Scientific study by Holz and De Leeuw of the Cincinnati Milling Machine Company[11] made the teeth even coarser and did for milling cutters what F.W. Taylor had done for single-point cutters with his famous scientific cutting studies.

Primary clearance angle (7) is the angle of the land of each tooth measured from a line at right angles to the centerline of the cutter at the cutting edge. This angle prevents each tooth from rubbing against the workpiece after it makes its cut and provides additional clearance for passage of cutting oil and chips.

The machinist needs three values: S, F and Depth when deciding how to cut a new material with a new tool. However, he will probably be given values of Vc and Fz from the tool manufacturer. S and F can be calculated from them:

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Woodbury provides citations[9] of patents for various advances in milling cutter design, including irregular spacing of teeth (1867), forms of inserted teeth (1872), spiral groove for breaking up the cut (1881), and others. He also provides a citation on how the introduction of vertical mills brought about wider use of the endmill and fly cutter types.[10]

Interpolation is also not necessary when using a hollow mill; this can result in a significant reduction of production time.

There are 8 cutters (excluding the rare half sizes) that will cut gears from 12 teeth through to a rack (infinite diameter).

Selecting a milling cutter is not a simple task. There are many variables, opinions and lore to consider, but essentially the machinist is trying to choose a tool that will cut the material to the required specification for the least cost. The cost of the job is a combination of the price of the tool, the time taken by the milling machine, and the time taken by the machinist. Often, for jobs of a large number of parts, and days of machining time, the cost of the tool is lowest of the three costs.

Milling cutters are classified by their shape, the orientation of cutting edges, and number of flutes they have. In most cases, cutters are specially designed and named for the job they best used for.

An adjustable hollow mill is a valuable tool for even a small machine shop to have because the blades can be changed out for an almost infinite number of possible geometries.

Ball nose cutters or ball end mills (lower row in image) are similar to slot drills, but the end of the cutters are hemispherical. They are ideal for machining 3-dimensional contoured shapes in machining centres, for example in moulds and dies. They are sometimes called ball mills in shop-floor slang, despite the fact that that term also has another meaning. They are also used to add a radius between perpendicular faces to reduce stress concentrations.

Milling cutters come in several shapes and many sizes. There is also a choice of coatings, as well as rake angle and number of cutting surfaces.

Milling cutters can also be described by their intended use or the type of workpiece they are designed to cut. For example, a cutter may be described as a “roughing end mill,” a “finishing end mill,”or a “Woodruff cutter.”

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More advanced hollow mills use indexable carbide inserts for cutting, although traditional high speed steel and carbide-tipped blades are still used.

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Milling cutters are cutting tools typically used in milling machines or machining centres to perform milling operations (and occasionally in other machine tools). They remove material by their movement within the machine (e.g., a ball nose mill) or directly from the cutter's shape (e.g., a form tool such as a hobbing cutter).

A shell mill is any of various milling cutters (typically a face mill or endmill) whose construction takes a modular form, with the shank (arbor) made separately from the body of the cutter, which is called a "shell" and attaches to the shank/arbor via any of several standardized joining methods.

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Hollow mills offer an advantage over single point tooling. Multiple blades allow the feed rate to double and can hold a closer concentricity. The number of blades can be as many as 8 or as few as 3.  For significant diameter removal (roughing), more blades are necessary.

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The cutting edge usually has 5 degrees primary clearance. Sometimes teeth are manufactured with off-set nicks to break up chips and enable coarser feeds.

These cutters are a type of form tool and are used in hobbing machines to generate gears. A cross-section of the cutter's tooth will generate the required shape on the workpiece, once set to the appropriate conditions (blank size). A hobbing machine is a specialised milling machine.

Cutters of this form factor were the earliest milling cutters developed. From the 1810s to at least the 1880s they were the most common form of milling cutter, whereas today that distinction probably goes to end mills. Traditionally, HSS side and face cutters are used to mill slots and grooves.

The history of milling cutters is intimately bound up with that of milling machines. Milling evolved from rotary filing, so there is a continuum of development between the earliest milling cutters known, such as that of Jacques de Vaucanson from about the 1760s or 1770s,[3][4] through the cutters of the milling pioneers of the 1810s through 1850s (Whitney, North, Johnson, Nasmyth, and others),[5] to the cutters developed by Joseph R. Brown of Brown & Sharpe in the 1860s, which were regarded as a break from the past[6][7] for their large step forward in tooth coarseness and for the geometry that could take successive sharpenings without losing the clearance (rake, side rake, and so on). De Vries (1910)[7] reported, "This revolution in the science of milling cutters took place in the States about the year 1870, and became generally known in Europe during the Exhibition in Vienna in 1873. However strange it may seem now that this type of cutter has been universally adopted and its undeniable superiority to the old European type is no longer doubted, it was regarded very distrustfully and European experts were very reserved in expressing their judgment. Even we ourselves can remember that after the coarse pitched cutter had been introduced, certain very clever and otherwise shrewd experts and engineers regarded the new cutting tool with many a shake of the head. When[,] however, the Worlds Exhibition at Philadelphia in 1876, exhibited to European experts a universal and many-sided application of the coarse pitched milling cutter which exceeded even the most sanguine expectations, the most far-seeing engineers were then convinced of the immense advantages which the application of the new type opened up for the metalworking industry, and from that time onwards the American type advanced, slowly at first, but later on with rapid strides".[8]

Standard milling cutters for your mill drill machine are made of high-speed steel (HSS). Tungsten carbide (TC) is more expensive than HSS, but harder, and used for high performance cutting. HSS can withstand high temperatures, but is not as hard as carbide and does not hold an edge as well or last as long.

End mills (middle row in image) are those tools that have cutting teeth at one end, as well as on the sides. The words end mill are generally used to refer to flat bottomed cutters, but also include rounded cutters (referred to as ball nosed) and radiused cutters (referred to as bull nose, or torus). They are usually made from high speed steel or cemented carbide, and have one or more flutes. They are the most common tool used in a vertical mill.

Roughing end mills quickly remove large amounts of material. This kind of end mill utilizes a wavy tooth form cut on the periphery. These wavy teeth act as many successive cutting edges producing many small chips. This results in a relatively rough surface finish, but the swarf takes the form of short thin sections and is more manageable than a thicker more ribbon-like section, resulting in smaller chips that are easier to clear. During cutting, multiple teeth are in simultaneous contact with the workpiece, reducing chatter and vibration. Rapid stock removal with heavy milling cuts is sometimes called hogging. Roughing end mills are also sometimes known as "rippa" or "ripper" cutters.

Another type of shell fastening is simply a large-diameter fine thread. The shell then screws onto the arbor just as old-style lathe chuck backplates screw onto the lathe's spindle nose. This method is commonly used on the 2" or 3" boring heads used on knee mills. As with the threaded-spindle-nose lathe chucks, this style of mounting requires that the cutter only make cuts in one rotary direction. Usually (i.e., with right-hand helix orientation) this means only M03, never M04, or in pre-CNC terminology, "only forward, never reverse". One could use a left-hand thread if one needed a mode of use involving the opposite directions (i.e., only M04, never M03).

Trepanning is also possible with a hollow mill. Special form blades can be used on a hollow mill for trepanning diameters, forms, and ring grooves.

A fly cutter is composed of a body into which one or two tool bits are inserted. As the entire unit rotates, the tool bits take broad, shallow facing cuts. Fly cutters are analogous to face mills in that their purpose is face milling and their individual cutters are replaceable. Face mills are more ideal in various respects (e.g., rigidity, indexability of inserts without disturbing effective cutter diameter or tool length offset, depth-of-cut capability), but tend to be expensive, whereas fly cutters are very inexpensive.

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Regular fly cutters (one tool bit, swept diameter usually less than 100 mm) are widely sold in machinists' tooling catalogs. Fly bars are rarely sold commercially; they are usually made by the user. Fly bars are perhaps a bit more dangerous to use than endmills and regular fly cutters because of their larger swing. As one machinist put it, running a fly bar is like "running a lawn mower without the deck",[2] that is, the exposed swinging cutter is a rather large opportunity to take in nearby hand tools, rags, fingers, and so on. However, given that a machinist can never be careless with impunity around rotating cutters or workpieces, this just means using the same care as always except with slightly higher stakes. Well-made fly bars in conscientious hands give years of trouble-free, cost-effective service for the facing off of large polygonal workpieces such as die/mold blocks.

Slab mills are used either by themselves or in gang milling operations on manual horizontal or universal milling machines to machine large broad surfaces quickly. They have been superseded by the use of cemented carbide-tipped face mills which are then used in vertical mills or machining centres.

Carbide cutters are better for high precision, but are more brittle than HSS and more easily broken. Cutters can also be made of aluminum or steel with insert teeth made of harder materials to reduce the cost. Some cutters have special hard coatings of polycrystalline diamond (PCD) or cubic boron nitride (CBN) to improve durability.

Milling cutters are measured using a combination of their diameter and the number of flutes they have. The diameter of a milling cutter is measured from one side of the cutter to the other, passing through the center of the cutter. The number of flutes is the number of cutting edges that are present on the cutter.

Spiral or helical teeth (8) are usually found on plain milling cutters more than 3/4 inch in width. A spiral-tooth milling cutter produces a better and smoother finish with less effort. A plain helical-tooth milling cutter is desirable when milling an uneven surface or one with holes in it.

To get the best results from your mill drill machines when milling and drilling metals, you need to use the correct cutting tools for the job. Selecting and fitting the correct milling tool is essential knowledge for setting up your mill drill machine.

Cutter location is the topic of where to locate the cutter in order to achieve the desired contour (geometry) of the workpiece, given that the cutter's size is non-zero. The most common example is cutter radius compensation (CRC) for endmills, where the centerline of the tool will be offset from the target position by a vector whose distance is equal to the cutter's radius and whose direction is governed by the left/right, climb/conventional, up/down distinction. In most implementations of G-code, it is G40 through G42 that control CRC (G40 cancel, G41 left/climb, G42 right/conventional). The radius values for each tool are entered into the offset register(s) by the CNC operator or machinist, who then tweaks them during production in order to keep the finished sizes within tolerance. Cutter location for 3D contouring in 3-, 4-, or 5-axis milling with a ball-endmill is handled readily by CAM software rather than manual programming. Typically the CAM vector output is postprocessed into G-code by a postprocessor program that is tailored to the particular CNC control model. Some late-model CNC controls accept the vector output directly, and do the translation to servo inputs themselves, internally.

Hollow milling has an advantage over other ways of cutting because it can perform multiple operations. A hollow mill can reduce the diameter of a part and also perform facing, centering, and chamfering in a single pass.

Some jobs can be done with more than one type of cutter. For example, milling the square end on a shaft or reamer shank can be done with one or two side milling cutters, a fly cutter, or an end milling cutter.

Although there are many different types of milling cutter, understanding chip formation is fundamental to the use of any of them. As the milling cutter rotates, the material to be cut is fed into it, and each tooth of the cutter cuts away a small chip of material. Achieving the correct size of chip is of critical importance. The size of this chip depends on several variables.

Hollow milling cutters, more often called simply hollow mills, are essentially "inside-out endmills". They are shaped like a piece of pipe (but with thicker walls), with their cutting edges on the inside surface. They were originally used on turret lathes and screw machines as an alternative to turning with a box tool, or on milling machines or drill presses to finish a cylindrical boss (such as a trunnion). Hollow mills can be used on modern CNC lathes and Swiss style machines. An advantage to using an indexable adjustable hollow mill on a Swiss-style machine is replacing multiple tools.  By performing multiple operations in a single pass, the machine does not need as can accommodate other tools in the tool zone and improves productivity.

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There are several common standardized methods of mounting shell mills to their arbors. They overlap somewhat (not entirely) with the analogous joining of lathe chucks to the spindle nose.

A bull nose cutter mills a slot with a corner radius, intermediate between an end mill and ball cutter; for example, it may be a 20 mm diameter cutter with a 2 mm radius corner. The silhouette is essentially a rectangle with its corners truncated (by either a chamfer or radius).

The most common type of joint between shell and arbor involves a fairly large cylindrical feature at center (to locate the shell concentric to the arbor) and two driving lugs or tangs that drive the shell with a positive engagement (like a dog clutch). Within the central cylindrical area, one or several socket head cap screws fasten the shell to the arbor.

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Most fly cutters simply have a cylindrical center body that holds one tool bit. It is usually a standard left-hand turning tool that is held at an angle of 30 to 60 degrees. Fly cutters with two tool bits have no "official" name but are often called double fly cutters, double-end fly cutters, or fly bars. The latter name reflects that they often take the form of a bar of steel with a tool bit fastened on each end. Often these bits will be mounted at right angles to the bar's main axis, and the cutting geometry is supplied by using a standard right-hand turning tool.

This modular style of construction is appropriate for large milling cutters for about the same reason that large diesel engines use separate pieces for each cylinder and head whereas a smaller engine would use one integrated casting. Two reasons are that (1) for the maker it is more practical (and thus less expensive) to make the individual pieces as separate endeavors than to machine all their features in relation to each other while the whole unit is integrated (which would require a larger machine tool work envelope); and (2) the user can change some pieces while keeping other pieces the same (rather than changing the whole unit). One arbor (at a hypothetical price of USD100) can serve for various shells at different times. Thus 5 different milling cutters may require only USD100 worth of arbor cost, rather than USD500, as long as the workflow of the shop does not require them all to be set up simultaneously. It is also possible that a crashed tool scraps only the shell rather than both the shell and arbor. To also avoid damage to the shell, many cutters, especially in larger diameters, also have another replaceable part called the shim, which is mounted to the shell and the inserts are mounted on the shim. That way, in case of light damage, only the insert and maximum the shim needs replacement. The shell is safe. This would be like crashing a "regular" endmill and being able to reuse the shank rather than losing it along with the flutes.

Another important quality of the milling cutter to consider is its ability to deal with the swarf generated by the cutting process. If the swarf is not removed as fast as it is produced, the flutes will clog and prevent the tool cutting efficiently, causing vibration, tool wear and overheating. Several factors affect swarf removal, including the depth and angle of the flutes, the size and shape of the chips, the flow of coolant, and the surrounding material. It may be difficult to predict, but a good machinist will watch out for swarf build up, and adjust the milling conditions if it is observed.

Both convex and concave spherical radii are possible with a hollow mill. The multiple blades of a hollow mill allow this radius to be produced while holding a tight tolerance.

There are a wide variety of milling cutters available and they come in different materials and sizes. Knowing more about milling cutters will help you make cost-effective decisions when purchasing milling tools for your mill drill.

When sizing a milling cutter for a particular job, it can make the cut in a single pass if it is large enough to span the entire work surface. If this cannot be done, remember a small diameter cutter will pass over a surface in a shorter time than a large diameter cutter moving at the same speed.

Milling cutters descriptions often include shank type and the type of mounting they use. An end mill might be described as having a “straight shank” or a “weldon shank,” or a face mill might be described as having a “shell mill mounting.”

The illustration shows a standard milling cutter. Most cutters have similar features that are used to describe them. There are six key features:

The side-and-face cutter is designed with cutting teeth on its side as well as its circumference. They are made in varying diameters and widths depending on the application. The teeth on the side allow the cutter to make unbalanced cuts (cutting on one side only) without deflecting the cutter as would happen with a slitting saw or slot cutter (no side teeth).

Most shell mills made today use indexable inserts for the cutting edges—thus shank, body, and cutting edges are all modular components.

In addition to the diameter and the number of flutes, milling cutters are also described by their cutting edge configuration and the material from which they are made. An end mill might be described as a “1/4-inch diameter, 2-flute HSS end mill,” and a ball end mill might be described as a “3/8-inch diameter, 4-flute carbide ball end mill.”

A common use of a hollow mill is preparing for threading.  The hollow mill can create a consistent pre-thread diameter quickly, improving productivity.

Whereas a hob engages the work much as a mating gear would (and cuts the blank progressively until it reaches final shape), a thread milling cutter operates much like an endmill, traveling around the work in a helical interpolation.

A face mill is a cutter designed for facing as opposed to e.g., creating a pocket (end mills). The cutting edges of face mills are always located along its sides. As such it must always cut in a horizontal direction at a given depth coming from outside the stock. Multiple teeth distribute the chip load, and since the teeth are normally disposable carbide inserts, this combination allows for very large and efficient face milling.

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It is not difficult to make perfect cuts with a high quality metal cutting band saw. Every cutting task is made easier by following the correct sequence of operations to ensure safe, efficient, clean and accurate cutting. Let’s look at how to operate your band saw machine to get the best results possible.