ASME B18.2.5M-2009 pdf free download.Metric 12-Point Flange Screws.
8 WRENCHING HEIGHT
Corners of the 12 points shall be fully formed and re.1s4)nably uniform over the wrenching height, Ku.. Head drive root radius. R4. applies to the entire length of the wrenching height. K, (see Table I).
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 (ill, and width across corners. Gage A shall be placed over the head and shall seat on the flange. Gage H 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 pvsitional tolerance 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, 1). The datum shall be as clese to the head as practicable, hut within 0.51) 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 of the flange shall be conical or slightly rounded (convex). Radius, R,, applies both at the corners and at the flats of the 12 points. The contour of edge at flange periphery. between the maximum flange diameter. 1),. maximum, and the minimum bearing circle diamtier, D. minimum, shall be optional provided that the minimum flange edge thickness, C minimum, is maintained at the minimum bearing circle diameter. D minimum.
12 BEARING SURFACE
The plane formed by the bearing circle shall be per. pendicutar to the axis of the shank, over a length under the head equal to the nominal screw diameter, 0, within the circular runout as specified in Table 3. The measurement of bearing face runout shall be made at the actual bearing clnIe (i.e., at the line of highest points on any radial line, e.g., by use of straight edge anvil). The datum shall be as close to the head as practical, but within 0.5D from the head, and shall be either wholly plain body cw wholly thread major diameter, not including the thread runout or the underhead fillet,
14 BODY DIAMETER
The diameter of the body, D, 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 maximum, specified in Table 1, nor be less than the
minimum body diameter, D。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 spedified, the body diameter, D2, shall be within the limits speified in Table 6. The SCrew shall have a shoulder under the head. The diameter, D., and length, L2, of the shoulder shallbe 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 scTew. Tolerances for screw lengths are specified in Table 7.
16 POINTS
The end of the SCrew shall be chamfered or rounded at the manufacturer’s option from approximately 0.40 mm below the minor diameter of the thread. The length of the point to the first ful-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 permissible. At the manufacturer ‘s option, the end of the screw may have a rounded point of radius, Re as specified in Table 8.