Web thickness is another important factor that determines end mill rigidity and size of the chip pockets.
The web thickness of a solid end mills is usually about 60% of the diameter. As the web thickness increases, the cross section widens and heightens rigidity. However, the chip pocket becomes narrower and the chip disposal properties deteriorate. On the contrary, decreased web thickness lowers rigidity and improves chip disposal.
The image to the right (Click on the link "Deflection of machined surfaces") shows a comparison between a surface machined with a standard 4-flute end mill with a web thickness of 60%, and a surface machined with a highly rigid 6-flute end mill with a thicker than usual web design.
The table shows the effect of web thickness.
Workpiece: JIS SKD11 60HRC
Tools: D1=10mm Coated carbide square end mill
Cutting conditions: vc=20m / min, n=650min-1, vf=100mm / min
fz=0.026mm / tooth (6-flute)
fz=0.038mm / tooth (4-flute)
Down cut milling