Recent advances in cutting tool materials have allowed reaming—traditionally a high-feed-rate/low-speed operation—to be performed at higher feeds and speeds. Exchangeable-head reamer designs have also been developed to offer users the option of replacing just the worn cutting head rather than the entire tool. Urma, a Swiss boring tool manufacturer, has combined these concepts into its CircoTec RX line of reamers, which offer long tool life, short cycle times and change-over ease that approaches that of swapping an end mill insert. The CircoTec RX system is available in the United States from Command Tooling Systems (Ramsey, Minnesota).
The heart of the system is a 4.3-mm-thick, solid carbide (or cermet) cutting disc with multiple cutting edges that bring bores to proper size, straightness and roundness. Think of the thin disc as an insert. According to Bob Rubenstahl, Command’s president, the first 2 mm of the reamer’s cutting edges is what wears out during use. In addition, he says only 4 mm of cutter thickness is required to impart a burnishing effect that enhances the quality of the bore’s surface finish. The reason that exchangeable heads might measure 8 to 15 mm thick, Mr. Rubenstahl explains, is because additional thickness simplifies handling of carbide tips as they are brazed onto the head.
The cutting disc’s rigid geometry and tapered interface with the reamer body allows the CircoTec RX system to provide less than 4 microns of runout. The disc attaches to the front of the reamer body using four screws (see photo), allowing the disc to be changed while the reamer body remains in the machine. No other adjustments are required. This differs from exchangeable-head designs, which use a single screw that travels the length of the body to attach the head to the body. To change heads on this design, an operator must remove the body from the machine to the screw at the back of the body, extending equipment downtime.
The CircoTec RX system is available in diameters ranging from 0.468 inch (11.9 mm) to 3.96 inches (100.6 mm) for through and blind hole applications. The maximum tool length to reamer diameter is 8-to-1. Carbide or cermet discs are available uncoated or with various TiN or TiCN coatings. The reamer bodies have internal passages that direct through-spindle coolant to the disc’s multiple cutting edges to extend cutter life and assist in chip extraction.