Abstract: A spectrometer apparatus is disclosed that includes at least one light source for irradiating a sample with light, an optical detection device for detecting light scattered by the sample, at least one optical filter device, which is arranged in front of and/or behind the sample, a contact sensor device for determining a contact between the sample and the spectrometer apparatus and for outputting a corresponding output signal, a control device for controlling the light source and the detection device in response to the output signal. The control device is designed such that the control device modifies at least one operating parameter of the light source and the detection device, when the output signal indicates the contact between the sample and the spectrometer apparatus. A method for operating a spectrometer apparatus is disclosed as well.

Abstract: Handheld power tools are adapted for magnetic stabilization based on the incorporation of one or more permanent magnets in a base thereof. One or more permanent magnets may be incorporated into the base of a handheld power tool (or a detachable rechargeable battery base) such that when the base is contacted with an inclined steel roof panel, a magnetic force is applied that is sufficient to secure the handheld power tool in an upright and non-operational configuration. The distal region of the base may include a spacer formed from a compliant material to provide a spatial offset between the one or more permanent magnets and a surface with which the base is contacted. In some example embodiments, a rechargeable battery pack may include one or more permanent magnets that are capable of supporting the weight of an associated charger when the battery pack is contacted with a vertical steel surface.

Abstract: A magnetic drilling stand is disclosed having a drilling unit (20), having an electromagnet (14) for fixing the magnetic drilling stand (10) on a component (12), having a voltage source which can be coupled to the electromagnet (14), and having a controller (28) for monitoring the holding force of the electromagnet (14), with the controller (28) having a device for monitoring the current level of the electromagnet (14), in order to identify a fault state or an adequate magnetic holding force, with a signal for an adequate magnetic holding force being produced only if, within a test phase, the current level of the electromagnet is below a respectively predetermined threshold value at at least two predetermined times after the start of the test phase.

Abstract: Tapping devices and methods for using such devices to tap into a pipe are described. The tapping device contains a drill connected to the proximal portion of a shaft, a tapping tool attached to a distal portion of the shaft, and a protection device attached to the shaft. The protection device itself contains containing an enlarged distal portion, an enlarged proximal portion, and a middle member extending therebetween. The user can hold and use the tapping device with a first hand on a handle of the drill and a second hand on the middle member of the protection device. The protection device protects the hand from hitting an object (including the pipe), the socket, or the drill, thereby improving the safety for the user. Other embodiments are also described.

Abstract: A pneumatic feed drill has a control unit that repeatedly advances and retracts the drill bit in peck cycles while drilling the hole. The drill has a hydraulic damper cylinder with a damper rod protruding from it that limits the speed of advancement of the drill bit. A retainer device is mounted to the damper rod and prevents the damper rod from resetting to its initial position during the peck cycles. The retainer device releases the damper rod to reset when the drill bit has reached total depth. A safety device is pivotally mounted to the housing and has a closure tab that blocks access to the start button of the drill unless the damper rod is in its initial position.

Abstract: A power tool includes a spindle assembly supported for rotation about an axis. The spindle assembly includes a plurality of engagement members, and at least two of the engagement members are disposed in spaced relationship less than one hundred eighty degrees from each other with respect to the axis of the spindle assembly. The power tool also includes a spindle lock assembly that selectively engages at least one of the plurality of engagement members to lock the spindle assembly against rotation about the axis.

Abstract: A guard for a power-feed drill having a fluid inducer protects an operator from coming in contact with a rotating drive assembly. The drive assembly is enclosed by a cylindrical housing having a slotted opening through which a fluid inducer connection extends. The guard comprises a rotatable tube concentrically disposed within the housing and sleeved over the drive assembly so as to cover the opening presented by the slot. The fluid inducer connection passes through a helical groove in the tube.

Abstract: A working machine includes a blade seat movable relative to a sheet plate, and a safety protective device mounted on the blade seat to cover the blades of the blade seat and including at least one swing member pivotally mounted on the blade seat, and a protective board pivotally connected to the at least one swing member. Thus, when any portion of the protective board is pushed by the sheet plate, the whole protective board is driven to pivot relative to the blade seat so that the protective board is moved upward and downward in a whole manner without deflection.

Abstract: A servo motor in die tapping unit provides built in shock protection for the motor by fixing a shock plate to the servo motor and floatingly mounting the shock plate to a base structure attachable to a stripper plate in a press. Sets of opposing springs allow movement of the shock plate relative the base plate to relieve shock loads when the press is operated, the shock plate guided on dowel pins fixed to the base structure. The shock plate, and tapping unit and base structure form a self contained assembly for mounting together in the press.

Abstract: A method of controlling a relative movement of a cutting blade and a workpiece which are moved relative to each other by a movement device in an operation with a machine tool. The method includes a step of bringing the cutting blade and an object into contact with each other, by moving at least one of the cutting blade and the object toward each other by the movement device, and a step of controlling the relative movement on the basis of a relative position of the cutting blade and the object which is detected by the movement device upon the contact of the cutting blade and the object with each other.

Abstract: A woodworking machine is disclosed. The machine includes a cutting tool and a motor adapted to drive the cutting tool. The machine further includes a detection system to detect a dangerous condition between the cutting tool and a person, such as a person coming into contact with the cutting tool. A reaction system is provided to disable the cutting tool, such as by covering, blocking, destroying, wrapping, etc., upon detection by the detection system of the dangerous condition.

Abstract: A method of controlling a relative movement of a cutting blade and a workpiece which are moved relative to each other by a movement device in an operation with a machine tool. The method includes a step of bringing the cutting blade and an object into contact with each other, by moving at least one of the cutting blade and the object toward each other by the movement device, and a step of controlling the relative movement on the basis of a relative position of the cutting blade and the object which is detected by the movement device upon the contact of the cutting blade and the object with each other.

Abstract: A power drill housing and chuck rotation indicator arrangement in which the power drill housing is formed of two symmetrical shells abutted against each other, the shells each having a front end terminating in a chuck guard defining a respective semi-circular mouth adapted to receive the chuck assembly of the power drill, keeping the chuck assembly protected within the chuck guards.

Abstract: A machine is described having at least one dangerous portion. The machine also includes a safety system to detect dangerous proximity between a person and the dangerous portion and perform a predetermined action to limit or prevent injury to the person from the dangerous portion.

Abstract: A drive shaft locking mechanism including a locking structure in the form of a gear which is secured to an input shaft of a rotary tool, a retractable interlocking mechanism which selectively couples to the locking structure, and a directional control mechanism coupled to the interlocking mechanism, controlling its movement. The locking structure comprises at least one engageable surface and a means for securing the locking structure to the input shaft. The interlocking mechanism includes a locking element slidably disposed within a tubular channel and selectively extensible therefrom at the urging of the directional control mechanism, to engage the locking structure along an engageable surface.

Abstract: A device for aligning a hand-held electric drill to a vertical position with respect to a flat workpiece includes a disc-shaped circular housing having a centered axis, upper and lower faces, and a channel centered on the axis in communication with both faces. A gripping feature associated with the channel permits removable attachment of the housing to a rotating component of the drill, such as the drill shaft or drill bit. A light-emitting component within the housing directs a narrow beam of visible light downwardly from the lower face. When the drill is vertically aligned, the beam of light produces a circular path on the workpiece.

Abstract: A power drill housing and chuck rotation indicator arrangement in which the power drill housing is formed of two symmetrical shells abutted against each other, the shells each having a front end terminating in a chuck guard defining a respective semi-circular mouth adapted to receive the chuck assembly of the power drill, keeping the chuck assembly protected within the chuck guards.

Abstract: An apparatus for guarding an operator from hazards produced at the point of operation of a machine tool. The apparatus comprises a mounting bracket for attaching the fixture to the dovetail of the ram of a milling machine (e.g., a Bridgeport vertical milling machine), the mounting bracket having a first end and a second end; a swing arm attached to one of the ends; and a guard attached to the swing arm. In some embodiments, a second swing arm attached to the other of the ends supports a second guard or a tube that carries oil to the work piece.

Abstract: A machine tool comprises a spindle stock and a worktable provided in front of the spindle stock to support workpieces thereon and capable of up-down movement and swivelling movement about a vertically extending center axis. Also employed in the machine tool is a splash guard arrangement which spatially divides the worktable into a machining region disposed in proximity to the spindle stock and a mounting region positioned distal to the spindle stock. The splash guard arrangement includes a rotary guard rigidly attached to the worktable for movement as a unit with the worktable, a stationary guard provided above the rotary guard and a sealing slider elevationally movably held by the stationary guard. The sealing slider remains in pivotal engagement with the rotary guard so that the slider can be subjected to up-down movement together with the rotary guard, while allowing the swivelling movement of the worktable and the rotary guard independently of the slider.

Abstract: A chuck assembly (22) for releasably attaching a cutting accessory (23) to a rotary driven tool such as a surgical drill (20). The chuck assembly includes a chuck head (30) from which a drive spindle (36) extends rearwardly. Clamping jaws (34) extend from the front end of the chuck head to hold the cutting accessory in place. The chuck head, the drive spindle and the clamping jaws can rotate in unison about a common axis of rotation. Alternatively, the chuck head and the drive spindle can be rotated relative to each other around this common axis to lock and unlock the jaws. A spindle lock housing (41) is located between the chuck head and the drill to which the chuck head is attached. The drive spindle (36) extends through the spindle lock housing (41). A moveable switch (88) is mounted to the spindle lock housing (41). The switch can be positioned to engage the drive spindle to prevent rotation of the spindle.

Abstract: Improvements made to a router include a switching system which is part of a router handle and which operates the router motor by connecting it to an external electrical power source. In a preferred embodiment, the present switching system comprises the use of a locking lever and trigger in combination to activate the motor, to hold the trigger in a locked-on position to maintain the connection of electrical power to the motor, and to lock the movement of the trigger from occurring before an operator attempts to engage the motor. The switching system may also be combined with a preferred router handle shape in order to make the long term operation of the router and its switching comfortable with extended use.

Abstract: A machine for use underwater and therefor subject to ambient hydrostatic pressure for tapping a pressurized pipeline has an elongated tubular tapping machine body with a boring bar therein that receives a cutter at its lower end. A passageway in a lower end portion of the tapping machine body senses the internal pressure of a pipeline after the pipeline is penetrated by the cutter, the passageway being connected to a pressure equalizer having communication with the interior of the tapping machine body to thereby balance hydraulic forces applied to the boring bar during a tapping operation.

Abstract: A drill for drilling crossties, particularly for use in the railroad sector, comprising a protective enclosure which is formed by a movable portion and by a fixed portion and is suitable to completely cover a chuck of the drill and a drilling bit coupled to the chuck; sliding means which allow the sliding of the movable portion with respect to the fixed portion when the movable portion is placed at an area to be drilled and at the beginning of the drilling operation; and resilient means adapted to bias the sliding of the movable portion with respect to the fixed portion and suitable to be loaded by the penetration of the drilling bit and, at the end of the drilling operation, to be released for the quick disengagement of the bit from a hole formed during the drilling operation.

Abstract: A guard apparatus for a rotational tool prevents direct contact of the cutting regions by an operator of the tool. The rotational cutting tool to which this invention is particularly applicable is the type having at least a shank portion and a toothed region, with the shank portion attachable to a holding attachment device to hold the tool, particularly during operation. The guard apparatus comprises a compressible guard housing for defining a guard circumferential area following a circular path parallel to but greater than a cutting circumferential area defined by the toothed region of the rotational cutting tool; and a first securement device having a first periphery at a first end for abutting the holding attachment device and a flared and tapered periphery at a second end for associating with the compressible guard housing.

Abstract: A protective cover comprising a tool covering portion and a pressure contact tube portion. The pressure contact tube portion is formed on its periphery with a multiplicity of resilient pieces. When the pressure contact tube portion is fitted over a front end portion of a tool holder, the resilient pieces come into pressure contact with a cylindrical case and a chucking nut, both of the tool holder, whereby the protective cover is securely attached to the tool holder.

Abstract: A chuck system for machine tools with a rotating jaw chuck has clamping jaws of the jaw chuck which can be radially adjusted relative to an axis of rotation. The clamping jaws are displaceably mounted in a bearer connected with a drive shaft, and in which engagement openings for the introduction of an adjustment tool for the positioning of the clamping jaws are arranged in the region of the bearer. The bearer is surrounded by a protective sheath that is guided so as to be displaceable in the direction of the axis of rotation. The protective sheath comprises through openings, which are arranged so as to be congruent to the engagement openings in a handling position of the protective sheath, and are arranged so as to be offset to the engagement openings in an operating position of the protective sheath. In the operating position, the clamping jaws are radially surrounded, at least in regions, by the protective sheath.

Abstract: An apparatus and method for securely, mechanically retaining an elongated tool holding arbor in the tapered bore formed in the spindle of a conventional, rotatable, power driven spindle machine. The arbor is mechanically secured to the spindle by bridging it to a key via a threaded fastener. The arbor includes a longitudinal hole formed therethrough having at least first and second concentric passageways of different diameters. The rectangularly shaped key is sized to be operatively received within and set upon shoulders formed by first and second diametrically opposed openings formed through the spindle. The key includes a tapped hole formed centrally, transversely therethrough. The arbor may be inserted into the spindle's bore, and a fastener having an enlarged head and a threaded shaft may be inserted through the arbor's hole with the threaded shaft passing freely through both first and second passageways, and the head passing through the first passageway but not the second.

Abstract: In a machine tool of the present invention, a spindle head rotatably supports a vertical tool spindle. On the spindle head base, a guide mechanism is provided so as to guide the spindle head in mutually orthogonal first and second horizontal directions and in a vertical direction. A workpiece is supported on a workpiece supporting base provided at a front side of the spindle head base. The workpiece is surrounded with a side cover assembly on the workpiece support base so as to define a machining area therewithin. The upper end of the side cover assembly is covered with a top cover assembly. The top cover assembly has a spindle hole through which a nose portion of the spindle head passes so as to permit the tool spindle to reach the machining area, and is flexibly operable to follow the movements of the spindle head in the first and second horizontal directions.

Abstract: This invention relates to a mechanism for controlling rotational direction of a direct current motor and a applying brake thereto and in particular to one including a cathode connected to a negative pole of a battery, an anode connected to a positive pole of the battery, a first directional electrode connected to a negative pole of a motor and normally contacting a brake conducting plate, a second directional electrode connected to a positive pole of the motor and normally contacting the brake conducting plate and a switch which cannot be pressed down before moved sidewards and will, when pressed, cause the first directional electrode to separate from said brake conducting plate on one hand but contact the cathode or anode on the other hand, and to cause the second directional electrode to separate from the brake conducting plate on one hand but contact the anode or cathode on the other hand and will, when released, cause the first directional electrode to contact the second directional electrode via the brak

Abstract: A processing machine comprises at least three powered guides (13,15,27) for movement along Cartesian axes for a support (12) to hold a tool (21) on a horizontal table (11). Motors (14,16,19) for movement along the three guides are connected to an integrated control device in the machine comprising a microprocessor sending to the motors movement signals reading data for position and moving from memories connected thereto. To the microprocessor are also connected a keyboard (130) for sending command signals and means (131) for display of operating information. The tool 21 is a router having its base (70) still attached so that a dust hood (76) incorporated in the base may be employed for dust extraction. A router (21) has a base (70) joined to a body (60) by columns (62,64), the latter being slidable in sleeves (66) in the body (60). A spring (90) between the base (70) and the body of the router serves as a guard for the router bit (76).

Abstract: A hand power tool has a tool holder, and a blocking device for the tool holder, the blocking device being connectable with the tool holder and provided with a key unlockable blocking body which secured the blocking device from undesired withdrawal. When the blocking body is connected with the tool holder it blocks the tool holder from insertion of a tool.

Abstract: An improved collet lock arrangement for a hand-held power tool having a housing is provided. The collet lock arrangement includes a powered rotatable shaft including a base portion and distal end portion defining a collet for adaptably connecting a driver tool attachment thereto and a locking structure for securely locking the shaft to the housing to selectively prevent the shaft from rotating when in a locked position while allowing the shaft to freely rotate in an unlocked position. The locking structure has a locking sleeve coaxially coupled around the shaft for axial movement relative thereto between the locked and unlocked positions, a clamp nut fixedly connected to the housing, and a sleeve guide non-rotatably coupling the locking sleeve to the clamp nut. The clamp nut and sleeve guide are coaxially arranged for coaxially receiving therethrough the shaft and the locking sleeve.

Abstract: The present invention relates to a safety tool having particular, although not exclusive, use in conjunction with machine tools in which a locking device is employed to lock and unlock a movable machine element and wherein a counterweight is employed in conjunction with a cap that fits over the locking device to overcome the inertial focus on the locking device which tends to urge the locking device toward a locked position.

Abstract: A mill suitable for use in an office environment because is constructed to collect particulates produced by the milling process without producing an undue amount of noise by this collection process. An isolation wall substantially eliminates particulate flow from the milling cavity into a motor/control cavity. A positive-pressure air flow through the motor/control cavity further reduces particulate transfer from the milling cavity into the motor/control cavity and draws these particulates into a particulate collection tray.

Abstract: A machine tool (10) comprises a spindle head (11) and a workpiece table (12), in which a first region is provided as a machining side (14) for first workpieces (17) for machining by means of a tool, and in which a second region as a loading side (15) can be loaded with second workpieces (17'), preferably while the first workpieces (17) are being machined. The two regions (14, 15) can be exchanged by means of relative positional change between the spindle head (11) and the workpiece table (12) occurring in the direction of a first coordinate (18) of the workpiece table (12). A spray shielding panel (16), extending in the direction of a second coordinate (19) approximately perpendicular to the first coordinate (18), is provided between the regions (14, 15). The spray shielding panel (16) is configured at least in sections with a variable length in the direction of the second coordinate (19).

Abstract: A portable electromagnetic drilling machine which is provided with an enclosed motor power control cord that connects the machine electrical control panel to a machine electric drive motor for a cutting tool spindle. The provision of an enclosed electric motor power control cord eliminates any wrongful or inadvertent lifting of the machine by said cord, and insures the lifting and carrying of the machine will be carried out by a handle on the machine housing.

Abstract: A drill rig which is equipped with one or more safety mechanisms designed to prevent injuries to rig operators. In a first embodiment, the safety mechanism includes a barrier which is shiftably mounted to the rig and surrounds the drilling tool when the barrier is in the closed position. The barrier includes a key member which must be fitted into a sensor-equipped keyhole in the rig for the drilling tools to operate. A brake may also be connected to the drill spindle to stop rotation until the barrier is closed. In a second embodiment, a sensor is connected to a delay timer. The sensor is also connected to the clutch and transmission and alerts the operator that the clutch is disengaged but the transmission is not in neutral by sounding a warning buzzer after a predetermined time. If the operator fails to actuate a disconnect switch by shifting to a neutral position within a second predetermined time, a second delay timer activates to shut off the engine.

Abstract: A first partition plate is fixed to an upper surface of a rotatable table to separate a work position from a standby position. A second partition plate is mounted to a lower end of a door, and a forked member is mounted to a lower end of the second partition plate. During rotation of the table, the upper end of the first partition plate does not contact the lower end of the forked member. During machining of a work, a cutting fluid splashing in the work position is substantially prevented from reaching the standby position.

Abstract: A pneumatic air feed peck drill adapted to drill in repetitive cycles including a rapid advance phase, a slower drilling phase, and a rapid retract phase. The rapid advance phase ends and the drilling phase begins at a set back position, an adjustable distance from the workpiece, to minimize a drill bit and workpiece damage. The drill includes a drill motor and feed cylinder powered by air to rotate and advance and retract the drill motor. The drill motor and feed cylinder is coupled with an air and mechanical control system including a hydraulic feed control unit having a piston rod coupled with the drill motor to dampen the advance of the drill motor during the drilling phase and to release for rapid retract and advance phases.

Abstract: A portable workpiece-mounted machine tool such as a drill is provided with a permanent-electromagnet attaching unit which has its reversible permanent magnets alternating with nonreversible permanent magnets so that, when electric current is applied to the reversible magnets, they are subjected to polarity reversal which causes flux closure through a workpiece of the reversible and nonreversible magnets in the "on" position and causes flux closure between a reversible and nonreversible magnet in an "off" position.

Abstract: A router including an arrangement for locking the shaft against rotation and preventing power from being supplied to the motor when the shaft is locked. The shaft is locked by movement of a lock bar which traps a flatted portion of the shaft in an appropriately dimensioned slot. A secondary switch in the power path to the motor is controlled by movement of the lock bar. In addition, an indicator lamp connected to the secondary switch is lit when the shaft is locked and the router is still connected to a source of power.

Abstract: A turret tool post for a machine tool has a turret having a plurality of turret faces each equipped with a tool for machining, a turret shaft for rotating the turret, a cam follower provided on the turret shaft, a cam having a cam surface engaged with the cam follower to cause the cam follower to rotate, and an indexing motor for driving the cam to index the turret faces. A straight raceway portion is formed on the cam surface of the cam so that the cam follower is not driven to rotate through a predetermined angle. Also disclosed is an apparatus for controlling indexing of the turret tool post which has a turret controller for controlling the rotation of the indexing motor. The speed of the indexing motor is controlled in accordance with whether a door attached to a cover covering the turret and other elements is open or closed.

Abstract: An apparatus for drilling into energized utility components without having to first de-energize them so as to allow continuous service to consumers is provided. The apparatus includes a drive shaft constructed of an insulating material terminating in a drill chuck and drill bit. The drive shaft is supported by an adjacent rod using pillar block bearing assemblies which allow the uninhibited rotation of the drive shaft. This attachment can be powered by a variety of power units.

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 power tool combination including a hammer drill, an adapter secured to the drill for attaching it to an elongated rod which bears on the floor, a pneumatic cylinder and piston unit mounted between the elongated rod and the drill for applying an uniform external force for moving the power drill into the ceiling, and a coupling member between the pneumatic piston and cylinder unit. The coupling member is rigid for transmitting axial forces therethrough under normal operating conditions but is capable of yielding to absorb abrupt shock forces in the event that the drill encounters an undesirable obstruction in the ceiling, the coupling member including structure for causing it to return to a normal rigid condition after the shock forces have been absorbed.

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: In a preferred form, the dust extraction system is intended to be used in combination with a conventional router. The system includes a plate, one side of which confronts the router's ring base. The plate has a relatively small hole through which the cutter bit extends and an offset larger hole through which dust-laden air is withdrawn. A recessed sub base, preferably of plastic, confronts the other side of the plate, the sub base also having a relatively large hole through which the bit extends. Both the plate and the sub base conform in shape to each other, having portions extending laterally to one side of the router's base. The offset hole in the plate is formed in its laterally extending portion and the recess or cavity in the sub base, forming a passage with the overlying plate, extends to this hole. A sleeve surrounding the hole enables a source of subatmospheric pressure to be connected in order to extract the dust produced by the router's bit.

Abstract: The power tool has a magnetic base with superimposed permanent magnet assemblies. The upper assembly can be moved relative to the lower assembly to shunt or reinforce the magnetic field. When the sensing probe is pushed into the base the electric motor can be switched on to rotate a spindle on which a rotary cutting tool is axially mounted. The tool feed is controlled by a handle which can be mounted on either side of the tool housing. A coolant reservoir on the base has a hose connected to a pump which is connected to a manifold supplying coolant to the interior of the cutting tool. The cutting tool is biased upwardly and pinches off the coolant when the tool is raised from the work.

Abstract: A powered hand tool as a housing containing an air pressure driven motor with an output spindle extending from a work side of the housing and a work device such as a grinding wheel mounted thereon. A guard is mounted with the work side of the housing and at least partially surrounds the work device or grinding wheel. A handle mounted with the housing is provided for an operator to hold the tool. An air pressure flow control valve is mounted in the handle and includes a valve actuator member extending from the handle. An actuating lever is secured to the housing by a removable lever mount located in a locking groove in the housing and held in place by a portion of the guard. With the guard in place the actuating lever mount is positioned for hand actuation upon grasping the handle.

Abstract: The power tool has a magnetic base with superposed permanent magnet assemblies. The upper assembly can be moved relative to the lower assembly to subtract from or reinforce the magnetic field. The upper assembly is somewhat shorter than the lower assembly so even when the upper assembly is positioned to shunt to subtract from the flux of the lower assembly there will be some magnetic flux attracting the base to a ferromagnetic material. When the sensing probe is pushed into the base the electric motor can be switched on to rotate a spindle on which a rotary cutting tool is axially mounted. The tool feed is controlled by a handle which can be mounted on either side of the tool housing.