Abstract: A method and apparatus for tightening an assembly including a pre-load indicating fastener is disclosed. Pre-load indicating fasteners are generally tightened until a crushable element, forming a portion of the pre-load indicating fastener, is plastically deformed. The present invention permits such fasteners to be tightened until the crushable element of the fastener is completely deformed. This reduces the problem of relaxation generally associated with such fasteners. The present invention permits joints including such fasteners to be tightened by automatic tightening systems, if so desired. The assembly is tightened until the crushable element of the fastener is fully plastically deformed and elastic deformation of the joint has commenced. Sensing means are provided in the automatic tightening system to enable detection of this point and to automatically stop the tightening system when this point is reached.

Abstract: A power tool speed and torque control mechanism is disclosed. An improved clutch assembly is provided for power tools of the type having a high speed/low torque mode for rapidly engaging a threaded fastener and a low speed/high torque mode for tightening the fastener. The clutch assembly includes a wrap spring clutch having two springs.

Abstract: A quick-acting panel fastener assembly for joining a panel to a sub-structure is disclosed. The fastener assembly includes a sleeve bolt, a grommet assembly which is attached to the panel and a receptacle assembly which is attached to the sub-structure. The sleeve bolt passes through the grommet assembly and engages the receptacle assembly thereby joining the panel and the sub-structure. The grommet assembly includes a retainer ring which engages a groove in the sleeve bolt when it is in its withdrawn position so that the sleeve bolt is retained in the panel and remains in its withdrawn position when the panel is disengaged from the sub-structure.

Abstract: A self-contained impact wrench having an adaptive control system for determining the yield point or some similarly significant tightened condition of a fastener assembly by detecting a signal representative of the forward rotation angle of the fastener assembly is disclosed. One embodiment utilizes a computed signal of time over a fixed interval of forward rotation angle, as an estimate of the torque applied by the impact wrench, and the torque estimate vs. rotation angle curve is differentiated to obtain the gradient thereof. Successive gradient values are stored and compared, and when the present gradient value has attained a predetermined relationship relative to a stored value of a gradient in a tightening region of the curve, further tightening of the fastener assembly is discontinued. This ensures that the yield point or other similarly significant tightened condition of the assembly has been reached.

Abstract: A fastener which includes an unthreaded bolt member having two groups of grooves formed therein is disclosed. All the grooves within each group have the same depth. The group of grooves furthest from the workpiece have a greater depth than the group of grooves adjacent to the workpiece, thus permitting a more uniform load distribution along the shank of the bolt.

Abstract: A fatigue resistant bolt, and method for making same, is disclosed. Bolts which are tightened to very high loads and are subjected to a dynamic environment are particularly subject to fatigue failure. It has been found that a bolt with fatigue resistant properties may be manufactured if its threads are formed while it is subjected to its design load. In another embodiment of the invention it has been found that the fatigue properties of the fillet at the bolt head and shank juncture may be significantly increased if the fillet is cold worked while the bolt is subjected to its design load.

Abstract: A hand operated tightening system for tightening a fastener assembly to its yield point is disclosed. The system includes a wrench for applying torque to a threaded fastener and means for mechanically differentiating the magnitude of torque applied with respect to the degree of rotation of the fastener. This differential represents the slope of the torque-rotation curve of the particular fastener assembly being tightened and is a constant while in the elastic range. Means are provided to signal a change in the magnitude of the differential so as to indicate when the yield point of the assembly has been reached. In one embodiment, the differentiating means emits an audible signal which is used to indicate that the yield point has been reached.

Abstract: A self-locking threaded fastener of the type having a resilient thermoplastic resin patch bonded to the thread surface and a method and apparatus for making such fasteners are disclosed. The fastener is heated to a temperature in excess of the plastic melting temperature by induction heating coils and powder is thereupon deposited on the surface of the threads over a predetermined area by gravity feed. Rolling pressure is then applied to the plastic material to form the patch, packing the material between the thread flanks and confining the height of the patch to a controlled radial height above the thread crests. The controlled radial height of the patch is within the normal envelope of the basic major diameter of the fastener thread.

Abstract: The preferred embodiment of the invention disclosed in this application includes a wrench, for example an operator powered wrench, for tightening a fastener assembly by the incremental application of tightening force. Also included is a control circuit for detecting a phenomena indicating that the joint assembly in which the fastener assembly is installed has been tightened to its yield point. The control circuit further includes checking means for determining that the fastener assembly is being tightened to assure that when the phenomena is detected, the joint assembly has been tightened to the yield point.

Abstract: An impact wrench having an adaptive control system for determining the yield point or some similarly significant point of a fastener assembly by detecting a signal representative of the peak deceleration of the hammer, one embodiment of which is the peak recoil value of the hammer after impacting with the anvil of the wrench, and a signal representative of the angular displacement of the output shaft of the wrench. Yield of the fastener is determined when the respective magnitudes of successive deceleration signals do not exceed the magnitude of a previously stored maximum deceleration signal by a predetermined fixed amount. Upon attaining the yield point or other similarly significant point, the wrench may be allowed to rotate the fastener an additional preselected number of degrees before shutting off.

Abstract: A blind fastener assembly includes a pin, an expander and a sleeve. The pin and expander may include, in one configuration, mating threads for drawing the sleeve axially over the expander toward the blind side of a workpiece, or the pin may be a pull-type wherein the portion of the pin opposite from the blind side end has pull grooves which are adapted to be gripped by a conventional pull gun. The sleeve is a tubular member having a portion of varying radial wall thickness between the ends thereof. The expander extends through aligned holes in the workpieces and has a tapered nose surface proximate the reduced thickness portion of the sleeve. When an axial force is exerted on the pin, the sleeve is forced over the tapered nose surface on the expander toward the blind side of the workpiece and is expanded in diameter.

Abstract: A tightening and control system is disclosed for automatically tightening a blind fastener assembly to a desired tightened condition in a workpiece, where the assembly is of the type which exhibits more than one installation region on a graph of two tightening characteristics during a complete tightening cycle. Typical of such assemblies are the types which first form an outwardly flared bulb adjacent the blindside surface of a workpiece and thereafter are tightened against the blindside surface to a predetermined clamp load condition. Such fasteners typically exhibit a curve of two related input tightening characteristics, such as torque and rotation, torque and time, or force and stroke. Each curve has a bulb forming region characterized by a generally linear portion followed by a marked drop off in the slope, an intermediate region, and a tightening region having a somewhat similar shape to the bulb forming region.

Abstract: A tightening and control system is disclosed for automatically tightening a fastener to a predetermined tightened condition in a workpiece, where the fastener is of the type which exhibits more than one installation region on a graph of two tightening characteristics during a complete tightening cycle. Typical of such fasteners are thread tapping fasteners, such as thread-cutting or thread forming types, which first generate a mating thread in a workpiece material and thereafter are tightened in the workpiece to a predetermined load condition. Such fasteners typically exhibit a curve of two related input tightening characteristics, such as torque and rotation, having a thread forming region characterized by a generally linear portion followed by a marked drop off in the slope, an intermediate region having several possible characteristic shapes, and a tightening region having a somewhat similar shape to the thread forming region.

Abstract: A blind fastener assembly includes a pin, an expander and a sleeve. The pin and expander may include, in one configuration, mating threads for drawing the sleeve axially over the expander toward the blind side of a workpiece, or the pin may be a pull-type wherein the portion of the pin opposite from the blind side end has pull grooves which are adapted to be gripped by a conventional pull gun. The expander extends through aligned holes in the workpiece and has a tapered nose surface at the blind side end adjacent a reduced thickness cylindrical portion which extends axially to a stop shoulder. The shoulder provides a transition to a normal thickness cylindrical portion which extends through the workpiece holes. The sleeve is a tubular member with a portion of its length having a normal radial thickness and a portion having a reduced radial thickness.

Abstract: A vibration resistant threaded fastener such as a set screw and method of forming the fastener wherein the load bearing flank of the thread surface of the screw is provided with a series of serrations. Each serration is formed with an inclined ramp terminating in a buttress forming a skewed angle with the radius of the fastener. The ramp surface is inclined in the direction of tightening the fastener so that the buttress presents a surface tending to act against rotation of the fastener to preclude its loosening. In forming the vibration resistant fastener a pair of flat thread roll dies may be used. Each die is provided with a mating segment near the end of the effective thread forming portion of the die having a configuration designed to impart the ramp and buttress serrations on the load bearing flank of the fastener rolled between the dies.

Abstract: A retention and release mechanism utilizes a collet with deflectable fingers to allow assembly of the mechanism onto an object which is to be retained. Movement of the object toward the mechanism causes a force to be exerted on the bottom end of a plunger and movement of the plunger, which is coupled to a lockpin by a plurality of spherical balls and a split ring, from a released to a retained position. In the retained position, the balls secure the lockpin in a fixed position relative to the collet while mating tapered surfaces at the ends of the collet fingers and the lockpin cooperate to retain the object to which an expendable bushing has been attached, the bushing being part of the mechanism. To release the object, a force must be exerted on the top end of the plunger to move it to an axial position wherein the balls are released from their fixed position relative to the collet and the mating tapered surfaces move away from each other.

Abstract: A self-locking threaded fastener of the type having a resilient thermoplastic resin patch bonded to the thread surface and a method and apparatus for making such fasteners are disclosed. The fastener is heated to a temperature in excess of the plastic melting temperature by induction heating coils and powder is thereupon deposited on the surface of the threads over a predetermined area by gravity feed. Rolling pressure is then applied to the plastic material to form the patch, packing the material between the thread flanks and confining the height of the patch to a controlled radial height above the thread crests. The controlled radial height of the patch is within the normal envelope of the basic major diameter of the fastener thread.

Abstract: A two piece grommet assembly comprising an inner and an outer member wherein each member has an enlarged head at one end formed to bear upon opposite sides of a panel skin. The outer member has a recessed area intermediate its ends and the inner member has a weakened section on the shank portion which is adapted to deform into the recessed section of the outer member upon the application of opposing axial force on the two members. The weakened section of the inner member is comprised of a reduced cross-sectional thickness portion which collapses upon the application of axial force, causing the reduced thickness portion to flow inwardly into intimate contact with the recess in the outer member, locking the members together in the panel skin.

Abstract: A preferred embodiment of the invention disclosed herein relates to a method of and tightening system for tightening a joint assembly including a fastener system to a yield point of one of the members in the assembly. According to the method, torque is applied and rotation is imparted to a fastener member, and the torque and rotational displacement of the fastener are determined at predetermined increments of rotation for use in determining the area between successive increments of rotation under the Torque-Rotation curve which could be plotted. The incremental areas are compared to determine when some member in the joint assembly has been tightened to its yield point or some similarly significant point. The tightening system includes a wrench and a control system associated with the wrench including measuring systems for developing a first signal representative of the torque applied to the fastener and a second signal representative of the rotation of the fastener.

Abstract: The preferred embodiment of the invention disclosed herein relates to a method of and a tightening system for tightening a joint assembly including a fastener system to a yield point of one of the members in the assembly. According to the method torque is applied and rotation is imparted to a fastener member and the instantaneous slope of the Torque-Rotation curve which could be plotted is determined between successive increments of rotation of the fastener member. Each instantaneous slope is compared with the preceding instantaneous slope to determine the change in the slope of the curve. When the instantaneous slope of the curve decreases a predetermined consecutive number of times equal to a predetermined span of rotation divided by the interval between successive increments of rotation, tightening is discontinued.