machines will have some rounding at the crests and roots of the threads, we believe that we can secure the objects for which this Committee was appointed in 1895, viz., to produce in a material form gauges which could be checked by a central authority, such as the Board of Trade or the National Physical Laboratory, and certified copies of which could be issued to manufacturers and buyers of screws to secure commercial interchangeability. We recommend, therefore, with reference to threads Nos. 0-11: 1. That sets of gauges should be made and verified, each set consisting of six pieces as follows, A-F. A. A male gauge screw of the pitch and effective diameter laid down for the distinguishing number in Schedule I., the thread having a V-shaped root, and a crest flattened cylindrically to the over-all diameter laid down in the table. The outline of the thread is in fig. 3, AC FKM PSU. This piece A is for the purpose of testing nuts and nut gauges to check the correctness of the pitch, angle of thread, effective diameter, and root diameter, and for checking the hole gauge E. B. A tap, a copy of A in all respects, except that it is fluted and backed off as a tap, and that the crests are left nearly approaching the sharp V form as is possible, so as to maintain a cutting edge with this angle of thread, i.e. 475 degs. The outline of this thread is in fig. 3, ABFLPT U. This piece B is to be used solely for cutting the thread of the nut gauge C. C. A nut gauge, the thread of which is cut by the tap B, the crest being afterwards reamered out to such a diameter as experience may show is necessary to give suitable minimum clearance at this point to ensure 1903. C C that machine-made screws will enter the nuts or tapped holes. line of this is ABEGLOQTU. D. A notch gauge to test the core diameters of male screws. The out E. A hole limit gauge to test crest diameters of male screws and to be checked by piece A. The diameter of this is diameter D, fig. 1, Schedule I. F. A cylinder plug gauge to test the diameter of the hole in the gauge nut C in commercial nuts or tapped holes. The diameter of this is diameter C, fig. 1, Schedule 1. 2. That the standard B.A. screw be defined as a screw which conforms to the gauges described above in all respects except in the form of the crest and root of the thread, which are unimportant. R. E. CROMPTON. J. M. GORHAM. G. K. B. ELPHINSTONE. C. VERNON Boys. APPENDIX. The Committee have had constructed for them by the Cambridge Scientific Instrument Company a machine for measuring small screws microscopically. In figs. 4 and 5 are given drawings of the instrument, of which fig. 4 is a plan of the compound stage with the microscope removed, and fig. 5 is an end elevation showing the arrangement of the microscope. The screw to be measured is held in a spring chuck in the spindle (A). By means of the two micrometer screws, S, S2, the screw is moved along geometric slides in two directions at right angles. The screw is aligned parallel to the micrometer S, by the adjusting screws B C. The pitch of the micrometer screws (which were supplied by the Browne and Sharpe Company) is 0.5 mm., and the heads are divided into fifty parts, enabling readings to be taken directly to 0.01 mm. The screw is illuminated from below by a plane mirror and is observed by the microscope M. Rough focussing is effected by sliding the microscope in the tube T, the fine adjustment being accomplished by the micrometer screw S3, which raises and lowers T. The tube T can also be rotated about its axis without disturbing the focus, and the amount of rotation measured by means of a scale on D. The eyepiece and objectglass of the microscope are by Zeiss. The eyepiece is furnished with suitable cross-wires in silver. A series of spring chucks for different diameters of screws accompanied the machine. Anthropometric Investigation in Great Britain and Ireland.-Report of a Committee consisting of Professor J. CLELAND (Chairman), Mr. J. GRAY (Secretary), Dr. T. H. BRYCE, Professor D. J. CUNNINGHAM, Professor A. F. DIXON, Mr. E. N. FALLAIZE, Dr. A. C. HADDON, Dr. D. HEPBURN, and Mr. J. L. MYRES. THE following circular, which was sent to certain persons and institutions known to be engaged in anthropometric work in the British Isles, and to a few of the more distinguished physical anthropologists in foreign countries, will explain the objects for which the Committee was formed: : British Association for the Advancement of Science. 1903. DEAR SIR, A Committee, consisting of Professor J. Cleland (Chairman), Mr. J. Gray (Secretary), Dr. T. H. Bryce, Professor J. D. Cunningham, Professor A. F. Dixon, Mr. E. N. Fallaize, Dr. A. C. Haddon, Dr. D. Hepburn, and Mr. J. L. Myres, has been appointed by this Association to organise Anthropometric Investigation in Great Britain and Ireland. The objects which the Committee have in view may briefly be stated to be as follows: 1. To establish uniform standards in Anthropometric Investigation. 2. To ascertain which measurements are likely to prove the most fruitful in result. 3. To formulate broad lines of co-operation. Much valuable work done in various parts of the country in this branch of Anthropological Science is at present very imperfectly utilised, owing to the difficulty of obtaining information as to the centres at which it is carried on, and because different methods of measurement are employed at different centres. The Committee, therefore, think it desirable to obtain information regarding these methods, in order to consider which are most to be recommended for utility, accuracy, and convenience, and in the hope that a consistent scheme may be formulated for general use throughout Great Britain and Ireland. For this purpose certain questions have been drawn up, which will be found on the annexed sheet, and I am desired by the Committee to request your co-operation in furthering its objects by answering these questions and returning your answers to me at your early convenience. I am, All communications should be addressed to me : J. GRAY. Anthropological Institute, London, W. |
