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ASME CA-1-2014 pdf download

ASME CA-1-2014 pdf download.Metric 12-Point Flange Head Screws.
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 whose diameter is equivalent to 2% of the maximum across flats regardless of feature size as speci- fied 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-point. 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 Runout of the bearing surface with respect to the axis of the body shall be within the specified FIM limits in Table 3. Measurement of FIM shall be made as close to the periphery of the bearing surface as possible while the screw is held in a collet or other gripping device at a distance of one-half of the screw diameter from the underside of the head and screw is rotated at least 360 deg. 13 FILLET The fillet configuration at the junction of the head and shankshall conformto either Type F, as shownin 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 2 be a smooth and continuous curve fairing smoothly into the bearingsurface and the shankwithinthe limits speci- fied. For Type F, no radius in the fillet contour shall be less than R 1 minimum specified in Table 4. 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 5. Screws of nominal lengths equal to or greater than the shortest nominal lengths specified in Table 6 maybe obtained withreduced diameterbody, ifso speci- fied. 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 shoul- der under the head. The diameter, D s , and length, L 2 , 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. 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. 17 STRAIGHTNESS At maximum material condition, the derived median line of the screw body and thread major diameter shall be within a straightness tolerance zone of a diameter equal to 0.006 times length, expressed as a two-place decimal. A gage and gaging procedure for checking screw straightness are given in ASME B18.2.9.

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