444 



KEFOKT — 190U. 



The appended table gives the pitches and diameters of the diffei-ent 

 threads modified in accordance with this recommendation. 



Table of the pitches and diameters of the British Association thread under the 



rule proposed above. 



In order to give practical effect to our recommendations we desire to 

 obtain a set of the proposed screws, with tools and gauges, for comparison 

 with the present ones. We shall thus be able to exhibit in a concrete 

 form the character of the thread, and also to show how far screws made 

 with the new tools are interchangeable with the existing stocks. We 

 recommend that the Committee shall be reappointed for this purpose with 

 a grant of 50^. 



APPENDIX. 



ReiJort of Ex^ierimenis on Screio llireads made hy J. Marshall 

 GoRiiAM and W. A. Price. 



The object of these experiments was to determine the relative advan- 

 tages of different angles for the threads of small screws, and two questions 

 -were proposed for trial. 



1. Which angle gives the greatest frictional torque to resist unscrew- 



2. Which angle gives the greatest resistance to tlie tearing of a steel 

 screw out of a brass plate or nut ? 



To answer these questions, six pieces, of the form of tjg. 3, were made 

 of steel. On one end, «, of each a thread was cut which was the same in 

 every case, and was used only for the purpose of connecting the pieces in 

 the testing-machine. The threads to be compared were cut on the ends h. 

 Three kinds of thread were tried, two pieces being made of each kind of 

 thread. 



The mode of trial is shown in fig. 4. A pair of these steel pieces, 

 A A, having threads of the same kind at the ends h h, were tightly screwed 



