If you run a milling machine and want to speed up production time, then you probably have had to deal with tool chatter. Machining at high speeds and feeds can cause tools to begin oscillating and undergoing countless tiny impacts against your workpiece. This translates to a high pitch sound that is both annoying and can fatigue your tools. Variable helix and variable flute end mills are designed to overcome natural tool oscillations by employing asymmetrical design features.
End Mill Basics
Before getting into what makes a variable flute end mills distinct, it’s important to define a few terms with regards to end mill construction.
● Shank – The shank is the non cutting area of the tool’s body. This will be held by the mill and is typically untreated.
● Cutting Surface – The cutting surface is the area of the end mill that will be doing the actual work. This part of the tool will often feature some kind of protective coating to improve the operation and lifespan of the end mill.
● Flutes – Flutes are spiraled grooves in the cutting surface of the tool that facilitates the removal of material from your workpiece. The edges of a tool’s flutes are sharpened. This sharp edge, combined with the grooved design of the flutes, helps to cut material from your workpiece and move the chips away from the cutting surface.
● Pitch – The pitch is the angle between the flutes of an end mill. You can find a tool’s pitch by imagining lines from the center of a tool to the points of each flute. In almost all cases, flute angles will be even between all flutes.
● Helix Angle – The helix angle measures the upward slope of a flute’s cutting edge. This angle can be found by looking at a tangent of a flute’s edge and measuring the angle against the central axis of the end mill.
Variable Flute End Mills
Normally the pitch between every flute is identical, but the exception is variable flute end mills. These tools have slightly different pitches between each of the flutes. The idea of an asymmetrical tool operating at high speeds may seem counterintuitive, but very tiny inconsistencies can actually improve performance at high speeds. This is because the difference in angle translates to a difference in distance between flute edges, which in turn leads to a difference in timing between cuts. The difference in timing means that the internal resonance of the tool being caused by contact with the workpiece is disrupted, increasing the stability of the tool.
Variable Helix End Mills
Instead of varying the angle between flutes, variable pitch tools feature different helix angles. The helix angle is consistent along each individual flute, but differs slightly from flute to flute. These differences help to prevent chatter by slightly disrupting the even distribution of force on the tool, which is another way to prevent the build up of natural oscillations. These cutting tools will still have symmetrical pitch angles
If you have heard good things about variable helix and variable flute end mills, it might be time to try them for yourself. One American manufacturer of high performance variable end mill is Online Carbide. All of their tools, which includes a wide range of end mills and drill bits, are ground from high quality micro grain tungsten carbide tool stock. This material is rigid and able to withstand high temperatures, giving carbide tools a longer tool life than tools made from steel alloys. You can check out all of the solid carbide cutters from Online Carbide by visiting their online store at www.onlinecarbide.com.