33 ^^/ 
Graduation of Agronomical Injlruments . 2 1 
I in reality thought myfelf much indebted to Mr, Hindley 
for this communication ; but though he fhewed me his engine, 
and told me, that the fcrew was cut by the rotation of the 
point of a tool, carried round upon a ftrong arm, at the dis- 
tance of the radius of the wheel from the center of motion, 
which arm was carried forward by the wheel itfelf, and the 
wheel was put forward by an endlefs fcrew, formed upon a 
cylinder to a proper fize of thread, cut by his chock lathe ; 
though he fhewed me alfo this chock lathe, and the method 
employed to make the threads of the fcrew equiangular with 
the axis, that is, to free the fcrew from what workmen term 
drunkennefs ; and alfo fhewed me how,- by the Angle fcrew of 
his lathe, he could cut, by means of wheel- work, fcrews of 
every neteflfary degree of finenefs * (and, by taking out a 
wheel, could cut a left-handed fcrew of the very fame degree 
of finenefs) ; by which means he was enabled not only to adapt 
his plain fcrew to the fize of the teeth of his wheel, but alfo to 
prevent any drunkennefs that otherwife the curved fcrew would 
be fubjefl to in confequence of being produced from the plain 
tions, the fpringing of the materials was fuch as in fome portions to amount to- 
conliderable errors. This remained with him in the fame Rate till the year of the 
firft ^Tranjit of Venus^ viz, 1761 ; when it. was fold to — - Constable, Efq. of 
Burton Confable , in Uoldernefs. Mr. Hindley, to remedy the evil above-men- 
tioned, applied balances to the different movements* He foon afterwards com- 
pleted one, de novo , upon this improved plan, for his Grace the late Duke of 
Norfolk. A method of balancing in much the fame way, without the know- 
ledge that it had been done before, has been fully explained, and laid before 
the Society, by our ingenious and worthy brother Mr. Nairne. Phil. Tranfc. 
toI. LXI. p, 108. 
* A machine for cutting the endlefs fcrew of Mr. Ramsden’s engine, upon 
principles exactly fimilar, is fully and accurately fet forth in his Defcription of his 
dividing Engine above-mentioned. 
one ;; 
