[ 146 ] 
of this method is not confined to the forming of very fine 
fcrews alone, but may be applied to the cutting of original. taps 
of any fize and of any number of threads required, as double, 
triple, &c. for what are called fwift {crews, and that with much 
lefs trouble and time than workmen are obliged to fpend in 
the common methods. 
I roox apiece of the beft fteel wire, of about a quarter of an: 
inch diameter and about two inches long, which I turned per- 
feétly cylindrical at one end, about three quarters of an inch in 
length to about one eighth of an inch or fomething more in dia- 
meter. I made a nick near the point, and faftened the end 
of avery fine piece of fteel wire to it, and then rolled the wire 
about the cylinder as far as the fhoulder, where | faftened it as at 
the point. I did not roll the wire quite as clofe as I could, 
but left room between one of the revolutions for the edge 
of a very fine knife. I then fet the edge of the knife at the 
beginning of the thread of the wire, and in the direction of 
the inclination of the threads, and preffed it down fo as to touch 
the fteel cylinder. I turned the cylinder about with my hand, and 
guiding the knife by the threads of the wire, by a few turns 
I made an impreflion on the fteel, fufficient, when I ftripped 
off the wire, to ferve as a guide for the knife to run in and 
cut the thread to a fufficient depth. 
Tuts method, on account of the difficulty of guiding the 
hand, and determining the proper degree of tenfion to be given 
to the wire on the cylinder, I found fubject to a confiderable 
variation with refpect to the finenefs of the {crew produced. 
For from the fame wire on different cylinders: Mr. Robinfon 
made 
far tat 
