Page 202 - Demo

200 ISCAR CENTER DRILLINGCenter drilling is a type of mechanical processing to produce centering holes. Center holes are purely technological elements and are used to provide support for parts that are machined between centers or with tailstock. There are different types of center holes. The form and dimensions of the center holes depend on the design of the part, technological machining operations, and part dimensions. The most common types of center holes are: Type A %u2013 also called %u201cplain type%u201dis a center hole with a single 60-degree chamfer. Figure 5.1Type B %u2013 also called %u201cbell type%u201d is a hole with 2 chamfers, a 60-degree chamfer and additionally a 120-degree chamfer at the start of the hole. The 120-degree chamfer protects the main 60-degree taper from damage and deformation that can cause inaccurate centering of the tailstock center. Such center holes are necessary for machining parts with a large number of operations. Figure 5.1Figure 5.1 Type A %u2013 %u201cPlain Type%u201dWithout Protective ChamferA%u00d8 DC 60%u00b0 max. SDL SDL2 120%u00b0 DETAIL ASCALE 2 : 1Type B %u2013 %u201cBell Type%u201dWith Conical Protective ChamferA 120%u00b0 60%u00b0 max. %u00d8 DC SDL SDL2 120%u00b0 DETAIL ASCALE 2 : 1