A number of ohflinges must be made to adapt a pencil to its new use. 
The friction that keeps the lead at the adjusted level must be eliminat- 
ed* Usually the pencil must be taken apart to accomplish this. Since 
the friction is caused in different ways in different makes of pencils, 
the exact procedure cannot be described. The point of the pencil is 
sawed or filed off sufficiently to let the lead holder project. If the 
housing is hexagonal, it should be replaced with a round tube, preferably 
of solderable material. The lead holder should be filed to a smaller dia- 
meter to allow more play between it and the core, or it can be replaced 
entirely with a piece of wire bent and filed into shape, «hen the pencil 
is reassembled the spiral should turn without friction. 
For the plunger a piece of 26 B, and S, gage brass spring wire is 
selected which has no kinks to prevent a tight fit. Any gentle bend 
resulting from the wire being wound on a spool may be straightened by 
pulling the wire between thumb and forefinger a number of times, but 
sharp kinks are difficult to remove and should be avoided. One end of 
the wire is ground off squarely, and the burred edges are polished. 
Then after the wire has been cut to the proper length, the other end is 
soldered into the hollow end of the lead holder. The length of the plung- 
er will depend upon the construction of the pencil and on the length of 
the completed glass tip. It should be slightly longer than the tip, etnd 
long enough not to slip out of its upper end i^en withdrawn as far into 
the pencil as possible. If there is still some bend in the plunger, it 
should be attached so that the back of the arch will rub against one of 
the sides of the core. Such a position will prevent the arch from push- 
ing the end of the glass tip against the spiral and possibly breatking 
it, and at the same time will prevent the end of the plunger from slip- 
ping out of the core groove when drawn into the pencil while no glass 
tip is present. 
To make a good glass tip requires some practice and the exercise 
of proper care. The first step is to draw out a supply of capillary 
tubing. Ordinary 6-mm. soft-glass tubing has been found very satisfac- 
tory for this purpose. Long sections of fairly uniform bore can best 
be obtained by heating a section of tubing about 1 inch long, drawing 
slowly at first until the center of the section is of about the right 
diameter, and then drawing more rapidly to a length of 3 to 4 feet, 
"^ith 26 gage (0.41-mm,) wire the inside diameter is tested until a 
piece of nearly uniform bore about 60 mm. long is found which fits 
closely. The glass is broken at the point where the end of the wire 
fitted most tightly, and this end is made the inside end; the larger 
end becomes the point of the syringe. The inner edge of the small end 
is ground under water by twirling on the pointed Arkansas stone, so that 
there will be no sharp edge to scratch the plunger and gradually decrease 
its diameter. The plunger should not be inserted from this end until 
the glass tip is completed and ready for mounting, and then only under 
the microscope, because the glass is easily broken if the plunger is not 
inserted perfectly straight. 
