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Machine Shop Work:
Action, Use and Care of Single Point Cutting Tools:
No. 2: Fundamentals of End Cutting Tools
"This is a motion picture study of representative single point end cutting tools in action. Six representative tools are shown and the various uses and characteristics of each discussed in detail. The film opens with views of the grooving and nicking tool. The parts of the tool are named, pointed out, and the relationship of each part to the other parts of the tool are explained. Attention is called by picture and commentary to the end cutting edge and to the fact that this is the widest part of the cutting end. Closeup views of the grooving tool in action serve to explain why all end cutting tools have a minimum heel clearance and are usually set on the center line and square with the work." Produced by the Calvin Company.
Originally a public domain film, slightly cropped to remove uneven edges, with the aspect ratio corrected, and one-pass brightness-contrast-color correction & mild video noise reduction applied.
The soundtrack was also processed with volume normalization, noise reduction, clipping reduction, and/or equalization (the resulting sound, though not perfect, is far less noisy than the original).
Wikipedia license: http://creativecommons.org/licenses/by-sa/3.0/
A tool bit is a non-rotary cutting tool used in metal lathes, shapers, and planers. Such cutters are also often referred to by the set-phrase name of single-point cutting tool, as distinguished from other cutting tools such as a saw or water jet cutter. The cutting edge is ground to suit a particular machining operation and may be resharpened or reshaped as needed. The ground tool bit is held rigidly by a tool holder while it is cutting...
Back rake is to help control the direction of the chip...
Side Rake along with back rake controls the chip flow and partly counteracts the resistance of the work to the movement of the cutter...
Nose Radius makes the finish of the cut smoother...
Originally, all tool bits were made of high carbon tool steels with the appropriate hardening and tempering. Since the introductions of high-speed steel (HSS) (early years of the 20th century), sintered carbide (1930s), ceramic and diamond cutters, those materials have gradually replaced the earlier kinds of tool steel... Most tool bits today are made of HSS, cobalt steel, or carbide.
Carbides and ceramics
Carbide, ceramics (such as cubic boron nitride) and diamond, having higher hardness than HSS, all allow faster material removal than HSS in most cases... The cutting edge is usually either screwed or clamped on (in this case it is called an insert), or brazed on to a steel shank (this is usually only done for carbide)...
Almost all high-performance cutting tools use indexable inserts...
Tool bits have been used for centuries...
A substantial technological advance occurred in the 1890–1910 period, when Frederick Winslow Taylor applied scientific methods to the study of tool bits and their cutting performance (including their geometry, metallurgy, and heat treatment, and the resulting speeds and feeds, depths of cut, metal-removal rates, and tool life). Along with Maunsel White and various assistants, he developed high speed steels... he also determined optimum geometry (rake angles, clearance angles, nose radiuses, etc.). He developed Taylor's Equation for Tool Life Expectancy. After Taylor, it was no longer taken for granted that the black art of individual craftsmen represented the highest level of metalworking technology...
Stellite soon joined high speed steels as a material for single-point cutters. Although diamond turning had been around for a long time, it was not until these new, expensive metals came about that the idea of cutting inserts became commonly applied in machining. Before this, most single-point cutters were forged entirely of tool steel (then ground at the tip)... Between 1900 and 1950, it was still not uncommon for a machinist to forge a tool from carbon tool steel.
Today, among the single-point cutters used in mass production (such as of automotive parts), insert tools using carbide and ceramic far outnumber HSS or cobalt steel tools. In other machining contexts (e.g., job shops, toolrooms, and hobbyist practice), the latter are still well represented..