Technical Guide

 

Selecting the right Endmill

Make sure that your machine tool is rigid with a solid spindle and that the holders have the least run-out. Endmills made from Carbide are preferred amongst many as they are capable of achieving optimum speeds and feed rates. Keep in mind that rigidity is critical to prevent tool chipping or breakage.

Although the initial cost of the carbide endmills is relatively higher; with proper set-up, the initial cost is overcome by greater productivity, better finishes and fewer tool changes.

Endmill Basics

Endmills are used for producing precision shapes and holes on a milling or turning machine. These tools allow us to have cost-effective manufacturing.

The correct selection and use of endmills is important with machining centers and lathes. Endmills come in a variety of design styles and materials to accommodate just about any job. Tools come in various shapes, sizes and coat varieties. These generally are for different materials that need to be machined, and also for the longevity of the tool.

It is very important that the endmill be held firmly by the tool holder otherwise the cuts would be inconsistent. The best way to mount an endmill is in a concentric tool holder.

Tool Characteristics

Basic tool characteristics that are taken into consideration before use are:

Length: Shorter tools minimize tool deflection during the operation. Select varied stub lengths, if possible, to save on tool costs.

Stub Length – Used for milling of shallow slots in all types of materials where heavy feeds are required and tool deflection is minimized.

Number of Flutes: The more the flutes, the better the surface finish, as long as the feed rate remains the same.

Rake Angle:  Depending on the material to be machined, it is possible to change the rake angles. Endmills typically have a 10-12 degree positive rake angle.

Helix Angle: The standard helix angle of an endmill is usually 30°. Higher helix angles provide better chip ejection and are useful in machining materials such as aluminum at a much faster rate.

Cutters

Ball End: The tip of the tool is rounded or in the shape of a half-ball. These endmills are used to mill die cavities and fillets, round bottom holes and slots.

Center Cutting and Non Center Cutting: Center cutting square endmills are essential for plunge milling. Use non-center cutting mills only for side milling.

Corner Radius: Corner radius tools remove more material faster than the traditional ball nose endmills, but consideration must be given to the shape of the cut. Best use is for mold applications because the ball end can remove more material faster than ball ends.

Roughers are useful for rapid removing of large amounts of material. The chip grove design allows more cutting fluid to the cutting edges and dissipates heat better.

Left-Hand Spiral – Used for milling multiple layers of thin sheets where chip flow is directed away from work.