78 W. R. TRAVISS ON AN EXPANDING STOP FOR 



just fit the full points of the pins that are to be used (if the hole 

 is so large that the pin will slip through up to the head it is too 

 big, as the pins will then quickly work loose), drill all the holes 

 and set the plate aside as No. 1 template (Fig. 1). 



Cut another circle from the same metal the same size as No. 1, 

 with concentric circle as before. Taking any point A ou this 

 latter circle, set your dividers so as to scribe the arc BD beyond 

 the centre, in order to give room for the pivot, and for other 

 reasons which will appear later. Drill the holes at A and B and 

 also the centre, and we have template No. 2 (Fig. 2). 



Now take the metal for the sheaves. If the dividers are made 

 sharp at the points, and are held firmly on the metal, which 

 should be laid on a piece of flat, hard wood — e.g. mahogany — by 

 turning the metal round several times under them, it will be so 

 nearly cut through that by carefully buckling the brass it will 

 break clean away. If the disc itself is found to be buckled, lay 

 it on a flat iron plate and rub the face of the hammer gently over 

 it to flatten it. Make a dozen or more of these discs. Now take 

 template No. 2, and with a pin put through the centre of one of 

 the thin discs, put it on the top and knock it into the mahogany 

 block just so that it will hold. Take another pin and drive it 

 carefully into A, and leave both pins there until you have knocked 

 a third pin into B. One having been done, all may be taken out 

 and the rest finished in the same way. 



In order to obtain the pattern of a sheave, set the dividers to 

 scribe a circle from the centre A, with a radius such that the arc 

 BC shall pass above the centre of the disc as shown in Fig. 3. 

 Now, keeping the dividers set as before, scribe another arc cutting 

 the arc BC, and, leaving enough metal round the points or holes 

 A and B, and rounding the angle of intersection of the arc as 

 shown, cut away the shaded portion with a pair of small sharp 

 scissors. The piece which is left is a sheave of the proper 

 pattern. 



In order to pin the sheaves the pin must be gently forced into 

 the small holes AandB, one in each face of the circle : they must 

 be kept upright and square to the face. Take a strip of blowpipe 

 solder, flatten it out with the hammer, and cut it into tiny strips; 

 these curl up, but can be easily straightened. Use salammoniac 

 dissolved in water as a flux, a pointed match to put it on with, 

 and a wing feather as a brush. Heat them over a very small 



