A bolt consists of a stem and a head. Bolt heads are of all
shapes--square, hexagonal, round, flat, etc.--while the stem is always
round. As a rule, the thickness of the head equals the thickness of the
stem, and the diameter of the head is about 1-1/2 times the thickness
of the stem. This proportion is generally kept for square and hexagonal
bolts.
[Illustration]
[Illustration: Bolt]
_Directions:_ Out of the piece of iron used enough of the end is upset
to make the head. To do this, heat 2-1/2 ins. from the end of the bar
to a bright red heat. Take the piece out of the fire, place the hot end
on the anvil, and with the bar in a vertical position hammer upon the
cold end. The cold end is driven into the hot end, thus shortening or
upsetting the bar. This is repeated. The end is heated again and the
hammering is continued until the enlarged end has the right proportion
for the head of the bolt. (See drawing.) Heat the enlarged end again
and pass the cold end of the stem through the heading tool. Place the
heading tool upon the anvil in such a position that the stem passes
through the hole in the anvil. The upset end is hammered down against
the heading tool until the head is the required thickness. Take it
off the heading tool and square it up with the hand hammer. If, after
squaring up, the head is found to be too small in diameter and too
thick, it is again put into the heading tool and hammered down. This is
repeated until the head is finished according to the drawing shown.
[Illustration: Bolt in heading tool]
All hand-made bolts are made on this principle, whether they are very
large or very small.
[Illustration: Collar]
[Illustration: Bolt heads]
If a six-sided bolt is desired the same method is used. The head is
made six-sided instead of being squared as was done in the first case.
The bolt is finally cut to the required length and the end is bevelled
off ready for threading. Bolts may be made without going through the
process of upsetting the stock. In that case the bars used are of any
diameter, depending upon the size of the stem needed. Bend a piece of
iron for a collar to give you the amount of stock required for the bolt
head. Heat the end of the iron bar. Put this hot end into the collar.
Upset it so that it fills the space in the collar. Put it into the
fire, then weld and finish as you did in making the head with the end
upset.
All bolts that are on the market except special bolts are made by bolt
heading machines. Up to 3/8 in. in diameter all bolts are made without
the use of heat. Those above that size are all heated red hot and the
principle is exactly the same as you used when you made the bolt by
hand. The machine upsets the head and at the same time shapes it into
any desired shape.