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320 SPEED OF MACHINERY.
SPEED OF MACHINERY.
The peripheral velocity of circular saws ought not to exceed
10,000 feet per minute. Table No. 37 gives the number of revo-
lutions per minute for circular saws of different diameters.
TABLH No. 37-
Diameter of
saw in inches.
I
8
I
10 12 14 16 20 24 28 32
Number of
revolutions
per minute.
1
4500 3600
i
1
3000 2585 2222 1800 1500 1285 1125
Band Saws.
Small band saws, such as are usually used in carpenter
shops, have a velocity of 3600 feet per minute. The reason
why band saws are run so much slower than circular saws is
that if the band saw is given too much speed the blade will be
pulled to pieces in starting and stopping.
Drilling Machines for Iron.
For drilling steel, the surface speed of a drill should not
exceed 15 feet per minute; cast-iron, 22 feet; brass, 27 feet;
malleable iron. 25 to 30 feet per minute. The feed will vary
according to the hardness of the stock. In cast-iron a %" drill
will drill a hole 1" deep in 125 revolutions. A X" drill will
drill a hole 1" deep in 120 revolutions. A 1" drill will drill a
hole 1" deep in 100 revolutions.
Lathes.
Cast-iron may be turned at a speed of 32 feet per minute
when Muchet steel is used for tools. Thus, lathes are usually
calculated to have a velocity of about 30 to 32 feet on the slow-
est speed, supposing that as large a diameter as the lathe will
swing is turned.
For wood-turning the surface speed may be from 3000 to
(>000 feet per minute ; but when the article to be turned is out of
balance the speed must be considerably slower.
Planers.
Cast-iron is planed at a speed of 25 to 27 feet per minute
;
wrought iron, 21 feet; steel, 16 feet per minute. A planer ought
to return at least three times as fast as it goes forward.
nilling Machines.
Rotating cutters working on Bessemer steel or other mate-
rials of about equal hardness usually have a surface speed of
* The speed of metal working machines may be greatly increased by using tools
made from high speed steel.
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