A468 REPORT—1899 
‘ 
II.— Report from Mr. H. J. Cuanery, Superintendent of the Standards 
Department of the Board of Trade. 
Standards Department, Board of Trade: July 10, 1899. 
My dear Sir,—I have now the pleasure to enclose, for the informa- 
tion of Sir William Preece, a statement showing the external dimensions 
of the three male screws which you forwarded to me on Thursday last, 
and which have been returned to-day by registered post. The dimensions 
were determined by contact comparisons (made by independent observers) 
of the screws with Board of Trade Standard cylindrical gauges, plane 
gauges, and wire gauges ; and in the case of the smallest screw (c), by 
microscopic comparison with a linear standard. 
Had time allowed, a more exhaustive examination of the three screws. 
might have been made ; but the present comparison may, I suggest, be 
relied on to + 0:0001 inch. The dimensions given in the enclosed paper 
(41023 mm., 0°16151 inch, &c.) are in each case the mean external 
diameter of the whole length of the screw, and show that although a and 
c have perhaps appreciable errors, the required dimensions have generally 
been closely followed by Mr. Bond. The screw-threads are in fact, in 
our opinion, of excellent workmanship ; but it is doubtful whether the 
screws are always perfectly cylindrical. For instance, the mean external 
diameter of the last eight threads of screw c (or the point of the screw) 
is 0008 mm. greater than the external diameter of the fifteen © 
middle threads of c. The external diameter of the seven last threads. 
(shoulder of the screw) of c agree in measurement with the diameter of 
the point of the screw. 
I should much like to see a copy of Colonel Watkin’s photographs. 
Yours faithfully, 
(Signed) H. J. Cmaney. 
W. A. Price, Esq. 
Fig. 2.—British Association Screw Threads. 
