US2496939A

US2496939A - Drill

Info

Publication number: US2496939A
Application number: US732226A
Authority: US
Inventors: Gonzalez Julio
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-03-04
Filing date: 1947-03-04
Publication date: 1950-02-07
Anticipated expiration: 1967-02-07

Description

Feb- 7, 1950 J. GONZALEZ 2,496,939

DRILL Filed March 4, 1947 3 Sheets-Sheet l zwl Ii l ATTORNEYS J. GONZALEZ DRILL Feb. 7, 1950 3 Sheets-Sheet 2 Filed March 4, 1947 INVENTOR 5. av 7 '9 K '1 Ram M- ATTORNEYS Patented Feb. 7, 1359 UNITED STATES PATENT OFFICE DRILL Julio Gonzalez, Hudson County,N

Application March 4, 1947, Serial No. 732,226

13 Claims. (01. lea-20) This invention relates to drilling machines and relates especially to drilling machines adapted to drill holes in hard, brittle materials such as glass, stone, hardened plastic materials, vitreous tiles and the like.

It is a purpose of this invention to provide a drilling machine of the character referred to which is capable of rapid and effective drilling of hard, rigid bodies. It is a further purpose of this invention to provide .a drilling machine which .is capable of successfully drilling holes in hard, rigid bodies such as sheets of glass, tiles and the like while reducing breakage to a minimum. It is a further purpose of this invention to provide a drilling machine of the character referred to which is relatively simple and inexpensive to manufacture but which, nevertheless, is capable of rapid and effective drilling of hard, rigid bodies with a minimum of breakage. It is a further purpose of this invention to provide an improved hollow drill bit which has outwardly directed slots in the cutting edge and which, while capable of extended periods of use involving substantial wearing away of the cutting edge of the drill bit, is strong and is maintained with the cutting edges adjacent the notches firmly held in undistorted position. It is a further purpose of this invention to provide a drill bit whereby a hole may be drilled in a hard, rigid body and whereby, during the same drilling operation, a concentric recess surrounding the hole may be formed in the hard rigid body.

Heretofore the drilling of holes in hard, rigid bodies .such as sheets of glass, vitreous tiles and the like has .occasioned considerable difficulty. Large, expensive, heavy machines have been designed for this purpose but even in such case there has been excessive breakage or cracking of the article being drilled. This has been particularly the case upon attempt to drill holes in close proximity to each other or in close proximity to the edge of the article being drilled. Such difficulties have been overcome according to the present invention. Notwithstanding that the drilling machine of my invention is relatively light in weight and aiTords a readily portable unit. it is rapid in its action as is evidenced by the fact that my drilling machine is capable of drilling a hole through a A inch glass plate in only about thirty seconds. My machine is capable of use with a minimum of breakage as evidenced by the fact that I have repeatedly drilled holes the diameter of which is of the order .of M1 inch .to 1 inch in glass sheets varyin in thickness between A; inch and inch With the spacing between adjacent holes reduced to as little as 1 5 inch without breakage of the glass between the holes. So far "as I .am aware such minimizing of breakage has not been accomplished in the case of previously known drilling machines regardless of their costliness and size.

The drilling machineoi my invention comprises. several novel and advantageous features which are preferably employed in combination but which may be employed-separately so as t obtain at least in part the benefits resulting from their use accord-ing -to this invention.

In a drilling machine embodying this invention a drill bit is secured in axial alignment with a spindle that is mounted for rotational and longitudinal movement while maintained in fixed axial alignment. l eatures of this invention relate to the means for maintaining {the axial alignment of the rotatable spindle and to the combination with the rotatable spindle of means for resiliently urging the :spindle in the direction toward the cutting edge of the drill bit during rotation .of the spindle. Other 'features oi this invention relate to the means for efiecting the rotation of the spindle with a minimum of moyi-ng .parts while permitting the 1on gitud-inaal movement of the spindle during rotation thereof. Another feature :of this invention relates to the combination with the rotatable and longitudinally {movable spindle of manually operable means :ior retractin the spindle during rotation thereof in the direction away from the cutting edge of the drill bit. Another feature of this invention relates to means for indicating the :hrogress oi thedrill 'bit through an article being drilled without retracting the drill bit .irom the article.

Other features of this invention relate 'to the means ii/hereby the spindle and the drill hit including the cutting edge thereof are maintained accurately in alignment. preferred embodiments of my invention' adapted for protracted periods of use, ,1 provideka drill ;bit comprising a hollow tube having outwardly'extending slots which are open ended at the cutting edge and incapable n successful use due :to the fact that 3. the slots so weaken the tube wall that distortion of the tube wall results under the influence of the forces exerted during drilling with resulting breakage of the body being drilled. It is one of the features of this invention that a cylindrical tube provided with elongated outwardly directed slots is provided with a clamping arrangement that is longitudinally slidable relative to the tube for positional adjustment adjacent the cutting edge of the tube. The clamping arrangement comprises an inner member in slidable contact with the inner surface of the tube and an outer member in slidable contact with the exterior surface of the tube and when the outer member is in such position as to substantially overlie the inner member, the portions of the tube between the slots in the tube are firmly held in place adjacent the cutting edge of the tube and distortion of the tube wall and breakage of the article being drilled are effectively avoid ed. As the cutting edge is worn away, the clamping arrangement can be correspondingly retracted for resetting at any desired proximity to the cutting edge of the tube that it is desired to have maintained. By thus firmly and accurately maintaining the metal of the tube adjacent the cutting edge thereof and, by accurately maintaining the axial alignment of the spindle to which the hollow drill bit is attached, minimum breakage of rigid brittle material is possible in the practice of my invention. The inner and outer members of the clamping arrangement are preferably independently slidable longitudinally of the tube and the inner member may conveniently be provided with a member which extends through at least one of the slots in the tube whereby the manual adjustment of the inner member of the clamping arrangement is facilitated.

It is a further feature of this invention that may optionally be employed that cross member means is providedwhich extends through slots in the tube so as to project substantially beyond the periphery of the tube, which is in spaced re lation to the cutting edge of the tube, and which is restrained from rearward movement. The cross member means aflords effective means for producing a recess in the article or body being drilled that is concentric to the hole which is drilled. The cross member means may be associated with the clamping arrangement in any of the manners that are described more in detail hereinbelow or may be otherwise carried by the cylindrical tube intermediate the ends thereof.

Further purposes, features and advantages of this invention will be apparent from the following description of the typical embodiment of my invention which is shown by way of illustration in the accompanying drawings, wherein Fig. 1 is a plan view of a drilling machine embodying my invention;

Fig. 2 is a left-hand end elevation of the drill ing machine shown in Fig. 1; V

Fig. 3 is a sectional elevation of a portion of the drilling machine taken on the line 3-3 of Fig. 1;

Fig. 4 is a left-hand end elevation of the portion of the machine shown in Fig. 3;

Fig. 5 is a section of the adjustable frame support of the drilling machine taken on the line 5-5 of Fig. 1;

Fig. 6 is a plan sectional detail view taken on the line 66 of Fig. 2;

Fig. 7 is a front elevation of an alternative tubular drill of relatively large size together with an of the parts to a body in which a hole has been drilled that is surrounded by a concentric recess; Fig. 11 is an end View of the drill bit shown in Figs. 9 and 10, viewing the parts from below, and

Fig. 12 is a detail view similar to Fig. 10 and showing the lower end of the drill bit as provided with an alternative cross member adapted for producing a recess having a tapered wall surrounding a drilled hole, and with an alternative form of centering plug.

Referring to the embodiment of this invention :hich is shown in Figs. 1 to 6, the drilling machine may be mounted on a suitable table or plate 29, to which the upright supports 2| may be secured as by suitable screws or bolts 22. Secured to and between the upright supports 2| are the L-shaped bars 23 which are disposed so as to provide a flat upper surface which is divided by a space between the innermost edges 24 of the bars 23. Supported by the L-shaped bars 23 is the carriage 25 which is mounted so that its position along the --shaped bars 23 may be adjusted as desired. This may be accomplished in any suitable way, as by the bolts 26 which are provided with enlarged head members 21 that underlie the L-shaped bars 23 so that by tightening the nuts 28 the carriage 25 may be firmly clamped in place. By loosening the nuts 28, the position of the carriage can be adjusted along the longitudinal extent of the L-shaped bars 23. The means employed to clamp the carriage 25 to the L-shaped bars '23 is shown in detail in Fig. 5.

Secured to the carriage 25 is a suitable motor 29, which may be an electric motor, having the power shaft 30. Also secured to the carriage 25 is the bracket 3!. The bracket Si is secured to the carriage 25 by the bolts 32 which, when loosened, are slidable in the elongated slots 33 in the carriage 25. The elongated slots are provided so that the position of the bracket 3! may be adjusted relatively to the power shaft 30 for tightening the belt 34. To adjust the position of the bracket, a. set screw 35 is used which is in threaded engagement with the ear member 353 that is rigidly secured to the carriage 25. The end of the set screw 35 abuts the end of the bracket 35 so that by turning the set screw the position of the bracket 3| relative to the carriage can be adjusted for tightening the belt 34. After the belt has been adjusted to the desired tension, the bolts 32 may be tightened down so as to hold the bracket 3| rigidly in place.

At the outer end of the bracket 3| is a bearing which is indicated generally by the reference character 3'5 and which is adapted to maintain the spindle 33 in fixed axial alignment while permitting both rotational and longitudinal move ment of the spindle 38. It is one of the features of this invention that the bearing 3'! is specially constructed so as to maintain with very great accuracy the axial alignment of the spindle 38 during rotation of the spindle notwithstanding the occurrence of wear at the interface between the spindle and the bearing. To this end, theheld in place by the arms 4! which contain trough-shaped portions surrounding the bushing 39 and the extremities of which are slightly spaced from each other. By tightening thebolts 42, the extremities of the arms 41 can be drawn together so as to constrict the bushing 39 and insure its being in closely fitted contact with the spindle 38. It is one of the features of this invention that the force exerted by the bolts is resiliently applied to the arms 4| by the use of lock washers 43 or the like. In this manner, it the tightness of the fit of the bushing about the spindle 38 is initially adjusted as desired by tightening the bolts 42, any progressive wear at the interface between the spindle and the bush.

ing will be compensated by the action of the lock washers 43 in urging the extremities ofthe arm 4i together so as to maintain a close fit between the bushing 39 and the spindle 38 at all times. Even a slight amount of wear at the interface between the spindle 38 and the bushing permits, at least to some extent, wobbling of the spindle 38 during use of the drill. In such case, there is danger of breakage of hard, brittle material such as glass during the drilling operation. By the arrangement above described, I have found that the axial alignment of the spindle 3B can be maintained extremely accurately during operation of the drilling machine over a long period of time, and that the accurate alignment thus obtained is an important factor in minimizing breakage. In the bearing above described, the bushing can initially be held in place prior to drawing the ends of the arms 4! together by any suitable means such as the set screw 44.

The spindle 38 is rotated in the bearing 31 by the belt 34 which passes over the pulley 45 secured to the power shaft 30 and the pulley 46 secured to the upper end of the spindle 38. With this arrangement, the spindle 38 can be moved longitudinally through a substantial distance while the rotation of the spindle is maintained. The moving parts are reduced to a minimum which results in economical construction and also long life. Any wear at the pulleys can be compensated for by adjusting the tension of the belt 34.

:As best shown in Figs. 2 and 3, means has been provided for resiliently urging the spindle in the direction toward the cutting edge of the drill bit carried by the spindle while the spindle is maintained in rotation. A preferred means for accomplishing the action referred to comprises the bar 41 which at the end thereof carries a thrust bearing 48 that bears against the small rounded boss 49 at the upper end of the spindle 38. With this arrangement, the inclination of the bar 41 relatively to the spindle can be varied considerably while" permitting the free rotation of the spindle 38 with the upper end thereof in contact with the thrust bearing 48. Adjacent the other end of the bar 41 is an aperture 50 which fits about a post 5| which is upstanding from the bracket 31 parallel to and spaced from the spindle 38. The post 5! is" surrounded by a compression spring 52 which bears against the end of the arm 41 and urges this end of the arm upwardly. At an intermediate point between the thrust bearing 48 and the post Ii. a manually adjustable fulcrum mem her is provided, which, in the embodiment shown.

is in the form of the wing nut 53 which is in threaded engagement with an elongated bolt 54 3 that is rigidly carried in the boss 55 upstanding from the bracket 3| by the lock nut 56. The bolt 54 passes through an aperture 51 in the bar 41. By adjusting the wing nut 53. the bar 41 can be tightened against the compression spring 52, and the force exerted by the compression .spring 52 is transferred to the thrust bearing 48 so as to resiliently urge the spindle during the rotation thereof in the direction toward the cutting edge of the drill bit carried by the spindle 38. The resilient force applied to the spindle 3B urges the cutting edge of the drill bit against a body to be drilled so that the force applied is constant. This also is important in minimizing breakage of hard and brittle bodies. During the drilling operation, the spindle moves gradually downwardly as it rotates until the desired amount of drilling has been accomplished.

In order to quickly retract the drill after a drilling operation has been accomplished and while maintaining the rotation of the spindle 38, I provide means for urging the spindle 38 up wardly against the force applied by the resilient means for urging the spindle in the direction toward the cutting edge of the drill bit. As more particularly shown in Fig. 4, I provide a lever 58 which is pivoted about a pin 59 which is rigidly secured to the bracket 31 At one end of the lever 58, there is carried a roller 60. The end of the lever which carries the roller 63 is held in normally retracted position by a small tension spring 3! which is connected at one end to the lever 58 and at the other end to the hearing 31. By depressing the end 62 of the lever 58, the roller can be brought into contact with the lower surface of the pulley 56 and force can be applied through the lever for urging the pulley 56 and the spindle 38 on which it is carried upwardly to the amount desired for Withdrawing the drill bit from the article in which a hole has been drilled. During normal operation of the machine while it is being used for drilling,

the lever 58 is in the position shown in Fig. 4.

It is frequently desirable to determine the progress of a drill bit during a drilling operation without withdrawing the drill bit from the hole that is being drilled b the drilling machine. A simple means for accomplishing this result is shown in the accompanying drawings,'

particular reference being made to Figs. 2 and 6. A small rod 63 is slidably mounted in a boss 64 protruding from a bearing 31. The rod 53 is disposed parallel to the spindle 3B and the upper end 'of the rod underlies the marginal portion of the pulley 46. The upper end of the rod 63 can be placed in any desired position and fixed in this position by tightening the wing bolt 65. The use of .rod 83 may be illustrated as follows.

If the end of the drill bit is placed in contact with a work piece and if it'is desired to drill into the work piece to the extent of 4 inch, the upper end of the rod 63 may be positioned inch below the undersurface of the pulley 46. During the drilling operation, the spindle moves downwardly, and when the pulley 46 comes into contact with the upper end of the rod 63. the operator 'isimmediately advised of the fact that the drill bit has penetrated A; inch into the work piece except for such wear as may have occurred at the cutting edge of the drill bit.

The construction of the improved drill bit which constitutes one of the features of thisinvention is shown particularlyin Figs. 2 and 3.

The drill bit is hollow and comprises'a cylindrical metal tube 66. One end of the tube 66 is in frictional engagement withthe'support plug 61 which is centrally and in'te'rhaliy threaded for securement with the threaded'end 68 of the spindle. The drill bit and spindle thereby main tained rigidly in alignment. To prevent relative' rotation of the metal tube 66 with respect to the support plug 6'1, the support plug may be provided with a small pin 89 that fits within a notch in the upper edge of cylindrical tube 66;: The cylindrical tube 65 is of substantial length so as to allow for gradual and substantial wearing away of the cutting edge 10. The" cylindrical tube 65' is provided with four outwardly directed slots H which are open ended at the cutting edge It and which extend throughout a substan-' tial portion of the length of the cylindrical tube 66. While four slots H are"employed in the embodiment shown, any'other number of slots may be employed depending largely on'the diameter of the cylindrical tube. The tube 66 may be made of any suitable steel or the like.

The provision of the elongated slots Il-in"thecylindrical tube 56 allows for extensivegradual wearing away of the cutting edge of the tube While affording at all times the provision of one or more slots at the cutting edge, which or-" dinarily are desirable for obtaining proper cut-- ting action of the tubular drill bit. Theprovision of the elongated slots presents difiiculties, however, due to the fact that during a drilling operation the forces applied to the portions of the metal tube between the slots tends to result in distortion which, even though slight, is a major cause for breakage of hard, rigid bodies.- I have found that this difficulty can be successfully over-- come by providing longitudinally slidable clamp-- ing means, the position of which can "be a'djusted in the region of the slots in the tube 66 so as to be at any desired position adjacent the cutting edge of the cylindrical tube. In the embodiment shown, the slidable clamping meanscomprises an inner member '12 in the form of a" ring which is in slidable engagement with the inner surface of the tube 66. An outer member 73 is also provided in the form of a ringwhich is in slidable engagement with the externalsurface of the tube 66. Preferably, the members 12 and 73 are independently slidable longitudinally of the tube. When the outer member 13 has been brought into position so that it substantially overlies the inner member 12, the portions of the tube-between the slots H are firmlyclamped inx By relative movement of the memposition. bers l2 and i3 so as to be brought into nonoverlying position, the position of these members relative to the longitudinal extent of the tubecan be readily adjusted due to the fact that when these members are in non-overlying position, a

very slight amount of flexure of the portions of the tube between the slots is permitted which lessens the friction between the tubeandthe member. It is apparent that when the inner and outer clamping members are in overlying position, the clamping therebetween of -theportions of the tube between the slots is due to .the fact that the external surface of the inner-member corresponds to the inner surface ofthe tube while the inner surface of .the outer-member corresponds to the exterior surface of the tube except:

that theparts are machined witha' slight tolmaterial such as brass.

erance so that the friction between the opposed surfaces will not-he so great as to render it excessively diificult to bring the members into and out of overlying position. When the portions of the tube between the slots are held firmly in position between the inner and outer clamping members as above described, the inner and outer clamping members are, of course, in pressure contact with the inner and outer surfaces of the tube, but upon moving the inner and outer clamping members relatively'to each other so as to bring them into non-overlying position, the bending of bringing the clamping members into and out of overlying position such operation can conveni-' ently be assisted by light tapping. However, experience has shown that the portions of the tube between the slots become firmly clamped in posi-' tion when the parts are machined so that the inner and outer clamping members may be brought into and out of overlying position merelyby manipulation with the fingers. In normal' use of the drill, the members 12 and 13 are brought to clamping position at a distance spaced from the cutting edge of the drill which is somewhat in excess of the depth of the hole to be drilled. For' example, if the drill is to be used in drilling a sheet of glass inch in thickness, the clamping members 12 and 13 may be placed in the neighborhood of A; to inch from the cutting edge of the drill. In'this manner, the portions of the tube betweenthe slots at the cutting edge'are held firmly in place and are prevented from any movement or distortion which might result in breakage of the work piece, After the cutting edge of the drill has been worn away as a result of many drilling operations, it is relatively simple" to readjust the position of the clamping members- 12 and '13 so as to maintain their desired distance from the cutting edge of the drill. This operation can be repeated until virtually all of the cylindrical tube has been worn away. When the' can readily be cylindrical tube 66 has worn out it replaced with-a new tube. 7 It is apparent from the foregoing that a very effective drill bit is aiforded'which has a verylong wearing life and which, at the same time,

is free from objectionable distortion. The drill bit is economical to' produce because it is a very simple operation to cut longitudinally extending slots in a metal tube. While the slots l'l inthe embodiment shown are in alignment with the axis of the tube 66, this is not essential, for it is apparent that the slots H, if desired, could be in some other form such as spiral form. However;

for economy in production, it is normally the case that the slots H are in alignment with the axis" of the cylindrical tube 66.

In the embodiment shown in Figs. 2 and 3, there is associated with the clamping members 12 and 13 the cross member means-aiforded'by the pins 74 which pass through slots H disposed on opposite sides of the cylindrical tube 66. The pins: 14 may be secured either to member .12 ortoi.

t H 9 member-13, altlijigli'it tefe're'me' to secure to the Iiinlb r12 as Shown SoIas to fi or'd means on the e'rj'dr orthe' tube etifor djust ing the pb'sl'tion of the inner member 12" of the clamping arrangement. Cfoss' member means such as the pin eentri'crecess ebeu af'l'iole which is drillediby the cutting edge" TB. of the tube" 66. Thus, when a' hole been drilled: the cutting edge 15, cdnti'nu'e'd m verhehtef the spindle 3'8 in a direiction toward" the eutting' edge of the drill bit will bring the pins 'ldi'nt'o" Contact with; the. see race df the" work iece: By' contiililed rt'atibfi of thdr'ill with tFiiepiiis" 1 4' in pressurecdiitactwith the vent p eee, the surface of the Work piece" will be worn away so astdprodue' a recess which is' conoeritr'fic' with a hoi drilledby the euttirigiedge df the wb se. trheem'pieyiheht orthe' tr is' in, or'eq'uitialent oros's'meinbefmans; is not ne'ese" Se 1n the prddtice of sv invention'inasmuch as'theclaiiiping errenee netit can be usedinthe" absence of s ueueresememuer means; the" cross memberniearis'isnot used; then the drill" functions in the eidnietry wefy fbr'diillihg" a. hole" andh l'ipio'd to theend thereof withinthe tube' a bite spring 1-6 which normally holds the center-mg pitg- 1- a djaib'ent the end of the'tub 66", bu't' which p'e'hmte the centering plug to be retracted. By placing the point of the eentering plug- 15' (in-the center fioi'nt of the hole to be drilled,-the drill -can aocu-ralt'el-y set'in p'o's tioh and' the spindlelowered so asto start the initial drilling of" the hole by the action of" the cutting edge 10 of the" drill bit. Fordrilli holes in articles which are 1 relatively th'in, h not necessary 'to' -withdralui the centering plug from the tube 66;- Howeter; I it isone tithe" ad vantages of thisinvention "that thefeentetirig -plug ca-n' be bodily reinoved from the cylindrical tube BIS-"after" the drilling ofirat-ion hasb'erf initiated, After the drilling opemtien has been initiated and after the centering" plug and backing-*- spring have been removed from the'cylindrieal tube 5 5, the drilling operation can be continued to -'afiord= a hole of any desireddepth.

In the embodiment of-this'i'nvention shown in- Figs. 1 t0 6,'the drill bitwhich is illustrated appropriate for drilling a "hole of moderate size; For drilling larger hole'scup to several inches -in diameter, a similar type of dril-l'bit may beem: played and a large size drill bit-is-shown by wayof illustration in Figs; '7 and 8; In this embody merit; of my invention; a cylindrical tube ll is employedwhichis of-relativelylarge diameter and which-because oi. its relativelyla-rge 'dia m eter, containsa.- greater number of slotslflthan thenumber of slots-used in the embodiment of my invention shownin the preceding figures. h In order toprevent distortionof the portions of the tube 11 between the s1ots 18, a clamping egr retnge ment is employed which'is similar to thatshowln in the preceding figures. Thus, in Figs. 7 and 8 there is an inner member 19 in the form-of a e-whi h; fit n. e d b wi ed. t t e inner; surface of'thecylindrical tube 11. There is also T4 nelblesone to producefa coneeeom: diameters; 'j nF Ii ri s m i j ab i b ie f f 'yii dr e tubes'or Bridal tube Ti isj Sets of wishe he e 1,. e i f we? am: rn ve e T21? 1 b n he? "ted rerun-11 mi Figs. 2 low nietalj tu e f jeee m Hi wit i i 1, pert 'mg a? wwit t e in at int-eh v i P by an eonventidnar drilling;- m teh iie r ches" t t e plug member 941,

collar 93 is in non-overlying relation with the plug 'memberis l, the position of the members Hand 96 can be adjusted relatively to the tube 84 so as to be at 'a'ny'predetermined desired distance from the cutting edge'84a of the tube. By moving the collar 96 so asto overlie the plug member 94, the portions of the tube 84 between the slots 93 are clamped'firmly in position as described more in detail hereinabove.

In Fig. 10, the drill'bit isshown in its relation to a work piece 9? which may, for example, be a sheet of glass. The cutting edge of the drill bit has penetratedthrough the work piece to produce the hole 98. The'drill'bit, including the cross bar 95, is shown in the position which it occupies as a'result of continuing to rotate the drill bit while'the' crossbar 95 is in pressure contact with the work piece 91. Such continued rotation causes the crossbar 95 to produce the recess H9 in the upper'surface of the work piece,

' this recessbein'g concentric with the hole 98.

The diameter of the recess 99' may be varied by varying the position of the cross bar 95 relatively to the tube 84. In Figs. 9 and 10, the cross bar 95 protrudes slightly further to the left-hand side than .to the right-hand side of the tube 94 so that the recess 99 is somewhat larger in diameter; than'if the cross bar protruded an equal distance from each side of the tube 84. By fitting the cross bar'95 in frictional engagement with the groove in the plug member 94, the position of the bar 95 can be adjusted as by tapping it lightlywith' a hammer. Of course, the cross bar 95 may,.if desired, be rigidly secured to the plug member 94.

In Fig. 12, the parts of the drill bit shown are the same as those shown in Figs. 9 to 11, and are indicatedby like reference characters, except that in the Fig.v 12 "the cross bar that is employed is the cross bar H30 which presents 'rearwardly inclined surfaces llll on each side of the tube 84. A cross bar'such as the cross bar lilll shown in Fig. '12 may be'employed when it is desired to produce in thework piece I02 a recess having an inclined side wall surrounding the hole cut in the work piece by the cutting edge of the drill bit.

In Fig. 12; a modified type of centering plug is shown which may be used with a clamping arrangement of the'type'shown in Figs. 9 to 12. i

As shown in Fig. '12,'the centering plug I03 fits in the end of the tube 84 and is provided with a conical backing spring I04. The centering plug may be used in the manner that has been described hereinabove in connection with the embodiment of this invention shown in Figs. 2 and 3. After the centering'plug has been used to properly locate the hole to be drilled, the centering plug, together with the backing spring, can be removed bodily as soon as the outline of the hole has been formed in the work piece by the cutting edge of the drill bit.

In the embodiments of this invention shown in Figs. 9 to 12, the cross bar 95 shown in Figs. 9 to 11 and the cross bar I shown in Fig. 12 may, of course, be dispensed with if it is desired to do so.

The operation of the drilling machine oi this invention is believed to be apparent from the foregoing description. A workpiece I may be placed on a suitable support on the table 20. The lateral position of the carriage is first adjusted so as to hem proper relation to the work piece and the carriage is then secured in place by tightening the nuts 28 on the bolts 26.

The motor is then started and by adjustment of the wing nut 53 on the bar 4! the spindle and the drill bit in axial alignment therewith are brought down so as to just contact the surface of the work piece. If desired, the centering plug may be employed to assist in properly positioning the drill bit. Ihe wing nut 53 is then further adjusted so that the cross bar will be in approximately a horizontal position, for when the cross bar is in this position an appropriate amount of resilient force is applied to the spindle as it rotates to urge it in the direction of the cutting edge of the drill bit. A suitable abrasive material is placed about the end of the drill bit so that it will be carried by the outwardly directed slots in the cutting edge. Any abrasive material may be used such as Carborundum powder in turpentine as a carrier. For some materials it is not necessary to employ an abrasive, although it is usually desirable to at least employ water so as to cool the end of the drill. In the case of a material such as glass, it is usually necessary to use an abrasive powder. All that is necessary to drill the hole is to start the motor and the machine automatically drills the hole 1 to the desired depth into or through the work drill bit piece. After the hole has been drilled, the operation of the motor is continued, and by .depressing the end 62 of the lever 58, the drill bit is retracted from the hole. If the centering plug has been used to initially locate the drill bit in reference to the work piece, the spindleand can be retracted by use of the lever 58 after the outline of the hole to be drilled has been formed in the surface of the work piece, thereby permitting removal of the centering plug. The spindle and drill bit thereafter may be lowered to afiord pressure contact with the Work piece and the drilling operation may be completed.

If it is desired to produce a recess in the work piece surrounding the hole that is drilled, the drill is provided with a cross bar or other suitable cross member means of the type described above and the rotation of the drill bit is continued while the cross member means is in contact with the work piece and until a recess of the desired depth is produced. A suitable abrasive can be used to assist the action of the cross member means in producing the recess. The surface of the cross member means is, of course, worn away to some extent in forming a recess, but when the cross member means is worn it is a relatively simple matter to replace it with the new one.

While the drilling machine shown in Figs. 1 to 6 comprises a drill bit in the form of a cylindrical tube having elongated slots combined with adjustable clamping means, it is not essential that the drilling machine be used with the particular type of drill bit which has been described in detail hereinabove. Thus, a hollow cylindrical tube with shallow outwardly directed notches in the cutting edge may be used, and in such case it is not necessary to employ the adjustable clamping arrangement. However, by employing the elongated slots in the cylindrical metal tube in combination with the adjustable clamping arrangement, a very inexpensive drill bit is afforded which is capable of prolonged periods of usage and which at the same time is free from objection because of distortion of the metal of the tube. 7

While this invention has been described in connection with certain specific embodiments shown ac om any n qq ithat hiahasbee o emerem-fbrthepua n s of llust a n a. y i al preferredaembodie 1. 1 1 of; nven ion; and; that, the scope; of: my inventionisto:be;gqverned solelyrby, the langua e. ofthe following claims. 1

I claim: 1

1A hollow r IL it. omnrisin za ylindrical me b one nd f:- Wh-icnisthe cutting: ed e; which is provided witha: plurality; of: slotsathat are open ended at the cutting: edge. of the; tube an a are of antial. lengthlongitud-inalia f h q Whi h h form; of," a. cone. tinuous, cylinder adjacent the endof said tube opposite to the cutting edge, and a clamping arrangment which is slidablelongitudinally of said tube in the region of said, slots and in spaced relation to said" portion of said tube that'is in the form of a continuous cylinder for positional adjustment adjacent the. cutting edge of the tube upon said edge wearing awayand whichcom;-. prises an inner member in slidable. contactwith the inner surface of the slotted. portion oi} said tube; and an outer member in slidable contact with. the exterior surface of the;slotted portion of saiditube said inner and outer memberswhen disposed with said outer member substantially overlying said inner member being adapted to clamp the portions of said tube between said slots firmly in place between said members and adjacent the cutting edge of said tube.

2. A hollow drill bit according to claim 1 wherein said inner and outer members of said clamping arrangement are each slidable longitudinally of the slotted portion of said tube independently of the other.

3. A hollow drill bit according to claim 1 wherein said inner and outer members of said clamping arrangement are each slidable longitudinally of the slotted portion of said tube independently of the other and wherein said inner member is provided with a member which extends through at least one of said slots to the exterior of said tube for effecting manual adjustment of said inner member longitudinally of said tube.

4. A hollow drill bit comprising a cylindrical metal tube one end of which is the cutting edge and which is provided with a plurality of slots that are open ended at the cutting edge of the tube and that are of substantial length longitudinally of the tube, aclamping arrangement which is slidable longitudinally of the tube in the region of said slots for positional adjustment adjacent the cutting edge of said tube upon said edge wearing away and which comprises an inner member in slidable contact with the inner surface of said tube and an outer member in slidable contact with the exterior surface of said tube, said inner and outer members when disposed with said outer member substantially overlying said inner member being adapted to clamp the portion of said tube between said slots firmly in place between said members and adjacent the amine cutting edge of said tube, and cross member 5 means substantially spaced from said, cutting edge of said tube and restrained from rearward movement by said clamping arrangement, said cross member means extending through slots comprised in said plurality of slots in said tube and projecting substantially beyond the outer surface of said tube for producing a concentric recess surrounding a hole drilled by the cutting edge of said tube.

5. A hollow drill bit according to claim 4 414 wherein, said? cross; member means: is; carried: by and is adjustable, as;to its1position longitudinally of. said tubev with onset said: members of said clamping means. V

6..A. hollow drill, bit. according tov claim, 45 wherein said cross. member means consists of a bar; Whichiextends; diametrically across, said tube in frictional engagement; with. a recess in. oneofsaid members ofsaid clamping arrangement" and is adjustable lengthwise thereof. relatively to; saidmember.

1 7;. A hollow drill bit according to claim. 4- wherein; said cross member means is rigidly se cured to the, inner member of said clampingar-v anse ent.

8. A hollow drill bit according to claim 4 wherein said crossmember means presents surfaces pnotruding; from; opposite sides of said tube and inclined; rearwardly from the cutting edgefor pnoducingga; recess haying an inclined side g a, hole drilled by the cutting:-

edgerof sai i 9; hollow drill bit. comprising a cylindrical: metalrtube: which is. provided with an outwardly directed slot in the; cutting-edge thereofand which carries cross; member means! intermediate the length theleof: protrudingfrom the exteriorsurface of said tube and adapted to produce a concentric recess surrounding a hole drilled by the cutting edge of said tube.

10. A hollow drill bit comprising a cylindrical metal tube, one end of which is the cutting edge and which is provided with a plurality of slots that are open-ended at the cutting edge of the tube and that are of substantial length longitudinally of the tube, a support which carries the end of said tube opposite said cutting edge with said tube in firmly aligned relation thereto for rotation of said tube therewith about the longitudinal axis of said tube, the portion of said tube comprising said slots extending beyond said support, and a clamping arrangement which is carried by said tube for rotation therewith which is slidable longitudinally of said tube between and relative to said support and said cutting edge in the region of said tube that comprises said slots for positional adjustment adjacent the cutting edge of the tube upon said edge wearing away and which comprises an inner member in slid able contact with the inner surface of the portions of said tube between said slots and an outer member in slidable contact with the exterior surface of the portions of said tube between said slots, said inner and outer members when disposed with said outer member overlying said inner member being adapted to clamp the portions of said tube between said slots firmly in place between said members and adjacent the cutting edge of said tube.

11. A hollow drill bit according to claim 10 wherein the inner member of said clamping arrangement presents a peripherally cylindrical surface in slidable contact with the inner surface of the portion of said tube comprising said slots and the outer member of said clamping ar rangement presents an internally cylindrical surface in slidable contact with the outer surface of the portion of said tube comprising said slots, each of said members being slidable longitudinally of the tube independently of the other for relative movement into and out of said overlying position.

12. A hollow drill bit comprising a cylindrical metal tube, one end of which is the cutting edge and which has at least one slot therein that is open-ended at the cutting edge of the tube and that is of substantial length longitudinally of the tube, a support which carries the end of said tube opposite the cutting edge with said tube in firmly aligned relation thereto for rotation of said tube therewith about the longitudinal axis of said tube, the portion of said tube comprising said slot extending beyond said support, and a clamping arrangement which iscarried by said tube for rotation therewith which is positionally adjustable longitudinally of said tube between and relative to said support and said cutting edge in the region of said slot and which comprises members adapted to clamp the inner and outer surfaces of said tube in the region of said slot firmly therebetween.

13. A hollow drill bit comprising a cylindrical metal tube one end of which is the cutting edge and which is provided with at least one slot that is open-ended at the cutting edge of the tube and that is of substantial length longitudinally of the tube, and a clamping arrangement which is slidable longitudinally of said tube intermediate between the ends thereof in the region of said slot for positional adjustment adjacent the cutting edge of the tube upon said edge wearing away and which comprises an inner member in slidable contact with the inner surface of the slotted portion of the tube and an outer member in slidable contact with the exterior surface of the slotted portion of said'tube, said inner and outer members each being in substantially spaced relation to the opposite ends of said tube and carried by the portion of the tube between said members and the end of said tube opposite to the cutting edge and said inner and outer members when disposed with said outer member substantially overlying said inner member being adapted to clamp the slotted portion of the tube adjacent the Hitting edge in firmly'maintained position. JULIO GONZALEZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS