CA1131897A - Chuck assembly and collet - Google Patents

Abstract

IMPROVED CHUCK ASSEMBLY AND COLLET
Abstract of the Disclosure The chuck assembly and the collet for retaining an end mill tool against axial pullout. The collet includes a radially compressible body having a tapered outer surface, a central bore and a radial aperture extending from the outer surface into the central bore. The radial aperture has an undercut or larger diameter medial portion with a movable pin mounted therein, said pin being movably mounted and, adapted to extend into the bore to retain the tool. The pin has a hole drilled through with a spring bar mounted therein. The ends of the spring bar are compressed to a length smaller than the diameter of the radial aperture and inserted into the larger undercut portions where the expansion of the spring bar retains the pin. The hole in the pin is larger than the diameter of the spring bar to allow the pin to move along its axis (radially into the collet bar). The pin has a lower chamfered end which is urged inwardly into the bore as the collet is tightened in the chuck assembly with the chamfered end engaging a rear bevel end on a flat surface on the tool to secure the tool within the collet, and whereby the pin can move outwardly to release the tool when the collet is removed Prom the chuck assembly.

Description

The preSellt :invelltion rela-tes to a colle-t and to a method of makin~J collet for retaininq a tool aga:inst axial pullout.
The present invention is related to and an improvement upon -the lnvention disc:Losed in Canadian Patent Application Serial No. 343,010, Eiled January 3, 1980, by l~illard Cummings entltled "Chuck Assembly and Collet" and assigned to the assignee of the present app]ication. This pa-ten-t application is referenced to as the "Non-Pullout Collet Patent".
The ~resent inven-tion i5 also related to Canaclian Patent Ap~lication Serial No. 3~2,988, filed January 3, 1980, by Better and Lehde entitled "Slotted Collet and Method of Making"
and assigned to the assignee of the present application. This patent application is referred to as the "Slotted Collet Patent".
FIELD OF TH~ INV~NTlON
The ~resent invention relates generally to a holding apparatus for cutting tools. More particularly, the present invention relates to a collet and chuck assembly for holding an end mill ~or similar) tool to prevent axial or rotational movement with respect to 'che apparatus during machining.
An end mill tool is a cylindrical cutting tool which has a cutting (or milling) edges around the round portion at one or more of its ends alon~ with cutting teeth on its end toward at least one of its forward ends. The tool has agenerally cylindrical rear or central shank withat least one beveled-ended flat surface which is secured in the coller and chuck assembly during machining.
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~ackground Art Various designs have been suggested for pro~iding a collet and chuck assembly for securing an end mill tool therein against axial movement of the tool out of the 5 assembly and against rotation of the t ool with respect to the assembly and collet.
Such designs generally include an aperture through the collet, with a movable pin mounted therein for engaging a flat surface on the end mill shank. Mounting and retaining the pin suitably has been a problem in the prior art collets, except for the Non-Pullout Collet Patent discusse~ later. The pin should be easily movable to secure an~ release the tool, while resisting accidental separation of the pin from the collet. However, for service or repair, the pin should be quickly and easily released. Further, the mounting and retaining mechanism ~hould not be on the external surface of the collet, to minimize the chance of damage thereto.
Cutting tools for chuck assemblies may range from only slightly smaller than the bore in the chuck to substantially smaller, with the thickness of ~he collet wall v~rying accordingly. An ideal collet for an end mill is not dependent on a particular w~ll thiokness. More particularly, a very thin-walled collet (i.e., where the ~5 tool shank is almost as the chuck bore)~ must suitably accommodate the pin and its retention system, while allowing limited pin movement.

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4~0-79-~30 One approach suggested in the prior art was to provide the outer collet body and pin with a groove, in which an external spring retaining ring is mounted.
Another prioc art approach was to drill a hole S through the collet body perpendicular to and intersecting the pin aperture. The movable pin is ~provide~ with a hole also, and a roll pin is inserted into the aligned pin hole and collet body hole to retain the ~ovable pin.
Typically, such designs have at least one of the following disadvantages: expensive to manufacture; time-consuming, difficult and/or expensive to a~semble; parts, other than the collet body and the pin itself, which are on the external surface of the collet and subject to wear and destruction.
Examples of such collets are shown in U.S. Patents 3,195,909 3,425,705; 3,~18,962; and others.
The collet design in the referenced Non-Pullout Collet Patent overcomes many vf the disadvantages and limitations of the prior artO However, for thin-walled collets, the desi~n in the Non-Pullout Collet Patent does not suffice. The pin and collet walls are si~ply shrunk to a thickness which does not allow an undercut and stepped radial aperture, respectively. To allow a radially-movably mounted pin.
It is thus apparent that ~here are disadvantages and limitations of the prior art collets for retaining an end mill tool. Lacking is a collet which is reliable and economical to manufacture~ while quickly engaging and disengaging an end ~ type tool without external parts to be damaged. Other disadvantages and limitations of the prior art collets and chuck assemblies will be apparent fro~ the following description of the present invention.

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The present in~ention is a chuck assembly and collet whicll overcomes -the lirnitations and disaclvantages of the prior art collets previously described.
The present invention is a chuck assembly and collet which provides a convenient means for securing an end mill or similar tool when desired and for quickly and easily releasing it. The collet is relatively inexpensive to manufacture and assemble, easily and quickly assembled and has a minimum of external parts. The collet also has a high reliability and resistance to damage and to accidental separation of parts which could lead to a loss of parts.
Further, the collet and chuck assembly of the present invention are equally useful in both thin and thick wall collets.
According to one aspect of the present invention there is provided a collet having a radially resilient body with a tapered outer surface and a tool receiving bore extending axially therethrough, the body having an aperture extending radially from the outer surface into the bore.
A tool-securing pin is provided which has a head portion at one end thereof and a tool-securing surface toward the other end thereof.` Means is provided movably mounting the pin within the collet aperture, the means including an undercut associated with the collet aperture providing a larger opening in the aperture mediate the collet hore and the collet outer surface. The means further includes an aperture extending through the pin and a compressible member for mounting the pin within the collet aperture. The ~ember includes end portions mounted within the undercut and a medial ~4 I mb/~¦t7!' ~ 4 ~ ~3~

portion extending through the pin aperture, with the pin aperture being larger than the medial portion of the member to allow limited movement of the pin for locking and releasing the tool within the colle-t so that the me~ber is compressible for mounting the member in the undercut.
According to another aspect of the present invention there is provided a method of making a collet for re~aining a tool against axial pullout, the method including the steps of providing a tool locking pin and a radially-resilient collet body having a central tool-xeceiving bore and an outer .surface and drilling a radial aperture through the collet of suitable size and shape for receiving the pin.
An undercut is made in a portion of the xadial collet aperture to provide a larger dimensioned por-tion intermediate the bore and the outer surface. A hole is drilled through the pin, and a spring bar is mounted within the hole in the pin. The spring bar is compressed to a length less than the size of the radial aperture and the pin and the compressed spring bar are insexted into the radial aperture. The compxessed spring bax is aligned with the undercut to allow the spxing bar to expand into the undercut and thereby retain the pin in the aperture.
The assembly of the present invention appears to be less expensive to manufacture than the design of the Non-Pullout Collet Patent~
The foregoing and other objects and advantages of the ~resent invention will become apparent to one skilled in the art in view of the following description and claims and the accompanying drawings.

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~ 7 480 79-0030 Brief Description of the Drawings FIGURE 1 is a cross sectional view of a chuck assembly and collet of the present inven~ion.
FIGURE 2 is a cros~ sectional view o the chuck assembly and collet of FIGURE 1, taken along the line II-II looking in the direction of the arrows.
FIGURE 3 is an enlarged cross sectional view of a pin, spring bar and collet portion prior to assembly.
FIGURE 4 is a cross sectional view of the collet portion of FIGURE 3, taken along the line IV IV looking in the direction of the arrows, with two positions of a cutting tool shown in phantom.
FIGURE 5 is a cross sectional view of the preferred spring bar oE the present invention.

~3~3~ 4~0-79-0030 Detailed Description of the Drawings FIGURE 1 shows a cross-sectional view of a part of a chuck assembly 10 of the present invention. The chuck assembly 10 includes a chuck body or collet holder 100 and a lock nut 200. A collet 300 is mounted within the collet holder 100 and has an end mill tool 400 mounted therein.
The chuck assembly 10 and its components are the same as described in the referenced Non-Pullout Collet Patent except for a pin and aperture structure, which patent should be consulted for greater detail.
The collet holder 100 is of a well-known and conventional design and includes a body 110 with external forward screw threads 120 and an internal, inwardly tapering bore 130 extending rearwardly from the forward end of the body. A rear portion 140 is a shank which is configured to be secured in a machine tool or spindle.
The lock nut 200 is also a conventional design. The lock nut 200 includes a body 210 with internal threads 220 adapted to mate with the external threads 120 on the collet holder 100. A second member 230 of the lock nut 200 is coupled to the body 210 with ball bearings 240 and the member 230 has a projection 232, the purpose of which will be explained later.
The collet 300 is preferably made of an appropriate spring-type steel which has been hardened and drawn, as is well-known and customary in making collets. The collet has a body with an internal tool-receiving bore and with an outside external surface which tapers generally to a smaller rear diameter.

4gO-~9-0030 The external surface o~ collet 300 has a ~or~ard portion 310 and a tapering rear portion 330, separated b~ an annular groove 320. The rear portion 330 seats against and engages internal walls of the tapered holder bore 130 when the colle-t 300 is fully inserted. Preferably, two (or more) spa-tially-separated surfaces of -the rear collet portion 330 are in contact with the bore 130 providing good engagement within the collet holder 100.
The lock nut projection 232 cooperates with the forward collet portion 310 and annular groove 320 to release the collet 300 from the collet holder bore 130 as the lock nut 200 is unscrewed in disassembly.
A radial aperture 370 extends -through the colle-t 300 medially along the length of the colletl The aper-ture includes a first por-tion 372 and an undercu-t diameter 374 portion. A -tool-securing pin 380 i9 posi-tioned within the aperture 370 and is held in place by a spring bar 390, The pin 380 has structure which is described in detail in connection with FIGURES 3 and 4. The pin 380 20 iS radially movable through a limited range of radial movement when assembled, as also will be discussed later.
The spring bar 390 is shown in FIGURES 3 and 5 and will be discussed in greater detail in connection with tnose ~igures.
The tool 400 iS a conventional tool (such as an end mill) whi.ch has forward cutting surfaces 410 and rear shank 420. The forward cutting surfaces 410 have side surfaces9 as well as end surfaces, for cutting and may have a tendency for axial pullover. Therefore 9 the sha-nk 30 420 of an end mill tool has one or more ~lat surfaces with ~orward and rear beveled ends 432, 434 for tool reten-tion.
The beveled ends 432, 434 have a 45 angle wi-th respect to the axis of the tool. The beveled flat surface, when suitably engaged within the coll~t, prevents the tool from being pulled out o~ the holder.
-~ 480-79-0030 FIGURE 2 is a cross sec-tional view of the chuc~
assembly 10, showing -the chuck body 110, the lock nut 200, the collet 300 and the tool 400. The collet 300 include slots 305 o~ the -type described in the referenced Slo-tted Collet Paten-t to provide radial compressibility and resilienc~ al-ternatively, other slo-tting me-thods of providing radial compression and resilency are known and could be used. The tool 400 has -the flat surface 430 ~hown in this view sligh-tly above -the bottom of the -tool locking pin 380. The spring bar 390 i5 shown in a side, cross sectional view.
FIGURE 3 is an enlarged ~iew o~ the pin 380, spring bar 390, aperture 370 and tool 400 prior to assembly of the pin i~to the aperture 370.
1~ The pin 380 is generally cylindrically and includes a radiused or rounded head 382. A radial hole or aperture 384 extends through the pin below the head 382. The pin 380 has a lower chamfered portion 387 which has a 4~ angl.e for engaging the 45 beveled sur~ace 432 o~ the tool 400.
The spring bar 390 has ends 392, 394. The spring bar 390 is mounted within the hole 384 of the pin. The ends 392, 394 extend beyond the pin 380 normally, bu-t may be compressed to a size no larger than the pin diameter. The 0nds 392 7 394 are compressibly mounted to the spring bar 39 as discussed.in ~IGURE 5, The hole 384 in the pin is ~arger than the diameter o~ the spring bar 390 to allow the pin 380 to move radially with respect to the collet 300 (up and down in FIGURE 3) without movement o~ the spring bar 390. This movement allows the pin 380 to lock and 30 release, as desired, the tool 400, The aperture 370 has a chamfered entry 371, a portion 372 of generally uniform diameter and an undercut portion 374.
The undercut portion 374 receives the encls 392, 394 of the spring bar 390 when the pin is inserted in the aperture 370.
FIGURE 4 shows a cross sectional portion of the collet 300. The portion 372 of the aperture îs shown, as is the undercut portions 374. The undercut portions 374 may be formed without requiring a separate setup of the collet 3Q0 by using a Woodruff cutter and moving the collet 300 slightly hack and forth when the Woodruff cutter is in place. Dotted lines 601, 602 show the extremes of the movement of the cutter to form the undercuts 374. Of course, other suitable methods of making the undercut could be employed to advantage.
FIGURE 5 shows a cross sectional view of the spring bar 390 taken along the line V-V in FIGURE 3. 5'he spring bar 390 is preferably of the type used to mount a watch band to a watch and is available commercially from Polly Trading Co.
(N.Y.~ N.Y.) under the names *Quick Fit.or *Regal. The spring bar 390 includes the ends 392,.394~ The ends 392, 394 have enlarged portions 392a, 394a, respectively, which are held within a body 396. Ends 396a of -the body are crimped over ~or have other suitable retaining) to hold the ends 392, 394 in. A spring 398 urges the ends outward normally. The ends 392, 394 may be compressed or urged inwardly by compressing the spring 398.

* Trade Marks mb/!\!i~ ' -- 10 --:~3~ t7 The foregoing desc.riptlon of the preferred embodiment is merely exemplary of the present invention. The structure shown may be modified in one of several ways known to those skilled in the art, and further, some features of the present invention may be used without the corresponding use of other features. For example, other configurations of spring bars or sprilng members could be substituted, either wi~h or without changes to the structure of the aperture of the pin~ The collet aperture could be made in one of the several diverse manners. The pin might be oF uniform size on it~ ends and need not be round. Accordingly, the present description is illustrative of the present invention only and should not be taken as li~iting the scope of the invention which is solely by the following claims.

Claims (2)

Having thus described the invention, what is claimed is :

1. A collet comprising:
a radially resilient body having a tapered outer surface and a tool-receiving bore extending axially therethrough, said body having an aperture extending radially from the outer surface into said bore;
a tool-securing pin having a head portion at one end thereof, and a tool-securing surface toward the other end thereof; and means for movably mounting the pin within the collet aperture, said means comprising:
an undercut associated with the collet aperture providing a larger opening in the aperture mediate the collet bore and the collet outer surface;
an aperture extending through the pin; and a compressible member for mounting the pin within the collet aperture, said member including end portions mounted within the undercut and a medial portion extending through the pin aperture, with the pin aperture being larger than the medial portion of the member to allow limited movement of the pin for locking and releasing the tool within the collet, whereby the member is compressible for mounting the member in the undercut.

2. A method of making a collet for retaining a -tool against axial pullout, the steps of the method comprisings providing a tool locking pin and a radially-resilient collet body having a central tool-receiving bore and an outer surface;
drilling a radial aperture through the collet of suitable size and shape for receiving the pin;
making an undercut in a portion of the radial collet aperture to provide a larger dimensioned portion intermediate the bore and the outer surface;
drilling a hole through the pin: .
mounting a spring bar within the hole in the pin;
compressing the spring bar to a length less than the size of the radial aperture;
inserting the pin and the compressed spring bar into the radial aperture; and aligning the compressed spring bar with the undercut to allow the spring bar to expand into the undercut and thereby retain the pin in the aperture.