Blade of twist drill S gets pointed characteristic and its application

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The structure of twist drill and geometrical parameter see a picture 1. Y of horizontal blade bevel is to be in end panel is umbriferous in horizontal blade and advocate the included angle between cutting blade, the accident of the size of Y and horizontal blade depends on the size of the horn after relying on to get what core is in and vertex angle. When vertex angle is certain, horn is jumped over after big, criterion Y is smaller, horizontal knife is longer (be in Y control commonly 55 ° of 50 ° ～ the) inside limits. 2 twist drill suffer force to analyse twist drill to get the case getting power when cutting more complex, basically have workpiece stuff be out of shape fight force, twist drill and hole wall and cut the attrition force between bits to wait. Broach will get on every cutting blade Fx, Fy, Fz3 the action of component of force. If the graph is shown 2 times, below good case, cutting blade suffers force to basically be balanced each other. The force of the others is axial force and circumferential force, circumferential force forms torque, add man-hour to consume main power. Twist drill arises below cutting strength effect transverse cupping, fore-and-aft bend reach seize change form, seize change form among them most remarkable. Torque is main by advocate the cutting force on cutting blade arises. Classics is finite yuan of analysis computation is knowable, 80% what the torque on blade of the common cutting that get a tip occupies total torque about, the torque that horizontal blade produces is occupied about 10% . Axial force basically arises by horizontal blade, common the axial power that gets the generation on pointed horizontal blade occupies 50% ～ about 60% , advocate the axial force on cutting blade is occupied about 40% . It is with diametical D=20mm twist drill exemple, in other parameter the change below changeless circumstance gets core ply, cong Jigang spends metabolic curve (3) seeing a picture can see, increase as D of the diameter that get core, stiffness Do increases, deflection is reduced. This shows, the ply that get core increased to increase the axial power when twist drill works apparently, affect performance of cutting tool cutting directly, and the size of cutting tool stiffness is influential also to machining geometrical precision. Because the horizontal blade of common twist drill is cutting of the horn before be being lost greatly, get the meeting when cutting to produce serious extruding, want to produce bigger axial to fight force not only, and should produce bigger torque. To a few thick broach that get core, like parabola broach (G broach) with broach of partial hard alloy (one of its characteristics are to will get core ply by the 11% ～ of diameter of common twist drill 15% increase 25% ～ 60%) to wait, its tigidity is better, bore linearity is good, bore diameter is accurate, feed can be increased 20% . But the accretion of the ply that get core brings about horizontal blade necessarily longer, increased axial force and torque accordingly, raised installation negative charge not only so, and can produce bigger effect to machining geometrical precision. In addition, because the contact of horizontal blade and workpiece is linear contact, when getting a needle to enter cutting state, be controlled hard by the positional precision of treatment aperture and geometrical precision. Accordingly, slant to prevent to bring in machining a process, often need to drill central hole beforehand with central getting. To solve afore-mentioned problems, use the method that in horizontal blade two end open cutting slot to reduce horizontal blade length commonly, reduce extruding, reduce axial force and torque thereby. But in be being machined actually, the problem of the cutting of the horn before losing that gets a tip and difference of function of centering of means of straight line contact not from go up at all get settlement. For this, people undertakes study ceaselessly and be improvemented in pointed to getting appearance all the time, s blade gets a needle to solve one of better methods of this one problem namely. The classification that 3 S blade gets a tip and characteristic S blade get a needle to also call Wen Siliu to get a tip, from end panel umbriferous look, blade of its horizontal stroke is S form. From the front umbriferous can see auger the needle is mid summary beat, submit parabola coronal form. Because S blade gets a needle to be curvilinear blade, the instantaneous that gets a needle to enter cutting and workpiece are point contact, reach stability from centering sex consequently all excel is common twist drill, axial force is reduced, cutting function is improved, broach life is lengthened, be raised significantly by treatment aperture quality, the positional precision of aperture and geometrical precision are satisfactory, auger cut feed and feed speed to rise further. According to parabola coronal shape and horizontal blade appearance, s blade gets a needle to basically can be divided for 3 sort model, namely blade of small S of blade of blade of Gao Guan S, low coronal S and low coronal (4) seeing a picture. Blade of S of the 3 sort that graph 4S blade gets a tip Gao Guan gets blade of S of pointed Gao Guan to get a tip with the United States bit grinding machine repairs Jidingsi Louis the Wen Siliu that grind (Winslow) gets a needle to be. Have as an attached institution of this machine tool a special cam mechanism, long grind the S blade that go out to get pointed cutting part (L0) is longer, curvature of shape of S blade coronal is bigger. Characteristic: Because S share is higher (L0 is longer) , eliminated the role before losing basically, can come true even before horny cutting, need not add chamfer of horizontal blade cutting additionally so. Long grind efficiency tall, comfortable grind the thick cutting tool that get core at repairing. But get pointed most advanced ministry to divide relative weakness, intensity is poorer, do not suit high speed to process tall hardness work. The data that the material that get a tip requires to collect appliance to have better tenacity character (be like high-speed steel kind) . Blade of low coronal S gets blade of S of pointed low coronal to get a tip with Germany 5 axes grinder (provide process designing software by Swiss Numroto) long grind get a needle to be a delegate. The cutting part that get a tip (L0) is shorter, curvature of shape of S blade coronal is lesser. From end panel umbriferous direction can see horizontal blade is big S form, among local can be line of one small Duan Zhi, horizontal blade part has two small chamfer, can reduce the before losing role of the part that get a tip. Characteristic: Because of cutting part (L0) is opposite shorter, get a tip most advanced reach advocate cutting blade strength is better; Because get curvature of shape of coronal of pointed S blade small, because this reachs stability from centering sex all blade of S of excel Gao Guan gets a tip. After the horn before blade opening a horizontal stroke, auger cut function to be improved apparently, withheld blade of Gao Guan S to plunge sharp good point already, rose to get the intensity with most advanced needle again. Apply to the work that processes harder data (like steel, cast-iron wait for) . Broach material can use data of tall hardness of steel of high speed tool, hard alloy or other character. Of this kind of broach long grind more complex, the demand is higher. Blade of low coronal small S gets a tip this kind of appearance that get a tip and blade of Gao Guan S get a tip more similar, blade of its horizontal stroke also is small S form, the vertex angle that get a tip (2Ø) relatively afore-mentioned get a tip two kinds bigger, advocate cutting blade is short (L0 is opposite shorter) , coronal shape curvature is lesser. Characteristic: Because of advocate cutting blade is shorter, the torque in be being machined accordingly is lesser; As a result of advocate cutting blade intensity curvature of shape of tall, coronal is small, it is good that because this is mixed from centering sex,stability all compares blade of Gao Guan S to get a tip. Additional, small S blade gets a needle not to have generation of the horn before losing, because this does not need to add groove in horizontal blade point, commanded axial force already, reduced torque again, can improve cutting performance greatly. Comfortable wear tall hardness stuff at repairing (like hard alloy kind) broach of small helix angle. 4 S blade gets a tip long grind S blade to get pointed figure complex, long cross is spent big, repair the blade look that wears an ideal very hard with handiwork or common bit grinding machine, the bit grinding machine that general need makes appliance has special cam mechanism or implementation of ability of numerical control grinder are repaired accurately grind. The graph is shown 5 times repair simply for what S blade gets a tip grind a principle. Will be repaired to grind broach water paper-cover to be placed at A axis, after repairing emery wheel of the taper when grinding and contact of blade of cutting tool cutting, b axis is rotational inside XZ plane, a axis linkage (helix of face of the knife after pressing rises Cheng to ask to rotate) ; In the meantime, emery wheel photograph is in to cutting tool Y axis direction drops, form face of the knife after helix and blade of S form horizontal stroke. What blade of graph 5 S gets a tip is simple write the coronal account that grinds a principle to get a tip tall by conic emery wheel (taper is 60 ° of 30 ° ～ ) repair those who grind the circular arc size that give and helicoid to rise Cheng to lead a decision, certificate of the coronal when rate rising Cheng increases is high reduce, circular arc is bigger coronal shape is raised taller (5) seeing a picture. In addition, the radius that coronal shape reachs S curve high and the ply that get core is direct and relevant. Repair when grinding blade of low coronal S to get a tip, to improve cutting performance, can getting sharp point to leave with emery wheel of 75 ° horn give two small slot, make between two semicircle of its angle and S even the line basic parallel, can maintain already so advocate the intensity of cutting blade, can reduce S blade again the before losing horn of mid generation, make coronal shape parabola mid of edge before horn is equal to 0 or be less than 0 (R ≥ 0) . Like common twist drill, it is very important also that S blade gets pointed vertex angle, the top that get a tip horn is repaired grind limits to be commonly between 135 ° of 90 ° ～ . By the graph 1 knowable, vertex angle (2Ø) is smaller, advocate cutting knife is longer, cutting negative charge is bigger. What get a tip as a result of S blade is better from centering sex, because this need not use the method that reduces vertex angle to improve by the geometrical precision of treatment aperture (this method is machining the effect in practice and not apparent) , increase cutting negative charge in order to avoid. Contrary, to improve performance of cutting tool cutting, raise cutting tool intensity and cutting rate, the vertex angle design that gets S blade the tip commonly is 118 ° above (can amount to 140 ° ) even. In addition, the horn after the predestined relationship decided ministry of the predestined relationship outside getting a tip cuts the size of horn of the wedge when workpiece outside. The size of horn of cutting tool wedge should the basis is decided by the hardness of treatment workpiece material, when workpiece when data is weaker, need to choose bigger hind horn. The applied example that 5 S blade gets a tip we plunge S knife the needle to repair in grinding a technology to apply at the treatment of engine connecting rod is small aperture, obtained favorable result. Technology design: 20 foreword: Bore Ø17+0.

07mm, machine tool revolution: 200r/min, cutting speed 10.

68mm/min, feed 0.

45mm/r. 40 foreword: Ø17 of aperture of bore with a reamer.

5+0.

05mm. When using drill of Ø17mm common twist drill, because broach is reached from centering function,get cut stability difference, the aperture that gets often is achieved or exceed Ø17.

5mm, cause a product to discard as useless, handlers is forced to be repaired by hand grind get a tip, but long grind quality very flabby calm. We repair broach wear vertex angle the blade of low coronal big S of 6 ° gets the part after the horn after 118 ° , axial is 7 ° , circumferential pointed, s blade radius is 1.

5mm, two semicircle are even line length 0.

5mm, use 80 ° conic emery wheel to open a two slot in horizontal blade point, make the horn before coronal shape is more than or be equal to 0, can assure cutting tool already so advocate cutting blade place needs strength, avoided the extruding appearance that cutting of the horn before losing produces again, reduced auger cut axial force, improved cutting performance. Treatment carries out a proof, used this broach to control the geometrical precision of aperture effectively not only, and manufacturing efficiency rises significantly, percent defective drops greatly. The common twist drill that get a tip and S blade get Ø17mm the treatment effect contrast of pointed twist drill sees next tables. The watch is common the treatment effect contrast that gets needle and S blade to get a tip gets peaked kind blade of the common S that get a tip gets level of Ø17mm(of diameter of pointed twist drill) Ø17mm(standard) mural surface roughness is unqualified eligible (12.

5µm) cutting speed 10.

68mm/min, cannot raise 11mm/min, can raise ≥ of Ø of precision of 200r/min aperture of ≥ of 200r/min of machine tool rotate speed 17.

5mmØ ≤ 17+0.

07mm CNC Milling