A drive system with full surface drive contact. The drive system tends to maximize the surface contact pattern or area at typical bit-recess reaction (drive) torque values, thereby tending to minimize bit-recess surface contact stresses, coating damage, recess ream and premature bit fatigue failure.

A drive system including a bit with a bit end configured to provide targeted frictional engagement with a fastener. The bit end has an outer leading wall tapered with respect to the bit end longitudinal axis at a leading wall angle selected from leading wall angle values ranging within a leading wall angle tolerance band and the fastener has an inner recess wall tapered with respect to the fastener longitudinal axis at a recess wall angle selected from recess wall angle values ranging within a recess wall angle tolerance band, wherein the leading wall angle values within the leading wall angle tolerance band and the recess wall angles values within the recess wall angle tolerance band do not overlap when the outer leading wall contacts the inner pilot recess wall at a targeted focal area to achieve a desired level of frictional engagement between the pilot end and the fastener.

The invention provides a screw in which the screw head (1) has a slot (2) in the upper surface of the screw head, an upper peripheral wall (9) of regular planform extending down from the rim of the slot into the screwhead, the upper peripheral wall (9) being generally aligned with the axis of the screw to form a recess (3), a sloping transition surface (15), extending downwardly and inwardly with respect to the lower edge of the upper peripheral wall (9), and a further recess (11) extending downwardly from the lower edge of the sloping transition surface (15), in which the dimensions of the screw head are such that when the screwhead is engaged by a tool (6) having upper (16) and lower (17) engagement sections, and in which the upper engagement section (16) extends downwardly with respect to the axis of the screw to which the tool is to engage and the lower engagement section (17) extends further downwardly, and in which there is at least one protrusion (or rib) (21) on the inside wall (12) of the further recess (11), so that there is a stick fit between the protrusion (21) on the inside wall (12) of the further recess (11) and the lower engagement section (17) of the tool (6).

A fastener is provided to be pre-assembled to a substrate. The fastener comprises a shaft having a first end and a second end opposite the first end, and a thread portion adjacent to the second end; a head disposed on the first end; and a unidirectional retention member between the head and the thread portion. The unidirectional retention member is configured to pass through a mounting hole of the substrate in one direction such that the fastener is retained on the substrate once the unidirectional retention member has passed through the mounting hole.

A bit cutter is used to cut a bit, where the bit cutter matches the configuration of a recess in a corresponding fastener. The resulting bit contacts the top of the recess of a fastener, along a plurality of lines of contact. The fact that the contact is along a plurality of lines, as opposed to mere points, provides for improved frictional adhesion or stick fit between the bit and the fastener.

A fastener system includes a fastener and a driver, each of which have three alternating lobes and troughs that define the drive surfaces. Each alternating lobes and troughs is defined by an outer radius portion, a drive side transition, an inner transition radius, and a reverse drive portion. The fastener recess and the driver each also have a side wall defined by the outer transition radius that tapers at a taper angle relative to a rotational axis. The fastener side wall may taper at about 60. The driver side wall may taper at about 60. Alternatively, the driver side wall may taper at an angle at least 10 less than the taper angle of the recess side wall, such as 42. The drive side transition defines a drive angle, which may be between 0 and 5.

A drive system with full surface drive contact. The drive system tends to maximize the surface contact pattern or area at typical bit-recess reaction (drive) torque values, thereby tending to minimize bit-recess surface contact stresses, coating damage, recess ream and premature bit fatigue failure.

This invention relates to a plug bolt (1) and more specifically, but not exclusively, to a plug bolt (1) for use with a device such as an air-cooled heat exchanger. One of the problems with conventional plug bolts is that when the bolts are over tightened, it may damage the thread of the device it is installed in. Once the thread is damaged it has to be repaired, causing downtime, or where it is not possible to repair, the device will have to be replaced. It is accordingly an object of this invention to provide a plug bolt (1) which, at least partially, alleviates some of the problems associated with the prior art. It is envisaged that the invention will provide a plug bolt (1) which fails before it is overtightened to prevent damage, is easy to manufacture, and is as simple to use as the prior art.

A torque transmission driver has a main body having a first end portion adapted to receive and transmit torque from a torque generation source and a second end portion opposite the first end portion having a series of four, five or six lobes and troughs about a rotational axis, and a drive side transition between each lobe and trough on at least one side of each lobe forming a negative drive angle between 2 and 10. A fastener corresponding to the torque transmission driver has a drive end portion adapted to engage the torque transmission driver and a lead end portion adapted to fasten the fastener, the drive end portion having a series of four, five or six lobes and troughs about a rotational axis, and a drive side transition between each lobe and trough on at least one side of each lobe forming a negative drive angle between 2 and 10.

To provide a tensioning device capable of tensioning a bolt from a bolt head side while suppressing increase in the number of components. A tensioning device is configured to apply upward tension to a bolt fastened to a fastened member H. A first male thread portion is formed on an outer circumferential surface of a head of the bolt. The tensioning device includes a connection member having a first female thread portion to be threadly engaged with the first male thread portion, a tensioning mechanism for tensioning the bolt via the connection member in a state where the first male thread portion is threadly engaged with the first female thread portion, and a tension bearer which is disposed around an outer circumference of the connection member, and bears a reaction force applied from the fastened member H in tensioning performed by the tensioning mechanism.