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In today's fast paced
get it done now manufacturing
environment sometimes using the
proper tools and setups gets thrown
to the wayside. Most of us either
don't know how to or don't have the
time to calculate the proper
specifications for every tool and
application. Some rely on the
cutting tool suppliers to tell them
what to use and others just guess.
This article is for
those people wanting to know how and
why to setup there sawing
applications for the best tool life,
cut quality, and efficiency. Below
you will find formula's and charts
to make the chore a little easier. |
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Without the right
formulas to calculate your
information all of this is
worthless. So below are the correct
variables, specifications, and
formulas.
Variable Definitions
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RPM = Rotations
per Minute
-
Chip Load =
Material Removed by Each Cutting
Edge in Inches
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Feed Rate = Rate
which the part is feed into the
cut in Feet per Minute
-
Diameter = The
Distance from the center of tool
to the farthest cutting edge
multiplied by 2.
-
p
(Pi) = 3.14159265358979323846
(Round as Necessary)
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Rim Speed = The
speed in feet per minute that a
tool spins at its diameter
-
# Wings = The
number of teeth in the cutting
tool
Formulas
Feed Rate = (Chipload
x # Wings x RPM) / 12
Max RPM* = (12 x Max
Rim Speed) / Diameter x
p
Chip Load = (Feed
Rate x 12) / (RPM x # Wings)
Rim Speed = (Diameter
x
p
x RPM) / 12
*Just a note, Max RPM
is the fastest you should run each
blade. The recommended RPM's are
usually between 50% and 75% of Max
RPM.
As you can see all of
these formulas are interrelated in
that some of the information from
one formula is required to use the
other. This can be a real problem if
you don't have enough information up
front. So to make this process
easier we have included some very
useful charts below. |
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OK, now lets put all
this information to use. We will use
a scenario using Bob and his new
power feed for his table saw. Bob has
never used a power feed and has no
idea what speed to run for the best
tool life, cut quality, and
efficiency. He is going to rip cut
some softwoods using a 12" diameter
blade with 30 teeth.
First he calculates
the Max RPM:
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Max RPM* = (12 x
Max Rim Speed) / Diameter x
p
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Max RPM = (12 x
18,000) / (12 x 3.14159)
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Max RPM = 216000
/ 37.69908
-
Max RPM = 5,729
(Rounded to the whole number)
This means the the
best RPM's to run the blade at falls
between 2,865 and 4,297 RPM's. He
knows his machine runs at 3,450
RPM's so he will use that number to
figure the rest of his information.
From the Chip Load
chart he chooses a Chip Load for
softwood figuring that he needs a
midline finish quality. He picks
0.021 as his chipload from the with
grain softwood row in the chipload
chart.
Second he
calculates the Feed Rate:
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Feed Rate =
(Chipload x # Wings x RPM) / 12
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Feed Rate =
(0.021 x 30 x 3,450) / 12
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Feed Rate =
2,174 / 12
-
Feed Rate =
181 Feet per Minute
Bob's done. He now
knows the information needed to
setup his application.
Now all of this
information is for reference, and
gives guidelines to setup most
applications. Limitations of your
machine or application may cause you
to be unable to use the numbers you
get. If this happens simply plug in
the limiting specifications into the
supplied formulas. Adjustments in any and
all specifications may be needed to
fit your particular application.
These formulas are not law by any
means and you should use good
judgment and common sense in setting
up any cutting tool. Safety is
always your top priority. |
