175 



IX. — Anomalies in Objective Screw Threads. 

 By F. W. Watson Baker. 



(Read March 15, 1911.) 



The purpose of this short paper is : — 



1. To call attention to the great diversity which exists in the 

 objective screw threads made by the various makers and described 

 as of the Royal Microscopical Society's standard size. 



2. To indicate disadvantages connected with the present system 

 of sizing gauges and measurements as set out by the Royal Micro- 

 scopical Society. 



3. To consider how more uniform results can be attained. 



1. The Diversity of Objective Threads. That the objective of 

 one maker will frequently not screw into the nose-piece of the 



Max. -7982'' 

 No I Min. -7952" 



IIHHHMVffl 



■799N0.2. ■ -aAAfc BL^^J*_No3.-794 



•788 -794- 



•796 -799 



N06 •<!#» jAAJLuo.7. 



•785 788 



•797 *« 



NolO^AAAA. *mmm* No. 11. 



Fig. 24. 



Microscope of another maker is a matter of common knowledge, 

 but will not be cause for wonder when it is known how distant is 

 the approach to accuracy of the majority of the screw threads of 

 objective makers. 



For the purpose of this paper I have photographed the standard 

 sizing gauge supplied by the Royal Microscopical Society (fig. 24, 

 No. 1), in order to show the shape and size of the screw threads and 

 the objectives of ten different makers in comparison with it (fig. 24, 

 Nos. 2-11). 



n 2 



