a NT ae 
ON THE SCREW GAUGE, 527 
Screw Gauge.—Report of the Committee, consisting of Mr. W. H. 
PREECE (Chairman), Mr. Conran W. Cooke (Secretary), Lord 
KELvw, Sir F. J. BRAMWELL, Sir H. Trueman Woop, Major-Gen. 
Wesper, Mr. R. E. Crompton, Mr. A. Stron, Mr. A. LE Neve 
Foster, Mr. C. J. Hewitt, Mr. G. K. B. Evpninstone, Mr. T. 
Bucxney, Col. Warkin, Mr. E. Riae, and Mr. W. A. Price, ap- 
pointed to consider means by which Practical Effect can be given to 
the Introduction of the Serew Gauge proposed by the Association in 
1884, (Drawn up by the Chairman.) 
CONTENTS 
PAGE 
I. The Past ° . . . . . . . . . . - ont 
II. The Present : 5 ' e : . : : ; 7 ; . 529 
Ill. The Future : : : : ° , . : 5 ; : . 531 
APPENDIX I.—Fnlarged Shadow Photographs of Screns. By y Col. WATKIN, 
CB eieAs jens 532 
II. — Gauges Sor Verifying the Aceu "acy of Screws. (for Workshop 
Use only). By A. STROH. . 534: 
yy“: LL.— Working Dimensions in Millimetres and Thousandths of an Inch. 
By A. LE NEVE FostER 3 . 536 
Tests of B.A. Serens by Hervé Diameters. By W. A. Price . 537 
I. Tue Past. 
A UNIFORM system of screw threads was first proposed by the late Sir 
Joseph Whitworth in 1842, and his thread, a compromise of the numerous 
threads then in use, has poe of almost universal use for all large 
screws—that is, screws of over | in. diameter—in the United Kingdom. 
Mr. William Sellers in 1864 introduced another thread in the United 
States of America, which has come into very general use in that country, 
and this thread has recently been accepted by the French. 
In 1881 the British Association formed a committee to determine a 
gauge for the manufacture of the various small screws used in electrical 
apparatus, clock work, and for other analogous purposes ; and after three 
years of unremitting labour this committee, in 1884, recommended a screw 
gauge which has come into very general use in this country. [t was 
based on the metrical system, and with one slight modification on the 
system adopted in 1880 by the Swiss watchmakers. 
The series of screws recommended is given in the following table :— 
British Association Screw Gauge. 
Dimensions in Millimetres | Dimensions in Thousandths | 
of an Inch | Threads 
Number (———W— ona a | per 
Diameter | Pitch Diameter Pitch inch 
| | 
I BEsphao (ern tll Iv Mattes cick 
0 6-0 1-00 236 394 | 25-4 
1 | «BB 0:90 208 35-4 | 282 
2 4-7 0°81 184? 31-9 31-4 || 
3 41 0-73 1622 28-7 348 
4 3°64 0°66 142 26:0 38°5 
5 3-2 059 126 23-2 | 43-0 
6 2-8 | O53 110 20:9 47-9 
7 25 | 48 98 18-9 | 52-9 
8 2-2 | 43 87 16:9 | 591 
9 19 0°39 15 15°4 65:1 
