Toroidal Tools for Tight Areas
Toroidal end mill in hardened steel mold machining of helical bores in 54 HRc H13 steel.
When cutting hardened tool steels for moldmaking toroidal tools are best for tight areas such as helical bores and ribs or when the cutter diameter is close to the radius of the part. The toroidal shape of the tool plays an important role and offers many advantages. Its robust shape creates a chip thinning effect that allows the tool to cut at faster feedrates. The radius is smaller than a traditional ball end tool, so you can increase step-overs and still maintain flat floors without the large cusps generated by ball end tools.
Helical bores and ribs are great applications for toroidal tools because they naturally have a lot of surface contact on the cutter. Using a two-flute cutter with the toroidal shape will minimize surface contact, heat and deflection. In these two applications, the toroidal tool is usually encapsulated in the cut.