Abstract: A tool change mechanism in a machine tool includes a tool change arm arranged to attach a protection cover member to the forward end of a spindle head for protection of a ring secured to the forward end of a tool spindle in the spindle head and to remove the protection cover member for replacement with a tool holder of large diameter. The tool change arm is further arranged to insert the tool holder into the tool spindle and remove it from the tool spindle, the tool holder having a ring gear secured thereto for meshing engagement with the ring gear of the tool spindle and a protection cover part integrally formed therewith to be coupled with the forward end of the spindle head for protection of the ring gears meshed with each other when the tool holder has been inserted into the tool spindle. The tool change arm has a pair of tool grippers each having a first grip portion for engagement with the protection cover member and a second grip portion for engagement with the tool holder.

Abstract: A machine tool (10) comprises a revolving spindle (11). A plurality of tool holders (14) each of which is provided with a taper (13) and can be transferred by means of a gripper arm (20) from a magazine position remote from the spindle (11) and mounted by their tapers (13), one by one, in the spindle (11) in a machining position, while the other tool holders (14) remain in the magazine position. In order to avoid that metal chips may get into contact with and stick to the tapers (13) of the tool holders (14) while the latter are in the magazine position the tool holders (14) are accommodated in a cavity (40) providing a closed cover at least for the tapers (13).

Abstract: A storage system for cutting tool collets comprises a cylindrical drum with a plurality of bored recesses on the front face. These recesses serve to hold individual collets. A pair of cut slots serve to allow easy access to the collets. The drum is mounted upon an elongated version of the normal pivot pin of a milling machine. A rotating cover provides for individual access to the collets and keeps away foreign debris.

Abstract: A break away machine tool assembly includes a support to which a bearing plate is pivotally mounted in overlying and contiguous relation. A tool element overlies and is contiguous the plate and is movable therewith. Securement elements releasably secure the plate and the tool element in overlying relation to the support for permitting the plate and the tool element to move relative to the support within a defined range upon being subjected to an impact.

Abstract: A shield unit which is removably attachable to a machine tool having a cutting member. A rigid transparent sheet is attached to an elongate stem. Also attached to the elongate stem is a clamp. The clamp is adapted to be removably attached to a portion of the machine tool. With the clamp attached to a portion of the machine tool, the transparent sheet is positioned adjacent a cutting member of the machine tool to protect the operator of the machine tool. Preferably, the machine tool is provided with a threaded rod such as a spindle adjustment rod, and the clamp has a threaded portion which threadedly engages the threaded rod to secure the position of the clamp with respect to the threaded rod and to secure the position of the transparent sheet with respect to the cutting member.

Abstract: A protective device for the top surface of a slotted milling machine table preferably comprises a rubber cover sized to overlay a desired length of the table at one end thereof, the surfaces of the cover each having a raised peripheral lip and longitudinally extending beads and ribs. The downwardly directed beads fit within the slots of the milling table to hold the cover in place while the downwardly directed ribs provide air space between the placed cover and the table, thereby inhibiting rust. The upwardly directed raised lip prevents coolant spillage from the top of the cover while the coolant return holes enable excess coolant to be returned to the slots residing therebeneath. To provide protection for a reduced length table, the cover is made reversible by providing a transverse lip portion on one of the surfaces, located inboard of the coolant return holes.

Abstract: A machine tool is provided with an enclosure with a charging door (10) arranged therein. In a first end position, the charging door closes the enclosure against the outside while in a second end position it occupies a position in which it is pivoted substantially about a horizontal axis in its upper portion. In this latter position, the lower rim of the charging door (10) is displaced into the interior of the enclosure. The charging door (10) is guided during its movement in such a manner that its lower edge is located at a higher level between the two end positions than in the said end positions.In order to facilitate opening and closing of the door for an operator, a power-operated drive (95, 100, 101) is arranged in a lateral bay (90) in the enclosure for opening and closing the charging door (10).

Abstract: A machine tool comprises a spindle stock and a worktable having an upper surface thereon for mounting and machining workpieces. The worktable and the spindle stock are alternatively displaceable relative to each other in a plane parallel to the upper surface from a first position at which a first portion of the upper surface is disposed proximate the spindle stock and serves as a processing area and a second portion of said upper surface is disposed distal to said spindle stock and serves as a mounting area, to a second postion at which the upper surface second portion is disposed proximate the spindle stock and serves as a processing area and the upper surface first portion is disposed to the spindle stock and serves as a mounting area. A splash guard wall is provided for separating the processing in the mounting areas. The splash guard wall is attached to the table upper surface by means of a hinge defining a first pivot axis.

Abstract: A sealing mechanism acts between a quick-change tool holder and a tool adapter receivable therein. The sealing mechanism is an elastomer seal in the form of a V-flange elastomer seal ring mounted on a metal member which has a coaxial cylindrical outer surface and an axially inwardly facing shoulder to establish the elastomer seal member in position. This seal member has a generally conical seal member first portion with an external peripheral surface engaging a planar surface on the quick-change tool holder. This prevents contaminants, such as fine chips, from entering the interior of the quick-change tool holder. The foregoing abstract is merely a resume of the one general application, is not a complete discussion of all principles of operation or applications, and is not to be construed as a limitation on the scope of the claimed subject matter.

Abstract: A protective covering for a machine tool where work pieces can be mounted on a worktable comprises a loading door which can be pivoted between two end positions and which in a first end position closes the protective covering while in the second end position it clears an opening in the protective covering providing access to the work piece. The bottom of the loading door describes during this movement an upwardly curved locus extending above and across the work piece. It is proposed for this arrangement that the loading door be provided on its inside with a device for diverting liquid flowing down its inside towards the lateral edges and that the said loading door does not project beyond the outer contour of the said protective covering during its movement.

Abstract: A tool stand including a vertical support panel with a horizontal work-supporting table mounted for vertical adjustment thereon. The support panel horizontally mounts a power router with the router bit overlying the table. An elongate retainer rail mounts on the table outward of the bit, and a finger guard mounts on the rail and extends inwardly therefrom in overlying relation to the bit. The retainer rail is adjustable on the table for varying the width of the work area between the rail and the support panel. The guard is spring-biased to an extended position overlying the bit for selective retraction thereof as may be required upon the introduction of a workpiece.

Abstract: A method and apparatus by which the degree of wear and useful life limitations of a drill, end mill or other types of metal removal tools can be detected. The method is based on the short circuit current, open circuit voltage and/or power that is generated during metal removal by the utilization of an insulated rotary tool bit to which electrical contact is made by a non-rotating conductor and an insulated or non-insulated workpiece, with an external circuit connecting the tool and workpiece through a measuring device. The generated current, voltage or power shows a sharp increase or change in slope upon considerable tool wear and/or at the point of failure.

Abstract: A link-band cover for guideways and moving parts of machine tools, as well as for other structural elements of machine tools that could lead to accidents. The cover includes individual rigid strips that can be sequentially arranged in a plane. Each strip has long sides, with adjacent long sides of adjacent ones of the strips each being provided with a respective slot that is open toward the adjacent strip and has an undercut base. Hinge members in the form of hinge eyes are disposed between each two adjacent strips to pivotably interconnect the same, with each hinge eye being anchored in one of the slots of the strips. Hinge eyes between two adjacent strips are aligned on a pivot shaft, with adjacent hinge eyes being anchored in the slots of different strips.

Abstract: An apparatus for machining the edge of a lens. A fixed housing having a lid and a bulge is provided. Two half shafts mounted in the housing, with a lens being adapted to be held between these half shafts. A rotatable edge-machining tool in the form of a milling tool is disposed in the housing. A motor is provided for driving the milling tool, with this tool and the motor being movable relative to the housing in two horizontal coordinate directions, whereby the milling tool is adapted to be moved between a rest position in the bulge and an operating position that is in the housing but out of the bulge.

Abstract: A machine tool comprises a displaceable work table (12) having a first area which in a first position in which it serves as the processing side carries workpieces for being processed by means of a tool of the machine tool, and a second area which in a second position in which it serves as the mounting side can receive another workpiece, the two positions of the said areas being exchangeable by displacement of the table (12), and at least one splash guard (28) which can be moved relative to the work table being arranged between the said table areas.In order to ensure that one always has a larger working space available on the processing side to permit the spindle stock to be moved over the full area and to permit bulky and/or heavy workpieces to be loaded on the surface of the work table (12) from the mounting side, the splash guard (28) subdivides the working space defined by the areas asymmetrically.

Abstract: An attachment for a vertical mill having a quill and a spindle rotatably mounted within the quill which is adapted to rotatably drive one end of a milling cutter. The attachment includes an elongated housing having a semi-cylindrical cavity and in which one end of the housing is clampingly secured to the quill of the vertical mill. In doing so, the milling cutter is contained at least partially within the cylindrical cavity. A rotatable center is rotatably mounted to the other end of the housing and the center is positioned within a conical recess at the lower or free end of the milling cutter or, alternatively, a pilot on the cutter is rotatably received in the other end of the housing. The housing together with the center thus allows the cutter to freely rotate with the spindle while simultaneously supporting the cutter against lateral deflection with respect to its axis of rotation.

Abstract: In a machine tool having a palette change-over device protected by a movable U-shaped hood, to prevent injury to the operator or accidental damage during movement of the hood the hood is provided with a probe and an automatic circuit breaker arranged to shut down at least the driving mechanism of the hood on contact with the operator or another foreign body in the path of movement of the hood.

Abstract: The invention has as an object to provide a reliable, failure-free tool holding apparatus which allows digitization of a tool holding apparatus having a tool moving function, is free from various problems encountered upon digitization, and does not cause an erroneous operation upon scattering and attachment of chips or cutting oil. In order to achieve this object, a scale member and a moving amount detecting means are arranged to oppose each other. The scale member is arranged at the side of a slide movable in a predetermined direction, and is moved following the movement of the slide. The moving amount detecting means is arranged at the side of the main body and supplies a predetermined number of oscillation pulses to a display in accordance with the moving amount of the scale member. The scale member is enclosed with stretchable members such as bellows members, and is moved in the enclosed, sealed space.

Abstract: Disclosed is a nose piece for a power drill and hand drill with certain modifications made to nose piece and using telescopic bushing having a drill motor, a drill spindle and a drill bit attached to the spindle, the nose piece being capable of macro longitudinal adjustment with respect to the length of the drill bit and rotational adjustment of its position with respect to the drill motor and the work piece.

Abstract: A dust guard cap for the tool holder in a hand-held drilling device is formed of a casing secured on the tool holder and a cover member mounted on and extending across one end of the casing. The cover member forms an opening through which a tool can be inserted into the tool holder. Attached to the cover member and extending inwardly from the through opening is a resilient sleeve-like torus which forms a seal around the tool. An outwardly projecting bead is formed on the inner end of the torus and bears against the casing.

Abstract: A tool abnormality detector for use with a machine tool for detecting any abnormality of a tool mounted on the tool mounting shaft. When the tool mounting shaft is in a correct position with respect to the tubular body secured to the spindle, the air pressure is kept constant. When an abnormal resistance is applied to the tool mounting shaft, the latter will lag in rotation with respect to the tubular body, so that the exhaust air passage will be blocked. A pressure sensor detects an abnormal increase in the air supply line, giving a signal for stopping the spindle of the machine tool. This prevents the tool from damage.

Abstract: A wood shaper utilizing multiple vertical cutting shaper assemblies mounted on the opposed end portions of a horizontal shaft. Each shaper assembly has, to the opposite sides thereof, an elongate guide fence and an elongate finger guard selectively adjustable relative to each other and the shaper assembly therebetween. Each guide fence mounts a pair of horizontal support bars for independent vertical adjustment relative to each other. The support bars align with the intake and discharge sides of the associated shaper assembly. As a variation, a second commonly driven horizontal shaft can be provided parallel to the first shaft. The second shaft will mount, at one end thereof, a third vertical shaper assembly received between an elongate guide fence with dual support bars and a laterally adjustable finger guard.

Abstract: An electric drill safety device is provided for dynamically braking a drill when there is contact between the drill bit and an electrically conductive material. A first direction voltage is applied to the motor winding to turn the motor forward. When contact is detected between the drill bit and an electrically conductive material, voltage to the windings is discontinued momentarily and thereafter a reverse direction voltage is provided to the motor windings for a predetermined time.

Abstract: A router comprises a cage supporting a drive unit having a shaft on which a cutter can be fixed. A rest plate is provided with an aperture for moving the cutter therethrough. The rest plate is connected to the cage through two guide columns on which it is displaceable in axial directions of the cutter and arrestable in a selected position. The rest plate is a hollow structure open downwardly where it is closed by a detachable cover having a smooth outer surface. A cavity of the plate communicates with and encircles the aperture 21 for the cutter and grows toward an exhaust connection which extends tangentially to the cutter, i.e. in the direction in which the millings are thrown. The exhaust connection can be connected to an exhauster. Laterally on the rest plate, an adjustable slide stop may be provided having an angled leg which can be brought into a position flush with the bottom surface of the rest plate or moved downward therefrom.

Abstract: A transparent enclosure for automatic metal shaping machinery effective to contain cutting fluids, chips, shavings, broken tools and the like having a smooth planar interior wall surface for shedding readily chips, fluids and other matter striking the wall during the course of machine operation.

Abstract: A tool adapter for use in drilling, tapping and milling operations with the spindle of a machining center having a collet type tool holder which holds the tool which upon advancement into the work piece at a programmed feed rate to a programmed depth rate utilizes a spring loaded unit to signal the computer numerical control through a transducer of the machining center in the event a tool is broken during the machining operation to automatically stop said operation.

Abstract: A unit case having the shape of a hollow cylinder is demountably mounted in a tapered hole of a spindle by use of a unit holding member and a stock suction nozzle is demountably mounted on the tip end portion of said unit case through a cover member. An end of a suction pipe led to the inside of the hollow of said unit case is fixed on the rear end portion of said unit case, and a stock suction means such as a vacuum pump is provided on the other end portion of said suction pipe through a cleaner.

Abstract: This safety shield is collapsible and for use with a vertical drill press to protect the press operator from injury. The shield includes a pair of interconnected telescoping hollow cylinders, with the top cylinder of elongated shape that is mounted to a non-rotating, vertically movable drill housing member, while the lower cylinder is also of elongated shape and it is suspended from the top cylinder and is capable of telescoping with respect to the top cylinder. The top end of the top cylinder has a novel adjustable clamping collar so the collar may expand and contract, and fastening means are used for tightening and loosening the collar with respect to the drill housing member. The lower cylinder of the shield is also fitted with an enlarged collar adjacent its top end of about the same size as the adjustable collar of the top cylinder.

Abstract: A safety shield, adapted for securement to a milling machine, drill press, and the like, is rotatable to permit easy access to a workpiece, and is provided with a drag resistance to such rotation to prevent inadvertent return of the safety shield to the original workpiece area when not so desired.

Abstract: The invention relates to an overload protection device for a machine tool, in which a carriage carried on the machine bed is displaceable, between the tailstock and the headstock by a lead screw [driven] by a drive motor and a feed gearing, and in which the lead screw nut is joined to the carriage by at least one joining bolt. To permit a very quick restoration of the machine to service after a collision between the carriage and a component present in its path of movement, while the predetermined dimensional relationship is restored without additional readjustment, the overload protection device is constructed such that the joining bolt has a break-away section in the area of the junction between the carriage and the lead screw nut.

Abstract: Method and apparatus for collecting dust and shavings produced by a drum and disc lathe. The apparatus comprises a sealed housing which is adapted to enclose the entire grinding or cutting area of the lathe and trap airborne particles suspended therein. A brake drum or disc is attached to the lathe arbor within the housing through a housing access door prior to the machining operation. The cutting tool extends from the lathe into the housing through an orifice which is covered by a plurality of sealing strips. As the drum or disc is machined, the suspended asbestos and metal dust is removed from the housing to a collection receptacle by the directional air flow from a fan and the heavier metal shavings are collected in a tray located on the housing floor.

Abstract: A debris collector for an electric drill is disclosed. The debris collector attaches to the body of the drill and under the drill bit. The flexibility of the collector allows the collector to flex during drilling when the drill bit advances into the work. The debris collector may also be handheld to increase the versatility of the tool such as when drilling oddly angled surfaces.

Abstract: The invention relates to an apparatus for carrying out a process for separating electrolysis bath residues on used anode units removed from electrolysis cells for the production of aluminum by the Hall-Heroult process, said units comprising a cabon residue 5 or "butt", in which are sealed discs 3 interconnected by flanges 2 welded to a suspension rod 13, the axes of the discs 3 being parallel to the axis of the suspension rod 13, said process comprising passing at least one rotary milling cutter 9, of which the axis of rotation 10 in the working position is substantially parallel to the axis of the rod 13, through the space situated between the discs and around the discs 3 and defined by the upper face of the carbon butt 5 on the one hand and the flanges 2 on the other hand.

Abstract: A drilling monitor employs laser optics and an associated signal processing device to provide intelligent control capable of making the optimum decision to maintain hole quality and maximize drill life during the drilling of via holes in a circuit board. Twist angle, bending and temperature of the drill are monitored and the drill motor and/or the board is controlled accordingly in response to present data being compared to preprogrammed acceptable standardized data.

Abstract: A Drill Bit detector for use with numerically controlled drilling machine capable of sensing missing or broken Drill Bits in the range of 1 mil to 30 mils in diameter, or larger, is described. An infrared emitting diode is driven at a predetermined frequency with the pulsed light being directed through fiber optic cable directed at a portion of the Drill Bit to be detected. A change of light intensity occurring when a Drill Bit is missing is detected and the pulsed light detected converted to a pulsating electrical signal at the input frequency of the pulse light source. A frequency responsive circuit converts the pulsating electrical circuit to a digital signal indicative of the absence of the sensed Drill Bit. A timer determines whether or not the sensed digital signal occurs for a predetermined threshold time period, and causes it to be ignored as spurious if less than the predetermined time interval, or causes the drilling machine operation to be halted if occurring longer than the threshold time period.

Abstract: A block assembly is adapted to be removably fixed to a vertically disposed way of a machine having systems for automatically supplying lubricating oil to the way and for supplying a dissimilar liquid coolant to a workpiece; the block assembly serving to collect lubricating oil flowing downwardly along the machine way and prevent its contaminating the coolant. The block assembly comprises a multi-sectional block shaped to provide an oil collection reservoir adapted to be placed in flow communication with a separate oil collection tank or sump.

Abstract: By providing a removable and repositionable panel member cooperatively mountable to a support panel in a plurality of alternate positions, which support panel is mountable to a machine tool, a unique, universally applicable safety shield is achieved. Preferably, the safety shield also incorporates a front panel pivotally mounted to the support panel, and constructed of cooperative mounted engagement of the removable and repositionable panel in a plurality of alternate positions therewith. If desired, a plurality of removable and repositionable panel members are employed to further enhance the alternate configurations obtainable using the safety shield of this invention.

Abstract: When a drill is overloaded, while cutting a hole in a workpiece, a torque limiter disconnects the drill from a main spindle. As the drill is disconnected from the main spindle, the torque limiter generates high-level elastic waves. The elastic waves are converted by a transducer into a voltage signal. The level of the voltage signal is compared with a threshold value.

Abstract: An adjustable T-slot cover for covering T-slots in such as a table of a machine tool and consisting of two intermeshing elongated section members. Each section member has in the crosssection a vertically extending web extending along the side wall of T-slots and which web has on the upper end a projection for engaging with chamfered upper edge of the side wall and on the lower portion a guide for resiliently abutting with the side wall. One section member has sidewisely extending first and second arms, and the other section member has a third arm extending between the first and second arms. Intermeshing indentations are formed between the second and third arms.

Abstract: A disposable cutting edge to be installed upon a lawn mower rotor and an audible tone generator to warn the operator when the disposable cutting edge is not properly installed. A disposable cutting edge providing a quick and safe snap-on/snap-off installation/removal upon a specially constructed rotor containing an edge positioning sensor, and capable of generating an audible alarm.

Abstract: To determine whether an object, such as a tool, is worn or broken, there is embedded in the object an elongate fiber optic. One end of the fiber optic is at a surface of the object and such that a second, light emitting end of said fiber optic is located within the body of said object and spaced a distance from a further surface of the object, such that a portion of the object overlies the other end. When the object is broken or worn to such an extent that the other end of the fiber optic is exposed, light directed at the first mentioned end of the fiber optic will be detectable at the other end. Thus, by directing light onto the one end, and by detecting any light emitted at the second end, a worn or broken object is readily detected. The invention has particular use in the automatic inspection of tools in automated manufacturing.

Abstract: A contact detecting apparatus for detecting the contact between a workpiece and a tool in a machine tool which includes a coil mounted on a spindle head and connected to an AC power source for generating an induced current in a looped secondary circuit including the workpiece, a work table, a machine body, a spindle head, a brush, a clamp bar for clamping the tool on a tool spindle, springs interposed between the spindle and the clamp bar, the tool spindle and the tool, when the workpiece and the tool are moved relatively into contact with each other. The brush is kept contact with the clamp bar at the rotational axis of the tool spindle. A detector is connected between the AC power source and the coil for detecting a change in an electric signal caused by the contact between the workpiece and the tool.

Abstract: A machine tool has a pallet transfer system comprising a rotary deck having a pair of pallets oppositely disposed about a vertical rotary transfer axis, wherein at the transfer position, the pallets are further movable along a horizontal linear transfer axis toward and away from the pallet transfer system. A vertical guard plate is affixed to the rotatable section or deck of the transfer system, and the plane of the guard plate passes through the rotary transfer axis at an oblique angle to the linear transfer axis. The rotatable guard plate interacts with an elastomeric seal at the interface of a guard opening in a stationary guard assembly on a machine tool to substantially confine coolant overspray and the like within the machine guard enclosure. By passing obliquely across the linear transfer axes of the pair of parallel pallets, substantially full access of a stationary pallet lying outside the machine guard enclosure may be had.

Abstract: A table for supporting an electric power tool is provided with a safety shut-off device. A bar is pivotably mounted on the side of the table and a shut-off switch is mounted to the table behind the bar. The bar is biased away from the shut-off switch by a spring. If an operator falls or leans against the bar, the switch is actuated to shut off the power to the tool.

Abstract: A broken bit detector for use in conjunction with printed circuit board drilling machines or the like. The detector includes a light emitter and a light sensor contained within a pressure foot. The light emitter projects a beam of light through a central opening in the pressure foot and toward the light detector. Normally, the beam will be broken by a drill bit which passes through the opening. If a bit is not present, the light beam will not be broken and will be detected by the photosensor. Pressurized air is forced outward from both the light emitter and light detector in order to prevent any chips created by the drilling operation from striking the emitter or detector. The use of the air creates a shield which results in an accurate detector having a long life.

Abstract: A contact detecting apparatus for detecting the contact of a workpiece and a tool which comprises a coil mounted on the periphery of a spindle head and connected to an AC power source for generating an induced current in a first looped secondary circuit formed by the workpiece, a work table, a machine bed, a column, a spindle head, a tool spindle and a tool in the tool spindle when the workpiece and the tool are moved relatively into contact with each other, and a second looped secondary circuit formed by a tool change device, the tool, the tool spindle and the spindle head when a tool change operation is performed. A detector is connected between the AC power source and the coil for detecting a change in an electrical signal caused by contact between the workpiece and the tool or contact between the tool change device and the tool to output a contact detecting signal. Another detector is provided to detect that a contact detecting signal is not generated, even if a tool change operation has been performed.

Abstract: A wood routing machine accepts a length of wood stock, e.g., a length of preformed crown molding, and thereafter in automatic sequence clamps the wood stock at lengthwise spaced locations, routs evenly spaced notches along the length of the stock and after each router operation automatically unclamps and indexes the stock a predetermined distance, again clamps the stock and repeats the router operation sequence until the entire length of stock has been notched to form a length of dental block type wood molding.

Abstract: A power drawfinger system for selectively locking and releasing a toolholder or arbor in the socket of a power driven machine tool spindle. The system includes a collet device actuated by a power drawbolt using hydraulic means for expanding said device and a resilient member for contracting same to disengage or engage the toolholder. The collet device and drawbar mechanisms are constructed to be fail safe in event of breakage of the collet or loss of power.

Abstract: An accessory for tool machines is provided comprising a tool holder isolatedly carried on bar springs to effect a floating mount. The holder yields in response to selective load stress during cutting and is restricted to a linear force path to relieve stress. The yielding movement relieves stress and can operate signals in the event of overload or operate control means such as switches to cut off tool machine motors.

Abstract: An improved drafting instrument is provided for scribing small dots on a drafting medium comprising a substrate provided with a removable surface coating. The drafting instrument includes a drive motor and rotatable cutter which are slidably mounted as a unit for vertical movement toward and away from the drafting medium. A manually operable actuator is provided for moving the drive motor downward to bring the cutter into engagement with the surface coating of the drafting medium. A control switch responds to downward movement of the drive motor and cutter by a predetermined distance for automatically actuating the drive motor before the cutter is moved into engagement with the drafting medium. The drafting instrument includes an adjustable depth limit feature to control the depth of penetration of the cutter into the surface coating of the drafting medium. The operation of the drive motor and rotation of the cutter are automatically terminated when manual pressure on the actuator is released.