408 KEPORT— 1901. 



insuflQcient to induce tbem to perfect the processes necessary for making 

 them accurately interchangeable. In short, the British Association screw- 

 gauge of 1884 was of too complicated a form to allow of its accurate 

 realisation except at a cost which has proved prohibitive. 



That very accurate gauges with rounded threads can be produced is 

 not disputed, but the diiEculty of doing so for small screws is very great. 

 The names of three firms in America and of one in Germany have been 

 proposed to the Committee as being competent, and probably willing, to 

 undertake <he production of gauges and tools of the rounded thread. The 

 Birmingham Small Arms Company, who produce interchangeable work on 

 a very large scale, and to a high degree of perfection, use only round- 

 topped screws, fitting all over, for bicycle work ; and Mr. Clements 

 exhibited gauges used by that firm illustrating his paper read before the 

 Section at Bradford. This firm does not produce these gauges for sale. 

 The American firm of Pratt & Whitney have manufactured a large 

 number of sets of gauges and screwing tools for the English Government, 

 but declined to submit these to the Committee on the ground that they 

 were not sufficiently accurate to satisfy us. After long delay they 

 submitted to us three specimens, which were reported upon by this 

 Committee at the Dover meeting. Though the best we had seen, they 

 were distinctly infei-ior to the screws used in the ordinary micrometers 

 purchasable in tool shops, which have threads of the character which 

 this Committee has recommended for adoption. 



While the round thread is only produced satisfactorily by a very few 

 firms, who have made a special study of this class of work, the Committee 

 believe that the form of thread they have proposed can be made in 

 any fairly equipped tool room ; and that this facility in producing or 

 obtaining the necessary appliances must very greatly encourage the 

 maintenance of an accurate standard in small screws, to promote which 

 has been the object in the view of the Committee. If, on the other hand, 

 these tools and gauges are very special, and perhaps costly, appliances, 

 obtained only by the refined processes of certain factories, their use 

 in workshops will extend slowly. The Committee aim at putting the 

 matter on such a footing that the common everyday appliances in the 

 hands of workmen shall be of a good order of accuracy, and this is 

 only possible if they are produced easily and cheaply. 



It is not suggested by the Committee that the form of thread 

 recommended is the best for all purposes and for all sizes of screws, and 

 they have expressly excluded sizes of screws below No. 1 1 British Associa- 

 tion gauge, which are produced by pressure and not by cutting. Their 

 recommendation applies only to the screws used in instrument making 

 and similar trades for assembling parts, of which screws a large 

 proportion — perhaps 95 per cent. — are of brass. Considerations affecting 

 the use of screws for other purposes ha\e been put before the Committee, 

 especially by Mr. Clements in the case of bicycle and gun screws, and by 

 Mr. Taylor in the case of lens screws. These have thrown suggestive 

 light on the question before the Committee, and will be closely considered 

 by them if reappointed. 



Since tlie last report the Committee's proposals have attracted much 

 attention, but no sets of gauges or tools of the new thread have been 

 submitted to them, and so far their recommendation has had no practical 

 result. They are informed, however, that one firm of manufacturers in 

 England is occupied in producing tools and gauges for their own use, and 



