 (SAE composition: C 1.0; Mn 0.6; Cr 5.25; V 0.4 optional; Mo 1.1) - is an air-hardening tool steel containing five percent chromium. Replaces the oil hardening (O1 type) when safer hardening, less distortion and increased wear resistance are required. Typical applications include thread roll dies, long punches, rolls, precision tools, gauges, coining dies, mandrels, shear blades and slitters.

A4 (ASM composition: C 1.0; Mn 2.0; Cr 1.0; Mo 1.0) – low hardening temperature of the steel is combined with good toughness, though wear resistance is lower than the other non-deforming steels. Suitable for punches, blanking and forming dies, and gauges.

CARBON TOOL STEELS – SOME UNKNOWN GRADES

Oldies but Goodies: Non-AISI Grades of HSS

Just to make matters even more confusing some makes and grades of HSS do not conform to any of the AISI classes. The table below lists just some of these steels. No doubt there are more ‘non-conforming’ tool steels out there.

Products Made by Fagersta Stainless AB & Erasteel Inc

Fagersta WKE-4 or WKE 4 is a cobalt HSS and is now obsolete. Typical analysis is C 1.25%; Cr 4.1%; Mo 3.1%; V 3.1%; W 9.0% and Co 9.0%.

Fagersta WKE-42 or WKE 42 is a conventional cobalt HSS with typical analysis of C1.27%; Cr 4.0%; Mo 3.6%; W 9.5%; Co 10.0% and V 3.2%.

Fagersta WKE-45 or WKE 45 was originally made in Sweden, it is a molybdenum, super-cobalt HSS with 11% cobalt and has greater red hardness and more wear resistance than almost any other HSS making it excellent for cutting 300-series stainless steel. Typical analysis: C 1.4%; Cr 4.2%; Mo 3.5%; W 9.5%; Co 11.0%

Products Made by Darwins Ltd

Darwins Ltd, Fitzwilliam Works, Sheffield made a wide variety of alloy and special steels. The range included many well-known brands of high speed steels, tool steels, hot-work steels, steels for aircraft parts, stainless steels, and steels specially developed to meet the needs of modern engineering generally including "Darwin 505" Cobalt Tungsten HSS, and "Cobalt Fastwork" and "Vanadia" hacksaw blades.

Tool Steel Manufacturers Past and Present

Fig 15: Samual Osbourne & Co., Sheffield, U.K. - Steel Advertisement - 1892.

Fig 16: Jonas & Colver Limited, Sheffield, U.K. - Steel Advertisement - 1920.

REFERENCES

ALLEGHENY LUDLUM STEEL CORPORATION Tool Steel Handbook. Allegheny Ludlum Steel Corp, PA, USA, 1951

ATLAS STEELS LTD The Selection and Treatment of Tool and Machinery Steels. Atlas Steels Ltd, Canada, 1960

BETHLEHEM STEEL CO Bethlehem Tool Steels. Catalog 257-A, Bethlehem Steel Co., Bethlehem, PA, USA, 1954

BRADY, George S Materials Handbook. McGraw-Hill, New York, 5^th edition, 1944

CARPENTER STEEL CO Carpenter Matched Tool and Die Steels. The Carpenter Steel Co, Reading, PA, USA, 1955

COMMERCIAL STEELS (Australia) LTD English Steel Corporation Products – Steels. Commercial Steels Ltd, Sydney, no date

COMMONWEALTH STEEL CO LTD Comsteel Alloy and Tool Steels. Commonwealth Steel Co Ltd, Waratah, NSW, Australia, no date (c.1965)

CRUCIBLE STEEL COMPANY OF AMERICA The Crucible Steel Pocket Data Book. Crucible Steel Co., Pittsburgh, USA, 1959 (ADV 176-100M-3/59)

CRUCIBLE STEEL CORPORATION Crucible Rex High Speed Tool Bits - Price List. Crucible Steel Corp, Pittsburgh, PA, USA, July 1968

CRUCIBLE SPECIALTY METALS DIVISION Crucible Steel and High Speed Steel Selector. Colt Industries, Syracuse, New York, USA

CRUCIBLE STEEL COMPANY Tool Steel …. For the Non-Metallurgist. Crucible Steel Co, Pittsburgh, PA, USA

CTMA Classification and Identification of High Speed Steels and Cemented Carbide Cutting Grades. Cutting Tool Manufacturers Association, Birmingham, USA, 1980

DELORO STELLITE LTD Machining with Stellite. Deloro Stellite, Swindon, England, 1963, Brochure B14E

BALFOUR, Sir Arthur Hints to practical users of tool steel. The Eagle & Globe Steel Co Ltd, Sheffield, England, no date

FIRTH STERLING INC Catalog 55R. Firth Sterling Inc, Pittsburgh, PA, USA, 1956

Le GRAND, Rupert The New American Machinist’s Handbook. McGraw-Hill, New York, 1955

SEED, Alec T Pioneers for a Century 1852-1952: A history of the growth and achievement of Samuel Osoborn & Co., LimitedClyde Steel Works Sheffield. no date

TIMKEN Practical Data for Metallurgists. The Timken Company, 15^th edition, 2006

WOLDMAN, Norman E and Albert J DORNBLATT Engineering Alloys: names, properties, uses. American Society for Metals, 1936