US2226226A - Counterboring tool - Google Patents

Description

Dec. 24, 1940. Q Q HED|N 2,226,226

COUNTERBORING TOOL Filed Oct. 10, 19159 v Patented Dec. 24, 1940 OscarC. Hedn, Minneapolis, Minn.; assig'rr tol f The Weldon Tool Company, Cleveland; Ohiov a f corporation of Ohio Application october 10,1939, seriaiigoioggg@ 9 Claims.

, This invention relates to` improvements in pilots forfmetal cutting .tools with which al pilot is o r canbe used, particularly tools of the countercutting type,s uch as reamers and counterbores. The inventionhas found valuable application in a tool of the counterbore type.

Objects of the invention are: To so detachably mount the pilot that pilots of different diameters can be quickly substituted, and to provide a character of `mount which cannot becomey loosened in use and which will prevent such movements of the pilot as will mar or dull the I cutting ends of the tool, Oras will allow the pilot to assume eccentric positions.

I -am aware that various attempts have been made to provide removable pilots but', insofar as I know, there exists no detachable pilot which is entirely satisfactory..

.In some cases the pilot hasbfeen made ref movable by providing it Vwith a small shank which is inserted in an opening in the stern of the tool, wherein it is locked by a sety screw. When sucha pilot is in operative position the rear or innerfend of the `pilot bears against the ends of vthe cutting lips. This type of pilot becomes loose andV vibrates or chatters,vand the inner end surface of the pilot can'chew up or mar or deface the cutting lips. When this inarring occurs during use ofr a larger size'pilot, and onewishes to use the tool with ya smaller size pilot, it is found thatv the cutting tool hasbeen so chewed up or marred that it is necessary to re-sharpen the same, This takes time andneedlessly shortens thel life 4of the cutting part of the tool. Insofar 'as I am aware, in allA of the manufacturing tools which have ,had detachable pilots, it vhas been L,necessary to use set screws or the like for holding them in place.v The main objection is that those pilots work loose, with the results above'mentioned.' The videal pilotl must be rigid, ,and I have provided this rigidity in a detachable pilot.

An important 'feature of my invention consists in providing a mount for the pilot which is of one piece with the tool, that is, integral therewith.v

TheI mount is of one piece or integral with the stem, as distinguished from being separable w therefrom. Another feature is the provision of a tapered mount not necessarily of one piece, with the tool.

In my invention I turna tapered extension at the end of the tool which tapersconvergently in boring direction, and then Il form a corresponding tapered opening in the pilot. Each pilot of a series of pilots has a diierent outer diameter but -has the same diameter or dimension of taper, so

(o1. 'ivomi y that each fone'willfit `one and the same integral tapered extension.; l

yl'eatures'j c'nlhtloe, invention include: the use of a pilot-mountingextension which is of one piece l with the tool; the'use of a tapered mount, whereon the ypilot is frictionally held so that it can be loosened by a slight otap; the use ofa cylindrical mount of 'onefpiece .with the tool; the use of screw l@threads to ,secure the pilot to a mount which is integral. with 'the tool; the scheme of the substitution Lof pilotso'f different diameters on one and thesamelamount; vand all details of construction sh'flivvnl...A Y,

.O jects', vfeatures and advantages of the in,-r fventionwill kbe setforth in the specification and irl Said-drawing; Figurelfis an elevation cfa counterbore tool showing my inventionapplied'thereto and show'- ing the, toolfin nterboring .position in relation to thewok; I

Figure Z'isjan enlargedsection of the lower .part "of' the' k tool with my invention applied thereto; l .Figu res' 3,' 4 *and 5 are sections, respectively, of pilots'of' different outside diameters, any one of which pilots can be applied to one and the same pilot mountof `this invention; v.ligure isfan enlarged section of a modification showing vthe pilot attached by screw threads; ':Figure j lis a section of another modification showing' thepilot vheld on a cylindrical mount;

' ,Eigurevis anfaxiallsection of a centering or sharpepingpilot.' f

my finventionas applied to a counterbore tool haVmgtWolips only; but it will be understood 'that` the invention mayl be applied to any tool on which a'pilotcan be used or is needed, to pro.- videfnieanswhereby a4 detachable pilot is unfailingly rigidly centered for performing its function and .yetis quickly 'and easily removable so thatpilots f other outside diameters can be .substitutedf on fone andthe same mount.

'Thenunieralfl lindicates the shank of the tool andfgthe Irnneral 2 indicate the cutting lips. Nun 1`l"=.rals A34 indicate the cutting edges of the lips. Atfthe' upper, endof the tool is a centering depression v5f c :jorresponding to a similar depression atthe opposite'endof. the tool, as hereinafter described. means of these depressions the tool can"'againv be supportedfor operations which will belaterdejs'c ri b ed. v

.jRlef'erijing'now;` o'Figure 2, a salient feature of 55 15 drawingforming.apartlof this application, and

my invention is the provision of a pilot support or extension which is of one piece with the stem I, and which is turned and/or ground as the stem is turned and/or ground so that perfect centering can be accomplished. This extension is generally indicated by the numeral I0 and it is noted that it is tapered convergently in boring direction. The pilot element per se is indicated at II and has a correspondingly tapered opening which has an accurate t with said projection so that good frictional contact is obtained, which alone secures the pilot in position on the projection or extension I0. It is desirable to have the inner end or surface I2 of the pilot II spaced from the cutting edges I3 of the lips 2, and it is desirable to always maintain this relation after sharpening of the lips has occurred, which operation shortens the lips in an axial direction (see dot-and-dash lines I3' roughly indicating the position of the cutting edges after sharpening). If it is desired to maintain the predetermined special relation between the face I2 and edges I3, the mount element is also ground, and so that the same taper is maintained. For this purpose the tool is centered in the grinder by means of the centers 5 and I4.

Figures 3, 4 and 5 show sectional views of pilots of different diameters, said diameters being respectively indicated by the letters A, B, C. In these figures it will be noted that the internal diameter of the conical opening indicated at D remains the same as the diameter D' (see Figure 2) of the tapered projection Ill. The result is that either of the pilots respectively indicated at I6, I1, I8 can be frictionally, immovably, rigidly held on the projection I0 of Figure 2. For ease of manufacture, of course, it might be considered most convenient to make the pilot extension cylindrical, and Figure 7 shows such construction.

The important feature is the making of the pilot extension I0 or its equivalent, of one piece with the stem I to assure rigidity, and so that the mount can be machined with the stem and can be re-ground to maintain the proper relations between a pilot mounted upon it,and the cutting edges of the tool as the cutting edges are sharpened back in an axial direction.

To further define the meaning of the expression of one piece with, as used to describe the character of the extension upon which the pilot is mounted, it may be said that the most practicable way to form the extension is by turning during manufacture. However, if the tool is cast, then of course the extension should be formed by casting and would be of one piece with the shank. It is conceivable that the extension might be welded in place, and if it were this would be another way of obtaining a rigid, non-removable support for the pilot. These ways of obtaining this rigidity are mentioned to make clearer the meaning of the terms of one piece with or integraL By making this tapered extension of one piece with the shank or with the tool a rigid mount is obtained. This tapered extension may be called a sub-pilot, and upon this sub-pilot can be driven a master pilot of the desired outside diameter, this'master pilot having, as before mentioned, a tapered hole which permits it being driven into frictional engagement with the sub-pilot or tapered extension. Thus, there is here combined all the virtues of the solid type of counterbore with the advantage of interchangeability of pilots. As an extreme example, consider several screws, all of which have heads one inch in diameter but in each of which the shank has a diameter difering from that of the other, for example, ranging in diameter from 5/gths to lths of an inch. To do counterboring for the heads of these screws whose shanks vary in diameter there would ordinarily be required as many counterbores with solid or integral pilots as there are different diameters of screws. Thus, it can be seen what advantages accrue from having a counterbore with interchangeable or replaceable ilots.

p My invention gives a construction which has a maximum strength and rigidity and more nearly approaches the solid type pilot than any other device known to me.

By the scheme herein or method of manufacture constant concentricity of pilot and counterbore diameter is assured. The taper of the sub-pilot is ground at one and the same time as the outside diameter of the counterbore proper. The master pilots are easily made accurately, with-their outside diameter concentric with the axis of the tool. It is to be noted that lack of concentricity between pilot diameter and cutting-lip diameter is the most frequent cause of pilot breakage.

Another advantage of the present invention resides in the fact that the taper can be ground so as to follow back as the cutting ends of the lips are ground farther and farther back from their position when the tool is new. As the lips are ground back in sharpening, the tapered extension can also correspondingly be ground back so that the inner end of the pilot, that is, the end which is nearest the lips, can always be made to assume a desired predetermined spaced or other relation with the cutting lips. However, by the use of this invention, even though the inner end of the pilot AWere against the cutting lips, there would be no chattering with marring or dulling of the tool, because there is positively no relative movement of the pilot. y

In Figure 6 I have shown a modication in which the sub-pilot or pilot mount or projection 'is threaded as at 20, and the pilot 2| is correspondingly threaded. In this case two methods may be employed for threading the sub-pilot: (a) the threads may be cut before the tool is hardnened, or (la)` the threads may be ground thereon after hardening. Then as the cutting lips are sharpened back, the pilot is simply screwed on lfarther.

In Figure 7 I have shown a modification in which the sub-pilot or mount 24 is cylindrical, rather than tapered.4 In this case the master pilot or part 25 has a slightly under-sized hole and the pilot 25 is either pressed or shrunk, or has a driven t with the extension. In this case, .as the cutting lips are sharpened back, means must be so exerted as to permit proper spacing l between the elements.

Although the greatest number of advantages of this invention accrue from having the mounting extension for the pilot of one piece with the tool, I believe I am also the first to provide a sub-pilot which is integrally attached to the tool and which has a surface which convergently tapers in a directionA away from the end of the tool and on which tapering surface a pilot is Secured frictionally, so that all that is necessary to remove the pilot is to lightly tap that end of it which is nearest the cutting lips of the tool.` The lfeature can be used with or without having the pilot mount or sub-pilot of one piece with the tool.

This invention, therefore, provides the feature of interchangeability from a minimum size compatible with strength, to a maximum size, such that the pilot may be a few thousandths of an inch smaller than the diameter of the cutting lips, in which case the counterbore has become a reamer for the accurate finishing of the hole to its final size, .which feature and/or function is a valuable one.

The type of support herein is very easy to manudacture and therefore much cheaper to manufacture because there is no extra drilling or fitting ror threading for setscrews, as in previous devices.

Mysub-pilo-t or tapered extension can be made very hard, and it is only submitted to such compression as results from driving on the master pilot. However, the strength of the master pilot :is assured by the fact that it is surface-hardened pnly, and has a tough and stronger core under lthe hard surface, which gives it sui'icient strength to withstand being driven onto the sub-pilot, and the necessary amount of flexibility to permit it to strongly, frictionally engage when driven onto the sub-pilot. At the same time being tapered it is readily driven off or removed from the subpilot by a light, snappy blow with a hamer and/or screw driver. n

As before explained, because of various manufacturing requirements, the same maximum diameter of counterbore portion or lips is often re- Iquired for a variety of screw holes of different sizes. For example, consider several screws, all {having heads one inch in diameter, but each havting a shank of a diiferent diameter ranging from 5/8 of an inch to of an inch. It will be seen that for the same diameter or cutting area replresented by the letter E in Figure 2, any one of the pilots I6, II and I8 can be substituted on mount I0. The dimension E corresponds in the example to a head which is one inch in diameter and the elements I6, I'I and I8 correspond to shank sizes ranging from 5A; of aninch to of an inch.

The present invention can be applied to any tool which uses a pilot. For example, it can be used in or for a spot-facing tool. The principal difference between counterboring and spot-facing involves dimensions and proportions. Counterboring provides a recess which receives generally the entire head of a screw. Spot-facing provides, in relation to a bored hole, a circular, flat area concentric with and surrounding the hole at the surface. Generally the diameter of the .area is proportionately much greater than that lof the dia-meter of the hole, and is of very shallow depth. The spot-facing tool has cutting lips and a pilot, and this invention assures that the spot-y '.faced area will be concentric with the hole, and also that the flat area will be in a plane' at right angles to the axis of the hole. In the case of a part to which a smaller part is to be bolted, the hole is drilled for the screw and this drilling operation is followed by spot-facing, thus providing a flat supporting area. By the same procedure, and more frequently, a flat surface is provided on which the head of a cap screw may rest, and in this case the screwis entirely above the surface. Usually in counterboring the screw head becomes flush with or below the surface.

This'invention may also be applied to a reamer. The drilled or bored hole is reamed and the reamer removes but a slight amount of material. The hole may be a few thousandths of an inch -out of round and the reamer will correct this condition, or the hole may be a few thousandths erallypdone throughout the length of the hole,

that is, all the way through the material. For example, if a truly round, straight and accurate hole is requiredto be finished to .5000 of an inch,

the initial operation would be to drill and/or to bore the hole to a diameter of a few thousandths less than .5000 of an inch. Then with a reamer having a cutting lip diameter of .5000 of an inch, and with a pilot of my invention having a diameter corresponding to the original hole, my tool is run through the hole and reaming action is performed. l

The invention herein results in a very simple, easily manufactured, fool-proof, accurate and strong counterbore mounting, and while I claim specifically the" tapering counterbore mount, I believe that the invention is broader than the specic shape of the mount and believe that I am the first to conceive of making this extension or mount integral or of one piece with the shank or tool, thereby obtaining positive rigidity and assuring concentricity between the pilot and cutting-lip diameter. The master pilots can be easily and accurately made and so made as to be positively held only by friction, but easily and quickly removable.

It is to be noted that in order to resharpen the cutting lips, as well as to sharpen the same at thetime of manufacture, the tool is supported by the work-supporting centers of a grinding machine that engage the centers 5 and I4. Inasmuch as the lips Will be subjected to many resharpenings, and inasmuch as it is desired to maintain the special relation between the end of the pilot and the cutting lips, it is also necessary to cause the taper to follow back by re-grinding in correspondence to the sharpening back of the lips. After this re-grinding operation, the outer end of the sub-pilot is ground off or cut off so that it will not protrude beyond the outer end of the master or control pilot. After this cutting-ofi` operation has occurred a suflicient number of times, the centering opening I4 disappears, and it is therefore necessary to apply the device shown in Figure 8 which I call a centering pilot.

.This device merely has a taper which fits the taper of the sub-pilot, and has a centering depression 28 which, in conjunction with depression 5, allows the proper centering in a machine. This centering or sharpening pilot can be driven onto the taper.

The wedging, attaching action of the pilot mount is a valuable feature. By making the mount tapered, the pilot, by its circumscribing, constricting and wedging action, serves to reinforce the mount, and to provide the much desired immobility of the pilot when the tool is bein used.

I claim as my invention:

l. A tool of the counter-cutting type having extending beyond its boring end a projection which is of one piece with the tool, and a pilot element removably mounted on said projection by means of a tapering friction t which permits said pilot to be loosened and removed by a blow applied against that end of it which is nearest the boring end of the tool.

2. A tool of the counter cutting type having extending beyond its boring end, a projection which is of one piece with the tool, said projection being convergently tapered in the direction away from said end, and a pilot element removheld thereon only by the frictional engagement with said projection.

3. A tool of the counter-cutting type having cutting lips and having at a point beyondy said lips at its boring end, an axial projection which is of one piece with the tool, said projection being convergently tapered in the boring direction of the tool, and a pilot element mounted on and having an accurate tapering lit with said projection, said pilot element being held only by the frictional engagement of a tapering surface with the tapering surface of the projection.

4. A tool of the counter-cutting type having extending beyond its boring end an extension which is of one piece with the tool and a pilot removably mounted on said extension and secured thereon only by frictional engagement of surfaces of said pilot and projection and so that said frictional securing action can be annulled by moving said pilot axially.

5. A tool of the counter-cutting type, having a stem having cutting lips adapted to be sharpened by grinding in an axial direction and away from the boring end of the tool, said stem having of one piece therewith and at a point immediately adjacent the cutting ends of said lips a pilotmounting extension, and a lpilot removably mounted on said extension and rigidly secured thereon only by frictional action, said pilot having its inner end occupying a predetermined position with respect to the cutting ends of said lips, whereby as the lips are ground in an axial direction to sharpen them, the extension can also be correspondingly ground axially in order that the inner end of the pilot shall always occupy said predetermined relation to said lips after sharpening of the same.

6. A counterboring tool having, extending beyond its cutting end and of one piece with the shank of the tool, an outwardly convergently tapered pilot mount adapted to receive and wedgingly detachably cooperate with a correspondingly tapered opening of a pilot element.

7. A one-piece counterbore having cutting portions Which face and cut in an axial direction only, and having extending beyond those cutting portions a pilot-mounting projection which is of one piece with the tool, and a pilot element as a separate piece removably but rigidly mounted on said projection.

8. A one-piece counterbore having cutting portions which face `and cut in an axial direction only, and having extending beyond those cutting portions a pilot-mounting projection which is of one piece with the tool, and a pilot element as a separate piece removably but rigidly mounted on said projection, said pilot having its inner end adjacent but spaced from said cutting portions in an axial direction.

9. A one-piece tool ofthe counter-cutting type having a stem and cutter elements extending radially beyondthe stem and extending longitudinally of the stem and having cutters which -face and cut only in an axial direction, said tool having extending beyond said cutters a pilot mounting projection which is of one piece with' the tool and a pilot element as a separate piece removably but rigidly mounted on said projection.

OSCAR C. I-IEDIN.

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