Hard Milling with Ceramic Inserts

Hard milling with ceramic inserts can help a mold shop to reduce manufacturing costs in several ways. First, a mold shop can replace several operations with one operation. Instead of machining, hardening and remachining, the use of ceramic inserts enables a shop to harden the steel first and then machine the part in the hardened form. This reduces manufacturing time and improves job tracking by reducing the number of times that you must set up and move a component through various manufacturing phases. Furthermore, roughing a hardened part with ceramic inserts also can eliminate expensive and time-consuming EDM operations, as well as the need to make one or more electrodes.

Second, ceramic inserts are capable of machining hardened steel at much higher speeds than conventional carbide cutting tools. Combine the higher operating speed with the proper feedrate and a healthy step-over and the shop can achieve some impressive metal removal rates. Another key factor in increased production rates when hard milling is the cutter density. Every additional tooth in a cutter increases the cross feedrate. Higher speed and more feed add up to lower cycle times and money saved.

Third, many times the surface finish achieved by rough milling with ceramics leaves less work for a finish milling operation, and reduces finishing and polishing time. Milling at relatively light feedrates in hardened steel with carbide usually leaves a good finish, but many times with ceramic inserts the rough finish is even better than the required finish. In some cases, additional milling, grinding and polishing can be eliminated, saving several hours of manufacturing.

Cylinder Boring with CBN or PCD Inserts

Boring out cylinders to accept oversized pistons or sleeves has long been a common practice in the engine rebuilding business. Boring allows worn blocks to be salvaged, and stock cylinder bores to be enlarged for more displacement. More recently, boring is also being used to install special cylinder liners with hard surface treatments in high performance racing engines. The hard liners almost eliminate ring and bore wear so the engine can run race after race with no increase in bore clearances blowby.

Like most other machine tools in today's shops, the equipment used to bore engines is also evolving to keep pace with changes in engine technology and the aftermarket. Small shops want equipment that is versatile and can do more than just bore holes. For this end of the market, combination boring/milling machines have become popular. At the other end of the spectrum, production engine remanufacturers (PERs) want equipment that works harder, works faster and requires less operator input. For this type of user, automated high speed boring equipment provides the needed boost in productivity and quality.

Tooling has also been improving. The latest generation of coated carbide inserts provides longer life and better cutting action. For high speed boring, polycrystaline diamond (PCD inserts) provides the longevity needed for this type of operation. The speed at which the boring bar turns has a significant impact on tooling life. High speeds just kill the bits unless you use a PCD or cubic boron nitride (CBN inserts) type of insert. The high speed boring machines that go up to 1,500 rpm need these type of inserts.