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| ①,screw of these lengths and shorter shall have undercut heads. ②,Where specifying nominal size in decimals, zeros preceding the decimal and in the fourth decimal place shall be omitted. ③,“R" in the recess size tabulation means regular depth recess. ④,Square recesses incorporate a slight taper on the sides of the recess. This taper can result in loss of penetration gaging depth on finished fasteners due to the build up of plating in the recesses. The recess penetration dimensions specified here are for finished (plated) product. Manufacturers should be advised that they should not use all this tolerance in the heading process, or an out-of-tolerance condition could exist after plating. ⑤,Machine Screw Length of Thread: 1) Sizes No.5 and smaller. Screws of nominal lengths equal to three diameters and shorter shall have full-form threads extending to within one pitch (thread) of the bearing surface of the head, or closer, if practicable. Nominal lengths greater than three diameters, up to and including 1-1/8 in., shall have full-form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal lengths shall, unless otherwise specified, have a minimum length of full-form thread of 1 in. 2) Sizes No.6 and smaller. Screws of nominal lengths equal to three diameters and shorter shall have full-form threads extending to within one pitch (thread) of the bearing surface of the head, or closer, if practicable. Nominal lengths greater than three diameters, up to and including 2 in., shall have full-form threads extending to within two pitches (threads) of the bearing surface of the head, or closer, if practicable. Screws of longer nominal lengths shall have a minimum length of full-form thread of 1.5 in. unless otherwise specified. |
