Drilling tools Cutting edge geometry and its influence As shown in the table below it is possible to select the most suitable cutting edge geometry

Drilling tools Cutting edge geometry and its influence As shown in the table below it is possible to select the most suitable cutting edge geometry

Drilling tools Cutting edge geometry and its influence As shown in the table below it is possible to select the most suitable cutting edge geometry for different applications. If the most suitable cutting edge geometry is selected then higher machining efficiency and higher hole accuracy can be obtained. Cutting Edge Shapes Grinding name Shape Features and effect Application Conical 4 r The flank is conical and the clearance angle increases toward the centre of the drill. General Use Flat r The flank is flat. Easy grinding. Mainly for small diameter drills. Three flank angles As there is no chisel edge the results are high centripetal force and small hole oversize. Requires a special grinding machine. Surface grinding of three sides. For drilling operations that require high hole accuracy and positioning accuracy. Spiral point To increase the clearance angle near the centre of the drill conical grinding combined with irregular helix. S type chisel edge with high centripetal force and machining accuracy. For drilling that requires high accuracy. Radial lip i The cutting edge is ground radial with the aim of dispersing load. High machining accuracy and finished surface roughness. For through holes small burrs on the base. Requires a special grinding machine. Cast Iron Aluminium Alloy For cast iron plates. Steel Centre Point drill 4 r 2 This geometry has two-stage point angle for better concentricity and a reduction in shock when exiting the workpiece. For thin sheet drilling. WEB THINNING The rake angle of the cutting edge of a drill reduces toward the centre and it changes into a negative angle at the chisel edge. During drilling the centre of a drill crushes the work generating 50-70% of the cutting resistance. Web thinning is very effective for reduction in the cutting resistance of a drill early removal of cut chips at the chisel edge and better initial bite. Shape Xtype XR type Stype N type Features The thrust load substantially reduces and the bite performance improves. This is effective when the web is thick. The initial performance is slightly inferior to that of the X type but the cutting edge is hard and the applicable range of work is wide. Popular design easy cutting type. Effective when the web is comparatively thick. Major Applications General drilling and deep hole drilling. Long life. General drilling and stainless steel drilling. General drilling for steel cast iron and non-ferrous metal. Deep hole drilling. Q025 TECHNICAL DATA