Bsi bs a 254, bs a 255, bs a 256, bs a 257, bs a 258, bs a 259 1976 (2008)

BRITISH STANDARD AEROSPACE SERIES BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259 1976 Incorporating Amendment Nos 1 and 2 Hexagonal head titanium alloy bolts 160 000 lbf/in2 (1100 MPa) UDC[.]

BRITISH STANDARD AEROSPACE SERIES Hexagonal head titanium alloy bolts 160 000 lbf/in2 (1100 MPa) UDC 629.7.02:621.882.211:669.295.5 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Incorporating Amendment Nos and Confirmed April 2008 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Foreword This British Standard has been prepared to provide a range of 160 000 lbf/in2 (1 100 MPa) to 180 000 lbf/in2 (1 250 MPa) titanium alloy bolts with UNJ profile threads and close tolerance shanks for aerospace use The lengths of the bolts are in fractional increments When considering the use of cadmium plated titanium bolts, attention is drawn to DARD Technical Circular No 292 which recommends certain limitations on their use A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This British Standard, having been approved by the Aerospace Industry Standards Committee, was published under the authority of the Executive Board on 31 March 1976 © BSI 02-2000 The following BSI references relate to the work on this standard: Committee reference ACE/12 Draft for comment 72/37963 DC ISBN 580 08706 This document comprises a front cover, an inside front cover, pages i and ii, pages to and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover Amendments issued since publication Amd No 2647 2812 Date of issue July 1978 April 1979 Comments Indicated by a sideline in the margin BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Contents Page Foreword Inside front cover Scope References General requirements Example of call up Identification and marking Appendix A Table for the conversion of inches to millimetre equivalents Figure — Basic dimensions Figure — Alternative bolt head manufacturers option Washer face and/or dimpled head Figure — Typical disposition of the various markings Table — Dimensions (standard shank diameters) Table — Oversize shank diameters Table — Material Table — Bearing length L, overall length E and dimension M © BSI 02-2000 i ii blank BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Scope This British Standard specifies the materials, dimensions, finish and inspection requirements for titanium alloy bolts with hexagonal heads and UNJ thread for aerospace use References This standard makes reference to the following British Standards and Ministry of Defence publications: BS 4084, Unified screw threads of “UNJ” basic profile BS A 101, General requirements for titanium bolts BS A 242-245, Hexagonal castle nuts (of class 3B UNJ thread) BS TA 28, Forging stock and wire of titanium-aluminium-vanadium alloy (tensile strength 100–1 300 MPa) (limiting ruling section 20 mm) DTD 904, Cadmium plating DTD 942, Anodising of titanium and titanium alloys DEF STAN 91–19/1, Lubricant, solid film, heat cured The latest editions of these standards shall be used NOTE The values in imperial units are to be regarded as the standard The table in Appendix A provides millimetre equivalents of inch dimensions and is based on the tables in BS 350 “Conversion factors and tables” General requirements 3.1 The bolts shall be manufactured, inspected and tested in accordance with the requirements of BS A 101 3.2 All bolts shall conform to the dimensions and tolerances given in Table 1, Table and Table 4, and Figure and Figure Unless otherwise specified, the dimensions are those before the application of surface treatment The material requirements shall be as specified Figure — Basic dimensions © BSI 02-2000 Figure — Alternative bolt head manufacturers option Washer face and/or dimpled head BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 (1) Table — Dimensions (standard shank diameters) 03 04 05 06 07 08 10–32 1/4–28 5/16–24 3/8–24 7/16–20 1/2–20 13 Diameter code 03 04 05 06 07 08 0.1900 0.2500 0.3125 0.3750 0.4375 0.5000 14 15 0.1895 0.2495 0.3120 0.3745 0.4370 0.4995 0.125 0.140 0.171 0.203 0.234 0.265 0.1890 0.2490 0.3115 0.3740 0.4365 0.4990 16 17 R Min 0.110 0.125 0.156 0.188 0.219 0.250 ÌA Type BS A 257 (3) Max × Pitch Min 0.1895 0.2495 0.3120 0.3745 0.4370 0.4995 T 0.1885 0.2485 0.3110 0.3735 0.4360 0.4985 Ref Min 0.063 0.071 0.083 0.083 0.100 0.100 0.381 0.443 0.506 0.615 0.631 0.757 Table — Dimensions (standard shank diameters) D Max Type: BS A 254 BS A 255 BS A 256 (2) Max Min Diameter Nominal Nominal shank Code thread diameter size UNJF ÌA Max Min 0.025 0.025 0.025 0.025 0.030 0.030 0.015 0.015 0.015 0.015 0.020 0.020 18 19 ÌG ÌJ ÌK (9) 0.073 0.083 0.104 0.125 0.146 0.167 Min ± 0.020 0.130 0.184 0.239 0.302 0.354 0.416 10 11 B Max 12 C Min Min 0.376 0.439 0.502 0.564 0.690 0.752 0.367 0.430 0.492 0.553 0.679 0.741 0.419 0.491 0.561 0.631 0.775 0.845 20 21 22 23 24 25 (8) N ÌP S ÌU W +0.008 –0 0.063 0.063 0.063 0.063 0.079 0.079 +0.005 –0 0.047 0.047 0.047 0.047 0.063 0.063 +0 –0.012 0.020 0.020 0.020 0.020 0.024 0.024 0.357 0.420 0.482 0.543 0.669 0.731 +0.015 –0 0.073 0.083 0.104 0.125 0.141 0.167 ± 0.010 0.19 0.25 0.31 0.38 0.44 0.50 (1) The screw threads shall conform to the basic thread form, diameter and related pitches specified in BS 4084, “Unified screw threads of “UNJ” basic profile” (class 3A) (2) Before application of protective treatment (3) After application of protective treatment (4) The runout of the thread shall comply with the relevant requirements of SBAC publication RS 678 (5) See Table for length dimensions “L”, “E” and “M” (6) To suit hexagonal castle nuts specified in BS A242–245 (7) Holes shall have the sharp edges removed (8) Kmax = Bmin (9) For diameter codes 03, 04 and 05 the tolerance shall be +0.005 For diameter codes 06, 07 and 08 the tolerance shall be +0.0070 Table — Oversize shank diameters All dimensions in inches Diameter code Nominal thread size UNJF 03 04 05 06 07 08 10–32 1/4–28 5/16–24 3/8–24 7/16–20 1/2–20 First oversize (code X) ÌA Type: BS A 254 BS A 255 BS A 256 (2) Max Min 0.2026 0.2651 0.3276 0.3901 0.4526 0.5151 0.2021 0.2646 0.3271 0.3896 0.4521 0.5146 ÌA Type: BS A 257 (3) Max 0.2026 0.2651 0.3276 0.3901 0.4526 0.5151 Min 0.2016 0.2641 0.3266 0.3891 0.4516 0.5141 Second oversize (code Y) ÌA Type: BS A 254 BS A 255 BS A 256(2) Max Min 0.2182 0.2807 0.3432 0.4057 0.4682 0.5307 0.2177 0.2802 0.3427 0.4052 0.4677 0.5302 10 ÌA Type: BS A 257 (3) Max 0.2182 0.2807 0.3432 0.4057 0.4682 0.5307 Min 0.2172 0.2797 0.3422 0.4047 0.4672 0.5297 © BSI 02-2000 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Basic BS number BS A 254 BS A 255 BS A 256 BS A 257 BS A 258 BS A 259 © BSI 02-2000 Type of material Titanium alloy to BS TA 28 Table — Material Mechanical properties Protective treatment 0.2 % proof stress: not less None than 140 000 lbf/in2 (970 MPa) Anodized in accordance with DTD 942 Tensile strength: not less than Anodized in accordance with DTD 942 + MoS 160 000 lbf/in2 (1 100 MPa) in accordance with DEF STAN and not more than 91–19/1 180 000 lbf/in2 (1 250 MPa) Cadmium plated in accordance with DTD 904, on nickel strike Elongation on 5.65 Ỉ S0: Not yet allocated not less than % Not yet allocated BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Table — Bearing length L, overall length E and dimension M NOTE Unallocated diameter/length codes shall not be used All dimensions in inches 10–32 UNJF 1/4–28 UNJF 5/16–24 UNJF Dia./length L M E Dia./length L M E Dia./length L M E ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 code code code 0301 0302 0303 0304 0305 0.062 0.125 0.188 0.250 0.312 0.468 0.531 0.594 0.656 0.718 0.333 0.396 0.459 0.521 0.583 0401 0402 0403 0404 0405 0.062 0.125 0.188 0.250 0.312 0.530 0.593 0.656 0.718 0.780 0.365 0.428 0.491 0.553 0.615 0501 0502 0503 0504 0505 0.062 0.125 0.188 0.250 0.312 0.593 0.656 0.719 0.781 0.843 0.423 0.486 0.549 0.611 0.673 0306 0307 0308 0309 0310 0.375 0.438 0.500 0.562 0.625 0.781 0.844 0.906 0.968 1.031 0.646 0.709 0.771 0.833 0.896 0406 0407 0408 0409 0410 0.375 0.438 0.500 0.562 0.625 0.843 0.906 0.968 1.030 1.093 0.678 0.741 0.803 0.865 0.928 0506 0507 0508 0509 0510 0.375 0.438 0.500 0.562 0.625 0.906 0.969 1.031 1.093 1.156 0.736 0.799 0.861 0.923 0.986 0311 0312 0313 0314 0315 0.688 0.750 0.812 0.875 0.938 1.094 1.156 1.218 1.281 1.344 0.959 1.021 1.083 1.146 1.209 0411 0412 0413 0414 0415 0.688 0.750 0.812 0.875 0.938 1.156 1.218 1.280 1.343 1.406 0.991 1.053 1.115 1.178 1.241 0511 0512 0513 0514 0515 0.688 0.750 0.812 0.875 0.938 1.219 1.281 1.343 1.406 1.469 1.049 1.111 1.173 1.236 1.299 0316 0317 0318 0319 0320 1.000 1.062 1.125 1.188 1.250 1.406 1.468 1.531 1.594 1.656 1.271 1.333 1.396 1.459 1.521 0416 0417 0418 0419 0420 1.000 1.062 1.125 1.188 1.250 1.468 1.530 1.593 1.656 1.718 1.303 1.365 1.428 1.491 1.553 0516 0517 0518 0519 0520 1.000 1.062 1.125 1.188 1.250 1.531 1.593 1.656 1.719 1.781 1.361 1.423 1.486 1.549 1.611 0321 0322 0323 0324 0325 1.312 1.375 1.438 1.500 1.562 1.718 1.781 1.844 1.906 1.968 1.583 1.646 1.709 1.771 1.833 0421 0422 0423 0424 0425 1.312 1.375 1.438 1.500 1.562 1.780 1.843 1.906 1.968 2.030 1.615 1.678 1.741 1.803 1.865 0521 0522 0523 0524 0525 1.312 1.375 1.438 1.500 1.562 1.843 1.906 1.969 2.031 2.093 1.673 1.736 1.799 1.861 1.923 0326 0327 0328 0329 0330 1.625 1.688 1.750 1.812 1.875 2.031 2.094 2.156 2.218 2.281 1.896 1.959 2.021 2.083 2.146 0426 0427 0428 0429 0430 1.625 1.688 1.750 1.812 1.875 2.093 2.156 2.218 2.280 2.343 1.928 1.991 2.053 2.115 2.178 0526 0527 0528 0529 0530 1.625 1.688 1.750 1.812 1.875 2.156 2.219 2.281 2.343 2.406 1.986 2.049 2.111 2.173 2.236 0331 0332 0334 0336 0338 0340 1.938 2.000 2.125 2.250 2.375 2.500 2.344 2.406 2.531 2.656 2.781 2.906 2.209 2.271 1.396 2.521 2.646 2.771 0431 0432 0434 0436 0438 0440 1.938 2.000 2.125 2.250 2.375 2.500 2.406 2.468 2.593 2.718 2.843 2.968 2.241 2.303 2.428 2.553 2.678 2.803 0531 0532 0534 0536 0538 0540 1.938 2.000 2.125 2.250 2.375 2.500 2.469 2.531 2.656 2.781 2.906 3.031 2.299 2.361 2.486 2.611 2.736 2.861 0342 0344 0346 0348 0350 2.625 2.750 2.875 3.000 3.125 3.031 3.156 3.281 3.406 3.531 2.896 3.021 3.146 3.271 3.396 0442 0444 0446 0448 0450 2.625 2.750 2.875 3.000 3.125 3.093 3.218 3.343 3.468 3.593 2.928 3.053 3.178 3.303 3.428 0542 0544 0546 0548 0550 2.625 2.750 2.875 3.000 3.125 3.156 3.281 3.406 3.531 3.656 2.986 3.111 3.236 3.361 3.486 © BSI 02-2000 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Table — Bearing length L, overall length E and dimension M All dimensions in inches 10–32 UNJF 1/4–28 UNJF 5/16–24 UNJF Dia./length L M E Dia./length L M E Dia./length L M E ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 code code code 0352 0354 0356 0358 0360 3.250 3.375 3.500 3.625 3.750 3.656 3.781 3.906 4.031 4.156 3.521 3.646 3.771 3.896 4.021 0452 0454 0456 0458 0460 3.250 3.375 3.500 3.625 3.750 3.718 3.843 3.968 4.093 4.218 3.553 3.678 3.803 3.928 4.053 0552 0554 0556 0558 0560 3.250 3.375 3.500 3.625 3.750 3.781 3.906 4.031 4.156 4.281 3.611 3.736 3.861 3.986 4.111 0362 0364 0366 0368 0370 3.875 4.000 4.125 4.250 4.375 4.281 4.406 4.531 4.656 4.781 4.146 4.271 4.396 4.521 4.646 0462 0464 0466 0468 0470 3.875 4.000 4.125 4.250 4.375 4.343 4.468 4.593 4.718 4.843 4.178 4.303 4.428 4.553 4.678 0562 0564 0566 0568 0570 3.875 4.000 4.125 4.250 4.375 4.406 4.531 4.656 4.781 4.906 4.236 4.361 4.486 4.611 4.736 0372 0374 0376 0378 0380 4.500 4.625 4.750 4.875 5.000 4.906 5.031 5.156 5.281 5.406 4.771 4.896 5.021 5.146 5.271 0472 0474 0476 0478 0480 4.500 4.625 4.750 4.875 5.000 4.968 5.093 5.218 5.343 5.468 4.803 4.928 5.053 5.178 5.303 0572 0574 0576 0578 0580 4.500 4.625 4.750 4.875 5.000 5.031 5.156 5.281 5.406 5.531 4.861 4.986 5.111 5.236 5.361 0382 0384 0386 0388 0390 5.125 5.250 5.375 5.500 5.625 5.531 5.656 5.781 5.906 6.031 5.396 5.521 5.646 5.771 5.896 0482 0484 0486 0488 0490 5.125 5.250 5.375 5.500 5.625 5.593 5.718 5.843 5.968 6.093 5.428 5.553 5.678 5.803 5.928 0582 0584 0586 0588 0590 5.125 5.250 5.375 5.500 5.625 5.656 5.781 5.906 6.031 6.156 5.486 5.611 5.736 5.861 5.986 0392 0394 0396 5.750 5.875 6.00 6.156 6.281 6.406 6.021 6.146 6.271 0492 0494 0496 5.750 5.875 6.000 6.218 6.343 6.468 6.053 6.178 6.303 0592 0594 0596 5.750 5.875 6.000 6.281 6.406 6.531 6.111 6.236 6.361 © BSI 02-2000 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Table — Bearing length L, overall length E and dimension M All dimensions in inches 3/8–24 UNJF 7/16–20 UNJF 1/2–20 UNJF Dia./length L M E Dia./length L M E Dia./length L M E ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 code code code 0602 0603 0604 0605 0.125 0.188 0.250 0.312 0.766 0.829 0.891 0.954 0.551 0.614 0.676 0.739 0702 0703 0704 0705 0.125 0.188 0.250 0.312 0.781 0.844 0.906 0.968 0.616 0.679 0.741 0.803 0802 0803 0804 0805 0.125 0.188 0.250 0.312 0.907 0.970 1.032 1.094 0.717 0.780 0.842 0.904 0606 0607 0608 0609 0610 0.375 0.438 0.500 0.562 0.625 1.016 1.079 1.141 1.203 1.266 0.801 0.864 0.926 0.988 1.051 0706 0707 0708 0709 0710 0.375 0.438 0.500 0.562 0.625 1.031 1.094 1.156 1.218 1.281 0.866 0.929 0.911 1.053 1.116 0806 0807 0808 0809 0810 0.375 0.438 0.500 0.562 0.625 1.157 1.220 1.282 1.334 1.407 0.967 1.030 1.092 1.144 1.217 0611 0612 0613 0614 0615 0.688 0.750 0.812 0.875 0.938 1.329 1.391 1.453 1.516 1.579 1.114 1.176 1.238 1.301 1.364 0711 0712 0713 0714 0715 0.688 0.750 0.812 0.875 0.938 1.344 1.406 1.468 1.531 1.594 1.179 1.241 1.303 1.366 1.429 0811 0812 0813 0814 0815 0.688 0.750 0.812 0.875 0.938 1.470 1.532 1.594 1.657 1.720 1.280 1.342 1.404 1.467 1.530 0616 0617 0618 0619 0620 1.000 1.062 1.125 1.188 1.250 1.641 1.703 1.766 1.829 1.891 1.426 1.488 1.551 1.614 1.676 0716 0717 0718 0719 0720 1.000 1.062 1.125 1.188 1.250 1.656 1.718 1.781 1.844 1.906 1.491 1.553 1.616 1.679 1.741 0816 0817 0818 0819 0820 1.000 1.062 1.125 1.188 1.250 1.782 1.844 1.907 1.970 2.032 1.592 1.654 1.717 1.780 1.842 0621 0622 0623 0624 0625 1.312 1.375 1.438 1.500 1.562 1.953 2.016 2.079 2.141 2.203 1.738 1.801 1.864 1.926 1.988 0721 0722 0723 0724 0725 1.312 1.375 1.438 1.500 1.562 1.968 2.031 2.094 2.156 2.218 1.803 1.866 1.929 1.991 2.053 0821 0822 0823 0824 0825 1.312 1.375 1.438 1.500 1.562 2.094 2.157 2.220 2.282 2.344 1.904 1.967 2.030 2.092 2.154 0626 0627 0628 0629 0630 1.625 1.688 1.750 1.812 1.875 2.266 2.329 2.391 2.453 2.516 2.051 2.114 2.176 2.238 2.301 0726 0727 0728 0729 0730 1.625 1.688 1.750 1.812 1.875 2.281 2.344 2.406 2.468 2.531 2.116 2.179 2.241 2.303 2.366 0826 0827 0828 0829 0830 1.625 1.688 1.750 1.812 1.875 2.407 2.470 2.532 2.594 2.657 2.217 2.280 2.342 2.404 2.467 0631 0632 0634 0636 0638 0640 1.938 2.000 2.125 2.250 2.375 2.500 2.579 2.641 2.766 2.891 3.016 3.141 2.364 2.426 2.551 2.676 2.801 2.926 0731 0732 0734 0736 0738 0740 1.938 2.000 2.125 2.250 2.375 2.500 2.594 2.656 2.781 2.906 3.031 3.156 2.429 2.491 2.616 2.741 2.866 2.991 0831 0832 0834 0836 0838 0840 1.938 2.000 2.125 2.250 2.375 2.500 2.720 2.782 2.907 3.032 3.157 3.282 2.530 2.592 2.717 2.842 2.967 3.092 0642 0644 0646 0648 0650 2.625 2.750 2.875 3.000 3.125 3.266 3.391 3.516 3.641 3.766 3.051 3.176 3.301 3.426 3.551 0742 0744 0746 0748 0750 2.625 2.750 2.875 3.000 3.125 3.281 3.406 3.531 3.656 3.781 3.116 3.241 3.366 3.491 3.616 0842 0844 0846 0848 0850 2.625 2.750 2.875 3.000 3.125 3.407 3.532 3.657 3.782 3.907 3.217 3.342 3.467 3.592 3.717 0652 0654 0656 0658 0660 3.250 3.375 3.500 3.625 3.750 3.891 4.016 4.141 4.266 4.391 3.676 3.801 3.926 4.051 4.176 0752 0754 0756 0758 0760 3.250 3.375 3.500 3.625 3.750 3.906 4.031 4.156 4.281 4.406 3.741 3.866 3.991 4.116 4.241 0852 0854 0856 0858 0860 3.250 3.375 3.500 3.625 3.750 4.032 4.157 4.282 4.407 4.532 3.842 3.967 4.092 4.217 4.342 0662 0664 0666 0668 0670 3.875 4.000 4.125 4.250 4.375 4.516 4.641 4.766 4.891 5.016 4.301 4.426 4.551 4.676 4.801 0762 0764 0766 0768 0770 3.875 4.000 4.125 4.250 4.375 4.531 4.656 4.781 4.906 5.031 4.366 4.491 4.616 4.741 4.866 0862 0864 0866 0868 0870 3.875 4.000 4.125 4.250 4.375 4.657 4.782 4.907 5.032 5.157 4.467 4.592 4.717 4.842 4.967 © BSI 02-2000 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Table — Bearing length L, overall length E and dimension M All dimensions in inches 3/8–24 UNJF 7/16–20 UNJF 1/2–20 UNJF Dia./length L M E Dia./length L M E Dia./length L M E ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 ± 0.010 ± 0.015 ± 0.010 code code code 0672 0674 0676 0678 0680 4.500 4.625 4.750 4.875 5.000 5.141 5.266 5.391 5.516 5.641 4.926 5.051 5.176 5.301 5.426 0772 0774 0776 0778 0780 4.500 4.625 4.750 4.875 5.000 5.156 5.281 5.406 5.531 5.656 4.991 5.116 5.241 5.366 5.491 0872 0874 0876 0878 0880 4.500 4.625 4.750 4.875 5.000 5.282 5.407 5.532 5.657 5.782 5.092 5.217 5.342 5.467 5.592 0682 0684 0686 0688 0690 5.125 5.250 5.375 5.500 5.625 5.766 5.891 6.016 6.141 6.266 5.551 5.676 5.801 5.926 6.051 0782 0784 0786 0788 0790 5.125 5.250 5.375 5.500 5.625 5.781 5.906 6.031 6.156 6.281 5.616 5.741 5.866 5.991 6.116 0882 0884 0886 0888 0890 5.125 5.250 5.375 5.500 5.625 5.907 6.032 6.157 6.282 6.407 5.717 5.842 5.967 6.092 6.217 0692 0694 0696 5.750 5.875 6.000 6.391 6.516 6.641 6.176 6.301 6.426 0792 0794 0796 5.750 5.875 6.000 6.406 6.531 6.656 6.241 6.366 6.491 0892 0894 0896 5.750 5.875 6.000 6.532 6.657 6.782 6.342 6.467 6.592 Example of call up: Identification and marking The bolts shall have the manufacturer’s identification and full part number applied to the upper face of the head except for the 10–32 UNJF size in which case the diameter code (03) may be omitted The method of marking bolts and packages shall be as specified in BS A 101 Figure shows a typical disposition of the various markings Figure — Typical disposition of the various markings © BSI 02-2000 BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 Appendix A Table for the conversion of inches to millimetre equivalents in 10 mm 25.4 50.8 76.2 101.6 127.0 152.4 177.8 203.2 228.6 254.0 © BSI 02-2000 blank BS A 254, BS A 255, BS A 256, BS A 257, BS A 258, BS A 259:1976 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: 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