Production Machining

DEC 2014

Production Machining - Your access to the precision machining industrial buyer.

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A Standard Approach to Classifying Burrs By Mike Akuszewski, Contributor W hat is a burr and how is a burr defned? An unclear defnition of burrs was a problem manufacturing faced for many years. Every manufacturer and industry segment defned a burr diferently. Tese variations created problems for shops trying to provide deburring solutions and for customers trying to fgure out what solutions to look for. How can there be a standard solution to a non-standard problem? Te answer came in the development of a burr standard that was easy to understand and apply in the feld. A team of engineers began working with manufacturing and distribution channels to develop such a standard for classi- fying burrs. By looking at typical burrs on various materials and documenting the similarities and diferences of each, the team identifed fve types of burrs. Te characteristics of each type where defned and documented, and fve standard burr classes were developed. Tis standard was quickly adopted by manufacturing companies and embraced by distribution channels. Five Burr Classes Five standard burr classes were developed. Burrs can form on all types of materials, including steel, aluminum, ductile iron and titanium. Class 1 burrs are known as "micro burrs." Tese burrs can only be seen with magnifcation and look like sharp edges to the naked eye. Class 2 burrs are also small burrs, sometimes called "feather burrs." Tese burrs are able to be seen without magnifcation and can sometimes be scratched of of an edge using a fngernail. Burrs on steel and aluminum typically are classifed as Class 1 or Class 2 and can be removed with standard silicon carbide advanced technology brushing (ATB) brushes. Class 3 burrs are well attached burrs that are small in nature, but require signifcant, mechanical fnishing force in order to be removed. Class 4 burrs are well attached burrs that are large in nature, have signifcant route thickness and have a larger and stronger attachment point than Class 3 burrs. Class 3 and 4 burrs require a more aggressive deburring product. Some success can be achieved with short-trim wheel brushes. Adding bridles to disc brushes also helps control fare and shortens the trim of the brush to make it more aggressive in steel applications. However, tackling well attached burrs on exotic materials such as hardened steel, Inconel, Hastalloy, stainless steel and titanium requires a solution such as ceramic grit with a sharp, jagged grain that provides a deeper cut and removes material faster. Class 3 and 4 burrs require fnishing products that can stand up to the job and help shorten cycle times as well. Class 5 burrs are commonly known as "extruded burrs" and are not actually burrs, but rather a deformation of extruded material caused by drilling. Tese deformations typically indicate a problem within a process, whether it is too high of speed in drilling or in material feed. Tey appear as very large burrs that extrude from the base material. Te extruded or displaced material requires preconditioning with a chamfer or carbide cutter to remove the material. Preconditioning will leave the residual burr that is removed with brushing. Two Questions With an industry standard now in place, application engineers :: An unclear defnition of a burr has led to an industry standard for classifcation. Now shops can better under- stand the fnishing processes required based on the type of burr and the material on which it is found. TECH BRIEF 48 PRODUCTION MACHINING :: DECEMBER 2014

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