US2271717A

US2271717A - Countersinking and blind drilling machine

Info

Publication number: US2271717A
Application number: US350221A
Authority: US
Inventors: Arthur A Schwartz
Original assignee: Bell Aircraft Corp
Current assignee: Bell Aircraft Corp
Priority date: 1940-08-03
Filing date: 1940-08-03
Publication date: 1942-02-03
Anticipated expiration: 1959-02-03

Description

Feb, 3, 142, A. A. SCHWARTZ 3 COUNTERSINKING AND BLIND DRILLING MACHINE Filed Aug. 5, 1940 4 Sheets-Sheet l INVE TOR 3 mm. chwm;

Feb. 3, 1942. A. A. SCHWARTZ COUNTERSINKING AND BLIND DRILLING MACHINE Filed Aug. 3, 1940 4 Sheets-Sheet 2 Li I v' ATTO NEYS Feb. 3, 1942.. A. A. SCHWARTZ GOUNTERSINKING AND BLIND DRILLING MACHINE Filed Aug. 3, 1940 4 Sheets-Sheet 3 MLQ i 1%} E TN Zia i ATTO NEYS 1942- A. A. SCHWARTZ COUNTERSINKING AND BLIND DRILLING MACHINE Filed Aug. 3, 1940 4 Sheets-Sheet 4 m 102 m6 100 M99.

?atented Feb. 3, 1942 a own use iilli BLIND DRILLING Arthur A. Schwartz, Buflalo, N. Y. assignor to hell Aircraft Corporation, Buflalo, N. Y. 7

Application August 3, 1940, Serial No. 350,221

l illaima.

This invention relates to countersinking and blind drilling machines, and has for one of its objects the provision of a machine of simplified and improved construction that is particularly adaptable to semi-automatic production methods wherein the work pieces are to be drilled at mohtiple points accurately to prescribed depths. Another object of the invention is to provide in a machine of the character described improved means for automatically regulating the depth of the drilling into the work piece from the starting surface thereof. Another object of the invention is to provide, through automatically operating means, an improved cleaning of the drilled opening as a final step of the drilling operation, so that the work piece is accurately drilled to a smooth clean bore at all surfaces thereof. Another object of the invention is to provide in a machine of the character described an improved form of work piece locating device, wherei by the operator is enabled to process work pieces requiring multiple drilling operations in accord with a simplified technique and with minimum time losses therebetween. Another object of the invention is to provide in a machine of the character described improved control means whereby an improved form of semi-automatic operation is obtained. Other objects and advantages of the invention will appear in the specification.

In the drawings:

Fig. l is a side elevation of a machine of the invention;

Fig. 2 is a front elevation of the machine of Fig. 1;

Fig. 3 is a fragmentary view, partly in section and partly in elevation, on an enlarged scale, of a detail of the work holding and drilling head portion of the machine;

Fig. 4 is a section taken substantially along line IV-IV of Fig. 1, on an enlarged scale;

Fig. 5 is a section taken along line V-V of Fig. i, on an enlarged scale;

Fig. 6 is a section taken along line Vi -VI of Fig. 4, on an enlarged scale;

Fig. 7 is a section taken along line VH-VII of Fig. 4, on an enlarged scale;

Fig. 8 is a plan of the work piece supporting base of the machine;

Fig. 9 is a, fragmentary section taken along line IX-IX of Fig. 8; and,

Fig. 10 is a wiring diagram of the control mechanism of the machine.

The machine is particularly adaptable to drilling accurately to prescribed depths from the starting surface of the work piece, such as in connection with the counterslnklng of previously drilled relatively thin sheet metal stock preparatory to flush riveting the latter upon supporting structure. For example, in connection with the manufacture of airplanes of optimum aerodynamic characteristics, the finished outer surfaces thereof must be perfectly smooth and flush, and allowable tolerances for rivet head projections and/or depressions relative to the surface contour are often within one or two thousandths of an inch. Consequently, the form of the countersinks for receiving the rivet heads must accurately conform to that of the rivet heads, and the depths of the countersinks must be most accurate as measured inwardly from the starting surface of the work piece.

As illustrated in the drawings, the machine is mounted upon a base or pedestal it which supports a U-frame it. The lower jaw it of the frame it mounts a work piece supporting base designated generally by the numeral l6, and the upper jaw it of the frame i2 carries the drilling spindle 28 by means of bearings at 22, 23 and fit.

A drive pulley 23 is operatively associated with the upper end of the spindle 20 by means of a. keyed sleeve 3t supported by the bearing 22 and mounted in splined relation upon the spindle for rotation of the spindle through operative connection with a motor 30 through an endless belt 32. Thus the pulley 28 is permanently aligned with the motor pulley and belt 32. A thrust collar 36 is keyed to the spindle 20 to rotate therewith, and is substantially enclosed by a yoke member so having thrust bearings til above and below the collar 36. The yoke 38 is pivotally connected by opposite side pins 39 and through means of a pair of links d2 to a pair of corresponding rocker arms M by means of pivotal connections to; the rocker arms it being pivotally mounted intermediately of their ends upon the machine frame at M. Straps it are welded at their opposite ends to adjacent portions of the links M and are so arranged as to span the pivotal connections to with the rocker arms it so as to provide equalized loading at opposite sides of the rocker arm pivotal connections.

The links it extend downwardly beyond the points of pivotal connection 45 to carry at their lower ends a collar 50 bored concentrically of the spindle 20 and clampingly mounted upon a tube 52 disposed therebetween by means of a clamping stud 53 (Fig. '7). The links 42 are pivotally connected to the collar Ell through means of studs 5t which extend through openings in the links elongated as at 55 to provide lost-motion connections. The tube 52 is slidably fitted into the bearing 23 adjacent its upper end;

and a thrust sleeve 51 is slidably mounted upon the tube 52 and threaded into connection with a gland 58 which bears downwardly upon the upper end of a compression spring 60. The lower end of the spring 60 bears against the collar 50, and thus the tube 52 is normally urged downwardly by the spring 50 which simultaneously imposes downward pressure through the links 42 upon the spindle 20. A bushing BI supports the spindle 20 relative to the upper end of the tube 52. The tube 52 is rotatably carried at its lower end by the bearing 24, and a bushing 62 is disposed between the spindle 20 and the tube 52 adjacent the lower ends thereof to transmit the bearing support of the member 24 to the lower end of the spindle 20. The tube 52 is provided at its lower end with a shoe 64 as an integral part thereof; said shoe being in the form of an open end pedestal provided at opposite sides thereof with inspection openings 66 and a lower work piece contacting face 68. The lower end of the spindle 20 is in the form of a chuck and adapted to have mounted therein the drill or countersinking bit in such manner as to have its working end portion normally disposed slightly above the level of the work piece contacting face 68 of the pedestal.

A pair of tie rods 12 are pivotally connected at their lower ends to corresponding studs 54 and extend upwardly therefrom through spring boxes 14 which are fixed to the links 42 and contain preloaded compression springs I6. Abutments 18 are adjustably mounted upon the upper ends of the tie rods I2 by means of threaded nuts 80 to bear against the upper ends of the springs I6. Thus, the springs I6 function to resiliently urge the spindle to move downwardly relative to the pedestal tube 52.

A fiuid cylinder 80 is mounted upon the frame of the machine rearwardly of the spindle device thereof and is operatively associated with a piston rod 82 which couples at its lower end with the rocker arms 44 at 84. A solenoid operated valve 86 is provided in conjunction with the cylinder 80 for control of movement of fiuid under pressure into and out of the cylinder 80 in such manner that admission of fluid into the cylinder forces the piston rod 82 downwardly to pivot the rocker arms 44 and to cause the spindle 20 and the pedestal tube 52 to be raised bodily against the action of the springs 60 and I6 away from the work piece. A compression spring 88 is arranged about the piston rod 82 in such manner as to bear at its upper end against an abutment 90 on the rod 82 and at its lower end against a fixed abutment 92 extending adjacent the piston rod 82 so as to resiliently urge the piston rod upwardly at all times. thus assisting in the return of the piston rod 82 to its upper position when fluid pressure within the cylinder 80 is released.

The yoke 38 is provided at its lower face with an insulated contact plate 94, and the upper end of the tube 52 is provided with an oppositely disposed similar contact plate 95. The plate 96 is mounted upon the tube 52 through means of a platform 91 which is adjustably mounted upon the tube 52 by means of a screwthreaded comiection therewith and a clamping nut 98. The contact plates 94 and 9B are electrically connected to corresponding conductors indicated generally at 99 which lead to the control circuit for the solenoid valve 88 which will be described hereinafter.

A work support plate I00 is mounted upon the Jaw IQ of the machine framei'or bearing against the under side of the work piece; the plate I00 being vertically bored to carry a slide fitting pilot pin ifi2 as illustrated in Figs. 3 and 9. The pilot pin I02 is normally maintained with its outer end projecting beyond the face of the plate I00 by means of a spring I04 which permits the pin I02 to retreat under pressure, as when being pressed against by the drill bit l0. The pin I02 is located in line with the vertical movement of the bit I0, and the plate I00 is counterbored concentrically of the pin I02 and mounts therein a hardened steel countersunk die I06 to complement the end of the bit II in case the latter is accidentally moved into contact with the work supporting portion of the machine. a

A pair of control fingers I I0 are arranged to project upwardly beyond the plane of the work piece supporting plate I00 and at opposite sides of the pilot pin I02, and are adapted to be depressed by the weight of the work piece when disposed in operative position thereupon. The fingers IIO are mounted upon the jaw I6 by means of parallel links H2 and H4 which are pivoted thereto at IIS and H8 respectively, and the opposite ends of the links H4 are connected to switch operating finger I20 by means of a cross arm I22 and a rod I24.

The switch operating finger I20 is pivotally mounted upon the frame at I26 and is adapted to actuate the operating lever I28 of a micrometer type electrical switch I30 arranged adjacent thereto. Leaf springs I32 are mounted in cantk lever fashion at I33 and I34 upon the frame'and bear at their outer ends against the links H4 in such manner as to resiliently urge the control pins IIO upwardly, but to permit the latter to be depressed by the weight of the work piece when resting thereupon so as to elevate the rod I24 and to cause the operating finger I20 to pivot and momentarily depress the lever I28 of the micrometer switch. Particular attention is called to the fact that by reason of the spaced arrangement of the opposite pairs of parallel links connecting respective control fingers III] and the swivable character of the connections at I23, the cross arm I22 transmits a differential movement to the switch control actuating rod I24, in accord with the degrees of the separate movements of the pins IIO. Consequently, if both of the pins lIil are depressed by the work piece substantially equally and for a sufiicient distance, the necessary switch control movement will be transmitted to the operating finger I20. However, for example; when only one of the control pins III) is substantially depressed, as when the work piece is disposed upon the machine at an angle relative to the normal operative position thereof prior to final adjustment of the work piece into a position of readiness for the drilling operation, the differential action of the linkage connecting the opposite fingers I I0 to the switch operating finger I30 will prevent the latter from being moved sufficiently to actuate the micrometer switch. Consequently, the arrangement provides an important safety feature.

A spot light I40 (Fig. 1) is mounted upon the machine frame and provided with a condensing reflector I40 for projection of a relatively brilliant spot of light upon the upper surface of the work piece at the point of first contact with the bit I0. Thus, the work piece may be first disposed between the jaws of the machine and then moved laterally in the required direction to bring the portion thereof to be drilled into line with the bit 70 by simply moving the work piece until the point thereon to be contacted by the bit is directly under the spot of light projected by the light source I40. In connection with the countersinking of previously drilled holes, the Work piece will be initially disposed between the jaws of the machine in a substantially horizontal attitude, and then simply moved in the direction required to bring the previously drilled hole under the spot of projected light at which time the pilot finger I02 will project upwardly under the action of the spring I04 into the drilled hole, thus fixing the work piece in alignment with the countersinking bit I0. During the countersinking operation the pilot finger I02 will retreat under the pressure of the bit I0, as explained here: inabove, thus avoiding damage to the pilot finger. An adjustment screw I45 is provided in connection with the pilot finger actuating spring I04, for varying the pressure applied by the spring to suit different operating conditions.

The machine is semi-automatically controlled in its operation by means of an electrical system diagrammatically illustrated in Fig. wherein the power inlet conductors are designated at I50. The motor 30 is connected in series with the conductors I50, and the circuit thereto is controlled by one blade of a double blade snap switch I52. The solenoid valve 86 is also connected in series with the conductors I50, and the circuit thereto is primarily controlled by the other blade of the snap switch I52. The circuit to the solenoid valve 86 includes a time-delay relay I56 and a magnetic contact switch I58 which in turn is actuated in response to actuation of the micrometer switch I30 and the contact plates 94--96. In operation, the switch I52 is manually closed, and thus the circuit to the motor 30 is completed and the circuit through the solenoid of the fluid valve 66 is closed. This opens the compressed air control valve 86 and compressed air is allowed into the cylinder 80 to force the piston rod 82 downwardly, thus lifting the spindle 20 and work holding shoe 64 to the position illustrated in Figs. 1, 2 and 3. The work piece is then placed between the jaws of the machine by the operator and shifted to the position required to align the bit 10 with the center of the countersink to be drilled, as explained hereinabove. The work piece is then allowed to rest its full weight upon the control fingers H0, and the latter then actuate the micrometer switch I30 as explained hereinabove to momentarily actuate the magnetic contactor I58. This closes the circuit to the time-delay relay I56 which instantaneously opens the circuit of the solenoid of the'valve 86, thus discontinuing the pressure within the pneumatic cylinder 80 and allowing the springs 60 and I6 to force the work holding shoe 64 and the spindle 20 downwardly into operative contact with the work piece which is now firmly sup-ported by the bearing block I00. As explained hereinabove, this spring action involves two separate phases; that is, the spring 60 forces the shoe 64 against the work piece with a. predetermined pressure, and the spring I6 subsequently moves the bit 10 downwardly relative to the shoe 64 as the process of drilling the countersink proceeds. The

contact plates

94 and 96 are so relatively arranged as to provide normally therebetween a gap of such dimension as to allow the spindle 20 to move relative to the shoe 64 a distance equal to the desired depth of the countersink to be drilled in the work piece before the

members

94 and 96 come into bearing contact with one another. Thus, the

contact members

94 and 96 function as positive stop devices for limiting the movement of the drill spindle relative to the work holding shoe, and in every case the depth of the countersink so produced will be identical with the depth of the rivet head to be received therein, as measured from the outer surface of the work piece. Thus, inequalities in the thickness of the work piece will have no effect upon the depth of countersinks drilled by the machine, as would otherwise be the case if the depth of the countersinks were regulated by a device employing the work supporting surface as a datum.

Simultaneously with the contacting of the

members

94 and 96 at the end of the downward movement of the drill spindle, the circuit associated therewith and leading to the magnetic contactor I 58 will be thereby closed and the timedelay switch of the device I56 will be closed, initiating a predetermined timing cycle during which the circuit of the solenoid of the valve 86 will be undisturbed, but at the end of which said circuit will be again closed. Consequently, during the predetermined time-delay cycle the bit 10 will continue to rotate at the bottom of the countersink previously drilled so as to clean out and polish the surfaces thereof in an improved manner, but without further deepening of the countersink. At the end of the time cycle the cylinder 80 will cause the spindle and work holding shoe to be elevated against the action of the

springs

60 and 16 as explained hereinabove to the position illustrated in Figs. 1 to 3, thus enabling the operator to shift the work piece to the next position of drilling operation, whereupon the cycle of operation will be repeated in the manner described.

Thus, the machine embodies a work holding element adapted to efliciently clamp the work piece in operative position prior to and during the drilling operation, and simultaneously the work piece holding element functions as an accurategauging device which controls the depth of the drilling operation as measured from the surface of the work piece at which the drilling operation is commenced. Also, the work piece supporting element of the machine functions simultaneously to operate as a contact device for initiating the drilling cycle of the operation thereof, and in conjunction with the time-delay relay allows the cutting bit to perform a second improved finishing operation upon the previous-- ly drilled surfaces before release of the work line with the countersinks drilled by the bit 10.

Thus, it will be understood that upon closing of the valve 86 in conjunction with withdrawal of the drill spindle and holding shoe from the work piece, the air ejected by the cylinder will be simultaneously sprayed into the drilled openings to effectively clear the latter of anyshavings or dust, or the like.

It will be understood that in lieu of the arrangement of the

contact plates

94 and 96 as previously described wherein the contact plates the mach'me provides optLmim function simultaneously as positive stop means and'as electrical circuit closing means, any suitable form of separate electrical switch may be employed in conjunction with the relative movement of the spindle and the tube 52 so as to initiate the time delay cycle hereinabove described at the time of first contact of the plates 9| and 96, or slightly in advance thereof or slightly in lagging relation therebehind, as may be preferred in any given case.

Thus, the machine features a semi-automatic control system whereby it is impossible for the operator to start the drilling cycle of the machine operation unless the work piece is first disposed in proper position relative to the drill spindle. Also, the machine features a spindle feed device which is actuated by constant spring pressure, independent of the pressure in the fluid power system supplying power to the spindle 80 which is often subject to fluctuations. Hence, the drilling operation is of improved form, and performance both. from the standpoint of the quality of the openings drilled and the speed of the operation of the machine.

Although only one form of the invention has been shown and described in detail, it will be understood that various changes may be made therein without departing from the spirit of the invention or the scope of the following claims.

I claim:

1. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, means for moving said spindle axially toward and away from the work piece to be drilled, a work piece contacting shoe operatively associated with said spindle to move axially therewith into work piece contacting position, resilient means connecting said spindle and said shoe for resiliently urging said spindle to move axially relative to said shoe and to thereby move said cutter therebeyond into work piece drilling position, and positive stop means associated with said spindle and said shoe for limiting said relative movement therebetween within predetermined 2. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled,

a work piece contacting shoe operatively asso-" ciated with said spindle to move axially therewith into work piece contacting position, resilient means connectingv said spindle and said shoe for resiliently urging said spindle to move axially relative tosaid shoe and to thereby move said cutter therebyond into work piece drilling position, and positive stop means associated with said spindle and saidshoe for limiting said relative movement therebetween within predetermined limits.

3. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled, a work piece contacting shoe operatively associated with said spindle to move axially therewith into work piece contacting position, resilient means connecting said spindle and said shoe for resiliently urging said spindle to move axially relative to said shoe and to thereby move said cutter therebeyond into work piece drilling position, positive stop means associated with said spindle and said shoe for limiting said relative movement therebetween within predetermined limits, and means for simultaneously withdrawing said spindle and said shoe to remove said cutter and said shoe from work piece contacting position upon completion of the drilling operation.

4. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled, a workpiece contacting shoe operatively associated with said spindle to move axially therewith into work piece contacting position, resilient means connecting said spindle and said shoe for resiliently urging said spindle to move axially relative to said shoe and to thereby m ove said cutter therebeyond into work piece drilling position, positive stop means associated with said spindle and said shoe for limiting said relative movement therebetween within predetermined limits, and hydraulic means for simultaneously withdrawing said spindle and said shoe to remove said cutter'and said shoe from work piece contacting position upon completion of the drilling operation.

5. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled, a work piece contacting shoe operatively associated with said spindle to move axially therewith into work piece contacting position, resilient means connecting said spindle and said shoe for resiliently urging said spindle to move axially relative to said shoe and to thereby move said cutter therebeyond into work piece drilling position, positive stop means associated with said spindle andsaid shoe for limiting aid relative movement therebetween within predetermined limits, means for simultaneously withdrawing said spindle and said shoe to remove said cutter and said shoe from work piece contacting position upon completion of the drilling operation, and means initiated into action upon operation of said stop means to actuate said spindle and shoe withdrawal means.

6. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled, a work piece contacting shoe operatively associated with said spindle to'move axially therewith into work piece contacting position, resilient mean connecting said spindle and said shoe for resiliently urging said spindle to move axially relative to said shoe andto thereby move said cutter therebeyond into work piece drilling position, positive stop means associated with said spindle and said shoe for limiting said relative movement therebetween within predetermined limits, mean: for simultaneously withdrawing said spindle and said shoe to remove said cutter and said shoe from work piece contacting position upon completion of the drilling operation, and means initiated into action upon operation of said stop means to actuate said spindle and shoe withdrawal means subsequent to lapse of a predetermined time delay.

7. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled, a work urging said spindle to move axially relative to said shoe and to thereby move said cutter therebeyond into work piece drilling position, positive stop means associated with said spindle and said shoe for limiting said relative movement therebetween within predetermined limits, means for simultaneously withdrawing said spindle and said shoe to remove said cutter and said shoe from work piece contacting position upon completion of the drilling operation, and means initiated into action upon operation of said stop means to actuate a time delay device adapted to control said spindle-shoe withdrawal means in such manner as to withdraw the latter from work piece contacting position subsequent to a predetermined time delay.

8. In a drilling machine, a drilling spindle carrying a work piece cutter, means for driving said spindle, spring means for moving said spindle axially toward the work piece to be drilled, a'work piece contacting shoe operatively associated with said spindle to move axially therewith into work piece contacting position, resilient means connecting said spindle and said shoe for resiliently urging said spindle to move axially relative to said shoeand to thereby move said cutter therebeyond into work piece drilling position, positive stop means associated with said spindle and said shoe for limiting relative movement therebetween within predetermined limits, hydraulic means for simultaneously withdrawing said spindle and said shoe to remove said cutter and said shoe from work piece contacting positionupon completion of the drilling operation, and conduit means leading from said hydraulic means and adapted to convey the fluid ejected therefrom and to discharge the latter against the work piece in the region of the drilling operation.

9. In a countersink drilling machine, a frame, a drilling spindle rotatably mounted upon said frame and adapted to move axially thereon, means for rotating said spindle, a tubular member slidably mounted upon said spindle and having an end portion adjacent the cutter end of said spindle for contacting the work piece to be countersunk, a thrust collar integral with said tubular member, a second thrust collar integral with said spindle, a link member extending between and connecting said thrust collars with a lost motion connection therebetween, a'rocker arm pivotally mounted upon said frame and having a moving end portion connectedto said link in tween and connecting said thrust collars with a lost'motion connection therebetween, a rocker arm pivotally mounted upon said frame and having a moving end portion connected to said link in such manner as to be adapted to move said spindle and said tubular member axially, spring means operatively connecting said spindle and said tubular member in such manner as to normally urge the cutter end of said spindle to extend beyond the work piece contacting end of said tubular member, spring means acting between said frame and said tubular member in such manner as to resiliently urge the latter to move toward the work piece, means associated with said rocker arm for actuation of the latter to withdraw said tubular member and said spindle from work piece contacting position against the action of said springs, and additional spring means operatively associated with said rocker arm in such manner as to substantially balance the weight of the actuating elements of the device about the pivotal mounting of said rocker arm upon said frame.

11. In a' countersink drilling machine, a countersink cutter mounted upon a spindle for countersinking an opening drilled through the work piece to be countersunk, a work piece supporting piece to be countersunk, a work piece supporting plate adapted to support said. work piece under said cutter, a pilot pin slidably mounted within said supporting plate and spring-pressed so as to be adapted to project upwardly beyond the plane of. said work piece supporting plate when free to do so and adapted to project itself into the drilled such manner as to be adapted-to move said spindle and said tubular member axially, spring means operatively connecting said spindle and said tubular member in such manner as to nor mally urge the cutter end of said spindle to extend beyond the work piece contacting end of said tubular member, spring means, acting between said frame and said tubular member in such manner as to resiliently urge the latter to move toward the work piece, and means associated with said rocker arm for actuation of the latter to withdraw said tubular member and said spindle from work piece contacting position against the action of said springs.

10. In a countersink drilling machine, a frame, a drilling spindle rotatably mounted upon said frame and adapted to move axially thereon, means for rotating said spindle, a tubular member slidably mounted upon said spindle and having an end portion adjacent the cutter end of said spindle for contacting the work piece to be countersunk, a thrust collar integral with said tubular member, a second thrust collar integral with said spindle, a link member extending beopening of said work piece when the latter is moved into proper position under said countersink cutter, and a pair of control fingers mounted within said supporting member adjacent said pilot pin and spring-pressed to normally extend above the plane of said supporting member and adapted to be moved inwardly thereof under the weight of the work piece when disposed thereon in operative position under said countersink cutter, said control fingers being operatively coupled by means of a transverse connecting link operatively associated intermediately of its connections with said control fingers with a control device for controlling said means for moving said spindle axially in accord with a composition of the separate movements of said control fingers.

13. Inv a blind drilling machine, a rotating spindle, constant pressure means operatively associated with said spindle to apply the latter against the work piece, positive stop means associated with said spindle and with the surface of said work piece in the region of the opening to be drilled therein, control means operatively associated with said stop means and fluid actuating means for causing said spindle to be retracted from contact with said work piece subsequent to lapse of a predetermined time delay, and a disappearing spring-loaded pilot pin adapted 'to project into a previously formed opening in said work piece to locate said work piece in proper position relative to said spindle.

14. In a blind drilling machine, a rotating spindle, constant pressure means operatively associated with said spindle to apply the latter against the work piece, positive stop means associated with said spindle and with the surface of said work piece in the region of the opening to be drilled therein, control means operatively associated with said stop means and fluid actuating means for causing said spindle to be retracted from contact with said-work piece subsequent to lapse of a predetermined time delay, a disappearing spring-loaded pilot pin adapted to project into a previously formed opening in said work piece to locate said work piece in proper position relative to said spindle, and a spot light device adapted to project a focused beam of light upon said work piece at a position thereon corresponding to a position of alignment of said retreating pin and said previously drilled opening.

15. In a blind drilling machine, a work piecemovements of said control pins to said machine control device. v ARTHUR A. SCHWARTZ.