Abstract: A drill press assembly having a base mountable to a work bench, a vertical column attached to the base and a drill head assembly having an electric motor and a quill. The drill head assembly is movably attached to the column. A rack is rotatably attached to the top of the column and is engaged by a crank and pinion mechanism attached to the frame of the drill head assembly which permits the drill head assembly to be displaced vertically and rotated about the column. A tilt table is attachable to the base of the drill press. A locking mechanism having a bolt passing through a longitudinal slot in the supporting base of the tilt table and a transverse slot in the base is engaged by an eccentrically mounted camshaft to lock the supporting base of the tilt table to the top surface of the drill press base. A pivoting frame is pivotably attached to the supporting base and contains a table plate. A fence is attachable to the top of the pivoting frame.

Abstract: A tapping device and method are provided for tapping tubing. The device comprises a tube portion which substantially encloses a tube, a spring portion which provides a clamping force to the tube portion, and a guide portion which guides and supports tube piercing instruments and taping fixtures. In normal operation, a section of tubing is inserted into the tube portion and the spring portion is pressed together to create a clamping force in the tube portion. Locking members are provided for maintaining the spring portion in a force producing position. Tube piercing instruments and tapping fixtures may then be inserted in the guide portion. The device ensures that the instruments and fixtures are inserted in the correct orientation and the device helps prevent leaks from occurring.

Abstract: In a machine tool having a base member, a table supported on the base member, on which a workpiece may be positioned to be machined, and a toolhead assembly supported on the base member, provided with a tool engageable with the workpiece positioned on the table for performing a work function relative thereto wherein the table and the toolhead assembly are displaceable relative to each other along a line of travel, an assembly for holding down a workpiece positioned on the table upon relative displacement of the table and the toolhead assembly along the line of travel generally consisting of at least one upper roller having an axis disposed transversely relative to the line of travel and engageable in rolling contact with an upper surface of a workpiece positioned on the table, a set of lower rollers each having an axis disposed transversely relative to the line of travel and engageable in rolling contact with an undersurface of the table and means supported on the base member and operatively interconnecting t

Abstract: A cradle for a hand-held tool for machining of cylinder head valve guide holes. The tooling has a pilot portion. A collar has a passage for the tooling and is shaped to engage a least worn portion of a valve seat associated with the valve guide hole around the circumference thereof without engaging more worn portions of the valve seat. The cradle comprises a bracket which has a passage for the tooling without passage of the collar so that the bracket can bear on the collar. Force is applied to the bracket to hold the collar in engagement with the valve seat.

Abstract: A PCB working machine includes a work table for holding a PCB substrate in place with a suction force; a spindle carrying a cutting tool; a controller for moving the spindle in accordance with a predetermined pattern; a collet chuck provided at a distal end of the spindle for clamping the cutting tool; a floating head encircling said collet chuck at a distant position and having an end plate in which a plurality of air blowing holes are provided; and an adjuster for adjusting the positional relationship between the floating head and the cutting tool.

Abstract: A small, portable, light-weight pneumatic spot weld drill comprises a drill housing assembly which includes a trigger assembly for providing a supply of pressurized gas. A piston assembly is positioned within the drill housing assembly and is axially translatable thereto. The piston assembly is actuated by the pressurized gas so as to provide cutting pressure for the drill bit. A motor assembly is contained within the drill housing assembly. The motor assembly has a rotatable output shaft for securing a drill bit and for providing rotary movement of that drill bit. A control valve is provided for receiving a supply of the pressurized gas and for controllably discharging the pressurized gas to the motor assembly. The control valve provides cutting pressure at a desired level and provides rotary motion of the drill bit.

Abstract: A line-piercing valve assembly comprising first and second clamp housings, adapted to releasably clamp onto a line or section of tubing, a piercing pin insertable within the internal bore of a projection formed on one of the clamp housing, and, a separate one-way valve which mounts within the projection after removal of the piercing pin and can itself be removed and replaced in the event of damage or malfunction.

Abstract: A combination pipe piercing fitting and valve including a housing formed of a weldable plastic and having a valve casing communicating with a branch nipple. In the valve casing a valve stem and a boring tool are disposed for axial movement so as first to pierce a pipe welded to the housing and to then selectively open or close the branch nipple from the pipe. A sleeve for guiding the boring tool is axially and rotationally secured in the valve casing and extends at least past the area where the branch nipple enters the valve casing. This guide sleeve has a valve seat at its bottom end and an opening adjacent the branch nipple. This combination fitting and valve assures high operating reliability without leakage both during piercing of the pipe and during operation as a valve.

Abstract: A pressure foot (7) of a printed circuit board drilling apparatus is supported on a spindle (2) of the printed circuit board drilling apparatus slidably in the axial direction, and includes a pressing face (13) which presses a printed circuit board (5) at the time of drilling operation, a discharge port (11) formed in a side wall (8) so as to discharge chips produced by drilling operation, the discharge port (11) being connected to a suction device, and a compressed air supply conduit (20A) formed in a side wall so as to eject the compressed air toward a drill bit (4) of the printed circuit board drilling apparatus. A cooling fluid supply device (21) is connected to the compressed air supply conduit (20A). In place of the compressed air supply conduit (20A), a fluid supply conduit (14) for ejecting a cooling fluid toward the drill bit (4) of the printed circuit board drilling apparatus may be formed.

Abstract: One aspect of the invention is a method of rapidly drilling holes in a workpiece on a drilling machine having first and second spindles holding first and second drill tools, a first and second pressure foot mounted on the first and second spindles and a work table mounted beneath the spindles on which workpieces can be mounted.

Abstract: The invention relates to a multi-spindle boring machine with machine table and suction arrangement in which the spindles are held on a carrier, which can be rotated by means of a vertical drive shaft, and in which an extractor fan can be connected to a suction duct, which ends in the area of the tool set in the working position and received by the spindle. With a central suction unit and individual exchangeable tool coverings, which can be connected with a covering distributor with connecting ducts to the central suction pipe, the invention provides for optimum suction, which can be adjusted to the different tools used.

Abstract: A hand held power dowel tool includes a high speed universal motor coupled to a relatively simple two-gear transmission. The motor speed gear reduction combination is specifically designed for 1/4 inch and 3/8 inch drilling of wood, making the tool unusually lightweight for the power it delivers. The tool's drive shaft is especially long and well supported to rigidly hold a conventional drill bit without a need for a drill guide bushing. A smooth acting guide assembly aligns the tool to the board and accurately guides the drill bit to a preset depth. The tool also includes an adjustable viewing window that is kept clear by a stream of air discharged by the tool's cooling system. The adjustable viewing window and an adjustable chuck accommodates wood of various width and thicknesses as well as various dowel peg diameters. The tool's range of wood joining capabilities surpasses today's plate joiners.

Abstract: A machine tool for processing platelike workpieces, particularly for machining the contours of superimposed sheet metal elements, comprises a work-supporting deck having a supporting surface and workpiece-fixing means, and a tool unit, which is mounted on a tool carriage and is movable over the supporting surface, wherein a holding-down device is provided, which is movable over the supporting surface in unison with the tool unit and comprises a holding-down shoe, which is adapted to be forced against the top surface of the workpiece to hold the workpiece in position close to the location at which the workpiece is being processed.

Abstract: The present invention relates to a printed circuit board presser device in a drilling machine. The board presser device is arranged such that it includes an axially movable upper-plate presser device which is provided on the outer side of a contact surface of the board presser device with a printed circuit board so that a top end surface of the upper-plate presser device extends to the side of a table beyond the contact surface; and an urging device for pushing the upper-plate presser device against the table by a force larger than an attraction force generated from the board presser device. With such construction, an upper plate is suppressed from floating during drilling the printed circuit board, and a distance of useless transfer movement of a drill decreased, to thereby improve an efficiency of a drilling operation.

Abstract: A machine tool is received in a structure that is carried along with the tool and has a sleeve extension which will be received in a tapered element with radially spreadibly tongues having end beads which will lodge behind a shoulder in teplate thereby positioning and clamping the tool; the receiver is additionally urged against the template and the tool by a piston cylinder drive.

Abstract: The invention relates to a method and equipment designed to drill countersunk holes on surfaces of unknown positions in which a presser fitted to the tool support is placed against the surface to be drilled, and can move axially in relation to the tool; the presser is used as a limit switch to control tool return.

Abstract: A plate working machine comprising a metal plate supporting table (1), a pair of rails (2, 3) extending along the sides of the table (1), a driven support means (4) for travel along the rails (2, 3), said support means comprising a spaced pair of support beams (5, 6) extending from one rail (2) to the other (3) and joined at either end by cross members (7, 8). A drilling assembly (9) is mounted on tracks (10, 11) mounted on the beams (5, 6) and a plasma profiling head (12) is carried by the drilling assembly (9) and extends over the beam (6) and downwardly towards a position adjacent the table (1).

Abstract: A drilling machine and method of operation for drilling through holes in a workpiece while minimizing penetration of the drill tool into a back-up material which supports the workpiece. Before placing the workpiece on the machine, the vertical position of the back-up material is mapped. After selection of the drill site, the mapped position of the backup material proximate the drill site is retrieved. Using this information, a computer controller determines an absolute vertical position for a lower limit of the drill stroke. This lower limit is independent of the top of the workpiece or the thickness of the workpiece, thus eliminating the need to determine either of those values. The drill stroke is terminated once the drill tool reaches the lower limit, which is a nominal depth below the mapped position of the back-up material, insuring that a hole is completely drilled through the workpiece, while minimizing penetration of the back-up material.

Abstract: A tool holder assembly, having a central tool holding shaft (1) provided, on the one hand, with a mounting cone for securement in a machine tool spindle and, on the other hand, on the side opposite the cone, with an intermediate cylindrical body provided at its forward portion with securement structure for a tool. It is provided also with a feeler device (2) centered on the central shaft (1) and guided in translation on this latter, with lubricating structure and with cleaning structure for the machining region at the location of application of the feeler device (2).

Abstract: A method of and apparatus for effecting a machining operation, e.g. drilling, on a multi-layered printed circuit board utilizing a machining apparatus having a spindle for driving a tool. The spindle is movable in the axial direction of the tool and a pressure foot for pressing the printed circuit board during the machining is mounted on the spindle for relative movement with respect thereto. The method includes the steps of determining the position of the end of a tool with respect to the end of a pressure foot in the state before the pressure foot contacts the printed circuit board, setting the amount of relative movement between the pressure foot and the tool necessary for effecting the desired machining, on the basis of the position of the end of the tool and a predetermined set value of the machining depth; and effecting the machining on the printed circuit board by controlling the feed of the tool in conformity with the amount of relative movement.

Abstract: A method and apparatus for drilling holes into the mantle of a cylinder in a paper machine while the cylinder is in its place of operation in a paper machine is disclosed. After each cycle of drilling, a multi-spindle drilling machine is transferred along guide rails supported against a cylinder adjacent to the cylinder to be machined. Prior to drilling, the drill equipment is tensioned between the mantle face of the cylinder to be machined and the mantle face of the adjacent cylinder.

Abstract: A pressure foot for a microwave drill detection system has a cavity in the base, a cover closing the opening into the cavity, with the cover and the base being designed to inhibit microwave radiation leakage, whereby a microwave beam directed toward a drill bit in the cavity is substantially confined within the cavity.

Abstract: A printed circuit board boring machine bores printed circuit boards stacked on a table, by a drill while pressing the printed circuit boards with a pressure foot. A piece having a hole through which the drill may pass is detachably mounted on a tip end portion of the pressure foot with a center of the hole being aligned with an axis of the drill. The piece may be attached to the pressure foot before the boring work so that the boards and the piece may be simultaneously bored by the drill while the hole in the piece may be used as a guide for the boring work of the boards.

Abstract: A method for drilling very small diameter holes (0.005 inches or smaller) in a printed circuit board is described, employing an entry overlay sheet. The entry overlay sheet is a thin layer of a homogenous polymer material, having a thickness of 0.005 to 0.010 inches, but at least 1.5 times the drill diameter. To provide improved drilling characteristics the polymer may be filled with mineral filler particles such as talcum powder. The method of drilling the printed circuit board includes (i) placing a sheet of this entry material on top of the printed circuit board, and (ii) drilling through the entry material and printed circuit board in succession.

Abstract: In a method of and an apparatus for drilling a hole in a workpiece, a pressure foot associated with a drill is moved into contact with the workpiece, and a drill bit associated with the drill is moved from a drill-starting position into the workpiece, toward the drill-starting position and again into the workpiece while maintaining the pressure foot in constant contact with the workpiece. The drill is reciprocally fed by a plurality of times under the pressure of the pressure foot acting upon the printed circuit board. In either of the method and the apparatus, a hole with a high aspect ratio can be formed in a workpiece made from a thin, flexible material.

Abstract: An attachment for clamping a portable drill to a work piece includes a foot member which positions a portable drill with respect to a work piece. A contact pad applies pressure to the surface of the work piece. Located between the contact pad and the means for engagement of the portable drill is a guide path in which a housing is slidably mounted. Affixed to the housing is a means for applying a vertical force and a collet member. Said means being anti-back drivable. The vertical force is applied to a mandrel so that the mandrel expands the collet. Once the collet has been expanded, a force is placed on the contact pad and on the means for engaging the portable drill. Consequently, the portable drill is held in place at the desired location for drilling a finish hole using minimal force.

Abstract: A pressure foot for a machine for drilling a printed circuit board is supported to be slidable in an axial direction of a rotor shaft and is connected to a vacuum suction source. The pressure foot is adapted to depress the printed circuit board during a drilling operation. A first air pathway is formed from a first supply port formed in a side wall of the pressure foot to a plurality of first blow-out ports formed in a contact surface of the pressure foot with the printed circuit board. The first supply port is connected with a pressure air source. A second air pathway extends from a second supply port formed in the side wall to a plurality of second blow-out ports opened toward an interior of the pressure foot. The second air pathway is in communication with a supply source of a pressure air. Thus, the working time and cost are reduced.

Abstract: A method and apparatus for riveting together workpieces which, in their assembled relationship, have non-parallel exterior surface. Apparatus is provided for clamping the workpieces together between an upper clamp pad and a lower clamp pad, the lower clamp pad being mounted on a spherical bearing so that the lower clamp pad can conform to the workpiece surface. The lower clamp pad is provided with a conical aperture which can act as a pilot for tooling. The tooling is also mounted on spherical bearings so that when the lower clamp pad is in contact with the lower surface of the workpiece, and the tooling is moved towards the workpiece. The tooling will be piloted by the conical aperture to be normal to the surface. After the workpieces are clamped together, the workpieces are drilled from the upper surface and the upper surface is also countersunk.

Abstract: An apparatus for drilling a hole in a workpiece such as, for example, a printed circuit board wherein a pressure foot, associated with a drill, is moved into a position to exert a pressure on the workpiece. A drill bit associated with the drill is moved with respect to the workpiece, and an arrangement is provided for controlling the operations of the pressure foot and the drill bit in such a manner so as to move the drill bit from a drill starting position into the workpiece, then toward the drill starting position and again into the workpiece while maintaining the pressure exerted on the workpiece by the pressure foot.

Abstract: In a pressure foot used in an apparatus for drilling printed circuit boards, which includes a bearing for holding a spindle, and formed at the end portion thereof with an inner void space having a bottom hole for passing the drill bit, the end portion of the pressure foot is provided with an annular end surface possibly contacting with the printed circuit board and air injection ports for injecting compressed air into the inner space. The air injection ports are so directed that the air flow from each injection port is tangently contacts with the circumferential surface of the drill.

Abstract: An apparatus for boring a laminated plate includes a table having a first surface on which a laminated plate may be placed for boring and an opposing second surface, the table defining at least one passage therethrough; a supporting pad for urging a laminated plate to be bored towards the first surface of the table; and a cutter for boring a laminated plate to be bored, the cutter operable to bore in a direction generally opposite to the direction that the supporting pad urges and through the passage defined by the table. Further according to the present invention, the cutter includes a knife edge, a pivotal mechanism adapted to be pivoted about its axial center line, and a stepping mechanism for moving the knife edge in one direction and unsuccessively further in a second direction so that successively deeper boring may be performed.

Abstract: In a method of drilling a printed circuit board according to the present invention, an entry feed rate at which a drill is fed into the printed circuit boards during the initial stage of drilling is made slightly smaller than a drilling feed rate at which the drill is fed while it is drilling a hole through the printed circuit boards, so as to enhance the accuracy at which holes are located. One drilling operation includes a plurality of drilling feeds of the drill, and pulled-out positions of the drill which are reached by the drill between adjacent drilling feed rate are set within a range in which the pressure of a pressure foot is effective. This can prevent the stacked printed circuit boards from shifting and increase the accuracy at which the holes are located.

Abstract: A numerically controlled machine for processing printed circuit boards, including a workpiece holder and at least one operating unit that includes a motor arbor with an exchangeable tool, and a feed mechanism with a drive motor, a control mechanism, and a first movement-measuring system. For each operating unit, there is provided a respective second movement-measuring system that is disposed thereon, and a respective reference measuring point on the workpiece holder, with the aid of which there can be measured a distance between a tip of the tool and an abutment surface of the operating unit that rests upon a workpiece during a processing operation. Prescribed drilling depths are correctable in the control mechanism of the feed mechanism via the measured distance value. This compensation of respective tolerance values is effected independently for each operating unit.

Abstract: A cutting machine has a planar support surface for supporting a work piece and a carriage supported for movement above the planar surface. The carriage independently supports a vacuum shroud having a body portion partially defining a chamber and at least one duct portion outwardly extending therefrom. The body portion is adjustably fixed to the carriage through a connecting flange which extends upwardly from the body portion. The body portion also has a base portion that supports a resilient layer and a contact elements, the layer when it is compressed, exerts a force between the base portion and the contact element contacting the work piece supported on the planar support surface.

Abstract: A drilling spindle having a pressure foot is disclosed for handling drilling tools having relatively large diameter shank regions and relatively small diameter drilling bit portions regions. The pressure foot assembly includes a shutter plate which contacts and clamps the workpiece during drilling operations. The shutter plate translates along an axis transverse to the rotor axis to align either a small aperture or a large aperture with the rotor axis. The small aperture is sized to receive the drilling tool region of the drill, and permits the drilling region to be extended therethrough while providing good clamping of the workpiece during drilling. The large aperture is sized to receive the shank region of the tool, and permits the tool to be inserted or withdrawn from the spindle during tool changing operations.

Abstract: A printed circuit board is supported at its peripheral portion and is moved and positioned by a drive mechanism. During the drilling of a hole in the circuit board, the thrust of the drill acting upon the circuit board is born by a sliding contact surface on a stand disposed on the side of the board opposite the drill. Ultrasonic vibration is applied to the printed circuit board via the stand during the drilling operation to prevent the occurrence of expoxy smearing.

Abstract: An apparatus for drilling sheet material comprises a reciprocating subframe which rotatably supports an annular drill and pressing means. The pressing means holds the material down during drilling and strips the material from the drill when the subframe is raised.

Abstract: An apparatus for performing machining operations in poorly accessible locations includes a fastening head, which is held at one end of a shaft stub, while the other end is in engagement via a bevel gear drive with a drive shaft which is retained in a longitudinal housing. A longitudinally displaceable telescopic guide is provided on the longitudinal housing at right angles thereto. The telescopic guide is compressible counter to the pressure of a spring. A micrometer screw is provided for fine adjustment of the distance between the fastening head and the telescopic guide.

Abstract: A drilling apparatus especially useful in drilling holes in wooden joists and studs, through which plumbing and electrical cables are to be routed, includes a bracket for engaging a joist or stud and a movable carriage supporting an electric motor and drill bit. A lever mechanism moves the carriage, and hence the motor and drill bit forcibly toward the bracket, forcing the drill bit through the joist. Countertorque from the drill bit is resisted by the coaction of the bracket and the drill bit in the hole being drilled. This avoids possible loss of balance by the operator.

Abstract: A device for drilling holes into a stack of plates such as a stack of printed circuit boards, characterized by an arrangement to provide a cover tape beneath a pressure member of a clamping arrangement to be held by the clamping arrangement on the surface of the stack during the drilling operation to prevent damage to the uppermost plate of the stack. The arrangement for providing the tape preferably includes a supply reel, a takeup reel and a feed device and the tape is preferably guided on the pressure member of the clamping arrangement by a guidance groove.

Abstract: A protective device for a fabric or other soft wall covering upon the drilling of a hole therethrough into a support wall behind the covering has a sleeve which closely surrounds the drill bit, a spring braced against the sleeve and a roller bearing to permit immobilization of the sleeve as the drill bit rotates and is axially displaced in the latter. The sleeve has a circular array of pins projecting from its face turned away from the chuck and adapted to penetrate the wall covering. A light supplementary spring can be provided on this side of the sleeve as well to compress the wall covering.

Abstract: The machine includes a feed-in station and a drilling station. The feed-in station comprises a carriage for advancing the glass sheets to be drilled. The carriage has a plurality of rollers, at least some of which are driving rollers, the rollers being effective to impart a forward movement to the glass sheet and are provided with a shroud with helical pattern ridges for combining this forward movement with an approaching movement of the glass sheet towards a reference element and an abutment member connected to the frame of the feed-in station and a gripper assembly for carrying said glass sheet towards an adjustable drilling position.

Abstract: An apparatus for punching a hole in a paper web, in particular for the production of liquid packs, has a movable punch which can be pressed against a counter-plate and which has a circular blade at its tip. In accordance with the invention, to permit the desired hole to be punched into the packaging material to the desired depth, using simple means, the punch has a rotationally driven cutter head. Due to the rotary movement of the punch or the blade-forming edge at the tip of the punch, the blade is no longer merely pressed into the paper web, as in previously known punching apparatuses, but in accordance with the invention it is rotated perpendicularly to the pressing movement, giving a cutting effect as when using a knife.

Abstract: A cutting device for the precision trimming of a symmetrical portion of the peripheral edge of a centrifugally cast lens secured within a cavity of a female mold without the need for extensive and complex prior alignment of the cutting tool with the lens.

Abstract: A drilling machine for drilling a stack of paper, comprises a first movable member moving along directions to press the stack of paper and to remote from the stack of paper and elastically supporting a pressing plate, a second movable member supporting a drilling mechanism and moving along the directions, and a control device for causing first and second driving mechanisms simultaneously to drive the first and second movable members respectively in the direction to release the stack of paper from compression and to separate the drilling mechanism from the stack of paper, whereby the stack of drilled paper is released from compression and the drilling mechanism is separated from the stack of drilled paper.

Abstract: An apparatus for driving fasteners, drills, bits, and similar insertable objects into ceilings, trusses, and other remote structures, comprises a drive head mounted on one end of an elongate support. The drive head has a retainer for holding a fastener or bit, and is powered by a rotary drill, impact motor, or the like, which drives the fastener/bit into the object structure. A clamping arm is mounted at the upper end of the support, and is positioned to converge and diverge with the drive head. The drive head motor and clamp arm are controlled from the lower end of the support, whereby during operation, the clamping arm abuts the object structure at a side thereof opposite from the drive head and is converged with the drive head to apply tip pressure to the fastener/bit and resist reaction forces developed therebetween.

Abstract: The collet-type drill includes improved clamping means having a pressure foot member that is in engagement with the work piece. The pressure foot member is connected with a drill motor and with a feed means. A collet is operably connected to and movable relative to the foot member, and when actuated, connects the drill to the work piece. A clamp bushing has one end pivotally connected with the collet and encircles a cylindrical sleeve that has a transverse slot extending therethrough. The bushing is connected to the pressure foot member. A clamping piston extends through the sleeve and carries a connecting pin that extends through the slot in the sleeve into the clamp bushing whereby the bushing and collet are movable together in response to movement of the clamping piston to force the collet into holding engagement with the work piece.

Abstract: In a numerically controlled, gantry-type routing machine, a workpiece pressure-foot assembly is disposed crosswise over an elongate workpiece supporting bed for providing an effective hold-down force for stacked workpiece sheets. The hold-down force is applied to the workpiece stack at locations adjacent a router tool that is held and turned by a motor driven spindle assembly movably mounted on a gantry for orthogonally related lengthwise and crosswise movements with respect to the bed and workpiece. The pressure-foot assembly includes a pair of spaced parallel rails, pivotally supported about axes parallel to the rails, and a plurality of pressure-bearing rollers mounted on axes directly underlying each of the rails for supporting the rails, and accommodating travel of the assembly over the upper surface of the workpiece. The pair of rails and supporting rollers are arranged crosswise of the bed, paralleling the gantry, and underlying the spindle assembly.

Abstract: An apparatus facilitates the support and positioning of an engine block for the purpose of boring the cylinders thereof and the support and positioning of the boring machine used simplifies the operation and permits it to be performed with greater ease, safety and precision. A novel method of suspension of the boring machine over the engine block simplifies the raising and lowering of the machine by levelling it and automatically effecting the proper alignment to insure the accuracy of the boring operation.

Abstract: A machine for machining sheets comprises an arrangement for compressing the sheets to be machined. The arrangement is rotatable about a longitudinal axis comprises at least two rollers for bearing resiliently against the sheets during machining, each of which rollers are rotatable about a transverse axis perpendicular to said longitudinal axis. The arrangement is driven by a motor via a pinion, which motor also drives reduction gearing connected to an angular control means whereby it is possible to control the angular position of the arrangement so that the axis of rotation of the rollers can be orientated in relation to the direction of machining. The control means are themselves controlled by programmable electronic means which operate with reference to the angular position of the machining head of the machine.