钻头基础培训.ppt

DRILLING钻头TAPPING丝锥MILLING铣刀 Twist drill made by P. Cook, 1770 40% of all metal cutting operations are drilling operations.40%的金属加工是孔加工 整体硬质合金钻头刃口结构 3-Flute Bore Drill Cutting edge 1 2 3 4 1 2 3 4 90° Drill sectioned along cutting edge showing change of rake due to flute form. 1 2 3 4 The drilling process - flute form and rake. Component Tool Rake angle Wedge angle Clearance angle 0° Basic cutting tool geometry. Neg. Corr. Pos. 0° Clearance angle hard materials heat treated materials soft materials hard materials Rake angle. Insufficient clearance causes the drill to rub behind the cutting edge. It will make the drill work hard, generate heat and increase axial thrust. Results in poor hole quality and drill breakage. Excessive clearance results in lack of support behind cutting edge with quick dulling and poor toollife despite initial free cutting action. Clearance angle behind cutting tip for general purposes is 8 - 12° average. Influence of clearance on performance. Metal Composites Non-Metallics Fe- metals Non-ferrous metals steels cas- tings light metals heavy metals unalloyed metals alloys Composition of different materials produced by: sintering cladding bonding spraying vapourizing brazing Natural products wood leather Synthetic products synthe- tics glass ceramics concrete Auxilliary products coolants glues (bonds) cleaning materials etc. Materials. Structural steels Constructional steels High grade steels Unalloyed con- structional steels General structural steels with Rm 500 N/mm2 (73,000 psi) Other steels up to 0.55% C or Rm 700 N/mm2 (102,000 psi) Alloyed steel Unalloyed high grade steels Structural steels with 0.5% C Tool steels 1. to 3. grade Alloyed high grade steels Structural steels, wear-resistant and bearing steels Tool steels, HSS Corrosion resistant steels, stainless and heat-resisting steels Structural steel grades Rm 690 N/mm2 (100,000 psi) and lower than 0.05% P and S