US2202819A - Twist drill grinding attachment - Google Patents

Description

June 4, 1940. J. A. YANTISS 2,202,819

TWIST DRILL GRINDING ATTACHMENT Filed May 2, 1938 3 Sheets-Sheet 1 /a 30 ZZ 7.2' 7 :3.

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ATTORNEYS June 4, 1940. J. A. YANTISS 2 3 TWIST DRILL GRINDING ATTACHMENT Filed May 2. 1938 3 Sheets-Sheet 2 Jana INVENTOR ATTORNEYS June 4, 1940. A. YANTISS TWIST DRILL GRINDING ATTACHMENT Filed May 2, 1938 .3 Sheets-Sheet 3 Zzss ATTO R N EYS ?atentati June 4, 1940 UNITED STATES PATENT OFFICE z,2o2,s9 'rws'r DRILL GRINDING ATTAcmmN'r Jesse Alvin Yantiss, nana, Palestine Application May z, 1938, Serial No. zoss z cams. (Cl. 51-219) This invention relates to twist drill grinders and more particularly to an attachment to an ordinary hand or power operated grinding wheel.

The prime object of the invention is toproduce a simple yet practical and highly eflicient device which may be readily applied to the tool rest or support in cooperative relation to a grinding wheel whereby to properly grind the drill point so as to produce the proper eccentricity of the cutting iips of the drill end.

Another important object is to provide for adequate adjustment of the attachment and the drill supporting means thereof to properly position the cutting lip of the drill with relation to the face of the grinding wheel and also in correlation to the pivotal axis of the drill supporting means.

A further object is to provide for the grinding of bits of different diameters.

With these and other objects to be attained as will hereinafter more iully appear, the invention consists in the general Construction and in the parts and combinations and arrangements of parts thereof, as hereinafter described and pointed out with particularity in the appended claims, reference being had to the accompanying drawings forming a part of the specication, and

` in which- Figure 1 is a plan view of one practical embodiment of the invention in a device as applied to a hand operated grinder;

Figura 2 is an elevation viewed from one side of the device;

Figure 3 is an elevation viewed from the opposite side;

Figure 4 is a fragmentary view, on an enlarged scale, showing details of the pivotal mounting of the drill holding means and the correlation of the pivotal axis to the face of the grinding wheel and further details of the working support for the drill:

Figure 5 is a substantial cross section on the line 5--5 of Figure 4, showing an end view of the drill bit and its supporting collet holding element in the trough of the attachment;

Figure 6 is a perspective view of a gauge ele-- ment which may be used in effecting the various adjustments of the attachments. Figure 7 is a side elevation of a modified form of the attachment;

Figure 8 is a section taken substantially on the line 3-3 of Figure 7;

Figure 9 is a fragmntary view, on an enlarged scale, illustrating details of the structure shown ,inFigure 7; and

` the inner side of the gear housing i3 is the grinding wheel i8 which is mounted on the stub shaft is and driven by the gearing (not shown) in said housing l 3 by means of the crank on the outer 35 side of the casing.

Mounted on the tool support 2| o! the grinder adjacent the periphery of the wheel !8 is a block 22 of substantial thickness and or general rectangular form. As shown, this block 22 has a re- 20 duced end portion 23 which rests on the tool-support or shelf 2! and is clamped thereto by an ordinary vise, said vise, as shown, including an elongated shani: or stem portion 24 having an arm 25 overhanging the top of the block portion 25 23, said stern or shank portion being longitudinally adjustable in a lower arm 26 which letter has a clamping screw 21 working therein andprovided with a head 28 at its upper end engaging the under side of the tool support or shelf z, ai) said screw element 21 having an elongated handle 29 at its lower end. said block 22, which as above noted, is of substantial thickness, provides a rigid supporting body for the drill grinding attachment of the present invention and its relative adjustability on the tool support is an important feature of the present invention as will later more fully appear.

Pivotally mounted on the inner face of the block 22, as at 30, is a plate 3| having an arcuate end portion 32 which is formed on a radius from the pivotal axis 30, said arcuate edge portion 32 abutting a stop screw or stud 33 projecting beyond the inner face of the .block 22 in the path of the upper and lower lugs 34 projecting from 5 the end of the plate 3i at the opposite terminals of said arcuate end portion 32 ot the plate for limiting the swinging movement of said plate 3I on its pivot`30.

Provided integrally or otherwise on the face of 50 the plate 3i is an angular bracket 35, on the diagonal marginal portion 36 of which a trough 31 is rigidly attached. This trough, which has right angular side walls, is open at its inner end but is closed by a wall 38 of substantial thickness at its ,u

In carrying' out the present invention, inter-- changeable collets or drill holding chucks are provided, said collets being of the same external dimensions but having axial bores of various diameters respectively corresponding to the different diameters of drills to be ground. These collets, one of which is shown in detail in Figure 4 of the drawings, each comprise a forwardly tapered head portion 4l which is joined by a reduced neck 42 to a rearwardly tapered shank portion 43, said shank portion being split longitudinally throughout its length so as to be received in the bore 44 of an elongated holder 45, one end portion of the bore 44 being reduced. as at 46, and into which portion the end of the collet enters with wedging' eil'ect whereby to securely clamp the inserted drill bit 41 against both rotative and endwise movement in the collet and also to prevent rotation of the collet in said holder 45.

The holder 45, as shown. is of square cross section so as to fit within the trough 31 without rotation but is capable of endwise movement therein so that the drill bit end may be pressed against the face of the grinding wheel s as will be presently described.

In setting up the attachment the block 22 is adjusted on the tool support 2| so that the axis of the pivot 30 is a definite distance from the inner side face of the grinding wheel IB, which distance is governed by the diameter of the drill to be sharpened and the character of the material on which the sharpened drill is to be used. For example, when the drill is to be used on iron or steel the distance between the face of the grinding wheel and the pivot center should be approximately one-fifth less than the diameter of the drill, whereas for brass or copper said distance should be approximately one-third less than the diameter of the drill. The nearer the pivot center is to the grinding wheel the keener will be the angle of the cutting lips on the drill as sharpened.

In the ordinary twist drill there are two opposed cutting lips, and for ideal performance in the drilling operation it is essential that each of said lips be ground with uniformity and exactness as to angularity and length thereof and this is accomplished by the use of the attach-,

ment of the present invention.

The drill bit 41 having been placed in the collet and the latter adjusted in the holder and the holder placed in the trough 31 with the protruding cutting end of the bit in abutting relation to the face of the grinding wheel s the trough is slowly raised from its lowered position by one hand of the operator while turning the crank 20 with his other hand to rotate the grinding wheel |8 and at the same time exerting pressure with the ngers 'of the hand which is lifting the trough whereby to rmly retain the holder 45 in the trough. In this connection, it is noted that the screw element 39 is adjusted to prevent outward endwise movement of the holder 45 in the trough 21 either by direct contact between the adlacent end of the holder 45 asoaec and said screw 39 or, in cases where the holder 45 is not of suflicient length to engage said screw element 39, a filier block 45 of* wood or metal may be interposed between the end of the said holder 45 and said screw element 39. as shown in Figures 1 and 2 of the drawings. The provision of this set screw 39 is for the primary purpose of maintalning the drill bit i'n the same endwise relation to the face ot the grinding wheel s when the holder 45 is turned over and replaced in the trough 31 to grind the second cutting lip.

While the trough 31 is mounted in fixed angular relation to the pivoted supporting plate Il. and the block 22, in the set up of the attachment, is disposed at right angles to the face of v the grinding wheel s, it is noted that some comparativeiy close relative adjustment between the pivotal axis 30 of the plate 3! and the face of the grinding wheel !8 is necessary to properly position the cutting lip of the drill bit with relation to said pivotal axis 30, and to facilitate such adjustment a special gauge 49 may be provided as shown in Figure 6 of the drawings. This gauge, as shown, is of the general form of an ordinary L-shaped square having one long leg and a short right angular leg 5l, the outer right angular margins being used to square the block 22 with the grinding wheel !5. purpose is attained by providing scales at the opposite ends of the square 49 for measuring the distance between the pivot center and the face of the grinding wheel. These Scales, designated generally by the numeral 52 may be marked to indicate millimeters or fractions of an inch, say. thirty-seconds. There is a third use for the scale in that the inner portion of the short leg 5i is beveled oil?, as at 53, and utilized for testing the height of the cutting lip of the drill bit in relation to the pivotal center of the plate SI. That is to say, this beveled portion 53 is of a length from the adjacent longitudinal side of the longer leg 50 corresponding to the distance from the top of the block 22 to the pivotal center 30 of the plate 3l so that, by resting the longer leg 50 across the top of the block 22 with the portion 53 depending above the end of the drill bit, it is readily determined if the cutting lip of the drill bit is in proper relation to the pivotal axis when the trough containing the drill bit is in uppermost raised position. In this connection, it is noted that the cutting lip must not be any higher than the pivotal center but should be as close to such center as possible, although if a trifle thereunder no harm will occur. If the cutting lip is too low the holder 45 may be raised in the trough 31 by the insertion of a shim or sh'ms therebetween. For this purpose it has been found practical to utilize thick paper or cardboard sheets of proper length and width which are scored on a median longitudinal line and bent to fit as a lining in the trough, or, obviously, sheet metal may be used for this purpose.

Instead of detachably securing the r'nain supporting block 22 on the tool rest or support 2! of the grinder as in the construction and arrangement hereinbefore described, a corresponding supporting block 22' of somewhat different polygona form, but having a similarly squared top edge portion secured firmly to the under side of the tool rest 2i' by suitable machine screws or bolts 54, is provided (see Figures 7 and 9).

Another Preferably, as shown, this block 22' has its opclearancefor the operator's hands in manipulating the drill supporting trough 31 and 'operating the crank 20 to rotate the grinding wheel BO. In this modification, instead of shiftlng the block 22' on the tool rest or support !I to vary thedistance between the pivotal axis of the trough carrying plate :I and the face of the grinding wheel !8, an adjustable pivot is provided on said blockl' for said plate 3l. As shown more clearly in Figure 10, this pivot comprises a stud which is provided with an axial bore through which a stub shaft 56 on the plate a extends, said stub shaft '58 having a retaining nut 51 at its outer end abutting the outer end of said stud 55 with a Washer B! interposed therbetween. The stud 55 is extended through a horizontal elongated slot 59 in said block 22' and it is provided at its inner end with a squared head 60 which is set in a rectangular countersink BI in the inner face of said block 22 and surrounding said elongated slot 59, the head 60 being fiush with the face of the block and by its slidable fitting in said countersink Bl preventing turning of the stud 55, yet permitting said stud to be adjusted lengthwise of said slot 59. The outer end portion of said stud 55 is externally screw threaded for the reception of a retaining nut 62 which is tightened against the outer face of the block 22' to hold the stud in'its respective adjusted positions in said slot 59.

Obviously, to conorm to the adjustment of the pivot hearing stud 55 a stop stud 33' corresponding to the herelnbefore described stop stud 33 for limiting the swinging movement of said plate 3! must be accordingly provided. This stud 33', as shown more clearly in Figure 8, is extended through a longitudinal slot 53 in said block 22' and it is provided with a collar ti adjacent its projecting inner end portion, said collar being received in a countersink 55 in the inner face of said block 22' and surrounding said siot 53, the outer end portion of said stud 33' being screw threaded, as at 66, and provided with a wing nut t? which is tightened against the outer face of said block 22' to lock the stud in its adjusted position.

Other than the diiference in the pivotal mounting and stop provisions for the movement of the plate ai, said plate isthe same in character as in the hereinbefore described modification, as are the trough t'i and the several drill holding elemente employed in the use of the attachment.

In order to facilitate the proper positioning ofthe drill bit with relation to the holder 45 for the proper presentation of the drill point to the face of the grinding wheel i@ the holder 45 is provided at its end with marks 88 extending diagonally from opposite corners to the bore opening u. By this provision, before the collet 4| is tightened in the bore of the holder 15, the bit n is turned to align its opposite lip portions with said marks tt, and after the bit has been so positioned the inner end of the holder 45 may be tapped with a hammer or other instrument or strucl; against a solid object so that the collet with' the bit therein is moved towards that end of the holder and becomes wedged in the reduced portion it of the bore, thereby tightly clamping the drill bit and the collet with the bit tlus clamped being securely held against rotation in the holder while the grinding operation is being performed. So, too, for the convenience of the operator in differentiatng between the two cutting lips so there can be no mistake as to which lip has been ground after placing the holder in the trough 31, suitable distiguishing marks may be provided on opposite sides of the holder. For this purpose it has been found practical to provide a single dot 69 on one side and two dots on the opposite side. one of which, of'

prising in combination' with a grinding unit including a grinding wheel and a tool rest, a supporting block mounted on said tool rest in stationary working position perpendicularly to the flat side face of the grinding wheel, a plate swingably mounted on the inner face portion of said supporting block about an axis relatively adjacent the side face of the grinding wheel and,

at right angles to the axis of said wheel, stop means for restricting the movement of said swingable plate, a trough member rigidly mounted diagonally on said swingable plate and movable with said plate and in correlation to the opposed side face of the grinding wheel, said trough being of right angular cross-section and drill holding means removably and reversibly fltting said trough, said means including an elongated holder element corresponding in square cross-section to the form of said trough whereby to be nonrotatable but movable endwise in the trough, said holder element having an axial bore, a bit receiving and retaining collet receivable in the bore of said holder element, and an adjustable abutment in said trough for the outer end of said holder element, the distance between the side face of the grinding wheel and the pivotal axis of said swingable plate and between said pivotal axis and the cutting lip of the drill end when applied to the face of the grinding wheel, and with said plate in its uppermost position, being such that the working contour of the bit end is formed and the angularity of the cutting lips is defined during the upward swinging movement of the plate and by reversal of the holder element a half turn about its longitudinal axis to separately grind each duplicately formed half of the cutting end of a conventional twist drill bit.

2. A grinding attachment for drill hits, comprising in combination with a grinding unit including a grinding wheel and a tool rest, a stationary supporting block mounted on said tool rest and extending perpendicularly beyond one fiat side of the 'grinding wheel in parallel relation to the axis of said wheel, a pivot hearing on said supporting block, the axis of said bearing being at right angles to the axis ofthe grinding wheel and said hearing being adjustable on said block whereby to vary the distance between the 'axis of the hearing and the adjacent side face of the grinding wheel, a plate swingably mounted on said pivot hearing in slidable contact with the inner face of said supporting block, adjustable stop means for limiting the up-anddown movement of said plate, the adjustment of said means corresponding to the adjustment of said pivot hearing, a trough member mounted' dlagonally on said plate with its inner end adjacent said pivot hearing and spaced from the opposed sldeface of the grindlng wheel. an adjustable abutment at the outer end of said trough member, and removable and reversible drlll holding means flttng said trough with endwse movement but non-rotatve therein, the bit in said drlll hodlng means being projected into engagementwith the !ece of the srinding whee with the cutting lip of the bit in parane! reltlon to the face of the wheel and in substantilly the same plane as the axs of seid pivot hearing.

mssn ALVIN nmes.

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