A CNC lathe with live-tool capability can save time by milling and turning a part in the same setup. However, a lathe that can mill in this way is not necessarily capable taking the same kinds of cuts that a machining center can. By necessity, a compact lathe has only a compact space in its turret for the milling spindle—it might not be equipped for high-powered milling. In addition, the setup on such a machine may not be as rigid as the clamping of the part and tool on a machine that was made for milling.
Johnson Machine, a contract shop in Collinsville, Oklahoma, faced this limitation on a valve part made of 316 stainless steel. The 4.5-inch-diameter cylindrical part has a 7/8-inch-wide slot in the circumference. The geometry of the cut made it ideal for generating with the C axis of a live-tool lathe. However, when the shop tried to mill the part this way, the high cutting force produced chatter.
Owner Robert Johnson says the shop solved the problem with an end mill that cuts with less force. The four-flute Sasquatch tool from Gorilla Mill includes a roughing design on two of the flutes that shreds the material. The other two flutes are finishing edges that cut at a slightly larger diameter. In effect, the roughing flutes break up the material and the finishing flutes clean up these passes. With this tool design, Mr. Johnson says the shop can make the cut on the stainless steel part with less feed pressure. The more stable cutting extends the range of work he can do on one of his more versatile machines.