NO820621L - RING HOLE CUTTERS. - Google Patents

Abstract

Annular hole cutting device, each tooth being provided with at least three cutting edges (34, 36, 38). which are designed to cut their respective chips. The two innermost cutting edges (34, 36) in the radial direction are formed on the portion of each tooth which corresponds to the thickness of the step between successive. teeth.

Description

J The present invention relates to an annular hole cutting device. j US-Reissue patent 28,416 relates to an annular hole-

cutting cutting device with a plurality of teeth which are spaced around the front (lower) end of the hole cutting device. Each

jitans provided with a plurality of circumferentially displaced ice cutter eggs. The cutting eggs are designed so that they cut individual chips. The radially innermost cutting egg

jextends radially over a shallow tooth gap which is designed in 1 step between successive teeth, and the outermost! !cutting egg extends radially over an outer rifle which extends spirally upwards along the hole cutting device between successive teeth. In accordance with

in the above-mentioned patent, the rifle has a radial depth equal to approximately half the thickness of the hole-cutting device's annular wall, and the riser a thickness equal to approximately one-half of the annular wall's thickness. Accordingly, it has

in the radial direction inner cutting egg on each tooth a radial extent which is also approximately half the wall thickness of the cutting device. Thus, the rifling has a radial depth sufficient to deflect chips that are cut

using both cutting eggs. I!

In the above-mentioned patent it is also proposed that - if mon

wish to provide three circumferentially offset cutting edges on each tooth, so that each tooth cuts three chips instead of two - the radial depth in each flute and the thickness of the step can be the same as with a cutting device with a two-step tooth, and the part of the wall of the cutting device which corresponds to the depth of the rifle is designed into two circumferentially displaced cutting edges instead of a single cutting edge. It

in the radial direction, the outermost cutting egg is formed by an outer tooth gap which has a relatively small axial dimension and is open to the rifle. However, the rifle has a radial dimension that is approximately half the wall thickness of the cutting device,

why it can easily absorb the chip that is cut off, in j radial direction the innermost cutting egg. In addition, the stepped part of the wall still has a cutting egg with a width equal to approximately half the wall thickness of the cutting device, and a chip that is cut with the help of this egg must be emitted -radially-^i

;rif len.

! IN

Although the cutting device according to the above patent

has a cutting effect that is very superior to the cutting effect of the ring-shaped cutting devices that have previously been used, the chip has, now the cutting device must be reused

.to cut holes on a production basis, tend not to move freely from the innermost tooth slot into the rifling. When this happens, the cutting effect is much slower and you get a tapered, oversized hole with a rough surface. In addition, the service life of the cutting edge is significantly reduced. The most practical way to overcome the problem of poor chip flow from the tooth hatch and riffle of an annular hole cutter is to provide a cutter that cuts thin, narrow chips that are easily aligned

i In the rifle as soon as they are cut. IN

i As soon as a chip is cut, it normally begins to curl into a spiral. The volume and stiffness of the spiral sponge is determined by its width and thickness. If a chip

.is wide, it does not bend easily and occupies a relatively large area

volume. The net result of a large volume of the spiral fo; armed chips is that less chip material can move up<p>ad through the channel formed by the rifling during a given period of time. However, if the chip is narrow, it bends more easily when it hits an obstacle, e.g. the wall in one

riffle or a hole, and requires considerably less depth when j

in it moves up through the rifling. A narrow chip can be moved more easily into the rifle and has less tendency to clog it. A narrow chip can also be easily influenced in ; above its elastic limit and therefore easily breaks into pieces

into smaller fragments. Also, a narrow chip forms an easily compressible, spring-like coil that tends to twine with others as it moves up a helical riffle. When such twisted spiral chips engage the wall of the hole provided in ; j by means of the hole-cutting device, the resulting friction tends to counteract their further rotation by the hole-cutting device, whereby they are forcefully combed upwards by means of the rear side wall of the spiral rifle without plugging it. It follows that the rifle can have a smaller cross-section

area when the chip width is reduced. It also follows that the cutting strength of the device increases due to the fact that with a side wall

Given thickness is increased between successive I

jteeth thicker now the size of the rifle is reduced. A thick layer provides greater rigidity, resulting in a more accurate hole with better surface smoothness. With increased strength

i of the cutting device, a thicker chip can be cut and/or ller! in bone, a greater number of teeth are used, whereby an i is also achieved

faster cutting action.

I! The main purpose of the invention is to provide a ring-shaped hole cutting device which cuts more efficiently and faster as well as more accurately and in addition provides a better surface and has a longer service life.

i Another purpose of the invention is to provide

a knurled, ring-shaped hole cutter that has greater resistance to breakage than a hole cutter of

previously known type of the same size. i 1 A more particular purpose of the invention is to o to-! provide a knurled, annular hole cutter wherein each tooth has at least three cutting edges, each preferably having a radial dimension substantially less than half the wall thickness of the cutter, so that the total radial dimension of the rifling can be as small as about one-third of the wall thickness of the cutting device and so on

I I

sufficiently deep to freely accommodate the chips that are cut using the widest cutting egg.

Another purpose of the invention is to provide a ring-shaped hole cutting device which is more efficient than the previously known hole cutting devices of the same size.

i This is achieved by each tooth in the hole cutting device!

be designed with at least three cutting eggs, each of which is

in intended to cut one separate chip, and of which two are out-! formed on the part of the side wall of the hole-cutting device which lies radially inside the rifle, i.e. in the step section between

on consecutive teeth.

Another purpose of the invention is to provide an annular hole-cutting device which is advantageously suitable for being designed as two axially adjacent sections which are telescopically connected to each other, -

I i jjdpsyå lrik ht vvait elkrdket etøt ytmefnranetmeenrre e iaeler down, ueptsaofm orrtmhi uertav t, ighkvasen tr ålfrh, uemolg lstsksitljæalmremes aenapv oarrdrt' neielinat gta:\.vvt

The Jhole cutting device can be made of cheaper material,

■ such as e.g. hardened, low-alloy steel.

Another purpose of the invention is to provide

|an annular hole cutter which is designed to<!>allow the manufacture of hole cutters of 1:.1 diameter and with significantly less tendency to induce<:>hairlike cracks when the rifling is sharpened or hardened. A further purpose of the invention is to provide an annular hole cutting device with such a design that allows a standard size hole cutting device to be easily reduced in diameter to provide a special size hole cutting device.

<1>A further purpose of the invention is to provide an annular hole cutting device which is well suited for cutting through a plurality of stacked workpieces. | j Another purpose of the invention is to provide a ring-shaped hole cutting device which is well suited for heavy cutting without the rifling and tooth hatches being blocked. The preferred embodiment of the hole cutting device

according to the invention has an annular sidewall which is designed with a plurality of circumferentially spaced teeth around its lower end and a corresponding number of spiral riffles around its outer periphery. Each tooth is designed with a plurality of circumferentially and preferably vertically offset cutting edges, of which at least two are arranged on the part of the tool corresponding to the thickness of the step between successive teeth, and the remaining cutting edges are j designed on the part of the tooth corresponding to the radial depth of the rifling. According to an embodiment of the hole-cutting device according to the invention, the total width of two inner cutting edges in the radial direction is greater than the total width of the remaining cutting edges, in which case the thickness of the step is greater than the depth of the rifle. In all conditions, the depth of the rifling is at least as great as the width of the widest of the two inner cutting edges. cutting device-

the .wall thickness of the ning can be dimensioned-to-provide

in a relatively narrow cutting path in order to thus maintain the force necessary to feed the cutting device through a workpiece at a relatively low speed.

In the following, the Invention shall be described in more detail with reference to the attached drawings which show examples of execution, and where: ; Fig. 1 shows in perspective an embodiment of a cutting device according to the invention;

i J Fig. 2 on a larger scale shows part of the hole cutting device in fig. 1 which is denoted by a circle 2;

FFig. . 3 4 vpeirsesr peksntiivtt isk etotg is in the lisnnjietn t v3 i- see 3 peå t pfaigrt. i<1>a<;>v a tooth in the hole cutting device;

Fig. 5 shows in perspective another embodiment of the hole cutting device according to the invention;

In Fig. 6 on a larger scale, it shows part of the hole cutting device in Fig. 5 which is denoted by a circle! 6;

Fig. 7 in perspective and in section shows a tooth in j'

in the hole cutting device in fig. 5;

Fig. 8 from below and on a larger scale shows the hole cutting device in relation to the workpiece through which it is fed; Fig. 9 perspectively shows a further hole cutting device, which is somewhat modified with regard to the one shown in fig. 5-8; Fig. 10 in vertical section shows a part of another embodiment of the hole cutting device according to the invention; Fig. 11 perspectively shows a portion of hole cutting in j the device in fig. 10; j ' in Fig. 12 in vertical section shows a part of the hole cutter device in fig. 10; j Fig. 13 shows the hole cutting device, seen from the end; Fig. 14 in vertical section shows a part of another embodiment of the hole cutting device, and j

fig. 15 shows the way in which the hole cutting device in fig. 14 is designed to cut through stacked workpieces.

In the drawing, an annular hole-cutting device according to the invention is generally denoted by 10 and has..._a stem... 12... and a shaft 14. The hole-cutting device's stem 12 has the shape of an inverted bowl with a side wall 16 and an upper wall 18 .. The one. The inner end of the side wall 16 is designed with a plurality; cutting teeth 20, which are preferably regularly spaced. i i A spiral rifle 22 extends upwards around the outer periphery of the cutting device, until each tooth 20. Successive rifles 22 are separated by means of a non-toothed part 24 on the outer periphery of the cutting device. In the case of the hole-cutting device shown, the riffles and the unthreaded parts extend over each other

the entire length of the side wall of the cutting device. In certain

'cases the cutting device works more efficiently when the riffles and the unthreaded parts are significantly shorter than the side wall. The portions of the annular side wall located between successive teeth 20 comprise steps 26. The radially outer surface 28 of each step 2 6 forms the radial inner wall of each riffle 22. Each riffle 22 has a, in the direction of movement the rain, front side wall 30 and a rear side wall 32.

in

In the embodiment according to fig. 1-4, each tooth 20 has three cutting edges 34, 36, 38. The cutting edge 34 is separated

forward in the direction of rotation from the cutting edge 36, and the cutting edge 36 is separated forward in the direction of rotation from the cutting edge 38. The cutting edge 34 is located at the lower end of the front surface 40 of an inner tooth hatch 42. The upper end of the tooth hatch 42 is inclined radially outwards in the direction

upwards, as at 44. The cutting edge 36 is located at the|lower end of the rear surface 46 of a second tooth hatch 48, which is formed in the step 26, directly next to the inner tooth hatch 44. The upper end that the second tooth hatch 48 is bent upwards in a radially outward direction, as at 50 above the inner tooth

hatch 42. The cutting edges 34, 36 are separated by means of a circumferential projection 51 at the lower end of the radial inner surface 52 of the tooth hatch 48. The cutting edge 38 is located at the lower end of the rear surface 32 of the rifle 22 and separated backwards from the cutting edge 3 6 by means of a shoulder 54 at the lower end of the rifle 22.

The bottom surface of each tooth is designed with two interruptions. ; or release surfaces 56, 58 . In the operational state of the cutting device, the release surface 56 is inclined axially upwards, and 1

In 11

.radially inwards, while the release surface 58 inclines axially upwards and 'radially outwards. Moreover, all these slip surfaces are inclined j;oip!plaid ten from the grdad , rfe.espkesk. ti8v° e - sk1j0æ°r, e-foegr g to in tpilevreifieerbrisik ngre entøndivngen!dig

■clearance for the cutting eggs. The two release surfaces 56, 58 intersect in a comb 60 which cuts it in the radial direction j outermost cutting edge 38. Although the release surfaces 56, 58 can be ground so that the comb 60 cuts any of the cutting edges

the eggs, this comb cuts preferentially in most or even the outermost cutting eggs. As a result of the slanting of the release floats 56, 58, the cutting edges 34, 36, 38 are slanted axially in a radial direction for offset vertically as well as circumferentially.

! An important feature of the cutting device according to opI p-!j

IN

the invention is that a lower end of each tooth 20 has two cutting edges 34, 36. In the execution of the cutting. the device in fig. i In 1-9, the step 26 has a radial dimension which is preferably j greater than the radial depth of the adjacent rifle 22. i As the cutting edges 34, 36, 38 are circumferentially displaced j in the manner shown, when the cutting device is rotated and j is fed into a workpiece, a separate chip is cut by h<y>er of the cutting eggs.<;>The relative dimen- | tions are such that the radial depth of the rifle 22 is not much less and is preferably greater than the width of the two ; cutting eggs 34, 36. Immediately after cutting, it will

i by means of the cutting edge 34 cut chips be directed into the tooth gap 48 and then into the rifle 22 at the radial J; inclined position of this cutting edge and the upper end parts 44 and 50 of the tooth hatches 4 2 and 48. In the same way, with the help of the cutting edge 36, the chip will be cut immediately after i l cutting, as a result of the radial inclined position of this

cut-egg and the curved wall 50 of the tooth socket 48, be guided in

in

in the directly adjacent riffle 22. The axial dimension of the second tooth slot 48 is preferably greater than the axial dimension of the tooth slot 42 to facilitate removal of the chip from the cutting edge 34 into the tooth slot 48 and then into the riffle 22, j' whereby the tendency to accumulation and packing of chips in the toe-hlaukr en en 4t2 eundnnegnås st. il Skå jølnedt e sdkren åsvteid llhinjgeelp n aavv ... dskenjänre e-egeg ggeskn år3nI 4e —!

chip upwards and outwards, i.e. in a direction perpendicular to the radial direction of the edge 34 and the plane of the slip surface 56, the circumferential extent of the tooth gap 42 must be sufficiently small to prevent the chip, which is cut off egtgen 34, i, to some greater extent, to curl in

iitannluken 42. If the dental opening 42 is sufficiently small

■ - i ■in the peripheral direction, the chips cut by means of the edge 34 tend to remain relatively straight and are directed more upwards and outwards in relation to the tooth gap and into the rifle '22. The circumferential width of the inner tooth hatch 42 should preferably be somewhat greater than approximately half the thickness of the step 26, and of the order of magnitude approximately one third of the thickness of the step 26. The tooth hatch 42 peri-

ferric dimension should vary inversely of the step 26 thickness. Thus, with the aid of the cutting edges 34, 36, the chips cut immediately after cutting will be directed radially outwards and axially upwards into the riffle 22. The chips cut with the aid of the cutting edge 38 are likewise fed upwards into the riffle 2i2.

As each of these chips is relatively narrow and hairy

spirals, j they are efficiently guided radially outwards by means of the toothed hatches. When

the spiral shavings from each; of the cutting edges move axially upwards and radially outwards into the rifle 22, they seek to twine with each other. As soon as the twisted spiral spins touch the wall of the hole provided, it seeks I

and then exerted friction to counteract the rotation of the chips with the hole cutter. When this happens, the rear surface 32 of the rifle in which they are located will engage the spiral chips and comb them upwards out of the rifle. Then the spiral shavings

are narrow, and especially if they are also relatively thin, they can easily be compressed between the inner surface 28 of the rifle and the wall of the hole provided in the workpiece. As the back surface 32 of each rifle 22 is designed as a continuous spiral, the flow of chips upwards in the rifles is continuous, uniform and unhindered. If, therefore, the tooth hatches.,4 2, 48 are designed and dimensioned so that they lead chips that have been cut by means of the cutting edges 34, 36 mainly directly into the rifle 22, and because the flow of chips in the upward direction through

If the riffle is not obstructed, a free flow of shavings upwards is ensured

of the rifle. The free flow of small chips up the riffle is more easily affected when the cutting device is fed internally

refrigerant under pressure. Because the chips are narrow and inherently weak, they also tend to break into pieces more easily when they exit the hole, and thus they do not have

tendency to wrap around the cutting device and/or

in

;the mandrel when they emerge from the cut hole and thus'block or prevent further exit of chips which are then cut. If the tooth gap 42 is narrow in the peripheral direction, then, as pointed out earlier, the tendency for the chips cut by means of the edge 34 to curl

is mentioned, so that it is led into the rifle 22 in a more created;

state. This reduces the likelihood of the chip getting wedged in and clogging the tooth hatch and the rifling.

If one wishes to provide a certain clearance between the inner periphery of the wall 16 and the cut-out cylindrical piece of wreckage, the inner periphery of the wall 16 can taper outwards at an angle of approx. 1° from the lower end, a short stretch, e.g. about. 12.5 mm, as shown at 62 in fig. 3 .j The part of the inner periphery of the side wall of the cutting device situated above the tapered part can be j

cylindrical, as shown at 64. On a small stretch above

the cutting edges have a clearance of approx. 0.2 mm to the outer peripheral surface of the scrap that is cut out of the workpiece. The clearance between the inner periphery of the wall 16 of the cutting device and in the cylindrical piece of wreckage can also be achieved by making the j j cylindrical inner periphery somewhat eccentric in relation to

to the outer periphery of the cutting device. As also shown in fig. 3, i can, if desired, the depth of the rifle 22 be made progressively larger in the upward direction by grinding the inner surface 28 of the rifle so that it tapers radially inwards up to the part 62 i,

somewhat greater extent in the upward direction than above this

party. This results in a radial clearance for it by means of

<1>of the egg 38 cut shavings immediately after this .«shaving erj

cut. The rifle as a whole can have a cross-section with a taper

area in an upward direction to facilitate the ejection of shavings from this. Each rifle may also taper so that it is peripherically wider at its upper end than at its lower.—- '

The arrangement of a stronger, stronger step part,

1 while keeping the width of all chips very narrow, has

Also with the advantage that an axially deeper internal tooth gap can be permitted. An axially deeper tooth gap contributes to a greater flow of coolant across the cutting teeth and to -

also allows the teeth to be kept sharp for a longer period of time before it becomes necessary to re-sharpen the teeth.

It will be appreciated that in order to reduce the force required to feed an annular hole cutter into a workpiece, e.g. of steel, it is necessary that the path or track cut by means of the hole cutting device is relatively narrow. For a hole-cutting device intended for cutting a small or medium-sized hole in steel. e.g. up to a diameter of 25.4 mm, is a practical sk ij

.dimension for the hole cutting device wall thickness approximately j 4.06 - 4.57 mm. With such a hole-cutting device, when each

tooth is provided with three cutting edges, as shown in fig. 1 - 4, and the side wall of the cutting device is approx. 4.57 mm thick,

and a thick step is desired, the radial depth of the rifle may be

of the order of 2.03 mm, and thus the thickness of the step can be approx. 2.5 4 mm. The two inner eggs 34, 3 6 can have a width of approx. 1.27 mm, or, if desired, the innermost cutting egg 3 4 can have a width of approx. 1.14 mm and

the intermediate cutting egg 36 can have a width of approx. 1.40 mm. With a relatively strong step and a relatively thin ring-shaped wall, each chip that is cut with the help of the three cutting edges can thus be easily accommodated in the riffle 22. The peripheral dimension of each riffle is preferably several times greater than the radial depth of each riffle. If that.however

a thick step is not required, the cutting device can be dimensioned

so that the step's thickness is approx. 0.25 mm less than the half wall thickness of the cutting device. If the side wall of the cutting device is approx. 4.57 mm thick, the thickness of the step can be approx. 2.03 mm and the rifle has a depth of 2„54 mm.! In this case, the cutting edges 34, 36 can each have a width of approx. 1.02 mm. In all cases, the depth of the rifling is greater than the width of the two inner cutting edges. When the

available power is limited, a hole-cutting device can'

of large diameter is provided with a thinner side wall to reduce the force required to rotate the cutting device. When the side wall is relatively thin, the step is preferably thicker than the depth of the rifle, whereby the hole cutting device becomes stronger, in the hole cutting device in fig. 5-8 differ in terms of design from those shown in fig. 1-4 mainly in one respect only. In the case of the hole cutting device in fig. 5-8, the part of each tooth corresponding to • the depth of the riffle 22 has two cutting eggs 70, 72 instead of a single cutting egg, as shown at 38 in fig. 1-4. In this case, each cutting egg 70, 72 may have a width equal to approximately half the depth of the tooth gap. The release floats 56, 58 on each tooth are inclined thereon with reference to fig. 1-4 described manner and preferably cut each other in a comb 74, which in turn cuts the outermost cutting egg 72 approximately in its centre. in in the hole cutting device in fig. 5-8 has a cut-: egg 72 which is circumferentially displaced from the cutting egg 70 i

very little degree, so that these cutting eggs provide

esn kjæenreeasntoe rdspnoin ngeson m er habr eestn emst entforar l sksvæerkninig ngasv lihnujell . in Hvstiå's lJi, the egg 72 must in practice be displaced by approximately only a quarter of the displacement of the other teeth, preferably no more than approximately 0.38 mm. The deformed, single, by means of the eggs ' 70' i> 7 2 cut chip breaks very easily as soon as it hits the j j

an obstacle. This weak chip, however, is immediately fed into the larger rifle 22, which eliminates the narrow chips

in

tend to pack in the portion of the rifling located between the shoulder 82 (Fig. 8) and the side wall 76 of the hole provided.

If the egg 72 is shifted backwards from the egg 70,

so that each of these edges cuts individual chips, the part of the riffle 22 that borders the edge 72 j is preferably designed as a tooth hatch 84 (fig. 9), which has a vertical extent which is essentially equal to the vertical extent of the tooth hatches 44, 50 When thus the egg 72 is sufficient

offset to cut a separate chip, it is guided thus

cut shavings using the tooth hatch 84 directly in. in the. -IN

IN

large rifle 22 and has no tendency to clog teeth

! hatch 84.

When the in fig. 9, the cutting device shown is rotated and fed into a workpiece, four separate chips will be cut using the cutting edges 34, 36 and 70, 72. With it on'

fig. 5-8 shown cutting device cuts the eggs 34, 36

> separate chips and, as explained earlier, the eggs 70, 72 will cut a single, more easily breakable chip. In both cases, the spurs that are cut by means of the cutting edge 34' will mainly immediately be directed outwards into the groove 22, and the chips that are cut by means of the cutting edge 36 will also be mainly immediately directed upwards and outwards into the groove 22. In the same way, the individual or separate chips that

is cut using the cutting edges 70, 72 directed upwards into the rifle22.

in ! j Mainly immediately after the chips are cut in by means of the cutting eggs 34, 36, 70 and fed into the rifle

22, however, they come into frictional contact with the side wall of the hole provided in the workpiece. As the chips, which have not been broken, normally have a certain spiral shape when they engage the side wall, the frictional force thereby created will try to<;>counteract rotation of the spiral chips with the cutting device. As a result of this, the chips will essentially immediately engage the rear side wall portion 78 of the rifle 22 (Fig. 6) and, in the previously described manner, are combed upwards out of the rifle without obstruction. Because of

the small circumferential extent of the attachment 82 in the embodiment in fig. 5-8, the chips will thus not engage in and thus be caught by the rear side wall part 80 of the rifle

.22. This is desirable as each sponge tends to tickle itself! between the outer periphery of the cutting device and the side wall 76i of the hole provided is significantly reduced. This is

especially the case if the chips are thin and easily breakable.

Furthermore, as the chips are narrow, they show less tendency to cut into the wall of the hole provided as they move upwards through the riffles. The narrow ones! chips, on the other hand, break more easily when they come out of the formed part. ii; hole and thus does not wrap around the cutting device and/or the mandrel and thereby does not prevent the free - flow-of-swarf- as —

, is then cut.

Another advantage of the embodiment according to fig. 5 - 8 and '9,' where the part of the tooth corresponding to the depth of the rifle is provided with two instead of one cutting egg, consists in that, if it is desired to arrange a cutting device which has an outer diameter such as e.g. is 0.50 mm smaller than a standard size cutting device, you only need to take a ready-made standard size hole cutting device and grind

■ at a distance of 0.25 mm from its outer periphery. The depth of the rifle 22

is thus only reduced by 0.25 mm, and it will still be sufficiently large to occupy the width of the chips that

is cut using the other three cutting eggs. It will be understood that also with the one in fig. 1-4 shown cutting device

can the outer diameter of the cutting device be ground down in order to provide the

substantially as large as the width of the widest cut chip.

A further advantage of the cutting device having at least two cutting edges in both the step portion and in the portion of the tooth corresponding to the depth of the rifling is that when a metal chip is cut it tends to '! expand as much as 10%. With cutting devices such as those according to fig. 5 - 8 and 9, the depth of the rifle is more than 10% staring than the width of the largest cutting-egg. Thus, the tendency for some of the expanding chips to attach to or clog the rifle 22 is further reduced. Although the eggs j 70, 72 in the cutting device according to fig. 5-8 only cuts a single chip, the chip has a central weakening line and thus easily breaks up into small, narrow chips.

Another advantage of having two cutting edges on the step part of the hole cutting device is that, if desired, a stronger wall can be provided and a wider groove can be cut. So far, difficulties have arisen when the width of the cutting edge on the step has exceeded approx. 2.54 mm, as it has been difficult to move the wide chip radially outwards in the rifle. By means of the present invention danni es ■! where two narrow chips with the help of the cutting edges on the step part of the hole cutting device, which chips can very easily move in radial, and..axial direction into the outer rifle,- and-a-cutter-

! ■;I i bp: aå i , npe rmoded uDke esn pjoå bnrfsebidgads. e i1ss0 .om - o1v5 evrsitstige ehr ul5l,0sk8 jmæm rekaanon rdlnetint goepr pnlåigsI nerII

Iij high degree hole cutting device according to fig. 1-4. In the hole cutting device in fig. 1 - 4, the release surface 56 is inclined radially inwards and axially upwards at an angle of approx. 20° - 25°, and it follows that the cutting edges 34, 36 are inclined

posed similarly. This is called here "positive internal slant-i i

angle". A bevel angle of this size is suitable for Iseg to cut holes with a chip load on the cutting device that does not exceed, for example, 0.051 - 0.076 mm

per revolution. The formed thin shavings are very flexible and break very easily. When a chip is cut, it is guided, as pointed out earlier, directly upwards in a path perpendicular to it

plane of the slip surface and perpendicular to the radial orientation of the cutting edge. With a relatively large positive internal angle of inclination, the chips are therefore guided by the cutting edges 34, 36 radially outwards towards the side wall of the hole which in

be cut. If the chips are thin, they break very easily

pieces of ice and it is not difficult to divert them upwards again

nom the riffles of the cutting device in the manner previously described.

If the chips are relatively thick, they do not bend so easily when they hit the side wall of the hole being cut;

i and they may tend to clog the rifles when it j

on a production basis, many holes are cut. For this reason is

it is not desirable to have a large angle of inclination for the cutting edges 34, 36, as shown in fig. 1-4, if the cutting device is used to cut a large number of holes on a production basis with a relatively high feed rate, e.g. j 0.152 mm chip load. If the cutting device is designed1! to be used under conditions that result in high chip load,! the radial inclination of the two inner cutting edges must be significantly less than 25°, so that the chips are directed in a more ! vertical direction upwards and less laterally outwards. By be-j

clear chip loads must the radial inclination angle

of the two inner cutting edges preferably lie within the range +10° - -3°. In the cutting device of fig. 10 is the inclination angle, a of the cutting edges 34 and 36 shown:-to be -approx.---H-10-^

and in the cutting device in fig. 14 and 15, the inclination angle b for these cutting edges is approx. -3°. Bevel angles of this magnitude tend to guide chips cut<i>!by means of these cutting edges in a more vertical path

compared to a tilt angle of 25°. At relatively small inclination angles, it is also advantageous to arrange these cutting edges with positive radial slip angles r i

relation to the inner periphery of the cutting device, as shown in fig. 13. When the radial drop angle for these eggs is somewhat positive, e.g. up to 10°, each chip that is cut is guided somewhat radially outwards and upwards with the help of these eggs. When

the inclination angle is approx. -3° (fig. 14), a small positive radial release angle (10°) will guide the chips somewhat radially outwards and vertically upwards, so that the chips will either just come clear of the upper inclined surfaces 44 and 50 ay

, the dental hatches 42 and 48, or interfere with these with a lot

small angle, so that they can be deflected outwards through the riffles 22 with very little distortion. A small bevel angle reduces the necessary impact or bending of the chip by means of either the upper ends of the tooth hatches 42, 51 or

the side wall of the hole being cut. Small inclination angles in the franca area. +10° to -*3° thus reduces the tendency for clogging of the riffles 22 with shavings, when the shavings are relatively thick.

These small inclination angles for the inner cutting edges have several other advantages. When the bevel angle approaches 0, it will be seen that the cutting edge becomes shorter and j at

the cut chip becomes narrower. A narrower chip is more easily fed up through the rifling than a wider chip and for this reason has less of a tendency to jam the rifling. If the shavings ! flows freely and evenly up the riffles, less force is required to rotate the hole cutter than if the chips j

'seeks to wrap himself in the rifles. If the cutting device is exposed to less torque, it can have a thinner side wall, and because it is less exposed to stresses, a longer lifetime can be expected for the tool.

A further advantage of relatively small, internal

bevel angles are the hole-cutting device's ability to cut holes in stacked material. On_ fig.^ 15 provide-

brings e.g. the hole-cutting device shown holes in two vertically stacked plates P1 and P2. Since the radial inner end of the cutting edge 34 forms the front edge of the tool, as soon as the inner end of the edge 34 has penetrated the upper plate P1, the wreckage S in the hole cutting device will be cut cleanly from the plate P1 and the cutting edge 34 can then easily penetrate the underlying plate P2. When the internal bevel angle increases to as much as +10°, the cutting device can still easily cut through stacked material. This is the case because when the comb

60 (fig. 10) penetrates through the uppermost piece in the stack, the radially outwardly facing flange on the central piece of wreckage is

very thin, and even if the wreck is cut free, is

sufficient moderate downward pressure on the hole-cutting device to cause it to easily penetrate the underlying workpiece and thus bend and cut through the thin remaining step or flange around the wreck!

i • piece that is cut out of the top piece of material. An internal inclination angle of approx. +3° has been found to provide-

bring excellent results with regard to both large chip loads and cutting through stacked material.

As mentioned earlier in connection with fig. 1-4,

the comb 60 represents the intersection between the two slip surfaces 56, 58 and preferably cuts the outer cutting edge 38. The cutting edge 38 preferably has a positive radial slip angle (not greater than about 10°) in relation to the outer periphery of the cutting device. At those in fig. 10 - 15, the outer cutting edge 38 is provided at its outer end with a further release surface 86 which is inclined upwards and radially outwards with a significant external inclination, e.g. j

40 - 45" on the horizontal plane. This angle is denoted!with

in c in fig. 10, and the external inclination angle of the landing surface

IN

58, which is preferably located in the area approx. 20° - 25°, is j

denoted by d. Experience has shown that the inclination of the outermost part of the outer cutting edge with a fairly sharp angle, such as 40 O - 45 O, has several advantages. The significant angle of inclination facilitates the guiding of the chip,

fsrom a. ver eggsken oareav t vdeed t hhujell lp soam v dsken jæyretrs e and skrjæersue-letgegre, ri-.-Ongnasdå , . i.b- oén rt...

IN

relatively large included angle e at the outer ends of the cutting edge 38, i.e. the angle between the outer periphery of the side wall of the cutting device and the lower slip surfaces. A I large inclined angle in this peripheral part of the cutting device results in less tooth chopping and a longer life for the tool.

As shown in fig. 13, the comb 60 cuts the edge 38 approximately midway across the depth of the rifle 22. Preferably, the ice cutting line 88 between the release surface 58 and the release surface 86 is about a quarter of the depth of the rifle inward from the outer periphery of the hole cutting device. As can be seen from fig. 13, the cutting edge 38 is connected to the shoulder 54 with a relative

large radius 90. This rounded shoulder 90 extends

in preferably forward to a place within at least approx. 1.02 mm from the cutting edge 36. Although the approach between

IN

these two cutting edges are curved to this extent, these cutting edges can cut two separate chips, provided that two cutting edges are separated vertically by a distance that exceeds the feed speed of the cutting device. It has been found that

as long as these eggs are separated approx. 0.25 mm, two separate chips are cut. The vertical distance between these eggs is determined by the length of the approach between them and the angle of inclination of the release surface. As pointed out earlier, have a chip

tendency to expand as soon as it is cut. A relatively strong chip tends to expand to a greater extent than a thin chip. The rounded shoulder 90 allows a strong j chip to curl and expand radially without causing any wedging effect between the wall of the hole being cut and the shoulder 54. The by means of the edge 38 cut, curled

shavings therefore float freely up along the rifle 22. |

With a cutting device according to the present invention, easy chip ejection and other advantages are achieved!

without reducing the strength of the cutting device. The reason for |<1>this is that at least three, and preferably four or i ii more cutting edges are arranged on each tooth, and the depth ay the rifle

in

can be significantly less than the width or thickness of the step portion between successive teeth. The strength of each annular hole cutting device, which has a fluted sidewall, is determined primarily by the thickness of the step. ■- If .-.it .

thus, for a special hole-cutting device, it is determined that the step must have a pre-determined minimum thickness, the actual wall thickness of the cutting device according to the invention can be smaller than with the previously existing hole-cutting devices, since the depth of the rifle, with the help of the present invention, may be less than the step thickness<p>g still sufficient to accommodate the widest chip cut with any of the cutting edges. For cost-related reasons, it is desirable to have a thinner side wall, and also to achieve a narrower cutting path. However, it must be pointed out that a thicker step is not critical. As indicated earlier, the chips are guided much more easily and more evenly into the outer flute, due to the step being designed j with two cutting edges. The stresses on the step are thus considerably less when it is designed with two cutting edges instead of one. The cutting device's strength properties are improved so<s>even if the thickness of the step is less than the depth of the riffle. IN

Another advantage of an embodiment of the cutting device according to the invention appears from fig. 3. As stated! t<I>j previously can be stepped 26 thickness near each tooth, if it ! is desired, be significantly greater than the depth of the riffle 22. This is because the part of the tooth corresponding to the step* thickness is designed with at least two cutting edges, each of which has a width that is preferably significantly less than the depth of the riffle . If, therefore, the inner wall of the rifle tapers radially inwards in an upward direction immediately near its lower end and relatively sharply up to approximately that in fig. 3 with 62 designated parts, with the help of the edge 38 cut into shavings, it has immediate clearance in the rifle. Then, in the same way, the inner periphery of the cutting device, near its lower end tapers radially outwards in an upward direction, has risen to its smallest thickness!

i j near the upper end of the side wall of the cutting device in the area designated by 8 6 in fig. 3. This part 86' then becomes the critical part of the cutting device with regard to the strength of the cutting device. From this it follows that with a cutting device of a conventional type, where the depth of the rifling near the tooth of the cutting device is as great as the thickness of the step, the total wall thickness of the cutting device must have been considerable in '<I>| larger if the cutting device had been designed with a rib

,with increasing depth in the upward direction and with clearance around its inner periphery. It also follows that with a cutting device according to the invention, a significantly greater clearance around the inner periphery of the cutting device can be achieved without the wall thickness of the cutting device needing to be increased. Greater clearance is also desirable due to the possibility of increasing the coolant flow rate to the cutting teeth.

The arrangement of a relatively thick step and a relatively shallow chute in the annular hole cutting device is also very important from a production point of view. When you try to grind a relatively deep groove in the side wall, there is

in that at a given wall thickness a very strong tendency to

small hair-like cracks develop in the step, which can result in a relatively short lifetime for the tool. Relatively deep channels also increase the tendency for hair-like cracks to form during curing. If, however, the channel is relatively shallow and the riser relatively thick, the riser part can absorb significantly more heat and thus reduce

in

the tendency for such cracking during the hardening and grinding of the rifles. A shallow rifle is also desirable in view of the production costs. It can be produced or sharpened in a shorter time and results in a proportionally increased lifetime for the tool.

Although not shown in the drawings, annular hole cutters require a central guide pin or<i>j a central guide drill. In practice, the bore must be 88 in the shaft

14 for retaining the steering pin or the steering drill have at least one predetermined size. The inner diameter of the hole-cutting device must thus be at least equal to that of the guide pin

in or the diameter of the pilot drill. Then the cutting device according to! ! the invention has a step that can be thicker than the chute's | depth, the outer diameter of the cutting device according to up- ;

In the invention, with a guide hole of predetermined size, j be smaller than the minimum practical outer diameter of a hole cutting device which is constructed in accordance with the existing practice.

Another advantage, which follows from the fact that the hole-cutting device- ! ning has a thicker step section, compared to so far,

occurring hole cutting devices, is that it can be produced

i, two pieces, namely a toothed section and a stem section, which are axially telescopically fixed together in the step portion and connected to each other by screwing, welding, etc.; The thicker step allows such a telescopic connection without significantly affecting the strength of the hole-cutting device. A hole-cutting device of such a two-piece construction is advantageous from a cost point of view. Only 1 the toothed section needs to be made of expensive steel. When in !:å tenernesntae tbtels ir isstleidtt enbf' oer høvheer le vhiduelrle skbjaæ'rree adnoern dtnainngneedne . section

1 in

A thicker step portion also allows the design of more teeth around the periphery of the cutting device, as it can withstand higher torque and pressure. A larger number of teeth results in more cutting edges and faster cutting

effect.

; In the case of hole-cutting devices of the type .

which is shown in fig. 5 - 8 and 9, where each tooth is designed

with four cutting eggs, it is, when no special considerations

available, it is advantageous to design the two inner cutting edges ! with approximately the same width and the two outer cutting edges with approximately the same width. However, special considerations may dictate otherwise. If you e.g. want to cut a - v. very flat surface on the central, cylindrical piece of wreckage, the innermost cutting egg 3 4 should be considerably narrower than in

then, in the radial direction the following cutting-egg 36. Uni there,;

everyone . ratio, the widest of these two edges must not be j wider than the depth of the groove 22. If, on the other hand, you want to cut an extremely even hole in the workpiece,!I

in . must the outermost cutting egg 72 be significantly narrower than; it

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i,radial direction subsequent cutting egg 70. If you • i want to cut both a hole with a flat wall and a centrally j tral piece of wreck with a flat wall, the innermost and the outermost cutting egg must be narrower than the intermediate ones 1 cutting eggs. Under all conditions, in the case of cutting, the device is intended for cutting holes in steel and.has

at least four cutting eggs, the best results normally when the widest cutting egg has a width that does not exceed approx. 1.59 mm. If, however, increased rigidity is desired, the width of this cutting edge can be increased as much as

three times.

. ; I! Although it is preferable to design the comb between the slip rafts 56, 58 so that it cuts the outermost cutting edge, for certain adaptations the slip surfaces can be ground so that the comb cuts one of the other cutting edges. Ifif.ex. the hole cutting device is used to provide

jet holes in two or more workpieces that are stacked on top of each other, and the innermost cutting egg has a relatively large positive radial inclination angle, e.g. 25°, the cam between two slip surfaces must lie very close to the inner periphery of the side wall of the cutting device. With such a hole cutting device it occurs, if the crest or the highest point

of the cutting device lies close to the inner periphery of the side wall, negligible difficulties in feeding the cutting device through both of the workpieces lying on top of each other. If, however, as shown in fig. 10 - 15, the innermost cutting egg has a small or negative angle of inclination, the two slip surfaces can cut each other along the outermost cutting egg, and the cutting device can still be used to cut holes in stacked material.

The cutting device's highest point can be moved ten!. the inner cutting egg 34 without changing the position of the comb 74 ij. As the release surface 56 slopes upwards in a circumferential ! direction, the comb 74 is located, if the length of the approach e j 51, 52 is significantly increased, above instead of below the edge 34 i In this case the edge 34 will begin the cutting actionj

and penetrate the uppermost workpiece before the comb 74. If the edge 34 is thus maintained with a very small width, the narrow lip left on the cut wreckage will not prevent this from moving upwards into the cutting device; in

ning's bore, so that the cutting device can penetrate freely;

into the underlying workpiece. j<1>

As a chip tends to expand somewhat immediately after 1 it has been cut, it is desirable to grind the surface 28 or j the riffle 22 so that the riffle has its maximum radial depth in the j transition between the surfaces 28, 32. The frictional resistance i between one of the edges 38 cut shavings and the inner wall of the gutter are thereby reduced to a minimum.

Claims (1)

<I> 1. Ring-shaped hole-cutting device, characteristic I serted by a substantially cylindrical, annular side-1 wall having a plurality of cutting teeth, circumferentially spaced ! around its lower end and means for mounting the hole cutting device on a rotating drive member, a plurality of rifles; which are circumferentially spaced around the side wall and extend upwardly from the lower end thereof, each tooth being connected to the succeeding tooth by means of a circumferential step at the inner periphery of the annular wall, which steps are located radially adjacent to the flutes, each having circumferentially separated and mainly radial front and rear side walls as well as a circumferential inner wall which forms the radial outer side of the step, while the teeth have at least three radial cutting edges, namely one in the radial direction inner in cut-egg, one radially intermediate cut-egg i and at least one radially outer cutting edge, of which the inner and intermediate cutting edges are designed on j in the steps and arranged in such a way x relative to each other that they each cutting its own chips when the cutting device is rotated and fed into a workpiece, whereby the combined width of them with the help of the inner and intermediate cutting eggs cut chips are equal to at least the thickness of the steps and each of the inner and intermediate cutting eggs has one In a radial extent that is below the thickness of the steps, which is formed with a tooth hatch extending upwardly from the inner and intermediate cutting edges and opening radially outward into the radially adjacent riffle at its upper end, the outer cutting edges at least partially forming, the lower end of the circumferentially rear side walls of adjacent riffles, and each riffle has a radial dimension which does not fall below the radial dimensions of the ! inner and intermediate cutting edges and a circumferential j dimension significantly greater than its radial dimension, 'hsvkojrævreed -edgge is spopn to ssotm egpdaarnnteies nae v of the skinniest eaong ormdnelilnogmenlis g-gseidndeveejgg I is directed upwards' through the associated tooth socket and into the i1 radial direction adjacent rifle reaches the cutting device is rotated and fed axially into a workpiece. in in 2;. H hole cutting device according to claim 1, k a r a k-,t| e r i s e r t in that each tooth is provided with three cutting edges. : I j3. Hole cutting device according to claim 2, characterized in that the cutting edges on each tooth are • .displaced circumferentially so that the radially outer end of the inner cutting edge is displaced forward in the direction of rotation of the cutting device from the radially inner end of the intermediate cutting edge and the radially outer end of the intermediate cutting edge -egg is offset 1 forward from the radially inner end of the outer one .! scrambled eggs. ; 4. Hole cutting device according to claim 2, characterized in that the thickness of the step is greater than the radial depth of the rifle. ,5. Hole cutting device according to claim 1, k" a r a k-t <;> erized in that each inner and intermediate cutting egg is inclined radially outwards and axially upwards at an angle that does not exceed 10° in relation to the horizontal plane, 6. Hole-cutting device according to claim 1, k a r a k- I| t.erized in that each inner and intermediate cutting egg is slanted radially outwards and axially at an angle of between +10° and -3° in relation to the horizontal plane. j j 7. Hole cutting device according to claim 6, characterized in that each inner cutting egg has a positive release angle in relation to the inner periphery of the side wall of the hole cutting device. 8. Hole cutting device according to claim 6, characterized in that each outer cutting edge has a positive radial release angle in relation to the outer periphery : of the side wall of the cutting device. 1 ; 9. Hole-cutting device according to claim 2, characterized in that each tooth is designed with a pair of radially oppositely inclined break-off or release surfaces which also incline axially upwards and backwards in the peripheral direction from each cutting edge, one of the slip surfaces having the same radial extent as at least the inner and intermediate cutting edges and is inclined radially outwards and axially upwards at an angle that does not exceed 10 ° in pre- 'hold to the horizontal plane. in 10. Hole cutting device according to claim 2, c a r a k-t, characterized in that each tooth is designed with a pair of opposite, inclined cutting or release surfaces, which also lean axially upwards and backwards in the peripheral direction from each cutting egg, one of the release surfaces having the same in radial extent as at least the inner and intermediate cutting edges and is 'axially inclined in a radia!. direction outwards at an angle of from +10° to -3° in relation to the horizontal plane. 11.. Hole cutting device according to claim 10, characterized in that the second slip surface extends backwards from the outer cutting edge and is inclined radially outwards and axially upwards at an angle that does not exceed approx. 25°. 12. Hole cutting device according to claim 11, characterized in that the latter release surface inclines j i radially outwards and axially upwards at an angle of between 20 and i i ■25°. in <!> 13. Hole cutting device according to claim 12, characterized in that each tooth has a third interruption or release surface which extends backwards from the outer cutting edge and radially inwards from the outer periphery of the cutting device side wall, which third slip surface is inclined radially outwards and axially upwards at an angle of approx. 40° - 45° in relation to the horizontal plane. in IN II-i,14. Hole cutting device according to claim 13, characterized in that the third release surface at the outer cutting edge has a radial extent that is equal to approximately one quarter of the adjacent rifle's radial depth. 15. Hole-cutting device according to claim 2, characterized in that each intermediate cutting edge is connected to the adjacent outer cutting edge by means of a shoulder extending in the peripheral direction, as in the .at least for a part has a curved surface that ends up to the outer end of the intermediate cutting-egg. 16. Hole-cutting device according to claim 15, characterized in that the attachment has a circumferential length that is greater than the radial extent of the intermediate cutting edge, and the curved surface is formed by a radius that lies mainly tangential to the part of it in .peripherally extending approach, which is located <r> immediately behind the radially outer end of the intermediate cutting egg. 17. Hole-cutting device according to claim 16, charac- terized in that the curved surface at its counter- at the set end is mainly tangential to the outer cutting egg. 18. Hole cutting device according to claim 2, characterized in that each tooth is designed with four radially extending cutting edges, of which the two outermost cutting edges form the lower end of the adjacent rifle's rear side wall sections. 19.. Hole cutting device according to claim 18, characterized in that the thickness of each step is at least somewhat greater than the radial depth of each rifle. f.