ASME B18.6.3-2003 pdf download

ASME B18.6.3-2003 pdf download.Machine Screws and Machine Screw Nuts.
Recess gaging values are included in the respective dimensional tables, including the reference dimensions of recess diameter, wing width, and total recess depth. The gaging method and specifications for gages are contained in Appendix III.
Recess wobble gages, gaging procedures, and permissible limits are given in Appendix IV.
2.1.4 Slot. The depth of the slot in slotted head screws shall be measured, parallel to the axis of screw, from the top of the head to the intersection of the bottom of the slot with the head surface or bearing surface.
The width of the slot shall be measured perpendicular to the axis of the screw, from the theoretical intersection of the bottom and one side of the slot, to the theoretical intersection of the bottom and the other side of the slot.
Unless specified by the purchaser, the slot width may be slightly tapered from the bottom to the top, or straight, at the option of the manufacturer.
2.1.5 Feature Positional Tolerances. The positional relationship of the heads and driving provisions of screws with respect to the shanks of screws (formerly defined as eccentricity) shall be as follows.
(a) True Position of Head. The axis of the head shall be located at true position relative to the axis of the screw shank within a tolerance zone having a diameter equivalent to 6% of the specified maximum head diameter, or maximum width across flats of hex and hex washer heads, regardless of feature size.
(b) True Position of Recess. The recess in cross recessed head screws shall be located at true position relative to the axis of the screw shank within a tolerance zone having a diameter equivalent to 12% of the basic screw diameter or 0.030 in., whichever is greater, regardless of feature size.
(c) True Position of Slot. The slot in slotted head screws shall be located at true position relative to the axis of the screw shank within a tolerance zone having a diameter equivalent to 12% of the basic screw diameter or 0.020 in., whichever is greater.
2.1.6 Underhead Fillets. Machine screws shall have a definite underhead fillet large enough to ensure that full fastener strength is achieved. The radius of the fillet under countersunk head screws shall be no greater than 40% of the basic screw diameter. The radius of the fillet under truss heads and number 6 sized pan heads shall be no greater than 25% of the basic screw diameter. The radius of the fillet under all other head styles shall be no greater than 15% of the basic screw diameter.
2.2 Length
2.2.1 Measurement. The nominal length of screw L shall be measured, parallel to the axis of screw, from the extreme point to the plane of the bearing surface for screws having perpendicular bearing surface type heads,
(1,) Sizes No. 6 and Larger. 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, unless otherwise specified, have a minimum length of full form thread of 1.50 in.
2.5 Points
Unless otherwise specified, machine screws shall have plain sheared ends. Where so specified, header points shall be as shown in Table 19. Other points or pointing of longer lengths to header point dimensions may require machining.
2.6 Diameter of Body
2.6.1 Machine Screws. The diameter of body on machine screws having other than trim heads shall not be less than the Class 2A thread minimum pitch diameter nor greater than the basic major diameter of the thread.
2.6.2 Trim Head Machine Screws. The diameter of
body on trim head machine screws shall not be less than the Class 2A thread minimum pitch diameter nor greater than the basic major diameter of the thread. Screws not threaded to the head shall have a 0.062 in., minimum length shoulder under the head with diameter limits as specified in the dimensional tables.
2.7 Material
2.7.1 Machine Screws. Unless otherwise specified, machine screws shall be fabricated from carbon steel and shall have a minimum tensile strength of 60,000 psi.
Machine screws, where so specified, may also be made from higher strength steels, corrosion resistant steel, brass, monel, aluminum alloys, or other materials, as agreed upon between the manufacturer and the purchaser.
2.7.2 Machine Screw Nuts. Machine screw nuts are normally supplied in steel, corrosion resistant steel, or brass as specified by the purchaser. Unless otherwise specified, no physical requirements shall apply.