ASME B18.2.5M-2009 pdf download.Metric 12-Point Flange Screws.
8 WRENCHING HEIGHT Corners of the 12 points shall be fully formed and reasonably uniform over the wrenching height, K w . Head drive root radius, R 4 , applies to the entire length of the wrenching height, K w (see Table 1). 9 GAGING OF 12-POINT FLANGE HEAD The head shall be gaged using two ring gages, A and B, to demonstrate the coincidental acceptability of wrenching height, corner fill, and width across corners. Gage A shall be placed over the head and shall seat on the flange. Gage B shall be placed on the top of the head normal to the screw axis. The two gages shall not be in contact (see Table 2). 10 POSITION OF HEAD At maximum material condition, the axis of the 12 points of the head shall be within a positional toler- ance zone of the diameter specified in Table 3 with respect to the axis of the shank over a distance under the head equal to the nominal screw diameter, D. The datum shall be as close to the head as practicable, but within 0.5D from the head, and shall be either wholly plain body or wholly the thread major diameter, not including the thread runout or the underhead fillet. 11 FLANGE The top surface ofthe flange shallbe conical or slightly rounded (convex). Radius, R 2 , applies bothatthe corners and at the flats of the 12 points. The contour of edge at flange periphery, between the maximum flange diame- ter, D c maximum, and the minimum bearing circle diam- eter, D w minimum, shall be optional provided that the minimum flange edge thickness, C minimum, is main- tained at the minimum bearing circle diameter, D w minimum.
14 BODY DIAMETER The diameter of the body, D s , on screws that are not threaded full length shall be within the limits specified in Table 1, unless the purchaser specifies screws with reduced diameter body. For screws threaded full length, the diameter of the unthreaded shank under the head shall neither exceed the maximum body diameter, D s maximum, specified in Table 1, nor be less than the minimum body diameter, D s minimum, specified in Table 4 or 5. Screws of nominal lengths equal to or greater than the shortest nominal lengths specified in Table 6 may be obtained with reduced diameter body, if so specified. Where reduced diameter body (or “Type R”) is specified, the body diameter, D 2 , shall be within the limits specified in Table 6. The screw shall have a shoulder under the head. The diameter, D s , and length, L 2 , ofthe shoulder shall be as specified in Table 6. 15 LENGTH The length of the screw is the distance, parallel to the axis of the screw, from the plane formed by the underhead bearing circle diameter to the extreme end of the screw. Tolerances for screw lengths are specified in Table 7. 16 POINTS The end ofthe screw shall be chamfered or rounded at the manufacturer’s option from approximately 0.40 mm belowthe minordiameterofthe thread. Thelengthofthe point to the first full-formed thread at major diameter, as determined by the distance the point enters into a cylindrical NOT GO major diameter ring gage, shall not exceed U maximum, specified in Table 8. The end of the screw shall be reasonably square with the axis of the screw, and where pointed blanks are used, the slight rim or cup resulting from roll threading shall be permis- sible. At the manufacturer’s option, the end of the screw may have a rounded point of radius, R e , as specified in Table 8.
20 MATERIALS AND MECHANICAL PROPERTIES 20.1 Steel Unless otherwise specified, steel screws shall conform to the requirements ofASTM F568M, PropertyClass12.9 or ASTM A 574M. 20.2 Corrosion-Resistant Steels Unless otherwise specified, corrosion-resistant steel screws shall conform to the requirements of ASTM F 738M. 20.3 Nonferrous Metals Unless otherwise specified, nonferrous screws shall conform to the requirements of ASTM F 468M. 21 IDENTIFICATION SYMBOLS Markings shall be raised or recessed on the top of the head or raised on the top of the flange unless otherwise specified by the purchaser. Markings shall be legible to the unaided eye with the exception of corrective lenses. When raised, markings shall projectnotless than 0.1 mm for M14 and smaller screws, and 0.3 mm for M16 screws, above the top surface of the head or flange; and total head height (head plus markings) shall not exceed the specified maximum head height, K maximum, plus 0.1 mm for M5 and M6 screws, 0.2 mm for M8 and M10 screws, 0.3 mm for M12 and M14 screws, and 0.4 mm for M16 screws.