ON THfi SMALL SCREW G^UGE. 



m 



ehangealjility of the screws. The resolution of 1900, modifying the form 

 of the thread, was intended to apply to the gauges only, and it was supposed 

 that the roots and crests of the thread in screws formed by dies or in nuts 

 formed by taps would still be rounded, and the form of the thread would 

 thus approximate very closely to that of the Montreal dehnitions. How- 

 ever, in view of the facts which have been put before them, the Committee 

 now think it l)est to state explicitly that they do not propose to alter the 

 form of the B.A. screw thread, and that they desire to withdraw the 

 recommendation accepted at Bradford in 1900. 



The original form of the British Association screw thread was laid 

 down in the Montreal Report, 1884, to the following effect, viz. : 



The angle of the thread was defined to be 47-5°. 



The values of the pitches and of the external diameters of the screws 

 were scheduled in millimetres ; the depth of the thread was defined to be 

 sixteenths of the pitch, and the radius of the rounding was to be the 

 same at root and crest. The radius of the rounding was very nearly 

 two-elevenths of the pitch by this rule. 



This definition, closely adliered to, led to inconveniently small frac- 

 tions in those quantities which had to be calculated from the scheduled 

 dimensions, but this may be avoided if we replace the definition by an 

 equivalent schedule of dimensions of all parts from which the insignificant 

 tisrures are omitted. 



Retaininc; the 



schedule 



angle of 47 "5° in 



all cases, we adopt the following 



British Assuciaiion Srretvs. 

 Schedule I. — Schedule of dimensions in milUinetres. 



