ASME B18.2.5M:2009 pdf download

ASME B18.2.5M:2009 pdf download.Metric 12-Point Flange Screws
1 SCOPE
This Standard covers the complete dimensional and general data for metric series 12-point flange screws recognized as American National Standard. The inclu- sion ofdimensional data in this Standard is not intended to imply thatall products described are stock production items.
2 COMPARISONS WITH ISO STANDARDS
Letter symbols designating dimensional characteris- tics are in accord with ISO 225, except where capital letters have been used instead of lowercase letters in the ISO standards.
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.
12 BEARING SURFACE
The plane formed by the bearing circle shall be per- pendicular 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 measure- ment 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 ofstraight 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 or wholly thread major diameter, not including the thread runout or the underhead fillet.
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.