Carbide and Carbide-Tipped

See also Tool Steel [might be worth treating the two terms together 4-9-08]

Carbide, as a term, according to the Oxford English Dictionary and my own Barnhart Dictionary of Etymology (1988) seems to have been coined circa 1865. However, check below for some recent evidence (3-29-07) about the use of the term in texts.

1851 carbide reference from MOA

The "snippet" of text "Metallic Iron" shows an 1851, "first use" of the term, carbide, in Dr C. Remigius Fresenius (1818-1897), Manual of Qualitative Chemical Analysis, page 140. (It comes from the database, Making of America, full-text" database that covers books and periodicals published in America between 1800 and 1920.

Carbide-tipped development: Henry B. Allen, "Improvements in Steels for Wood Knives and Saws", American Society of Mechanical Engineers. Transactions, v. 53 WDI, pages 43-47, 1930.

Discusses improvements in steels for wood knives and saws  giving various types now in use and their relative value for different woods including present developments of cemented tungsten carbide.

Carbide-tipped's Application to Amateur Woodworking (establishing date):

Some shaper cutter blades are carbide-tipped for much greater resistance to wear. As with other cutting tools, it is important to keep a sharp edge on the shaper cutters.

Source:Herman Hjorth, “The Router”, Home Craftsman 18 1949, pages 56-57.

A silicon carbide hone, especially shaped for router bits and shaper cutters, is available and is very useful for honing router bits and shaper cutters to keep them at peak cutting efficiency. It can be used on either high-speed steel or carbide-tipped tools.

Source:  Robert Campbell and N H Mager How to Work with Tools and Wood, Stanley 1952 page 312-315.

Carbide cutters have made a place for themselves and, when properly applied, run almost indefinitely without sharpening. Their use in saws and knives will increase as their qualities gain wider recognition.

Source: Judson H. Mansfield, "Woodworking Machinery: History of Development from 1852—1952", Mechanical Engineering: The Journal of the American Society of Mechanical Engineers, Dec 1952, pp 983-995.

Carbide Tipped Tools

Sintered carbides are a natural evolution of the art of powder metallurgy. Powder metallurgy involves the production, by mechanical or chemical means, of a metal powder and the union of this powder, below the melting point of the major constituent, into a reasonably strong solid form. Mention has been made of the fact that high-speed steels contained quantities of carbide-forming elements. The elements in steel forming carbides in great quantities are chromium, tungsten and molybdenum. The powder metallurgist has developed the production of several sintered metallic carbides.

Probably the best known of these is tungsten carbide, though much work has been done with carbides of tantalum, molybdenum, aluminum, zirconium, and columbium. Basically, the production of these carbides is about the same as that of tungsten carbide.

Tungsten is recovered from the ore by chemical means as metallic powder, freed of acid and water, and further reduced in a hydrogen atmosphere furnace to assure production of pure metallic tungsten powder. Variations of the conditions of production will vary the grain size and shape of the resultant metallic tungsten, which will vary the character of the tungsten carbide ultimately produced. The pure tungsten powder is mixed with pure carbon in the form of lampblack in the ratio of 94 to 6 by weight.

The thoroughly mixed tungsten and carbon are packed in graphite containers and heated, converting the mechanical mixture into a chemical compound. This chemical compound, true tungsten carbide, is broken up, ball-milled to proper size, mixed with a binding agent, and reformed to shape under pressure and again sintered. The carbide is now in final form possible of production in various grades dependent on the ingredients.

Source: R J DeCristoforo, DeCristoforo's Complete Book of Power Tools, Both Stationary and Portable New York: Harper, 1972, page 178

Explaining Carbide

From R J DeCristoforo, The Table Saw Book Blue Ridge Summit, PA: Tab Books, 1988. pp 71-73.

(Of all authors of woodworker's manuals, I think that I admire the most DeCristoforo's careful step-by-step progression, especially when he introduces concepts he thinks will be unknown by his readers. His strength is that he recognizes that many readers, especially newbies -- are not acquainted with the vocabulary in the field, and -- so limited -- without some background information, do not readily adequately understand what is being described. An example of what I mean about DeCristoforo's style is below.)

Saw Blades with Tungsten-Carbide Teeth

It wasn't too long ago that carbide-tipped saw blades became generally available. Now they are available in as many concepts as you will find in all-steel blades. The basic ones are designed as combination units, or specifically for crosscutting or ripping. One of the major advantages of a carbide-tipped blade is that, if it is correctly used and maintained, it will stay sharp longer than a steel blade.

Another asset is that the teeth on a carbide blade cut a wider kerf than the blade's gauge. So, since the teeth are not set, they generally will produce smoother cuts than comparable all-steel blades that must have set teeth in order to function efficiently.

What Is Tungsten Carbide?

If you use the words cemented carbide to describe the tooth material on a carbide-tipped saw blade, you will be technically correct. Tungsten carbide is man-made, an alloy of powdered tungsten and carbon permanently bonded by vacuum sintering, a combination of high temperature and extreme pressure. The final product can contain as much as 94 percent tungsten carbide, with the balance composed of a binder such as cobalt powder.

In order to understand what a carbide-tipped saw blade is and what it can do, you must know that there are many grades of cemented carbides used in the saw-blade industry. The most common of these are designated as C1,C2, C3, and C4. The difference between the grades has to do with resistance to shock and wear. C4 has the lowest shock resistance, but the highest wear resistance. C1 is low on wear resistance, but high on shock resistance. A C2 grade, which is about medium in both areas, is often used on special ripping saws that have a flat-top grind and extreme hook, and on blades with a triple-chip grind and minimum hook that are designed for sawing nonferrous metals. C4 seems to be the proper choice for general-purpose and crosscut blades.

Not all carbide-tipped saw blades are manufactured to optimum specifications. Some important aspects to examine before you buy follow:

The size of the carbide tips, since the larger the tips, the more times it can be sharpened before the tips must be replaced.

The braze connection between the carbide and the blade. If pit marks, tiny holes, are evident, then the blade has not been manufactured to high standards.

The way the tooth is mounted. As shown in Fig. 4-26, it should be seated in its own niche, rather than simply abutted against an edge.

You can expect much from a single carbide-tipped saw blade, but not everything. The characteristics of wood and other materials and the various methods of sawing affect the design of the super blades, just as they do all-steel blades. There is a clear difference, for example, between teeth that are shaped specifically for ripping and those that do an optimum job when crosscutting. You will find differences even among the blades designated as "all-purpose" and those listed as "combination" types. Examples of carbide-tipped saw blades are displayed in Figs. 4-27 through 4-31.

An important point to remember is that, while tungsten carbide is a very tough material —second only to diamonds in hardness—it is also very brittle. Any carbide-tipped saw blade should be handled, and used, with tender, loving care.

Sources:[Anonymous] "Your Quick Reference to Carbide-Tipped Circular Saw Blades", Wood No 20 December 1987, pages 60-62. ( Dated, maybe, but still a useful intro, especially given its large colored diagrams.) [Anonymous] "One Arizona Family's Daily Grind: High-Tech Saw-Blade Manufacturing", Wood no 22(April 1988), pages 60-63, and 80.