ASME B18.6.2 pdf download Square Head Set Screws and Slotted Headless Set Screws (Inch Series)
2.1.3 Head True Position. The axis ofthe head shall be located at true position within a tolerance zone having a diameter equal to 6% of the specified maximum width across flats of the head, relative to the axis of the screw shank, regardless of feature size. For referee purposes, the evaluation shall be made by holding the body in a collet or chuck one bolt diameter from under the head and rotating the part. With the indicator inlinewiththeaxisoftheboltorscrew,findandrecordthe lowestpointon each flatorthe highestpointon each lobe. The true position is one-halfofthe largestabsolute differencebetweenthehighandlowvalues foranyopposingset of flats or lobes.
2.2.1 Measurement. The length of square head set screws shall be measured parallel to the axis of the screw from the intersection of the side of the head with the undersurface to the extreme point.
2.2.2 Length Tolerance. The length tolerance for square head setscrews shall be as shown in Table 2.2.2-1.
2.3.1 Thread Series and Class. The threads on square head set screws shall be Unified Inch coarse, fine, or 8thread series, Class 2A, in accordance with ASME B1.1. For threads with additive finish, the size limits of Class 2A apply before coating, and the thread after coating is subject to acceptance using a basic Class 3A size GO thread gage and a Class 2A thread gage for either minimum material or NO GO.
2.3.2 Thread Gaging. Unless otherwise specified, dimensional acceptabilityofscrewthreads shall be determined based on System 21, ASME B1.3.
2.4 Thread Length Square head set screws shall have complete (full-form) threads extending over the portion of the screw length that is not affected by the point. For the respective constructions, threads shall extend into the neck relief, to the conical underside of the head, or within one thread (as measured with a thread ring gage) from the flat underside of the head. Threads through angular or crowned portions of points shall have fully formed roots with partial crests. Because standard thread gages provide only for lengths of engagement up to 1 1 ∕ 2 times the basic screw diameter, changes in pitch diameter of either or both the external and internal thread may be required for applications involving longer lengths of engagement.
2.5.1 Point Types. When unspecified, square head set screws shall be supplied with cup points. Cup points may beknurled(internallyorexternally) atthemanufacturer’s option. Specifications forcone, dog, half-dog, flat, and oval points are in Table 2.5.1-1.
2.5.2 PointAngles. The external pointangles specified shall apply only to the portions ofthe point that lie below the thread root diameter, as angles within the thread profile may vary due to manufacturing processes.
2.5.3 Dog Points. When the length ofusable (effective) thread is less than the basic screw diameter, dog points shall not be used. Half-dog points shall be used for such screw lengths.
220.127.116.11 Point True Position. The axis of the dog or half-dog points shall be at true position with respect to the axis of the thread within a tolerance zone having a diameter of 0.010 in. for sizes up to and including 3 ∕ 4 (0.750) in. and a diameter of 0.020 in. for larger sizes, regardless of feature size.
2.6 Material Whenamaterialis notspecified, squareheadsetscrews shall be made from case-hardened steel or through- hardened steel at the option of the manufacturer.
2.6.1 Case-Hardened Steel. Unless otherwise speci- fied, case-hardened steel square head set screws shall be low carbon steel, case-hardened to 83 HR15N minimum, with the following case depth:
2.6.2 Through-Hardened Steel. Unless otherwise specified, through-hardened steel square head set screws shall be alloy steel, quenched, and tempered to a hardness of 45 HRC to 53 HRC (450 HV to 560 HV or 428 HB to 532 HB), with a surface hardness at least equal to the core hardness but not exceeding 88 HR15N.