END MILL SELECTION GUIDE
SELECTING SUITABLE CHARACTERISTICS OF YOUR CUTTING TOOL
The information on the following pages will help you to determine the proper tool for your specific application. Consider the material, application, and type of cut to identify the end mill you need. Note that the information provided is basic in nature and we can not account for your particular machine, setup or application and there are many variables to consider. If you have any questions please do not hesitate to contact us.
TOOL MATERIAL SELECTION
We use only the finest materials available to meet our customers demanding a range of applications. Our stock includes high-speed steel (M-2, M-4, M-7, M-42), powdered metal (PM M-4, PM M 48, PM T-15), & virgin carbide (sub-micron grain, ultra-fine) in varying concentrations.
High-speed steel tools are economical for general purposes and very versatile. Cobalt is ideal for more difficult to machine materials and has increase abrasion resistance. Powdered metals (PM) use a special manufacturing process and are operable under higher feed rates and produce longer tool life.
Carbides are classified by the grain size and concentration of tungsten to cobalt binder. As the grain size of tungsten carbide gets smaller, the material becomes denser, more rigid and more wear resistant. Using only sub-micro and ultra-fine carbide allows a higher performance and quality to be achieved. Smaller grains allow a sharper edge preparation and precision grinding down to the micron.
The choice of tool material depends on several factors:
• Feeds and speeds
• Rigidity needed
• Preferred chip evacuation
• Method of tool engagement
• Depth of cut
• Desired finish
• Helical angle
• Workpiece hardness
• Workpiece condition
• Number of workpieces
CONSIDER THE NUMBER OF FLUTES
To determine whether a two, three, four or greater flute end mill is needed, several factors need to be considered. Two and three flute end mills have better stock removal than multiple flute end mills but a significantly decreased finish. End mills with five or more flutes are ideal for finishing cuts and cuts in harder materials but must operate at lower material removal rates due to their poor chip evacuation properties. When running at similar rates, multiple flute end mills will take a lighter chip load per tooth, resulting in an improved finish and smoother machining. Consider the type of cut needed to be performed, the chip space required based on the cut and material, the production and metal removal rate needed and the desired surface finish when selecting.
FLUTE CONSTRUCTION AND CONFIGURATION
Higher helix angles produce higher chip evacuation, thus the capacity to increase speeds and feeds and decrease horsepower requirements. Tool deflection is transferred vertically versus horizontally which dampens vibrations and increases speeds and surface finish quality.
Traditionally, roughing operations or hard to machine materials benefit from the improved flute strength of a lower helix end mill. While using general purpose end mills, this may still hold true, however newer high-performance geometries take into consideration flute and core strength while adding the benefits of a higher helix. Immediate edge build-up can occur with lower helix end mills and create excessive chatter.
For an axial plunge cut, it is essential to use a center cutting tool. Two flute end mills are center cutting, where multi-flute end mills can vary. Multi-flute end mills create better surface finishes due to a lighter chip load – per flute. Sideloading is dramatically reduced with lower helix angles, making it easier to mill thin walls.
ROUGHING END MILLS
Roughing cuts are generally for preparing the surface before the finishing cut. The purpose is to bring the diameter of the hole to a “rough” size of the final cut. How this cut looks is of little importance. Roughing cuts also allow for mistakes. Roughing cuts may consist of several heavy cuts and the primary purpose is to clear material away, in anticipation of the finishing cut.
FINISHING END MILLS
A minimal amount of leftover material from the roughing cut is removed with the finishing cut, machining the work to size in addition to refining the surface of the workpiece.