Text C Milling machine tooling

There is some degree of standardization of the tooling used with CNC Milling Machines and to a much lesser degree with manual milling machines.

CNC Milling machines will nearly always use SK (or ISO), CAT, BT or HSK tooling. SK tooling is the most common in Europe, -while CAT tooling, sometimes called V-Flange Tooling, is the oldest variation and is probably still the most common in the USA. CAT tooling was invented by Caterpillar Inc. of Peoria, Illinois in order to standardize the tooling used on their machinery. CAT tooling comes in a range of sizes designated as CAT-30, CAT-40, CAT-50, etc. The number refers to the Association for Manufacturing Technology (formerly the National Machine Tool Builders Association (NMTB)) Taper size of the tool.

 

CAT-40 Toolholder

An improvement on CAT Tooling is BT Tooling, which looks very similar and can easily be confused with CAT tooling. Like CAT Tooling, BT Tooling comes in a range of sizes and uses the same NMTB body taper. However, BT tooling is symmetrical about the spindle axis, which CAT tooling is not. This gives BT tooling greater stability and balance at high speeds. One other subtle difference between these two toolholders is the thread used to hold the pull stud. CAT Tooling is all Imperial thread and BT Tooling is all Metric thread. Note that this affects the pull stud only, it does not affect the tool that they can hold, both types of tooling are sold to accept both Imperial and metric sized tools.

SK and HSK tooling, sometimes called "Hollow Shank Tooling", is much more common in Europe where it was invented than it is in the United States. It is claimed that HSK tooling is even better than BT Tooling at high speeds. The holding mechanism for HSK tooling is placed within the (hollow) body of the tool and, as spindle speed increases, it expands, gripping the tool more tightly with increasing spindle speed. There is no pull stud with this type of tooling.

The situation is quite different for manual milling machines — there is little standardization. Newer and larger manual machines usually use NMTB tooling. This tooling is somewhat similar to CAT tooling but requires a drawbar within the milling machine. Furthermore, there are a number of variations with NMTB tooling that make interchangeability troublesome.

 

Boring head on Morse Taper Shank

 

Two other tool holding systems for manual machines are worthy of note: They are the R8 collet and the Morse Taper #2 collet. Bridgeport Machines of Bridgeport, Connecticut so dominated the milling machine market for such a long time that their machine "The Bridgeport" is virtually synonymous with "Manual milling machine." The bulk of the machines that Bridgeport made from about 1965 onward used an R8 collet system. Prior to that, the bulk of the machines used a Morse Taper #2 collet system.

As an historical footnote: Bridgeport is now owned by Hardinge Brothers of Elmira, New York.

History

Text D 1810s-1830s

Milling machines evolved from the practice of rotary filing—that is, running a circular cutter with file-like teeth in the headstock of a lathe. Both rotary filing and later true milling were developed in order to reduce the time and effort spent on hand-filing. The full, true story of the milling machine's development will probably never be known, because much of the early development took place in individual shops where generally no one was taking down records for posterity. However, the broad outlines are known. Rotary filing long predated milling. A rotary file by Jacques de Vaucanson, circa 1760, is well known. It is clear that milling machines as a distinct class of machine tool (separate from lathes running rotary files) first appeared between 1814 and 1818. Joseph W. Roe, a respected founding father of machine tool historians, credited Eli Whitney with producing the first true milling machine. However, subsequent scholars, including Robert S. Woodbury and others, suggest that just as much credit belongs to various other inventors, including Robert Johnson, Simeon North, Captain John H. Hall, and Thomas Blanchard. (Several of the men mentioned above are sometimes described on the internet as "the inventor of the first milling machine" or "the inventor of interchangeable parts". Such claims are oversimplified, as these technologies evolved over time among many people.) The two federal armories of the U.S. (Springfield and Harpers Ferry) and the various private armories that shared turnover of skilled workmen with them were the centers of earliest development of true milling machines (as distinct from lathe headstocks tooled up for rotary filing).

James Nasmyth built a milling machine very advanced for its time between 1829 and 1831. It was tooled to mill the six sides of a hex nut that was mounted in a six-way indexing fixture.

A milling machine built and used in the shop of Gay & Silver (aka Gay, Silver,, & Co) in the 1830s was influential because it employed a better method of vertical positioning than earlier machines. For example, Whitney's machine (the one that Roe considered the very first) and others did not make provision for vertical travel of the knee. Evidently the workflow assumption behind this was that the machine would be set up with shims, vise, etc. for a certain part design and successive parts would not require vertical adjustment (or at most would need only shimming). This indicates that the earliest way of thinking about milling machines was as production machines, not toolroom machines.

Text E. 1840s-1860

Some of the key men in milling machine development during this era included Frederick W. Howe, Francis A. Pratt, Elisha K. Root, and others. (These same men during the same era were also busy developing the state of the art in turret lathes. Howe's experience at Gay & Silver in the 1840s acquainted him with early versions of both machine tools. His machine tool designs were later built at Robbins & Lawrence, the Providence Tool Company, and Brown & Sharpe.) The most successful milling machine design to emerge during this era was the Lincoln miller, which rather than being a specific make and model of machine tool is truly a family of related tools built by various companies over several decades. It took its name from the first company to put one on the market, George S. Lincoln & Company.

During this era there was a continued blind spot in milling machine design, as various designers failed to develop a truly simple and effective means of providing slide travel in all three of the archetypal milling axes (X, Y, and Z—or as they were known in the past, longitudinal, traverse, and vertical). Vertical positioning ideas were either absent or underdeveloped.

 

Text F. 1860s

Brown & Sharpe's groundbreaking universal milling machine, 1861

 

In 1861, Frederick W. Howe, while working for the Providence Tool Company, asked Joseph R. Brown of Brown & Sharpe for a solution to the problem of milling spirals, such as the flutes of twist drills. These were filed by hand at the time. Brown designed a "universal milling machine" that, starting from its first sale in March 1862, was wildly successful. It solved the problem of 3-axis (XYZ) travel much more elegantly than had been done in the past, and it allowed for the milling of spirals using an indexing head fed in coordination with the table feed. The term "universal" was applied to it because it was ready for any kind of work and was not as limited in application as previous designs. (Howe had designed a "universal miller" in 1852, but Brown's of 1861 is the one considered groundbreakingly successful.)

Brown also developed and patented (1864) the design of formed milling cutters in which successive sharpenings of the teeth do not disturb the geometry of the form.

The advances of the 1860s opened the floodgates and ushered in modern milling practice.

Text G. 1870s-1930s

Two firms which most dominated the milling machine field during these decades were Brown & Sharpe and the Cincinnati Milling Machine Company. However, hundreds of other firms built milling machines during this time, and many were significant in one way or another. The archetypal workhorse milling machine of the late 19th and early 20th centuries was a heavy knee-and-column horizontal-spindle design with power table feeds, indexing head, and a stout overarm to support the arbor.

A. L. De Leeuw of the Cincinnati Milling Machine Company is credited with applying scientific study to the design of milling cutters, leading to modern practice with larger, more widely spaced teeth.

Around the end of World War I, machine tool control advanced in various ways that laid the groundwork for later CNC technology. The jig borer popularized the ideas of coordinate dimensioning (dimensioning of all locations on the part from a single reference point); working routinely in "tenths" (ten-thousandths of an inch, 0.0001") as an everyday machine capability; and using the control to go straight from drawing to part, circumventing jig-making. In 1920 the new tracer design of J.C. Shaw was applied to Keller tracer milling machines for die- sinking via the three-dimensional copying of a template. This made diesinking faster and easier just as dies were in higher demand than ever before, and was very helpful for large steel dies such as those used to stamp sheets in automobile manufacturing. Such machines translated the tracer movements to input for servos that worked the machine leadscrews or hydraulics. They also spurred the development of antibacklash leadscrew nuts. All of the above concepts were new in the 1920s but would become routine in the NC/CNC era. By the 1930s, incredibly large and advanced milling machines existed, such as the Cincinnati Hydro-Tel, that presaged today's CNC mills in every respect except the CNC control itself.

 

Text H. 1940s-1970s

By 1940, automation via cams, such as in screw machines and automatic chuckers, had already been very well developed for decades. By the close of Word War II, many additional ideas

involving servomechanisms were in the air. These ideas, which soon were combined with the emerging technology of digital computers, transformed machine tool control very deeply. The details (which are beyond the scope of this article) have evolved immensely with every passing decade since World War II.

During the 1950s, numerical control (NC) made its appearance.

During the 1960s and 1970s, NC evolved into CNC, data storage and input media evolved, computer processing power and memory capacity steadily increased, and NC and CNC machine tools gradually disseminated from the level of huge corporations to the level of medium-sized corporations.

 

S-present

Computers and CNC machine tools continue to develop rapidly. The PC revolution has a great impact on this development. By the late 1980s even mom-and-pop machine shops can have desktop computers and CNC machine tools. CAD/CAM disseminates throughout the economy.

 

 

Література

 

1. В.Н. Бгашев, Е.Ю.Долматовская «Английский язык для студентов машиностроительных специальностей», Москва, Астрель, АСТ, 2005.

2. И.П.Агабекян, П.И.Коваленко «Английский для технических ВУЗов», Ростов-на-Дону, Феникс, 2005

3. Л.М.Черноватий, В.І.Карабан «Переклад англомовної технічної літератури», Нова Книга, Вінниця, 2006

4. Є.О.Мансі «English» тексти,для студентів інженерних, аграрних, медичних вищих навчальних закладів, Київ, В.ц. «Академія», 2004

5. Інтернет джерела.