CA1105691A

CA1105691A - Rotary cutting tool with chip breaker

Info

Publication number: CA1105691A
Application number: CA312,071A
Authority: CA
Inventors: Evgeny I. Morgunsky; Valery A. Sidorenko; Nikolai V. Vishnev; Vladimir A. Plotnikov; Petr I. Yascheritsyn
Original assignee: Fiziko Tekhnichesky Institut Akademii Nauk Belorusskoi SSR
Current assignee: Fiziko Tekhnichesky Institut Akademii Nauk Belorusskoi SSR
Priority date: 1977-10-18
Filing date: 1978-09-26
Publication date: 1981-07-28
Also published as: NO783513L; JPS5484680A; GB2006651B; ES245513U; FR2406491B1; FI783021A; SE7810814L; GB2006651A; ES245513Y; FR2406491A1; AT356998B; NO147783B; DE2842183A1; CH633466A5; ATA708078A

Abstract

ROTARY CUTTING TOOL

Abstract of the Disclosure The herein-proposed cutting tool comprises a spindle carry-ing the cutting element shaped as a solid of revolution, and a chip-breaker knife which, according to the invention is made likewise as a solid of revolution and set on the spindle rotata-bly round its geometrical axis so as to provide a clearance in machined.

Description

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The present invention relates generally to the sphere o~
metal working and more specifically to rotary cutting tools.
The invention can ~ind most utility when applied for machin-ing both outside and inside cylindrical sur~aces, as well a~
i~tricately shaped surfaces and planes of workpieces made from hard-to-machine ductile metals characteri~ed by ~ormation of continuous chips.
~ n indlspensable prere~uisite 1or practic~l realization of the process of rotary cutting ~eatured by high machining speeds, is a success~ul solution o~ the chip brea~ing problem. ~he here-to~oro known chip breakin~ methods applied in rota~y cutting can be classified into two groups. Th~re belongs to the first ~roup the method o~ makin~ notches, grooves or checks on the tool cuttin~ face; said method though capable o~ stable chip brea~ing is, however, subjected to some disadvantages. First the pro~ision of notches, grooves; and the like reduces the nu~-ber o~ ~easible tool regrindings and hence its total service life; secondly, discontinuity o~ the cutting blade impairs the quality of sur~ace finish.
Provislon o~ attached stationary knives for chip breaking within the zone of the chip contact with the tool lace is in-strumental in chip breaki~g; however9 interaction of the chip with the cutting element and the attached stationary kni~e ra-sults in heavy impact loads imposed upon the both o~ them at the place of their contact with the chip~ so tha~ cyclic stresses

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are liable to arise on the cutti.ng blades thereo~, e~entuating ~ f in their premature wear and chipping-of~ which to a great extent affects adversel~ tool endurance and the quality o~ machined surface finish.
There pertains to the second group of` chip-breaking methods the one providing for chip thick~ess variation in the course o~
metal cutting process by virtue of a~ eccentric tool cutting lipu When cutti~g with such tools their top (i.e., the point on the cutting lip corresponding to a maximum depth o~ tool penetra-tion into the material being machined) which imparts the final shape to the machined surface, is displaced with respect to the workpiece a~is, and chip breaking occurs due to radial runout of the eccentric tool cutting lip.
The result is an altered actual cutting depth a~d af~ected quality and accuracy o~ machining.
One more rotary cutting tool is known to comprise the body accommodating the spindle car~yi~g the cutting element shaped as a solid o~ rev~lution, viz., cup-shaped, and the chip breaker kni~e.
~ he kni~e is set in the spi~dle bore and held by a nut. The knife blade is located as close as possible to the taper face o~
the cutting element and is spaced apart ~rom the cutting lip thereo~ at a distance not e~ceeding the zone o~ chip contact with said tool sur~ace.

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.' , ,' , ' The knife is made as an L-shaped member tigh~ly forced against the taper flank of the cuttin~ element.
When the spindle is running the cutting element removes the chip a~d the knife, in turn~ periodically cuts the chip into portions.
i A disadvantage inherent in the above tool co~struction resides in the fact that impact loads c~uses hi~h cyclic stres-ses, whereby the c~ttin~ lips of both the cutting element and the chip breaker kni~e are liable to badly crumble out at the points of their contact~
~ s a result~ the e~d~rance of the cutting element and the chip breaker knif'e is adversely affected and the ~ualit~ o~
surface finish is impaired~
It is a principal object o~ the present invention to provi--de a rotary cutting tool that would feature high endurance.
It is another object of the present invention to provide a rotary cutting tool that would produce high-quality machined sur~ace ~inish.
It is one more object of the p~esent i~vention to provide a rotar~ cutting tool that would feature a lon~er service li~e as compared to the known tools o~ the same type.
In keeping with the aforesaid and other objects the essence o~ the present invention resides in that a rotary cutting tool comprises: a bodyj a spi~dle housed in said body; a cutting ele-ment made as a solid of revolution a~d set on said spindle; and .' ~ 1~ _ .
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a chip breaker knife which, according to the invention is shaped as a solid of revolu-tion and is set on said spindle rotatably round its geometric axi5 in such a manner that a clear space is left in between the knife blade and the surface of the workpiece being machined.
The impact load is reduced as the knife engages the chip due to the knife being made in the form of a body of revolution and freely mounted on an axle. As a result of these structural features the knife engages the chip, cutting up or breaking the latter, and simultaneously rotates freely about its axis~ Since rotation is influenced by the chip engaged by the knife, the relative sliding speed between the knife and the chip drops and, conse~uently, the impact loads, depending on the relative speed, are reduced.
It is expedient that the knife be mounted on a spindle built up by two portions arranged eccentricall~
with respect to each other.
Setting of the knife on the spind]e through the agency of a mandrel enables one to adjust the clearance between the krlife blade and the face of the cutting element to suit the depth of the tool impression and, hence, the thickness of the chip removed.
It is common knowledge that the service life of a cutting tool depends on the resistanc~ of the material and the number of possible regrinding5 of the cutting part.
After the cutting part has worn down to a critical level, ît has to be reground, in which case the relative location of the cuttJ~ng element and the chip breaking knifé is disturbed . .. . . . . .

;. , . . i , inevitably, and the chip breaking process becomes unstable.
Accordingly, a blunt cuttiny element has to be replaced with a new one~ The claimed invention (featuring an eccentric ring) allows the relative position of the knife and the cutting element to be adjusted, so it is not required to discard a worn cutting element, but only regrinding is necessary. It is obvious that the general service life of the cutting element increases.
When the cutting element is reground the gap between it and the knife increases. and 30 in order to restore the original gap the ring mounted on an eccentric portion has to be turned until the gap has the necessary size. 1'he eccentric port:lon of the spind:Le, therefore, makes it possible to grind the cutting element several times, helping extend the service life of the cutting element.
The proposed rotary cutting tool may be so implemented that the chip breaker knife 'be set on the spindle through the agency of a ring held to the eccentrical spindle portion~
~o According to a further embodiment of the invention the 'knife may also be set on the spindle through the ayency of a shaft journalled in bearings and linked to the spindle through a roller held to the shaftl said roller being in essence the planet pinion of a planetary gearing. wherein used as the sun wheel is a flanye made fast on the tool body.
The aim of such a constructional arrangement is to prevent the knife from beiny jammed and thus add to the endurance of both the knife and the cutting element.

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, It ls expedient that the bearings he accommoda-ted ln an eccentric bushing located i.n the spindle.
In order to restore the original gap between the cutting element and the knife following regrinding of the cutting element, the eccentric sleeve wh:ich fits in the spindle has to be turned until the necessary spac.ing i5 obtained.

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It is also practicable tha~ provision may be made in the proposed rotary cutti~g tool for a component part held to the spindle and so shaped that one of the surfaces thereo~ is lo-cated as close as possible to the knife side surface~ while its other surface is in permanent contact with the ~ace of the cutt-ing element.
- ~he aforesaid component part and its being located o~ the spindle make it possible to prevent chips from getting into the space confined between the face of' th~ cutting element and the knife end face and hence to avoid ~nife jamming and thus incxea-se efficienc~ o~ the chip breaking process, as well as to add to ~he endurance of both the ~nife and the cutting element~
It is with a view to simplifying the setting-up procedure and increasin~ the ef~iciency of the chip breaking process and the endurance of the tool that the knife blade is expedient to have a regularly repeating profile~
It is most advantageous for the tool construction when the regularly repeating profile o~ the knife blade is a star-shaped one, as such a shape rules out knife jamming and knife regrind-ing can be dispensed with as chips are broken rather than GUt off. In addition, the chip breakin~ process occurs outside th~
cutting zone~ whereb~ setting up of the tool is rendered easi~r~
its endurance is incxeased and chip breaking efficiency is made higher.

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In what follo~s the present invention is illustrated by a detailed description o~ a speci~ic embodiment thereo~ and the accompanying drawings, wherein:
~ ig. 1 is a general longitudinal section~ ~ragmentarily cut-away view o~ a rotary cutting tool showing the chip-breaker k~ife ~et on the spi~dle through the ageny of a mandrel, ac-cording to the invention;
Fig. 2 is a general longitudinal section view of a rotary cutting tool showing the chip-breaker knife set on the spindle through the agency o~ a rin~, according to the invention;
Fig. 3 is a general longitudinal section view of a rota~y cutting tool showin~ th~ chip-breaker knife journalled in bearings a~d kinematically linked to the spindle through th~
agency o~ a planetary gearing, according to the in~ention;
E`igo 4 i3 a general longitudinal section, partly cut-away view o~ a rotary cutting tool showing the chip-breaker kni~e and a component part adapted to prevent chips ~rom getting into the space confined within the ~ace o~ the cutting element and the end ~ace o~ the chip-breaker kni~e, according to the inventioni Fig. 5 is a s~ction taken along the line V-V in ~i~ 4;
I~`ig. 6 is a ~eneral longitudinRl section, ~ragrnentarily cut-away view of a rotary cutting tool showîng the chip~brea~er ~ni~e whose blade has ~ star-shaped contour, according to the i~ention; and ~ ig. 7 is a view o~ th~ knife blade as taken along the arrow ~ in ~ig. 6.

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Referrin~ now to the accompa~ying drawings, proposed herein is the rotary cutting tool as illustrated in ~ig. 19 whose body 1 accommodates a spindle 2 carrying~ a cutting element shaped as a solid o~ revolution, and a chip breaker knife 3.
Used as a solid o~ revolution in this particul~r case is a cup 4 having a circular lip 5 and a taper side surface 6. q'he spindle 2 is journalled in bearings 7 inside the body 1.
According to the i~vention, the chip brea~er knife 3 is shaped as a solid of revolution and i8 set on the spindle 2 ro-tatabl~ round its geometrical axis in such manner that a clear space is le~t in between the knife!3 and .~ the surface of a workpiece 8 bein~ machined. Thls is conducive to lower impacts loads upon the cutti~g lips of both the knife and the cutting element and hence to lower stresses therein.
As different-thickness chips are to be removed in the course machining, the clearance between the kni~e blade and the ~ace of the cutting element is made adjustable.
Adjustment of said clearance can be done by a number of ways. ~hus, the kni~`e 3 can be set on the spindle 2 throu~h the ~genc~ of a ~landrel mado up by two portion~ 9 und 10 arranged eccentricall~ relative to each other, the portion 9 being fixed in positio~ in the spindle 2 through a screw 11, and the k~ife

3 is rotatably mounted on the portion 10.
Fig. 2 shows the chip breaker kni~e 3 to set on the spindle through the agency of a ring 12 which is mounted on an eccentric portion 13 of the spindle 2 through the usc of screw~ 14.
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-Fig. 3 illus~rates the chip breaker kni~e 3 to set o~ thespindle 2 through the agenc~ of a shaft 1~ journalled in bearin~s 161 while the other end of the sha~t 15 carrie~ a roller 17 which is in ef`fect the planet pinion of a planetary gearing. A ~lange 19 loaded by a spring 20 is bolted to the body ~, said ~lange being adapted to serYe as the sun wheel in said planetary gearing.
The bearings 16 are accommodated in an eccentric bushing 21 located in the spindle 2. ~:
Provision ca~ be made in the herein-proposed rotary cutting tool for a component part 22 (~igs. 4,5) secured on the spindle 2 and made so that its sur~ace 23 lS located a~ close as possible to a side surface 24 of the kni~e 3~.whereas the other surface 25 is in permanent contact with the ~ace 6 o~ the cutting ele-ment 4 Provision o~ the component part 22 prevents the knife 3-from getting jammedO
~ igs. 6 and 7 represent a rotary cutt~ng tool~ wherein the blade of the kni~e 3 has a regularly repea`ting profile made as, say, alternating projections 26 (lugs) and depressions 27 (cir-cular gashes), or star-shaped, single-lu~, double~lug, etc.
~ he rotary cutting tool o~ the present invention operates ~s ~ollows.
Once the machine~ wherei~ use is made o~ the proposed tool, has been star~ed, the tool is approached to the workpiece 8 being machined and a trial pass is per~ormed, whereupon a re~uired :. . . :, , cutting dep~h is set against the respective vernier and power feed motion is engaged to make a working pass. When the machine is operating the cutting element 4 (Fig. 1) engages the workpiece ~ and removes the chip with its cutting lip 5.
The chips flow along the side taper surface 6 bf the cutting element 4, and the knife 3 gets in contact with the chips to break the latter and at the same time rotates round its geometric axis.
When the taper face 6 of the cutting element 4 is resharpene~ the clearance between the face 6 and the blade of the knife 3 increases.
I'o compensate for wear and restore the required amount of said clearance the eccentric mandrel 9, 10 (Fig. 1) is turned or the ring 12 (Fig. 2) is rotated relative to the eccentrical portion 13 of the spindle 2.
Provision of the additional component part 22 ~Fig. 4) held to the spindle 2 prevents the chips from getting between the taper face 6 of the cutting element 4 and the side surface 24 of the knife 3 to avoi~ jamming of the latter.
The spindle 2 (Fig. 3) along with the cutting element

4 and the knife 3 performs rotary motion in the course of the cutting process. As a result, the roller 17 held in position to the shaft 15 which carries also the knife 3, interacts with the flange 19 to ride thereover, i.e., the knife 3 is imparted ~ .

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compound motion, viz., planetary motion round the tool axis and positive rotation round its own axi~. ~he positive rotation of the knife 3 enables its jamming to be precluded.
The sprin~ 20 p~t in between the ~lange 19 and the tool body 1 provides for a stable co~act between the roller 17 and -~
the ~lange 19.
Turning o~ the eccentric bushing 21 in the bore of the spind-le 2 changes the distance between the knife a~is and the tool axis, i.e., the clearance between the blade o~ the ~ni~e 3 and ~he taper ~ace 6 o~ the cutting eleme~t 4.
Just as the chip-breaker knife 3 gets in contact ~ith the chips removed by the cutting element 4 (Fig~ 6), the kni~e turns round its own axis, while the chip~ ~low down alo~g the taper ~ace 6 of' the cutting element 4. It i~ by virtue of rotation of the spindle 2 together with the cutti~g element 4 and the knife 3 that the latter catches up the chip outside the zo~e of cutting strikes fiercely thereagainst, thexeby breaking it into pieces.
At the moment when one of the lugs 26 of the chip-breaker ~ni~e 3 assumes the position above the ~ront surface 6 o~ the cutting olement 4 t the chip pieces get~ into the space between the latter and the knife 3 have no time to jam the latter as at the next moment the knife depression 27 stands over the face 6 of the cutting element 4. ~he broken chip pieces being not opposed by the chip brea~er ~nife 3, the~ are thxownl by virtue o~ cen~
tri~ugal ~orce, o~ the ~ace 6 o~ the cutting element 4.

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Thank~: to the :façt that the chip is broken mostly b~r the side sur~aces of the depression 27 it is no longer ~ecessarg to strictl;y maintain the amoun~i o;~ cleaxan6e b~twee~ the kni~e and the ~aco of the cuttin~; element which simpli:eie~ tool se t tin~---up .

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A rotary cutting tool, comprising: a body:
a spindle accommodated in said body, a cutting element shaped as a solid of revolution located on said spindle, a chip breaker knife made as a solid of revolution and set on said spindle rotatably round the geometrical axis of the knife in such a manner that a clear space is left in between the knife and the surface of the workpiece being machined for the chip to fall through.

2. A rotary cutting tool as claimed in claim 1, wherein the knife is mounted to the spindle by means of a mandrel composed of two portions with one of the portions arranged eccentrically with respect to the other.

3. A rotary cutting tool as claimed in claim 1, comprising: an eccentric portion of said spindle, a ring secured on said eccentric spindle portion and carrying said chip breaker knife.

4. A rotary cutting tool as claimed in claim 1, comprising: a shaft, bearings for said shaft to journal in, a planetary gearing adapted for said spindle to link to said knife and incorporating as the sun wheel, a flange made fast on said tool body, and a roller held to said shaft to serve as the planetary pinion.

5. A rotary cutting tool as claimed in claim 4, comprising:aan eccentric bushing located in said spindle and adapted for said bearings to accommodate.

6. AA rotary cutting tool as claimed in claim 1, comprising: a component part made fast on said spindle and so made that one of its surfaces is situated as close as possible to the side surface of said knife, while the other surface is in permanent contact with the front face of said cutting element.

7. A rotary cutting tool as claimed in claim 1, wherein the blade of said knife features a regularly repeating profile.

8. A rotary cutting tool as claimed in claim 7, wherein said periodic profile is a star-shaped one.