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 reasonably uniform over the wrenching height, Ku.. Head drive rxt radius, R1, applies to the entire length of the wrenching height, K11. (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 13 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 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, D. The datum shall be as close to the head as practicable, but within O.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 of the flange shall be conical or slightly rounded (convex). Radius, R2, 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, D maximum, and the minimum bearing circle diameter, 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 perpendicular to the axis of the shank, over a length under the head equal to the nominal screw diameter, D, within the circular runout as specified in Table 3. The measurement of bearing face runout shall be made at the actual bearing circle (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, hut within O.5D from the head, and shall be either wholly plain body or wholly thread major diameter, not including the thread runout or the underhead fillet.
13 FILLET
The fillet configuration at the junction of the head and shank shall conform to either Type F, as shown in Table 4,
which also specifies limits, or Type U, as shown in Table 5, at the option of the manufacturer unless the fillet type is specified by the purchaser. The fillet shall be a smooth and continuous curve fairing smoothly into the bearing surface and the shank within the limits specified. For Type F, no radius in the fillet contour shall he less than R1 minimum specified in Table 4.
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, 0, 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,, shall be within the limits specified in Table 6. The screw shall have a shoulder under the head. The diameter, D,, and length, L2, of the 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.