4 METHOD o CUTTING VERY FINE SCREWS, and 
SCREWS of TWO OR MORE THREADS, tsc, By the 
Rev. GILBERT AUSTIN, 4.M. M.R.L A. 
Havine lately wanted a micrometer {crew for an equa- 
torial inftrument of twelve inches diameter, made by Mr, Ro- 
binfon of Dublin, I fought in vain among the beft workmen 
in this town for one which might anfwer my purpofe. Screws 
of the neceflary finenefs are not generally ufed in mechanics. 
Rather, therefore, than fubmit to the delay and difficulty of obtain- 
ing one froni London, I determined to endeavour to make one. 
‘The machine for cutting fcrews of this defcription, ufed by Mr. 
Ramfden and the firft aftronomical inftrument makers in Lon- 
‘don, I underftood to be complex and of great nicety. Such 
a one would not fuit me. I thought I might poffibly hit upon 
fome fhort and fimple method of making fine {crews without 
it. That which I ufed I beg leave to fubmit to the Academy, in 
order that they may make it public, fhould they think it 
worthy their attention, and likely to be of fervice to the prac- 
aical aftronomer, who might otherwife find it difficult to fur- 
nifh himfelf with very fine {crews for micrometers. ‘The ufe 
Vor. IV. U of 
Read Nov. 5, 
1791. 
