Carbide End Mill Sets

Archive for the ‘Types of Tools’ Category

With excessive use it carbide tools will need to be sharpened from time to time in order to maintain their cutting edge. Cemented carbide indexable inserts usually require a special grind in order to form a contour on the cutting edge to suite a special purpose. Brazed type carbide cutting tools are re-sharpened after the cutting edge has become worn. On brazed carbide tools, the cutting-edge wear should not be allowed to become excessive before the tool has been re-sharpened. One method of determining when carbide tools need to be re-sharpened is by periodically inspecting the flank wear and the condition of the face, in addition, when amount of production decrease from that, which is usually achieved after re-sharpening is another indication that the tool requires re-sharpening.

Re-sharpening should never require the removal of more than 0.005 to 0.010 inch of carbide. The typical procedure for re-sharpening depends on the type of grinding operation that is required. If the procedure is to re-sharpen a dull tool, then a diamond wheel of 100 to 120 grain size is normally recommended. However, a finer wheel of 150-grain size is sometimes utilized in order to obtain a smoother finish. Some machine shops prefer to rough grind carbide with a vitrified silicon carbide wheel, the finish grinding is usually accomplished with a diamond wheel, with a final process designated as lapping may or may not be used to obtain an extra-fine finish.

Milling cutters can be sharpened by using the periphery of a disk wheel or the face of a cup wheel. The face of a cup wheel grinds the lands of the teeth flat, while the periphery of a disk wheel will leave the teeth slightly concave back of the cutting edges. The concavity created by the dick wheel will reduce the effective clearance angle on the teeth. This effect is more pronounced with smaller diameter wheels than with larger diameter wheels. It is for this reason that large diameter wheels are preferred for sharpening milling cutters.

Machine tools are powered mechanical devices that are generally used to manufacture metal components of machines by selectively cutting and removing metal. Depending on whom you ask, the creation of machine tools occurred when the direct human involvement was removed from the process of cutting, shaping, or stamping process required in creating the various types of tools. An example of this theory is the lathe machine tool. In 1751, Jacques de Vaucanson mounted the cutting instrument on a mechanically adjustable head, removing the process from the hands of the operator. However, many historians will argue that machine tools did not come about until after the development of the steam engine and the Industrial Revolution.

Today, they are powered by electricity and can be operated manually, or under automatic control. The early machines had flywheels that stabilize their motion as well as an intricate system of levers, and gears that controlled the machine as well as the piece that were being produced.

Numerical control or NC machines were developed after World War II. These machines used a series of numbers punched onto paper tape or cards to control their motion. Then by the 1960s, computers were gradually added to the machines to allow for more flexibility in the process. These new computerized machines were then know as computer numerical control machines, or CNC for short. With the development of the NC and CNC machines, more pieces that are complex could be produced. The reason for this is that these machines could precisely repeat sequences over and over.

It wasn’t long before these machines drastically changed the cutting and shaping of tools being used. An example of this change is the drill machine, which because of computerization can contain a magazine loaded with a variety is sizes of drill bits used to produce various size holes. In the past, the machinist would have to either manually change out the bit or completely relocate the piece being worked on to another station in order to perform the different operations. Both methods took time, thus reduced productivity.

Once the NC and CNC proved to increase production, the next step was to combine various machine tools together with each being controlled by a single computer. These combined machine tools were then known as machine centers, and like their predecessors, have dramatically changed the way parts are created. Today, highly complex machine parts can be finished in a matter of minutes instead of the hours that it used to take.

Milling cutters are cutting tools used in milling machined and are generally attached vertically. They are used to remove material by their movement inside the machine because they have two or more helix flutes. The names of milling cutters generally describe how the cutters perform. Milling cutters can be configured in several ways including a solid construction, holder, or inserts construction. Their tip or end geometries can also be of several different designs including square end, ball nose, and radius tip, or chamfer end. In addition, milling cutters can also have a finishing type such as roughing or hogging, or finishing.

Those that cut with their ends and on their sides are called end mills, whereas milling cutters that cut with their ends only are referred to as face mills. The creation of a flat face on the work piece, thus the term face mills. Face mills generally have larger diameters than the width of the workpiece, which is being faced. This means that the surface of the workpiece can be processed in a single pass. The largest types of face or end mills are shell mills. These mount onto an arbor, instead of having an integral shank.

Slab mills cut with their peripheral edges and generally have helical cutting edges. Slab mills are normally mounted horizontally to create plane finishes on the workpiece. Plunge mills are designed for plunging the cutter directly into the material being milled, whereas single angle cutters have one side angled in order to produce a chamfer or angle on the edge of the workpiece. Single angle cutters are angled on one side to produce an angle or chamfer on the workpiece edge.

The dovetail is specially designed tools used for cutting a dovetail groove into a workpiece. A dovetail is a fan-shaped tenon, which forms a tight interlocking joint when fitted into a matching mortise.

Keyseat cutters are used to produce a slot that acts as a seat for a corresponding engagement key. Keyseat cutters are used to key shafts to prevent unwanted rotation and provide positive engagement. The side cutting edges of the T-slot cutters feed into the workpiece to produce a “T” slot.

To create a convex feature or a male semicircle on a workpiece concave formed cutters are used, on the other hand, in order to create a concave feature or a female semicircle, convex formed cutters will be used.

To cut tooth forms on gears, machinists use gear hob milling cutters and to produce teeth of an involted form gear hobs and cutters are ground.

Button or copy cutters use round inserts known as “buttons” instead of square or triangular inserts. The round inserts permit enhanced feed rates and depth of cuts using lower power.

End mill cutters can be distinguished from ordinary drill bits, by their application, geometry, and how they are manufactured. In fact, end mill was once a slang term used by machinist’s that has come to be standard usage by industry publications, trade magazines, and manufacturer’s catalogs.

There is a wide category of end and face milling tools available, including flat bottom, ball nose, radius, inverted radius, and chamfer tools. In addition, each of these categories can be further divided by specific application and special geometry.

More and more traditional solid end mills are being replaced with better cost-effective inserted cutting tools. These end mill tools are initially more expensive. However, inserted cutting tools do reduce tool-change times and permit for a much simpler replacement of worn or broken cutting edges instead of having to replace the entire tool.

Both metric and imperial shank and cutting diameters are sold in the United States and in Canada. However, in the United States, metric end mills are not commonly used in every machine shop where as in Europe and Asia they are the standard.

End mills are used several different types of milling applications including profile milling, tracer milling, face milling, etc. The tool that is used will depend on the material, which is being milled, as well as the particular task that has to be performed.

End mills have flutes, which are spiral cutting edge on the end mill. End mills can have between 2 to 8 flutes, with most end mills having 2 and 4 flutes. End mills that have 2 flutes allow for the maximum amount of space for chip ejection and are used for general milling procedures. End mills with 3 flutes are perfect for slotting as well as general milling. End mills with 4 to 8 flutes reduce chip load and provide for a better surface finish.