Abstract: An improved method is provided for controlling a power tool having a rotary shaft. The method includes: disposing an inertial mass in a housing of the power tool, such that the inertial mass is freely rotatable about an axis of rotation which is axially aligned with the rotary shaft; monitoring rotational motion of the power tool in relation to the inertial mass during operation of the power tool; and activating a protective operation based on the rotational motion of the power tool in relation to the inertial mass.

Abstract: An object of the present invention is to provide an electric screwdriver device having a function for determining that a correct tightening operation has been carried out when the tightening operation has taken a time longer than a reference time predetermined for the tightening operation, characterized in comprising a novel means for determining the reference time.

Abstract: A torque tool comprises a torque converter, a power tool for actuating the converter and an attachment adapter, interposed between the torque converter and the power tool, for coaxially and firmly interconnecting the former to the latter. The power tool, having its chuck removed, includes, at its front part, an outwardly extending shaft of tubular configuration incorporating a dead hole of hexagonal cross-section. The torque converter includes several coaxially successive planetary gear assemblies, first of which being driven by a first sun gear. The latter together with a hexagonal shaft form a unitary element. The hexagonal shaft is shaped and sized to fit and drivingly engage the dead hole of the outwardly extending shaft.

Abstract: The present invention aims to provide a screw fastening machine for reliably switching and changing a driving force transmitting path with the seating on a work as a reference. According to the screw fastening machine in which a first pulley is connected to a first driving mechanism for applying high speed low torque drive to a drive shaft, a second pulley is fixed in an integrally rotatable manner to a transmission shaft for connecting the drive shaft, and an endless belt is interposed between the pulleys to obtain a configuration for high speed low torque drive, a second driving mechanism for low speed high torque drive is arranged on an extension of the transmission shaft, and the second driving mechanism performs the drive until a final fastening torque is reached when a screw component is seated on the work and the stall state is achieved, the final fastening torque is always reliably obtained and the work time is reduced without waste.

Abstract: A control system is provided for use in a power tool. The control system includes: a rotational rate sensor having a resonating mass and a controller electrically connected to the rotational rate sensor. The rotational rate sensor detects lateral displacement of the resonating mass and generates a signal indicative of the detected lateral displacement, such that the lateral displacement is directly proportional to a rotational speed at which the power tool rotates about an axis of the rotary shaft. Based on the generated signal, the controller initiates a protective operation to avoid further undesirable rotation of the power tool. The control scheme employed by the power tool may initiate different protective operations for different tool conditions.

Abstract: An impact rotary tool is provided that is switchable between an impact mode where the tool delivers an impacting torque on an output tool and a drill mode where the driver delivers a smooth output on an output tool. The impact rotary tool includes an impact mechanism and a hammer block that in the impact mode is movable parallel to the axis of the driver shaft and delivers reciprocating blows to rotate an anvil and in the drill mode substantially constantly engages the anvil. The impact mechanism includes a stopper that does not contact the hammer block in the impact mode and engages the hammer block in the drill mode to maintain the substantially constant contact between the hammer block and the anvil.

Abstract: A power tool includes a driving unit for performing screw tightening operations; a motor for rotatably driving the driving unit; a trigger switch for turning on and off the motor; and a control circuit, accommodated in a main body of the power tool, for monitoring the screw tightening operations. The control circuit having a screw tightening completion detection unit for detecting completion of a screw tightening operation, a screw tightening count unit for counting the number of detected tightening operations, a screw tightening number setting unit for presetting the number of screws to be tightened, a screw tightening completion notifying unit for notifying completion of the screw tightening operations when the number of detected tightening operations reaches the preset number of screws.

Abstract: An electric impact tool in which a rotating mass rotates in a forward direction to impact upon and transfer torque to an anvil, and rotates in a reverse direction opposite the forward direction in response to such impact. A direction sensor monitors the direction of rotation of the rotating mass, and a controller turns an electric motor on and off during respective forward and reverse rotation of the rotating mass. An energy storing mechanism may be used to absorb energy from reverse rotation of the rotating mass and release the absorbed energy to rotate the rotating mass in the forward direction. A controller may be used to store the angular position of the rotating mass upon each impact and turn off the motor prior to the following impact to avoid energizing the motor during stall.

Abstract: After it is tightened with a snug torque TA, a bolt is tuned by a total turning angle ?S equivalent to the sum of an initial-set turning angle ?A and a corrective additional-turning angle (?B+?C). The corrective additional-turning angle (?B+?C) is the sum of a first corrective additional-turning angle ?B and a second corrective additional-turning angle ?C, the first corrective additional-turning angle ?B being to compensate for a situation where a bolt turning angle ?22 corresponding to the snug torque ?A on an extension line of the bolt tightening torque properties C2 in a late tightening stage II is different from a bolt turning angle ?11 corresponding to the actual snug torque TA, the second corrective additional-turning angle ?C being to compensate for a decrease of an effective bolt axial force that is caused by an existence of the initial tightening stage I.

Abstract: A slaving and blocking device for transmitting a torque from a driving part to a driven part and for stopping the driven part at a torque engaging the driven part has a slaving unit fixable on the driving part fixed against relative rotation and having slaving claws that are offset from one another in a circumferential direction, a roller star wheel located in the slaving unit and connectable to the driven part fixed against relative rotation, clamping bodies located in freewheeling fashion between the slaving claws and points of a star of the roller star wheel, a stationary clamping ring located concentrically to the slaving means and the roller star wheel and having an inner annular face forming a counterpart clamping face for the clamping bodies, and radially displaceable centrifugal force elements located in the roller star wheel such that above a predetermined rpm the force elements clamp the roller star wheel firmly to the slaving means.

Abstract: A power tool includes a grip portion having a vertically extending axis; a main body provided at a top end of the grip portion and having an axis intersecting the vertical axis; a motor; an output portion projecting from the grip portion and rotatingly driven by the motor; a trigger provided for movement along a trigger moving zone; a stopper portion accommodated in the grip portion for protrusion and retraction into and from the trigger moving zone, the stopper portion adapted to selectively make contact with the trigger to thereby limit the maximum pulling amount of the trigger; and a stopper operating portion for operating the stopper portion. The stopper portion is protruded into or retracted from the trigger moving zone by slidingly actuating the stopper operating portion in a crosswise direction perpendicularly intersecting the axis of the main body as viewed from the top.

Abstract: An improved method is provided for controlling a power tool having a rotary shaft. The method includes: disposing an inertial mass in a housing of the power tool, such that the inertial mass is freely rotatable about an axis of rotation which is axially aligned with the rotary shaft; monitoring rotational motion of the power tool in relation to the inertial mass during operation of the power tool; and activating a protective operation based on the rotational motion of the power tool in relation to the inertial mass.

Abstract: The invention is based on a rechargeable battery-operated hand machine tool (10) having an electric drive motor (18) accommodated in a housing (12) and powered by a rechargeable battery (20), which motor is used to drive a tool (16), and having an actuating means (14) for switching the drive motor (18) on and off. A mechanism (22) is provided, which is capable of reducing the discharging of the battery (20) during operation.

Abstract: A damping drive axle includes an output shaft divided into a first portion and a second portion, a mounting seat having a centrally defined hole, a first compartment to correspond to and receive therein the first portion of the output shaft and a second compartment to receive therein the second portion of the output shaft, a hollow cylinder with having a triangle opening to allow an extension of the second portion of the output shaft, multiple columns rotatably received in a side defining the triangle opening to selectively lock/release the second portion of the output shaft, multiple cutouts defined in a bottom face of the cylinder and multiple legs extending out from the bottom face of the cylinder, each leg being sandwiched by two adjacent cutouts and an input device to rotate the sleeve of the hollow cylinder.

Abstract: The invention relates to an electric power tool having a control and/or regulating device for an electric motor. It is provided that the control and/or regulating device (4) is assigned an electronic memory element (5) for at least one operating state of the electric motor (1).

Abstract: A hand-held power tool has a motor output shaft, a tool driver, a torque-limiting unit with which a maximum torque transferred from the motor output shaft to the tool driver is adjustable by an operator; an actuating element that adjusts the torque-limiting unit, and a retaining element with a spring element, wherein the retaining element holds the adjusting element in a position set by the operator, and a spring element exerts a retaining force directed in an axial direction of the tool driver.

Abstract: Threaded member assembling can be performed using a rotational/axial-movement-transmitting unit including an upper frame; a motor held by the upper frame; a female threaded member secured to the upper frame; a male threaded member assembled in the female threaded member, the male threaded member having a rotational/axial-movement-transmitting end at one end, and having a driven rotary end at the other end; and a joint member connecting an output terminal of the motor to the driven rotary end for transmitting rotation torque from the output terminal to the driven rotary end and for allowing axial movement of the male threaded member relative to the motor.

Abstract: A battery-operated driver-drill (1) includes an epicycle reduction gear unit (8) which encases a switchover sleeve (26) having inner teeth (27) and outer teeth (28). The gear unit (8) is rotatably mounted on second and third internal gears (19, 20) and integrally slidably connected with a slide pate (37). By operating the slide plate (37), the switchover sleeve (26) may be slid between a first position, in which the slide plate (37) engages one of the second and third internal gears (19, 20) while engaging axial ridges (29) of a first gear case (5), and a second position, in which the slide plate (37) simultaneously engages both the second internal gear (19) and a first carrier (10) adjacent to the second internal gear (19) while disengaged from the axial ridges (2).

Abstract: A impact power tool includes a motor rotating a drive shaft, an output shaft holding a tool bit, and a hammer coupled to the drive shaft. The hammer is rotatable together with the drive shaft and is engageable with an anvil fixed to the output shaft so as to give a rotary impact to the output shaft. The tool includes a speed commander generating a target speed intended by a user, and a speed detector for detection of a speed of the drive shaft. A speed controller generates a control signal for driving the motor by referring to the target speed and the detected speed. The speed controller provides a detection time frame, and to adopt a predefined pseudo-detection speed as a substitute for the detected speed when no speed detection is available within the detection time frame. Accordingly, even if no speed detection continues, i.e.

Abstract: An improved hand-held fastener driving tool is provided with an adjustable torque limiting control. The tool is portable, and is electrically powered using either a battery pack or a power cord as a power source. The tool drives collated fasteners (e.g., screws) into solid objects. The motor current is measured to determine the amount of torque being applied to a screw by the motor and mechanical drive components. As the screw bottoms out, the motor torque increases to a point where it exceeds the user-adjusted torque limiting control. The motor is automatically turned off at that point, thereby preventing the screw from being stripped.

Abstract: An electrically powered hand tool is disclosed. The tool includes a motor, a power source, a work element and a controller. Various alternative features, embodiments and operative configurations are disclosed. The electrically powered hand tool may be a drill/driver configured to interrupt the rotation of the work element responsive to detection of a torque that exceeds a predetermined torque threshold.

Abstract: An electric screwdriver capable of reducing the reactive force produced on the occasion of a screw tightening work, etc. The electric screwdriver is designed to transmit the rotational driving force of a first motor to the bit through a bit holder, and it includes a flywheel rotatively driven by a second motor in the direction same as the direction of rotation of the bit holder, a brake generating a reactive force in the direction offsetting the reactive force transmitted from the bit to the body casing through the bit holder, by braking the flywheel, and a brake operating mechanism for operating the brake in response to the magnitude of the reactive force transmitted from the bit to the body casing through the bit holder.

Abstract: A hand power tool has an electric motor, which is located in a housing and by way of which a tool insert located in a tool retainer is drivable in rotation, a guard device with which an uncontrollable blockage of the tool insert is detectable via a sensor unit and with which the housing is blockable in its motion; the guard device includes a mechanical unlocking unit that is manually actuatable by a user's action force, and gear is actuatable via an on/off switch for actuating the unlocking unit.

Abstract: In a torque-limiting device, a first end engages a fastener, a second end receives an applied torque, and a magnetic torque limiter transmits the applied torque from the second end to the first end to rotate the first end in conjunction with the second end when the applied torque is less than a predetermined limit.

Abstract: Provide an air driver device which is simple in construction and easily realizable in compact size, and has excellent durability. In an air driver device designed to shut off the supply of compressed air to the air motor 3, by means of a tightening torque control mechanism 6 and a shut-off valve mechanism 7, in case the tightening torque reached the set torque value, and tighten screw members at prescribed tightening force, the tightening torque control mechanism 6 is composed of a clutch unit 61, a driving piston 62 on the back face of which is formed one clutch plate 61a so that the clutch plates 61a, 61b of the clutch unit 61 may move by making rotational differential motions relatively in case the tightening torque reached the set torque value, a cylinder 63 for storing this driving piston 62, a check valve 64 for operating the shut-off valve mechanism 7, in linkage with the driving piston 62 through an oil charged in the cylinder 63, and a torque control member 65 for regulating the set torque value.

Abstract: A pneumatic tool includes a rotor rotatably received in a housing, a driving shank coupled to the rotor, for being rotated by the rotor and by a pressurized air and having one end for driving a fastener. A pressure releasing device may release the pressurized air after the fastener has been tightly threaded onto the object to be fastened. A fluid container is rotatably received in the housing and coupled to the rotor, for partially receiving the driving shank. The driving shank has one or more paddles for being frictionally driven by the container and by the fluid. A pole is slidably engaged through the rotor, and actuated to release the pressurized air when the fastener has been tightly threaded onto the object.

Abstract: A power screwdriver is disclosed having a drive which is coupled via a clutch, disengaging as a function of torque, to a tool drive shaft for driving a tool. The screwdriver comprises an electronic control unit for controlling the drive, and a sensor which is coupled to the electronic control unit in order to switch off the drive when the clutch responds. The electronic control unit is designed for activating the drive with a certain output, preferably with a reduced output, for a limited time after switch-off.

Abstract: A process for controlling and a core drilling machine (1) having an electrical motor (2) for rotational drive of a core drill bit (3) having cutting edges (5) oriented axial to a work piece (4), a feeding means (6) for generating the feed of the core drill bit (3) against the work piece (4) and having a controller (7) for controlling, relative to a first one-to-one control parameter, detected by a sensor (8, 8?) for electrical power consumption (P) or torque (M). A force sensor (9, 9?) is connected to the controller (7) for detecting the contact pressing force (FN) of the core drill bit (3) as the second control parameter.

Abstract: It is an object of the present invention to provide a vibration reducing technique caused by air pressure fluctuations within a power tool. According to the present invention, a representative power tool may comprise a driving motor, a driver and a tool bit. The driving motor drives the driver to cyclically reciprocate. The tool bit is linearly driven by utilizing the pressure of air within the power tool. The air may be compressed by the reciprocating movement of the driver. The power tool changes the rotational speed of the driving motor in the cycle of the reciprocating movement of the driver so that vibration caused in the power tool can be alleviated.

Abstract: A novel air-driven screwdriver is integrally designed to perform three functions, hole drilling, thread tapping and bolt tightening with special characteristic in which a passive inner gear assembly is employed as a driver to replace the clutch as used by the prior art. When the torque reaches at a specified level, the cam in the inner gear assembly will jump up and down, working similarly as the clutch, coupling with the torque spring and torque adjusting mechanism to control the output of the actual torque applied. This design eliminates the attachment of the clutch, shortens the overall length of tool, reduces the total weight and becomes more practical and reliable tool machine.

Abstract: A system, and a method of using a system, for controlled tool operation. The method includes providing a tool used in a force application such as a such torque application. The tool communicates with a controller which can communicate with the tool, and to a display in communication with the tool and the controller. The controller can be programmed with operational information about a tool operation. Information related to the operational information is displayed to a user during use. Service information including at least information about an amount of force applied during use is recorded and stored in the controller. Also disclosed is a computerized system for controlled tool operation which sends operational instructions to the tool before use and retrieves service information from the tool after use.

Abstract: A battery-operated driver-drill (1) includes an epicycle reduction gear unit (8) which encases a switchover sleeve (26) having inner teeth (27) and outer teeth (28). The gear unit (8) is rotatably mounted on second and third internal gears (19, 20) and integrally slidably connected with a slide pate (37). By operating the slide plate (37), the switchover sleeve (26) may be slid between a first position, in which the slide plate (37) engages one of the second and third internal gears (19, 20) while engaging axial ridges (29) of a first gear case (5), and a second position, in which the slide plate (37) simultaneously engages both the second internal gear (19) and a first carrier (10) adjacent to the second internal gear (19) while disengaged from the axial ridges (2).

Abstract: A drilling machine drills foundation holes known as drilled shafts or bored piles with a drilling tool attached to an end of a kelly. The kelly is rotated with a rotary drive. The rotary drive has a first motor, a final drive gear coupled to the kelly so as to rotate with the kelly and a planetary gear set between the first motor and the final drive gear. A second motor is coupled to the ring gear on the planetary gear set. A clutch can also be connected to the ring gear. The rotary drive allows the drilling tool to be rotated at low drilling speeds and, without stopping rotation or shifting gears, removed from the hole and accelerated to high speeds to discharge spoil. A mid-range is also possible, wherein the drilling tool can process fluids in the hole. Another motor and planetary gear set can be coupled to the final drive gear and to the second motor.

Abstract: An intelligent tightening spindle comprises a drive output; a housing adapted to detachably mount to a moving platform of a multi-tool processing station, with the housing substantially enclosing: at least one electric drive motor having an associated servo amplifier; a gear unit operatively connecting the drive motor to the drive output; a spindle measurement transducer operative to monitor at least one of the drive motor, the gear unit, and the drive output; and a measurement data processing unit in communication with the spindle measurement transducer. An output signal port may have signals applied thereto representing measurement data that has been processed by the measurement data processing unit. The measurement transducer and/or the data processing unit may be removably coupled to the spindle via one or more electrical connectors. One or more of the tightening spindles may be used to form a multi-tool processing station.

Abstract: A method of controlling a motor (106) used to drive a screwdriver bit (105) such that screws (107) are seated to the optimum point of grip between the screw (107) and the work piece material. An electronic control circuit controls the speed and output torque of the motor (106). The control system utilizes pulse width modulation (PWM) to control motor (106) speed and torque. The PWM signal controls the duty cycle of the transistors that supply current to the motor (106). The amount of current flowing through the motor (106) coils is proportional to the amount of torque the motor (106) is producing. Motor (106) current is measured as voltage produced across a precision resistor that is in series with the motor (106) coils. As the current in the motor (106) increases, the voltage across the resistor increases (V=IR).

Abstract: This is a system for monitoring and controlling a compressed air driven, pulse tool. The system includes a means for measuring air pressure supplied to a pneumatic pulse tool and converting the air pressure into an electrical signal representative of the air pressure; a programmed microprocessor configured to identify a portion of the signal representative of the air pressure; and a means for controlling the flow of air to the tool. The programmed microprocessor is configured to identify and store timers to be associated with the signal representing the air pressure. The microprocessor is configured to report an acceptable condition if all of the timers are satisfied and the air flow to the tool has been shut-off by the microprocessor. The system is external to the tool.

Abstract: The invention is based on a hand power tool having an electric motor (12) located in a housing (10), via which an insertable tool (16) situated in a tool mount (14) is capable of being driven in a rotating manner, and having a safety device (18) with which a characteristic value for an occurrence of uncontrolled blockage of the insertable tool (16) can be detected via a sensor unit (20), and the movement of the housing (10) can be decelerated. It is proposed that the safety device (18) is formed at least partially by a motor control unit (22), via which the electric motor (12) can be actively decelerated when an occurrence of uncontrolled blockage of the insertable tool (16) is detected.

Abstract: A pneumatic tool includes a housing, a driving mechanism, a rear cap, a direction controller, a speed controller, and an operating member. The housing is formed with a component chamber and an intake passageway. The driving mechanism includes an output shaft rotatable about a rotary axis. The rear cap defines a cap chamber in spatial communication with the component chamber, and has a connecting passageway that intercommunicates the cap chamber and the intake passageway. The direction controller and the speed controller are mounted in the cap chamber for rotation about the rotary axis. The operating member is coupled to the direction controller, is accessible externally of the rear cap and the housing, and is operable to drive rotation of the direction controller about the rotary axis, thereby controlling direction of rotation of the output shaft. The speed controller is operable to vary torque and speed of the output shaft.

Abstract: The present invention relates to a hand-held working tool, such as a setting device used for driving fastening elements such as nails, bolts, pins and the like into a surface, or an at least partially percussive hand-held tool having a housing part (11) and a working mechanism such as a setting or striking mechanism arranged inside the housing of the device and having at least one sensing device (17) for sensing acceleration forces occurring during a setting or striking pulse as well as a handle. For improving this type of hand-held working tool (10) an interface (30) for data communication and data output is arranged on the hand-held working tool.

Abstract: A detector is disclosed that detects impact sounds, e.g., a hammer striking an anvil or oil pulses from an oil unit. The detector may comprise a receiver that selectively converts sound within a narrow frequency range into electric signals. Preferably, the impact sounds fall within the narrow frequency range of the receiver. A processor may be utilized to control the motor in order to stop the rotation of the hammer when a pre-determined number of impact sounds has been detected by the detector. In addition, the operating conditions can be set by a number of methods, including dials, sound sensors, keypads and remote control devices. Further, means for performing maintenance condition status checks are taught.

Abstract: The invention relates to a device for limiting torque to be transferred, having first and second shafts having a longitudinal axis; at least first and second transfer elements arranged coaxial with the longitudinal axis of the first and second shafts, the first transfer element associated with the first shaft and the second transfer element associated with the second shaft; the two transfer elements having substantially complementary engaging faces; at least one elastic element configured to bias the engaging faces of the first and second transfer elements into engagement with each other; wherein an engaging face of the first transfer element has a first engageable contour, and an engaging face of the second transfer element has a second engageable contour, wherein first and second engageable contours each have first and second active angles and a first passive angle.

Abstract: This invention relates to a power tool 1 of the kind having a driven member 15 adapted to releasably hold at least one working element 46. The power tool 1 can operate in either a working mode in which the driven member 15 is driven to enable the working element 46 to perform work, or an adjustment mode, in which the driven member 15 is adjusted to grip or release the working element 46. The power tool 1 includes a selector 17 operable to cause the power tool 1 to operate in either the working or adjustment mode. A power drill 1 is one form of power tool to which the invention is applicable.

Abstract: An electric hand tool apparatus (1) for driving a drill-like tool, which carries out an at least partial rotational movement, has within a housing (2), an electric motor (4) without or free of collector and slip ring, the rpm of which can be controlled by motor control electronics (3), wherein an rpm-dependent clutch (5) for transferring the torque is disposed in a force transfer path from the electric motor (4) to a transmission (6). Optionally, to prevent an excessively high twisting of the housing (2), a sensor (7) is evaluated and the rpm of the electric motor (4) is reduced in order to sever the transfer of force by the rpm-dependent clutch (5).

Abstract: A drill/driver is provided that includes a housing, a collar mounted at a front portion of the housing, a side handle mounting area provided forward of the collar, a handle mounted to the side handle mounting area, and a chuck mounted forward of the side handle mounting area. With the side handle mounted in front of the collar, easier access to the adjusting collar and easier reading of the collar settings is achieved.

Abstract: The invention comprises retrofit kits for power impact tools. The retrofit kits adapt modular control apparatuses to power impact tools that where not originally manufactured to receive a modular control apparatuses. The retrofit kits comprise a modular control apparatus and at least one fastener. The modular control apparatus may be specially manufactured to adapt retrofit tools or an adapter may be included in the kit. Adapters intercept the energy flow to the motor of the tool and re-channels the energy flow through a modular control apparatus, which then controls the flow of energy to the motor. The retrofit kit may include instruction sheets describing and illustrating the methods of using the retrofit kit.

Abstract: A battery-operated driver-drill (1) includes an epicycle reduction gear unit (8) which encases a switchover sleeve (26) having inner teeth (27) and outer teeth (28). The gear unit (8) is rotatably mounted on second and third internal gears (19, 20) and integrally slidably connected with a slide plate (37). By operating the slide plate (37), the switchover sleeve (26) may be slid between a first position, in which the slide plate (37) engages one of the second and third internal gears (19, 20) while engaging axial ridges (29) of a first gear case (5), and a second position, in which the slide plate (37) simultaneously engages both the second internal gear (19) and a first carrier (10) adjacent to the second internal gear (19) while disengaged from the axial ridges (2).

Abstract: The invention is based on a power tool, in particular a hand power tool, with a drive motor (12) disposed in a housing (10) and at least one adjusting device (14, 16), which can be used to durably set at least one parameter of the drive motor (12) and/or of a transmission during an operating phase. The invention proposes that the adjusting device (14, 16) have a reset unit (18, 20), which resets the adjusting device (14, 16) to a starting position depending on at least one operating parameter.

Abstract: A control process for an at least partially axially hammering and rotating electric hand-held machine tool (1) in which an electromagnetic clutch (4) arranged in the flow of force between an electric motor (2) and a tool receptacle (3) is controllably connected to computing device (5) connected to sensors (6a, 6b, 6c), wherein the clutch (4) is repeatedly alternately opened and closed in at least one process step controlled by the computing device (5).

Abstract: In a power impact tool for fastening a screw or a bolt, malfunction that driving of a motor is stopped before the screw or the bolt is fastened completely can be prevented. A fastening judger judged that the fastening operation is completed at least when a torque variation ratio becomes substantially zero and a reference index becomes equal to or larger than a threshold value of trouble judgment. The reference index is a number of impact of a hammer in a term in which the torque variation ratios take positive values, and the threshold value of trouble judgment is calculated with using a maximum value of the torque variation ratio in the term. Since the number of the impact of the hammer due to trouble in fastening operation is smaller than that due to the screw or the bolt is fastened completely, it is possible to distinguish the increase of the torque in the former case from the increase of the torque in the latter case.

Abstract: A drill/driver (e.g. an electric drill) with a screwdriver bit attachment, and a method of controlling the drill/driver, are described. This method of control will greatly reduce the occurrence of stripped screw heads on most types of screws. By periodically stopping insertion of a screw and reversing direction of the screwdriver bit, the screwdriver bit will be reinserted fully back into the screw head. By ensuring the screwdriver bit is always fully inserted in the screw head, the stripping of a screw head will be prevented. This can be easily implemented on most types of powered screwdrivers including the most common device used for screw insertion on a construction job site, the cordless drill/driver.