Tech Talk
What are the differences between a cutting tool's "Hand" and "Helix"?
Standard end mills are made with right-hand cut and right-hand helix. While left-hand cut, left hand helix end mills have always been available, most cutting tool manufacturers did not carry large inventories of these tools because of the limited demand. With the growth of NC machining, however, and the increase need for mirror-image parts, particularly in the aircraft/aerospace industry, demand for left-hand cut, left-hand helix end mills has increased. As a result, tool makers are offering both left and right hand cutters as standard in a broader range of sizes and styles than ever before. The helix angle of a standard end mill is designed to provide the best combination of shearing action and chip disposal for a variety of work materials. On most general purpose end mills, the helix angle will be somewhere between 25 and 35 degrees. Standard end mills are also available with helix angles as high as 45 degrees. These tools are referred to as fast-helix end mills, and are used primarily for milling aluminum aircraft components, high helix end mills provide increased shearing action and more positive chip ejection. These tools will also have modified rake and clearance angles to prevent build up of the soft metal on the faces of the tool which would otherwise occur in deep pocketing and slotting operations. End mills with relatively small helix angles (less than 20 degrees) are referred to as slow-helix mills. These tools are used for the more difficult-to-cut alloys.
