Original Date: 10/14/1988
Revision Date: 01/18/2007
Best Practice : Cubic Boron Nitride Grinding
Cubic boron nitride technology is used to greatly increase productivity and accuracy in grinding high precision gears. The precision requirements for these gears have led Bell Helicopter Textron, Inc. (BHTI) to search for methods that will allow for tight control of root radius, tooth profiles, and to use techniques that will allow for removal of a maximum of .006 inches of material from the blanks after heat treating. The cubic boron nitride grinding wheels are meeting these requirements.
Cubic boron nitride crystals rank next to diamond in hardness and are 2 to 3 times harder than conventional grinding abrasives. The crystals normally range from 30 to 600 microns in grain size. Depending on application, they are available in two types of grinding wheels: dressable and plated. BHTI uses the plated type wheels almost exclusively even though they are considerably more expensive. Plated wheels use a hardened steel base that has been ground to the specific tooth profile and then has a single layer of cubic boron nitride crystals electrolytically applied and nickel bonded. The advantages of the plated wheel include: more accurate form control; no dressing requirement; less tendency to burn; fastest form grinding method available; and consistently high accuracy. The disadvantages include: long procurement lead time; limited sources (principally Kapp in Germany); high cost; and different wheel required for each tooth form.
BHTI states that the use of these wheels has provided accuracies which challenge the ability of quality assurance inspection techniques and has shown a 400% increase over conventional methods in production per shift.
For more information see the
Point of Contact for this survey.