US20120013168A1

US20120013168A1 - Spring Biased Rotatable Tool

Info

Publication number: US20120013168A1
Application number: US12/835,995
Authority: US
Inventors: Phillip A. Sollami
Original assignee: Sollami Co
Current assignee: Sollami Co
Priority date: 2010-07-14
Filing date: 2010-07-14
Publication date: 2012-01-19

Abstract

A rotatable tool has a tool body that is generally symmetrical about a longitudinal axis, an enlarged cutting head, and a rearwardly extending shank. The shank joins the enlarged cutting head at an annular flange. A compressible sleeve is fitted around the shank and a wear ring is around the shank at the forward end of the sleeve. A disc spring is positioned between the radial flange and the sleeve to remove axial play between the shank and the sleeve and to seal the parts so that hard particles cannot enter and interfere with rotation of the tool.

Description

The present invention relates to rotatable tools for cutting machines and in particular to an improved tool that employs a disc spring to prevent dust particles from entering the tool holder.

BACKGROUND OF THE INVENTION

Machines that cut hard surfaces such as used in the trenching and mining industries, and that remove hard surfaces of concrete and asphalt prior to repaving a roadway require rotatable tools mounted in a wheel or rotatable drum. The tools have a tapered forward cutting end and located axially behind the cutting end is a cylindrical shank that rotatably fits within a complementary shaped bore of a tool holder. Between the forward cutting end and the shank, the tool has a rearwardly directed annular flange that contacts the forward surface of the tool holder. Force is applied through the rotatable drum or wheel to the tool holder and through the radial flange to the tool to thereby force the tool into the hard surface to be cut. The tools are mounted on the drum at an angle such that rotation of the drum causes rotation of the tools with the annular flange rotating against the planar surface of the tool holder.
To prevent wear to the forward end of the tool holder it has become customary to provide a wear ring that fits around the circumference of the shank of the tool with one surface of the wear ring engaging the annular flange of the tool and the other surface engaging the forward surface of the tool holder. The useful life of a tool used in road planing is at most one day during active use of the machine. It is therefore common to replace all the tools of a road planing machines at least daily. When the tool is replaced, the wear ring is also replaced such that the contact is between the annular flange of a new tool and the forward surface of a new wear ring.
In order for the parts to work properly, it is desirable (but not necessary) that the wear ring itself be non-rotatable with respect to the tool holder. There are several methods employed for preventing rotation of the wear ring with respect to the tool holder, one of which is described in my U.S. Pat. No. 7,229,136 B2 issued Jun. 12, 2007, which is incorporated herein by reference. Another structure is shown in Britzke, U.S. Pat. No. 5,931,542.
The tool further has a hardened forward tip that engages the hard surface to be cut. The rotation of the tool causes the forward cutting end of the tool to become worn symmetrically around its longitudinal axis. The rotation of the tool is therefore necessary to sharpen the hardened tip. Where the tool fails to rotate properly, the forward cutting end will wear unevenly and the hardened tip will gradually become blunted or develop a flat surface and the useful life of the tool will become shortened.
The rotation of the tool within the tool holder is inhibited by fine particles cut away from the hard surface by the tool which work their way between the walls of the cylindrical shank and the inner surface of a retainer sleeve that retains the tool body in the tool holder. The particles of debris increase the friction resisting rotation of the tool and can ultimately prevent rotation altogether. The retainer sleeve that retains the tool has fingers that abut a radial flange at the rear end of the tool shank. The parts are manufactured to a close tolerance and in order that they may assemble easily, the length of the sleeve is perhaps sixty thousandths of an inch less than the portion of the shank around which it is fitted. When the tool is subsequently hammered into a bore of a tool holder, the forward end of the sleeve is pressed against the rearward surface of the radial flange of the tool. As a result, the tool has a longitudinal play. That is, the tool body is moveable outward of the tool holder by the difference between the sleeve length (the distance between rear end of the fingers and the forward end of the sleeve), and the shank length (the distance between annular ridge of the shank and the radial flange).
As the drum that retains the tool holder and tool rotates, centrifugal force causes the radial flange of the tool to move away from the surface of the tool holder such that fine particles can enter the spacing between the tool holder and the flange and reach the spacing between the cylindrical shank and the bore in which it is received. When the tool subsequently engages the hard surface to be cut, the flange is rapidly forced against the forward surface of the tool holder causing hard particles that have worked their way under the flange to be forced or pumped down the bore of the tool holder. The play between the tool and tool holder therefore contribute to the accumulation in the bore of particles that inhibit rotation. It would therefore be desirable to provide a retaining structure for retaining the tool in the tool holder without allowing play between the tool holder and the shank. Such a structure would prevent the radial flange of the tool from moving away from the surface of the tool holder as a result of centrifugal force caused by the drum and thereby block the entry of particles behind the flange.

SUMMARY OF THE INVENTION

Briefly, the present invention is embodied in a rotatable tool for insertion in a bore of a tool holder where the tool has an enlarged cutting head and extending rearwardly of the enlarged cutting head, a cylindrical shank. Fitted at the forward end of the enlarged cutting head is a hardened tip and fitted around the circumference of the shank is a compressible retainer sleeve. An annular wear ring having a planar forward surface is positioned behind the flange. The wear ring rests, without rotating, on the forward surface of the tool holder and the radial flange is rotatable on the forward surface of the wear ring.
The shank of the tool has an annular ridge thereon and an annular retainer sleeve is fitted around the shank with a portion of the sleeve contacting the ridge to retain the sleeve to the shank. The retainer sleeve also has a forward end positioned behind the radial flange of the tool.
The length of the retainer sleeve that fits between the annular shoulder and the flange is many thousandths of an inch less than the length available on the shank to avoid assembly problems caused by the tolerance under which the parts are manufactured. As a result, the sleeve is axially moveable along the shank, that is, it has axial play along the shank.
In accordance with the present invention, a hardened disc spring is fitted behind the annular flange. The disc spring has concave and convex surfaces in its unstressed condition, but is axially compressible into a substantially planar configuration when biased. The disc spring has an axial compression length that is longer than the axial play of the sleeve along the shank.
When a tool having a disc spring fitted behind the radial flange is inserted into the bore of a tool holder, the disc spring is compressed and prevents axial movement of the tool, or play, in the tool holder. By preventing axial movement of the tool, the flange of the tool, the wear ring, and the disc spring are all snugly retained together and are retained against the forward surface of the tool holder, thereby preventing fine particles from entering between the parts.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the invention will be had after a reading of the following detailed description taken in conjunction with the drawings wherein:

FIG. 1 is a cross-sectional view of a tool assembly having a disc spring in accordance with the invention;

FIG. 2 is a cross-sectional view of a tool assembly shown in FIG. 1 inserted into the forward end of a tool holder;

FIG. 3 is a fragmentary enlarged cross-sectional view of the parts shown in FIG. 1;

FIG. 4 is a fragmentary enlarged cross-sectional view of the parts shown in FIG. 2;

FIG. 5 is a front elevational view of a hardened disc spring used in the tool assembly shown in FIG. 1;

FIG. 6 is a cross-sectional view of the disc spring and the tool assembly shown in FIG. 5 taken through line 6-6 thereof;

FIG. 7 is a side elevational view of a tool assembly having a disc spring in accordance with another embodiment of the invention;

FIG. 8 is an enlarged fragmentary cross-sectional view of the assembly shown in FIG. 7 with the wear ring assembled and the assembly attached to a tool holder;

FIG. 9 is a cross-sectional view of another embodiment of a tool assembly having a disc spring in accordance with the invention;

FIG. 10 is a fragmentary enlargement of the cross-section of FIG. 9 showing more clearly the contact between the disc spring and adjacent parts;

FIG. 11 is a cross-sectional view of yet another embodiment of a tool assembly having a plurality of disc springs in accordance with the invention;

FIG. 12 is a fragmentary enlargement of the cross-section shown in FIG. 11 showing the contact surfaces of the disc springs;

FIG. 13 is a cross-sectional view of a typical existing tool body fitted with a disc spring in accordance with the invention; and

FIG. 14 is a fragmentary enlargement of FIG. 14.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 and 3, a tool assembly 10 in accordance with the present invention is suitable for mounting in a tool holder 11. Where the tool holder 11 is a quick-change tool holder such as described in my previous U.S. Pat. Nos. 6,371,567 B1, 6,585,326 B2 and 6,685,273 B1, the text of which are all incorporated herein by reference, the tool holder 11 has an enlarged forward portion 12 and extending rearwardly of the enlarged forward portion 12 is a tubular rearwardly extending shank 14 for attachment to a base block unit, not shown, which in turn is welded to the drum of a machine, also not shown. The tool holder 11 also has a generally planar forward surface 16 and a bore 18, the axis of which is perpendicular to the planar forward surface 16.
The tool assembly 10 has a tool body 19 that is generally symmetrical about a longitudinal axis 20 and includes an enlarged forward cutting head 22 at the very forefront of which is a hardened tip 24. The enlarged forward cutting head 22 diverges radially outwardly from the tip 24 to a maximum diameter at the rearward end thereof with a rearward surface forming an annular flange 28. Extending axially from the center of the annular flange 28 is a cylindrical shank 30. Fitted around the cylindrical shank 30 is a compressible sleeve 32 that is retained to the shank 30 by an annular ridge 34 at the distal end thereof. The compressible sleeve 32 has a plurality of rearwardly directed fingers 33-33 each of which is bent at a small angle so as to partially project radially inwardly. The fingers 33-33 contact the annular ridge 34 on the shank 30 of the tool body 19 to retain the tool body 19 in the bore 18. Fitted around the circumference of the shank 30 and the forward end of the sleeve 32 is an annular wear ring 36.
The sleeve 32 is preferably made of a spring steel and has an unstressed diameter that is larger than the diameter of the bore 18 of the tool holder 11. When the shank 30 of the tool assembly 10 is inserted into the bore 18, the sleeve 32 is compressed or collapsed until the outer diameter thereof tightly fits within the bore 18 and the inner diameter is a little larger than the diameter of the shank 30 around which it is fitted. Accordingly, the sleeve 32 will hold the tool assembly 10 within the bore 18 and yet allow the tool body 19 to rotate therein.
Referring to FIGS. 3 and 4, in accordance with the present invention, the surface of the annular flange 28 is not planar. Instead, the flange 28 has an annular inner portion 50, the inner circumference of which is contiguous with the outer circumference of the cylindrical shank 30, and an outer portion 52, the outer circumference of which is contiguous with the maximum diameter of the enlarged cutting head 22. Between the inner portion 50 and the outer portion 52, the surface of the annular flange has an annular midportion 54 which extends between the outer circumference of the inner portion 50 and the inner circumference of the outer portion 52.
The annular inner portion 50 has an inner radius equal to the radius R1 of the shank 30 and outer portion 52 has an outer diameter R3 equal to the maximum diameter of the flange 28. An abrupt annular boundary joins the outer circumference of the midportion 54 to the inner circumference of the outer portion 54. The inner portion 50 is positioned axially forward of the outer portion 52 by a short distance 56. I have found that the distance 56 between the axial positions of the inner portion 50 and outer portion 52 need only be a small distance of perhaps 0.020 of an inch. The annular midportion 54 which transits the distance 56 between the inner and outer portions 50, 52 is concave and may have any configuration because the contour of the midportion 54 is not important to the invention. As shown in FIG. 3, the midportion 54 may be inversely frustoconical, but it may also be semispherical, or any other contour as may be formed during the manufacture of the part. As can be seen in FIG. 3, the inner portion 50 and the midportion 54 extend across a significant portion of the surface of the flange 28. The boundary between the midportion 54 and the outer portion 52 has a radius R2 that falls midway between R1 and R3. Preferably, R2 is approximately equal to or greater than one half the sum of the radius R1 of the shank 30 and the radius R3 of the annular flange 28.
Referring to FIGS. 1, 3 and 4, the wear ring 36 has a generally planar forward surface 38 that is positioned behind the rearward surface of the flange 28, a parallel planar rearwardly facing surface 40 that contacts the forward surface 16 of the tool holder 11, a cylindrical outer wall 42, and a generally cylindrical central opening 44. Preferably, the compressible sleeve 32 and wear ring 36 are of the type disclosed in my previously issued U.S. Pat. No. 7,229,136 B2 such that the wear ring 36 is retained against rotation with respect to the sleeve 32 by means of a projection 46 on the inner opening 44 of the wear ring 36 that extends into a cut out portion 48 in the compressible sleeve 32. My U.S. Pat. No. 7,229,136 B2 is incorporated herein by reference to provide a more comprehensive description of these parts.
Referring to FIGS. 3 through 6, positioned between the rear surface of the flange 28 and the forward surface 38 of the wear ring 36 is an annular disc spring 60 having a circular central opening 62 and a circular outer circumference 64. It is important that the radius of the central opening 62 is a little larger than R1 so as to slideably receive the shank 30, but smaller than the outer diameter of the collapsed sleeve 32. As a result, the inner portion of the disc spring 60 will abut the forward end of the sleeve 32 as is further described below. The radius of the outer circumference 64 is preferably at least equal to the radius R3 of the flange 28. In its unbiased condition, the disc spring 60 also has a convex surface 63 and a concave surface 65. In its unbiased conditioned, the portion of the disc spring nearest to the central opening 62 extends a compressive distance 66 forward of the outer circumference 64 of the part. Under a compressive force, the portion around the central opening 62 can be moved a compressive distance 66 until the opening 62 is nearly in planar alignment with the outer circumference 64.
As shown in FIG. 3, when the disc spring 60 is assembled in a tool body 19 having a flange 28 with a concave inner portion 50 and midportion 54, the disc spring 60 is oriented with the convex surface 63 extending into the concave inner portion 50 and midportion 54 of the flange 28 and the outer circumference of the concave surface 65 contacting the forward surface 38 of the wear ring 36.
The sleeve 32 cannot be manufactured with sufficient precision to snugly fit on the shank 30 with the fingers 33-33 contacting the annular ridge 34 and the forward end of the sleeve 32 contacting the flange 28. The parts can only be manufactured to tolerances of twenty to eighty thousandths of an inch. The sleeve length, that is the distance from the ends of fingers 33-33 to the forward end of the sleeve 32, is therefore made about sixty thousandths of an inch less than the distance between the annular ridge 34 and the flange 28 of the tool body 19. The sleeve 32 therefore has several thousandths of an inch of “play,” that is, room for longitudinal movement along the length of the shank 30 to which it is assembled. In FIG. 1, the sleeve 32 is depicted with the forward end thereof abutting the concave surface 65 of the disc spring 60 and the disc spring 60 abutting the flange 28 leaving play 35 between the end of the fingers 33 and the annular ridge 34. The disc spring 60 that is fitted around the shank 30 has a compressive distance 66 that is greater than the play 35 between the sleeve 32 and the shank 30.
When a prior art tool without a disc spring 60 is inserted into the bore 18 of a tool holder 11, the sleeve is pressed into the bore 18 by the radial flange or by a radial shoulder on the shank. The play therefore allows the tool body to be thrown outward of the tool holder 11 by centrifugal force as the drum on which the tool holder is attached rotates. Loose particles in the air surrounding the drum will work under the radial flange and into the space between the sleeve and the tool shank. The axial movement of the tool body as it is alternately thrown outward of the tool holder by centrifugal force then hammered back in as the tool contacts a hard surface drives loose particles from under the flange into the bore of the tool holder where they inhibit rotation of the tool.
Referring further to FIGS. 1, 2, 3, and 4, when a tool 10 in accordance with the present invention is inserted into the bore 18 of a tool holder 11, and the shank 30 is driven into the bore 18 with a hammer, the planar outer portion 52 of the flange 28 applies pressure to the disc spring 60 around the annular boundary at R3 to flatten the disc spring 60. As the disc spring 60 flattens the portion around the central opening acts like the end of a lever arm and forces the sleeve 32 rearward with respect to the shank 30 until the fingers 33-33 abut the annular ridge 34 of the shank 30 as shown in FIG. 2. The lever action of the disc spring 60 causes the sleeve 32 to be pushed so deep into the bore 18 that it absorbs all play 35 between the sleeve 32 and the shank 30. I have found that the sleeve 32 will often apply such pressure against the ridge 34 that it will interfere with the rotation of the tool body 19 within the tool holder 11. However, one additional blow to the tool head 22 with a hammer will loosen the tool body 10 from the sleeve 32 and allow it to rotate.
Once installed, the fingers 33-33 of the sleeve 32 will retain the flange 28 of the tool flush against the surface of the disc spring 60 and the wear ring 36. Also, the inner circumference 62 of the disc spring 60 is compressed against one member of the tool assembly 10 and the outer circumference 64 is compressed against another member such that the disc spring 60 acts as a seal between the parts and prevents hard particles from entering between the parts to reach the bore 18 of the tool holder 11.
The disc spring 60 will also reduce the incidence of breakage of the carbide tips 24 which occurs when the tool body 19 contacts an inordinately hard object such as a metal pipe. This is because the attachment of the tool assembly 10 to a tool holder 11 does not result in the entire compressive distance 66 of the disc spring 60 being consumed. The unconsumed portion of the compressive distance 66 allows the tool body 19 to move relative to the tool holder 11 in response to contact with an inordinately hard object thereby distributing the force of the impact load over a longer distance. The result is that the tool assembly 10 is more forgiving and less likely to result in breakage of the carbide tip.
Referring to FIGS. 7 and 8, where the play 35 cannot be absorbed using a disc spring 60 configured as above, the disc spring 60 can be reversed. In this embodiment, a tool assembly 70 has a tool body 71 with an enlarged forward portion 72, a radial flange 74, and a cylindrical shank 76 that extends rearward from the center of the flange 74. An annular ridge 78 extends around the rearward end of shank 76 and a compressible sleeve 80 is fitted around the shank 76 with fingers, unnumbered, that engage the annular ridge 78 to retain the sleeve 80 to the shank 76. A wear ring 82 is fitted around the forward end of the shank 76 and the rearward surface of the wear ring 82 is adapted to contact the forward surface of the tool holder 84.
In this embodiment, the disc spring 60 is positioned between the rearward surface of the flange 74 and the forward surface of the wear ring 82 with the convex surface 63 of the disc spring 60 directed toward the wear ring 82. As shown in FIG. 7, when the sleeve 80 is fitted around the shank 76, the disc spring 60 is partially compressed thereby taking out the play between the sleeve 80 and the shank 76.
When the tool assembly 70 is inserted into the tool holder 84, as depicted in FIG. 8, the disc spring 60 will retain the wear ring 82 flush against the forward surface 86 of the tool holder 84 and hard particles in the surrounding air will be unable to work between the wear ring 82 and the tool holder 84. Also, the central opening 62 of the disc spring 60 will fit tightly enough around the circumference of the shank 76 and the outer circumference 64 of the disc spring 60 will fit tightly against the surface of the wear ring 82. The force axially applied by the disc spring 60 will cause all the elements of the tool assembly 70 including the flange 74, the sleeve 80, the wear ring 82, and the disc spring 60 itself to be tightly compressed together thereby preventing dust particles from entering between the parts. The disc spring 60 will therefore block dust particles from entering between the inner wall of the sleeve 80 and the surface of the shank 76 of the tool body 71.
The disc spring 60 may be positioned between the radial flange (such as flanges 28 and 74 described above) and a wear ring (such as wear rings 36 and 82 described above) or it may be positioned rearward of the wear ring. Referring to FIGS. 9 and 10, a tool body 90 has a radial flange 92 and a shank 94. A compressible sleeve 96 is fitted around the shank 94 and a wear ring 98 is positioned immediately behind the radial flange 92. In this embodiment the wear ring 98 extends around a forward portion 100 of the shank 94 having a diameter that is larger than that for the portion around which the sleeve 96 is fitted thereby forming a shoulder 102. The disc spring 60 is positioned between the rearward surface of the wear ring 98 and the forward end of the sleeve 96. The concave surface 65 is directed toward the wear ring 98 and the convex surface 63 is directed toward the sleeve 96 such that the disc spring 60 will urge the sleeve 96 away from the radial flange 92 to thereby remove any play between the sleeve 96 and the shank 94. As with other embodiments, the disc spring 60 will also cause the annular parts to be compressed together thereby sealing the parts against the entry of dust particles.
Referring to FIGS. 11 and 12, in some circumstances, as for example when the play between a sleeve and a shank is large, it may be desirable to provide more than one disc spring 60. In the embodiment depicted, a tool body 110 has a radial flange 112, a shank 114 with a shoulder 116. A sleeve 118 is fitted around the shank 114 forward of the shoulder 116. A first disc spring 60 is fitted between the wear ring 120 and the radial flange 112 and a second disc spring 60′ is fitted between wear ring 120 and the sleeve 118. In this embodiment, the compressive distance of both disc springs 60, 60′ will be combined to absorb the play between the sleeve 118 and the shank 114. The disc springs 60, 60′ will thereby urge the sleeve 96 deep into the bore of a tool holder into which it is inserted and it will seal the parts to thereby prevent hard particles from entering around the parts to reach the bore.
Referring to FIGS. 13 and 14, the disc spring 60 can be used with any existing tool body of which tool body 130 is a typical example. It is desirable that the element immediately forward of the compressible sleeve 132 have an inner diameter that is less than the outer diameter of the collapsed sleeve 132. In this embodiment, the wear ring 134 is immediately forward of the sleeve 132 and has an inner diameter smaller than the outer diameter of the collapsed sleeve such that the wear ring 134, under pressure from the disc spring 60, will urge the sleeve 132 rearwardly to remove play between the sleeve 132 and the shank 136. It is the addition of the disc spring 60 to the tool assembly that causes the parts to be sealed. A tool assembly in accordance with this invention has been found to have a useful life that is fifty percent longer than a prior art tool assembly.
The purpose of the wear ring is to protect the planar forward surface (surface 16 in FIGS. 1 and 2) from wear as the tool rotates in the tool holder. It should be appreciated that a tool assembly that includes disc springs, such as a disc spring 60, may function without a wear ring. To function without a wear ring, the disc spring should be oriented with the convex surface directed toward the flange of the tool and the concave surface directed toward the forward surface of the tool holder. In this configuration, there will be greater resistance to rotation around the outer circumference of the disc spring where it contacts the tool holder than around the inner circumference that contacts the shank of the tool. As a result, the disc spring will not rotate with the tool.
While the present invention has been described with respect to two embodiments, it will be appreciated that many modifications and variations may be made without departing from the spirit and scope of the invention. It is therefore the intent of the appended claims to cover all such modifications and variations that fall within the spirit and scope of the invention.

Claims

1. A rotatable tool comprising

a tool body having a longitudinal axis, an enlarged cutting head and a cylindrical shank extending rearwardly of said enlarged cutting head,

a hardened tip at a forward end of said enlarged cutting head,

said shank joining said enlarged cutting head at an annular flange,

said cylindrical shank having an annular shoulder thereon,

an annular retainer sleeve on said shank,

said retainer sleeve contacting said annular shoulder for retaining said retaining sleeve to said shank,

said retainer sleeve also having a forward end, and

a disc spring on said shank axially behind said annular flange.

2. The rotatable tool of claim 1 and further comprising

a wear ring also on said shank behind said annular flange.

3. The rotatable tool of claim 1 wherein

said disc spring is between said forward end of said retainer sleeve and said annular flange,

said retainer sleeve has a compressed diameter for retaining said shank in a bore of a tool holder, and

said disc spring has a central opening with a diameter less than said compressed diameter wherein said disc spring urges said retainer sleeve against said annular shoulder.

4. The rotatable tool of claim 1 and further comprising

a second disc spring on said shank.

5. The rotatable tool of claim 1 wherein

said shank has a maximum radius R1,

said annular flange has an annular inner portion joining a forward end of said shank and an outer portion extending to a maximum diameter of said annular flange,

said annular flange having a maximum radius R3,

said annular inner portion being axially forward of said annular outer portion, and

a boundary between said inner portion and said outer portion having a radius that is generally midway between R1 and R3.

6. The rotatable tool of claim 5 wherein said disc spring has an outer diameter at least equal to an outer diameter of said flange.

7. The rotatable tool of claim 6 wherein

8. A rotatable tool comprising

a hardened tip at a forward end of said enlarged cutting head,

said shank joining said enlarged cutting head at an annular flange,

said cylindrical shank having an annular shoulder thereon,

an annular retainer sleeve on said shank,

said retainer sleeve having means for contacting said shoulder for retaining said retaining sleeve to said shank,

said retainer sleeve also having a forward end,

a disc spring between said forward end of said retainer sleeve and said annular flange wherein said disc spring urges said retainer sleeve against said annular shoulder.

9. The rotatable tool of claim 8 and further comprising

a wear ring around said shank, and

said wear ring having a surface contacting said disc spring.

10. The rotatable tool of claim 8 wherein

11. The rotatable tool of claim 8 and further comprising

a second disc spring on said shank.

12. The rotatable tool of claim 8 wherein

said shank has a maximum radius R1,

said annular flange having a maximum radius R3,

13. The rotatable tool of claim 12 wherein said disc spring has an outer diameter at least equal to an outer diameter of said flange.

14. The rotatable tool of claim 13 wherein

said disc spring has a control opening with a diameter less than said compressed diameter wherein said disc spring urges said retainer sleeve against said annular shoulder.

15. The combination comprising

a rotatable tool including

a hardened tip at a forward end of said enlarged cutting head,

said shank joining said enlarged cutting head at an annular flange,

said cylindrical shank having an annular shoulder thereon,

an annular retainer sleeve surrounding said shank,

said retainer sleeve contacting said shoulder and retaining said retaining sleeve to said shank,

said retainer sleeve also having a forward end,

a tool holder having a forward surface and an axial bore,

said shank and said retainer sleeve inserted into said axial bore, and

a spring disc around said shank and between said annular flange and said forward surface of said tool holder.

16. The combination of claim 15 wherein

an inner opening of said disc spring has a diameter less than a diameter of said axial bore and an inner portion of said disc spring contacts said retainer sleeve and urges said retainer sleeve into said bore.

17. The rotatable tool of claim 15 and further comprising

a wear ring around said shank and also positioned between said annular flange and said forward surface of said tool holder.

18. The combination of claim 15 wherein

one of said wear ring and said disc spring has an inner opening with a diameter less than a diameter of said axial bore, and

said one of said wear ring and said disc spring contacts said retainer sleeve wherein said retainer sleeve is urged into said bore by said one of said wear ring and said disc spring.

19. The combination of claim 15 wherein

said shank has a maximum radius R1,

said annular flange having a maximum radius R3,

20. The combination of claim 15 wherein