GB1584185A - Tool for machining a bore or hole in a workpiece - Google Patents

Description

(54) TOOL FOR MACHINING A BORE OR HOLE IN A WORKPIECE (71) We, KALININGRADSKY TEKNICHESKY INSTITUT RYBNOI PROMYSH LENNOSIT I KHOZYAISTVAX a Russian corporate body of Kaliningrad, Sovetsky prospekt, 1, USSR, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a tool for machining bores and holes in workpieces, especially deep holes having a depth which exceeds the diameter by at least tenfold. The tool is capable of machining holes to a high accuracy class, and can be utilized for machining holes having non-circular profiles.

According to the present invention there is provided a tool for machining the surface of a bore or hole in a workpiece, comprising a shank, a journal on the shank, and a head mounted on the journal for rotation and including at least one cutting edge, the cutting edge or edges on the head lying on a substantially spherical imaginary surface having an axis inclined to the shank axis and about which the head is rotatable on the journal, and the or each cutting edge being at an angle to the meridian planes of said imaginary surface.

Some embodiments of the invention will now be described in detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective general view of a tool in accordance with the invention; Figure 2 is a cross-sectional view of another tool in accordance with the invention, the cutting edges being defined by planar sections of the head; Figure 3 is a general view of a tool embodying the invention, and having a cutting edge extending along a helical line; Figure 4 is a general view of a tool head wherein the cutting edges are formed by projections; Figure 5 is a cross-sectional view of a tool in accordance with the invention, the cutting edges all facing in the same direction; Figure 6 is a cross-sectional view of a tool in accordance with the invention, the cutting edges facing in opposite directions; Figure 7 is a partly longitudinally sectional general view of a tool in accordance with the invention, the head being formed by a lamination of discs; Figure 8 is a general view of a tool in accordance with the invention, wherein the journal is of a stepped structure; Figure 9 is a plan view of the tool shown in Figure 8; Figure 10 shows the tool of Figure 8, as viewed from the end face of the head.

In Figure 1 there is shown a tool wherein a head 1 having cutting edges 2 which lie on substantially spherical imaginary surface A (Figure 2) is mounted on a journal 3 of a holder or shank 4.

The head 1 has a housing or body 5 shaped as a body of rotation with a central bore 6 for mounting the head 1 on the journal 3. The cutting edges 2 of the tool, defined by intersection of the front or leading surfaces 7 with the rear or trailing surfaces 8 of blades either integral with the body 5 or fixed thereon in any suitable known manner.

The journal 3 of the shank 4 is preferably cylindrical and is provided with means for retaining the head 1 in the axial direction, e.g. a nut 9 cooperating with the threaded end of the journal 3. To provide for self-aligning to the tool in a bore or hole 10 being machined, the head 1 may be disposed on the journal 3 with a clearance 11 left between the journal 3 and the central bore 6 of the body 5, or else the journal 3 itself can be mounted on the shank 4 for limited radial displacement (the so-called "floating") which can alternatively be attained in any suitable manner of arranging floating tool heads, known to a person competent in the art.

The shank 4 of the tool is preferably shaped as a body of rotation and has either a tail portion (not shown) for fastening it in a tool holder or flanges for securing it on a faceplate (not shown), in a spindle, or in the slide of the machine tool (not shown).

In accordance with the invention, the cutting edges 2 are inclined relative to the meridian planes of the spherical surface A.

The head 1 is mounted on the journal 3 for rotation about the geometric axis 0-0 of the journal 3.

In its turn, the journal 3 is arranged at an acute angle a relative to the axis GL of the shank 4. To provide for rotation of the head 1 on the journal 3, the body 5 accommodates therein suitable bearings 12, which can be either antifriction or plain bearings and are adapted to take up radial and thrust loads in the course of a machining operation.

The cutting edges 2 of the tool lie in planar sections of the head 1 (Figure 2), each cutting edge extending over at least a part of an arc BC of a circle. With the cutting edges 2 having this structure, the manufacturing of the tool is simplified, same as its sharpening and resharpening, which in this case can be done in machines, e.g. in tool grinding machines, without the use of any specifically designed devices.

The cutting edges 2 of the head 1 may also be arranged to extend along a helical line DE (Figure 3). In this case the stability and durability of the tool are enhanced, and the conditions of its cutting into the bore or hole 10 to be machined are improved.

As a further development of the present invention, to provide for machining faceted holes, the head 1 has made thereon projections or lugs 13 (Figure 4) extending along its meridian planes, and spaced apart by annular grooves 14 extending in transverse planes at an angle to these meridian planes, the profile of the tool with the lugs 13 is chosen in dependence upon the required profile of the holes to be machined. The cutting edges 2 of the tool in this case are defined by the edges of the lugs 13 facing the grooves 14.

The leading or front edges 7 and the rear or trailing edges 8 are shaped similarly to the working surfaces of a shaving tool. The grooves 14 separate the lugs 13 lying in a given meridian plane, each lug constituting a tooth 15 which can be either sharpened or backed-off.

The tool shown in Figure 5, has the front surfaces 7 of the cutting elements defining the cutting edges 2 facing in the same direction. This facilitates tool manufacture and automation of the operation of sharpening the tool.

Alternatively, the cutting elements may be formed with cutting edges 2 facing in different e.g.

opposite directions, as seen in Figure 6, whereby throughout the operation the tool is acted upon by symmetrical loads, which enhances the accuracy of machining. In this case the front surfaces 7 and the rear surfaces 8 of the cutting elements can be shaped as those of a shaving tool.

To enhance the machining quality and to protect the blades 2 against chipping-out, the rear surfaces 8 of the cutting elements are provided with chamfers 16 with the rear or back clearance angle up to about 150. Alternatively, the angle may equal 00, in which case the accuracy of the manufacture of the tool may be enhanced.

The head 1 of the tool can be in the form of a lamination of discs 17 (Figure 7) of which some can have a rounded profile providing for smoothing-out of the bore or hole 10 being machined. In this case throughout the operation, owing to the independent rotation of each disc 17, there are self-set the minimum speeds of sliding of the cutting edges 2 of the tool against the bore or hole 10 being machined, which enhances the stability and durability of the tool.

In the last-mentioned modification, the journal 3 of the shank or holder 4 may have a stepped structure, with a plurality of individual eccentric necks or subjournals 19 (Figure 8), which provides for simultaneous performance of all the discs 17 of the tool in a cutting mode and thus enables to speed up the cutting and to increase the cutting depth, to say nothing of the field of applications of the tool being expanded, owing to the tool being usable not only for finishing operations, but for semi-finishing ones, as well. The value of the eccentricity "e" of the alternate journals and its direction are selected to satisfy the condition that the apices P (Figures 9 and 10) of the cutting edges 2 of the adjacent discs 17 belong to the same plane perpendicular to the axis L-L of the bore or hole 10 being machined, about the perimeter thereof.

Thus, although the cutting edges do not lie on a strictly spherical imaginary surface, at any instant the effective portions thereof, i.e.

at the points P, do lie on a spherical imaginary surface.

The above described tools operate in the following manner.

The shank 4 of the tool is mounted either by its tail portion or its flange, as case may be, on the faceplate, or in the spindle of the machine tool. The drive of the machine tool is energized to rotate the workpiece or/and the tool about the same axis L-L, and to effect the predetermined axial feed. The tool is introduced into the bore or hole 10 of the workpiece being machined, wherein the head 1 of the tool is self-centered, owing either to the provision of the clearance 11 between the central bore 6 and the journal 3, or else to the radial freedom (floating) of the journal 3 on the shank 4. The engagement with the workpiece sets the head 1 into rotation on the journal 3 of which the geometric axis 0-0 extends at an acute angle a to the axis GL of the shank 4, the portions of the cutting edges 2 of the head 1, contacting at any given moment the surface of the bore or hole 10 of the workpiece being machined, being continuously renewed within the confines of an imaginary spherical band FGJK, owing to an oscillation or rocking of the cutting edges relative to the surface of the bore or hole 10 within an angle equalling 2a.

Thus, in the position shown in Figure 2 the the operative portions of the cutting edges 2 of the head 1 which are working, have a length or extent L, and adjoin the points F and J; upon the head 1 having rotated about the axis 0-0 through 1800, portions of length L and adjoining the points G and K will be the operative working ones. This means that the stability and durability of the tool, as compared with the tool of the prior art, is increased at least as many times as there are portions having the length L in the part of the arc BC or DE of each respective cutting edge 2 within the confines of the spherical band FGJK of the head 1. This continuous replacement of the working portions of the cutting edges 2 of the tool also results in a significant lowering of the temperature in the cutting zone, approximately by 200. . .300 "C., owing to the short duration of the contact of a portion of the blade with the surface of the bore or hole being machined, followed by relatively prolonged cooling. All these features combine to yield a greater efficiency, quality and accuracy of the machining operation.

The inclination of the cutting edges 2 of the tool to the meridian plane of the head 1 provides for their intersection with the vector of the cutting speed and for removing the shavings or chips in the machining process.

The oscillation or rocking motion is brought about as the outcome of the superimposition of the respective rotary motions of the head 1 and of the bore or hole 10 about the axes 0-0 and GL inclined at an acute angle a relative to each other. The tool may be used for machining either the entire perimeter of the bore or hole 10, or else just a portion thereof. Rotation of the head 1 on the journal 3 can be caused by the engagement of the head with the bore or hole 10 being machined, obviating the need for a special drive for rotating the head 1. This feature broadens the scope of the possible uses of the tool, to say nothing of the stability and durability of the tool being enhanced, owing to the extent or length of the cutting edges 2 being increased within the confines of the spherical band FGJK. Furthermore, there is effected chipping of the shaving produced by the cutting, owing to the periodic variation of the value and sense of the angle of inclination of the cutting edges 2 relative to the vector of the cutting speed, during each rotation of the head 1.

When the cutting edges 2 of the head 1 extend along a part of the arc BC (Figure 2) of a circle, and when the cutting edges 2 are arranged along a helical line DE (Figure 3), the machining of the bore or hole 10 is effected in its section perpendicular to the axis GL of the shank 4 and extending through the centre of the spherical band FGJK, with deviations from this section within the predetermined distribution of the machining allowance or feed between the cutting edges 2.

In the first-mentioned case there is used the multi-blade tool operating similarly to a countersink, a reamer or a shaving tool; in the other case it is even possible to use a tool having a single cutting edge engaging the perimeter of the bore or hole 10 being machined in many points, which makes the cutting-in of the tool more smooth and enhances the stability of the tool.

In cases where faceted holes i.e. holes with a cross-sectional configuration of a manysided polygon, are to be machined, there is used the tool wherein the cutting edges 2 are defined by the lugs or projections 13 on the head and defining a profile corresponding to the required profile of the hole 10, the grooves 14 separating the lugs in the same meridian plane being at an angle to these meridian planes.

The head 1 of the tool is introduced into the hole 10 being machined, into engagement therewith along an arc of up to 3600 with the axis 0-0 of the journal 3 either intersecting or spaced slightly from the axis of the hole 10. The cutting operation is performed continuously. The head is not rotated within the hole 10 in the workpiece, but the shank and workpiece are relatively rotated so that the lugs oscillate with respect to the surface of the hole. The operation is continued with either the tool or the workpiece being axially fed, until the required length or depth of the hole is machined.

When the tool having cutting edges 2 all facing in the same direction is used, throughout the operation each cutting edge 2 performs cutting during the first half-rotation of the head, and smooths out the surface of the bore or hole 10 of the workpiece during the second half of this rotation, this smoothingout being effected by the chamfers 16 provided on the surfaces 8 having a back angle from 0 to about 150.

To enhance the machining accuracy, the tool can be provided with cutting edges with front faces facing in different, e.g. opposing directions. In this case, notwithstanding the fact that each cutting edge 2, as just described, cuts during one half-rotation of the head 1 and smooths out during the other halfrotation, the machining is performed under the conditions of symmetrical loads applied to the head 1, owing to the reversed arrangement of the cutting edges.

The stability and durability of the tool can be additionally enhanced by making the head 1 in the form of a lamination of the discs 17 mounted on the journal 3 for rotation relative to one another. In this case the discs 17 are rotated by the engagement with the surface of the bore or hole 10 of the workpiece being machined independently of one another, and thus are self-set to the minimum speed of friction between the cutting edges 2 and the bore or hole 10. Furthermore, if the discs 17 are mounted on the journal 3 with the eccentric sub-journals 19, each disc independently and all discs jointly perform cutting of the bore or hole 10 being machined without smoothing out the surface of the latter.

This steps up the machining rate and broadens the field of applications of the tool which in this case is usable both for finishing and semi-finishing machining operations.

Attention is directed to our co-pending Application No. 32047/77 (Serial No.

1584186) in the complete specification of which there is described and claimed methods of finishing holes in workpieces as also described herein.

WHAT WE CLAIM IS: 1. A tool for machining the surface of a bore or hole in a workpiece, comprising a shank, a journal on the shank, and a head mounted on the journal for rotation and including at least one cutting edge, the cutting edge or edges on the head lying on a substantially spherical imaginary surface having an axis inclined to the shank axis and about which the head is rotatable on the journal, and the or each cutting edge being at an angle to the meridian planes of said imaginary surface.

2. A tool as claimed in claim 1, wherein a plurality of cutting edges are provided and formed on planar sections of the head, each of said cutting edges extending along at least a part of an arc of a circle.

3. A tool as claimed in claim 1, wherein the cutting edge or edges extend along a helical line.

4. A tool as claimed in claim 1, wherein the cutting edges are defined by projections provided on the head in the meridian planes and grooves inclined at an angle of up to 900 to the meridian planes, the projections defining a profile corresponding to the required profile of a hole to be machined.

5. A tool as claimed in claim 1, wherein the cutting edges face in the same direction.

6. A tool as claimed in claim 1, wherein the cutting edges face in different directions.

7. A tool as claimed in claim 1, wherein the cutting edges have a back clearance angle of up to 150.

8. A tool as claimed in claim 1, wherein the head includes a plurality of discs which define the cutting edges and are mounted on thejournal for rotation relative to one another.

9. A tool as claimed in claim 8, wherein the journal is stepped and has a plurality of eccentric portions.

10. A tool for machining holes in workpieces, substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

1. **WARNING** start of CLMS field may overlap end of DESC **.

   sub-journals 19, each disc independently and all discs jointly perform cutting of the bore or hole 10 being machined without smoothing out the surface of the latter.

   This steps up the machining rate and broadens the field of applications of the tool which in this case is usable both for finishing and semi-finishing machining operations.

   Attention is directed to our co-pending Application No. 32047/77 (Serial No.

   1584186) in the complete specification of which there is described and claimed methods of finishing holes in workpieces as also described herein.

   WHAT WE CLAIM IS: 1. A tool for machining the surface of a bore or hole in a workpiece, comprising a shank, a journal on the shank, and a head mounted on the journal for rotation and including at least one cutting edge, the cutting edge or edges on the head lying on a substantially spherical imaginary surface having an axis inclined to the shank axis and about which the head is rotatable on the journal, and the or each cutting edge being at an angle to the meridian planes of said imaginary surface.
2. 2. A tool as claimed in claim 1, wherein a plurality of cutting edges are provided and formed on planar sections of the head, each of said cutting edges extending along at least a part of an arc of a circle.
3. 3. A tool as claimed in claim 1, wherein the cutting edge or edges extend along a helical line.
4. 4. A tool as claimed in claim 1, wherein the cutting edges are defined by projections provided on the head in the meridian planes and grooves inclined at an angle of up to 900 to the meridian planes, the projections defining a profile corresponding to the required profile of a hole to be machined.
5. 5. A tool as claimed in claim 1, wherein the cutting edges face in the same direction.
6. 6. A tool as claimed in claim 1, wherein the cutting edges face in different directions.
7. 7. A tool as claimed in claim 1, wherein the cutting edges have a back clearance angle of up to 150.
8. 8. A tool as claimed in claim 1, wherein the head includes a plurality of discs which define the cutting edges and are mounted on thejournal for rotation relative to one another.
9. 9. A tool as claimed in claim 8, wherein the journal is stepped and has a plurality of eccentric portions.
10. 10. A tool for machining holes in workpieces, substantially as herein described with reference to the accompanying drawings.