Scientific American Supplement, No. 664, September 22,1888Various
History
Scientific American Supplement, No. 664, September 22,1888
Various
Science -- Periodicals
Broken pivots, as I have hinted, I place the arbor in a split chuck,
and if true, I drill into the staff with a drill, made from a nice
piece of steel wire, the old and ordinary shape of a drill, which is a
trifle larger at the cutting point than it is back of the point, and I
make these as I need them, and harden simply by holding the wire in a
flame till red hot, and then dash into an apple, potato, soap, or pure
rubber. Which is the best of these I have as yet been unable to
determine, so I use either as the most handy. Take a good, tough and
small pointed graver and turn a slight center in the end of arbor I am
to drill, and then by giving my lathe a back and forward motion, I
begin to drill, and by the sense of feeling I can tell whether my
drill is cutting or not, and if not, I have a small, smooth oilstone
at hand and sharpen the drill as often as it refuses to cut, and if
that drill will not cut, I make another.
I make my drills of very small wire, filing them at point and then tap
the point (holding the wire in a very fine pin vise), thus flattening
as well as spreading it, and then shape the cutting edges as spoken of
above. When you have drilled sufficiently to hold a plug firmly, then
have a piece of steel of spring temper filed so as to fit closely and
so straight that it will not act too wedging (and split the arbor),
drive it in, cut it off and turn down, finishing with an oilstone
slip, and polish by running the lathe rapidly and with a piece of thin
boxwood (or hard pegwood) charged with diamantine, being sure that the
end of the pivot has no burr, thrown either way, over end or on side,
for such a burr will cause a lack of freedom of a balance pivot
particularly. This matter of setting pivots requires a longer
experience than almost any other work, and it needs a long practice to
do a nice job. If your split chuck will not hold your staff or arbor
true, then use cement; but in this, too, you must be sure that your
center is true, and that the sound pivot enters it perfectly.
Sometimes you meet with steel so hard that you cannot touch it with a
drill, in which case draw the temper of the staff or arbor you are
drilling, and if it projects so little that you cannot draw the temper
without injury to the wheel, then unstake or separate the wheel, and
by drilling a hole into a piece of brass wire, about the size of the
staff you are drilling, insert the staff in this hole, and then heat
the wire near the staff and thus gradually and yet effectively draw
the temper.
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