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The contemporary square drive screw has all but replaced the Robertson screw proper and is commonly referred to as a Robertson because it has practically identical drive dimensions and the same colour identification system, but the contemporary square drive socket has parallel sides rather than tapered.
M6 and M8 triple square drivers End view of M10 triple square screw. The triple-square, also known as XZN, is a type of screw drive with 12 equally spaced protrusions, each ending in a 90° internal angle. The name derives from overlaying three equal squares to form such a pattern with 12 right-angled protrusions (a 12-pointed star).
The tool used to drive a slotted screw head is called a standard, common blade, flat-blade, slot-head, straight, flat, flat-tip, [6] or "flat-head" [7] screwdriver. This last usage can be confusing, because the term flat-head also describes a screw with a flat top, designed to install in a countersunk hole. Before the development of the newer ...
Up-close image of the Robertson square-head screwdrivers. He had originally established his company, the P.L. Robertson Manufacturing Company, in Hamilton, Ontario in 1907. [ 3 ] [ 4 ] Robertson then relocated the company to produce his screws in Milton, Ontario , the following year after the town had given a $10,000 loan for the factory's ...
The recess in the mating part must be designed to accept the particular plow bolt. ASME B18.9 standard recommends a No. 3 head (round countersunk head square neck) plow bolts and No. 7 head (round countersunk reverse key head) plow bolts for new designs. The necessary dimensions for the head styles can be found in the standard. [13] [14] [15]
The pilot drill may be a standard twist drill, another type of drill bit appropriate for the material, or, when the primary purpose is precisely locating a hole, may be made with a short, stiff center drill. The pilot hole also reduces the power needed to turn a large drill bit, and reduces the large bit breakage risk.
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The middle size is the No. 30 size, and all numbers with the 30 in them have a chuck shank size of 9/32" (7mm) diameter. The biggest size is the No. 31, and all numbers with 31 in them have a chuck diameter of 5/16" (8mm) diameter. A '1' in front of the number denotes a return spring fitted.