Post Slide Rule Instructions — models 1441, 1444, 1447, 1452 (Teledyne Post)
SLIDE RULE
INSTRUCTIONS
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P.O. BOX 803, CHICAGO, ILL. 60690 1452 a eee ee lille
72 $2. 90. 190
60
ft
When ordering specify
slide rule number and
follow with specific
part number.
1. Indicator Glass
No. 920
2. Complete
Indicator
with Glass
No. 900
3. Snap-on Magnifier
(not available for
/ 1441, 1444)
The cursor on your Stu-
dent Slide Rule can never
fall off accidentally. To
remove the cursor for
cleaning or replacement,
hold the rule vertically,
move cursor to center of
rule, press down on top
of cursor, and flip bottom
of cursor off.
“*® TELEDYNE POST
P.O. BOX 803. CHICAGO, ILL. 60690
SLIDE RULE
PARTS LIST
A professional tip .. .
If this is the first time you are preparing to
use a slide rule, perhaps these preliminary
remarks will be helpful.
Don’t let all those graduations on the scales
alarm you. Just a few minutes spent reading
the first pages of this booklet with a slide
rule in front of you will quickly prove that
the scales are easy to read. You start with
multiplication and division, and then go on
to simple examples of other slide rule cal-
culations.
As each section is completed, work out ad-
ditional similar problems before continuing
to the next section. Very soon, you will be
able to use your slide rule easily and quickly.
Reading the Scales
The C and D scales are most commonly
used for multiplication and division. These
scales have identical graduations and appear
on all slide rules.
Their left and right-hand ends are marked
with the numeral ‘1’, and are called /eft
index and right index, respectively. The
major divisions are marked from 2 through
9. Each major division is further divided into
tenths. More complete divisions are given for
values between 1 and 2, covering the left-
hand end of the scale. This section is further
sub-divided into ten major sub-divisions
from 1 to 9, representing the values 11 to 19
(on the POST four inch rule, only the 15
mark is numbered, due to lack of space).
The tenths are still further sub-divided into
tenths, fifths or halves, as space permits.
On the fold-out pages at the back of this
booklet, you will find that Figure 1 (10 inch
rules) and Figure 2 (5 inch rules) illustrate
how to read various values on a typical slide
rule scale. Familiarize yourself with the scale
so you will know how to find 205, 250,
255, etc.
First Digit is Guide
Note that all numbers that begin with the
numeral 1, regardless of the position of the
decimal point, are found somewhere be-
mani
tween the left index and the major division
2. This space covers approximately the left-
hand third of the entire scale. All numbers
beginning in 2 are found between the major
divisions 2 and 3, numbers beginning in 3
between major divisions 3 and 4, and so on.
When it is necessary to read a scale at a
point between two graduations, the setting
must be estimated to the nearest fraction
of a division.
All numbers that have the same digit
value (e.g. 0.00274, 2.74, or 27,400) are
found at the same point on the slide rule
scale, regardless of the position of the
decimal point.
MULTIPLICATION
To illustrate a typical slide rule pro-
cedure, solve the following simple problem
as shown in Figure 3:
2x 3=6
Set the left index of the C scale over 2
on the D scale. Set the cursor hairline over
3 on the C scale. Find the answer 6 on the
D scale under the hairline.
The slide rule solves more complex prob-
lems with equal ease. For example: 1960 x
3.25 = 6370.
Set the left index on C over 196 on D.
Set hairline over 325 on C and find the slide
rule answer 637 on D.
Decimal Points
In the above example, the location of the
decimal point can be determined by a quick
mental calculation using round figures close
to the numbers in the problem. Thus: 2000
x 3 = 6000. Our answer, therefore, must be
4 digits to the left of the decimal point,
or 6370.
Use of Right Index
If the values in a problem are such that
the multiplier on the C scale extends out
beyond the limits of the D scale, then use
the right index of C instead of the left index.
See Figure 4 for an illustration of this
example:
6x 2=12
If we set the left index of C over 6 on the
D scale, we find that 2 on the C scale goes
beyond the right-hand end of the D scale.
So we proceed as follows: Set the right
index of the C scale over 6 on the D scale.
Under 2 on the C scale, we now find the
answer 12 on the D scale.
Here is another example: 71.5 x 1.63 =
116.5. Set the right index of the C over 715
on the D scale. Set the cursor hairline over
163 on the C scale and read the slide rule
answer 1165 under the hairline on the D
scale.
The decimal point is located by making
a quick mental calculation (70 x 1.5=105.0)
Thus the answer in this example is 116.5.
DIVISION
The slide rule procedure for division is
just the reverse of multiplication. For ex-
ample to solve (See Figure 3): 8 = 2. Set 3
on the C scale over 6 on the D scale. Under
the left index of the C scale read the answer
2 on the D scale.
lf the slide extends to the left, as for
example when dividing 2 as shown in
Figure 4, then read the answer 6 on the D
scale under the right-hand index of the
C scale.
OTHER METHODS TO MULTIPLY AND
DIVIDE
The A and B scales, which are identical in
scale arrangement, are similar in construc-
tion to the C and D scales, except that they
are half size. This makes it possible to place
two segments end to end in the same length
occupied by the C and D scales. For con-
venience in use, the right-hand half of the A
and B scales is numbered from 10 to 100,
since this section is actually a continuation
of the left half (on Post’s pocket size rules,
the zeros are omitted because of lack of
space).
In Figure 3, the setting of the slide rule
illustrates the solution to the problem 4 x
9 = 36 solved on the A and B scales. The
left index of B is set under 4 on the A scale.
Over 9 on the B scale we read the answer
36 on the A scale.
Dividing with A and B Scales
For division we follow the reverse pro-
cedure. Example shown in Figure 3: 2. 4.
Set 9 on the B scale under 36 on the A scale.
Over the left index of the B scale, read the
answer 4 on the A scale.
Use of Cl Scale
Multiplication problems can be solved
very efficiently using the Cl scale in con-
junction with the D scale. The Cl scale is
exactly the same as the C scale except that
it has been turned end for end, and con-
sequently reads from right to left.
To multiply using the Cl and D combi-
nation of scales, refer to the setting in
Figure 3 for the solution of the problem
6 x 3.33 = 20.
With the cursor hairline set over 6 on the
D scale, draw the slide to bring 333 on the
Cl scale under the hairline. Under the left
index of the Cl scale, we find the slide rule
answer 2 on the D scale.
To locate the decimal point, we take as
round figures 6 x 3 = 18. Our answer,
therefore, is 20.
Multiplying More Than Two Factors
The CIl—C—D scale combination is par-
ticularly useful in solving multiplication
problems involving more than two factors.
For example: Find the volume of a wall
15.5 feet long by 8 feet high by 0.55 feet
thick.
Solution: Set the cursor hairline over 8
on the D scale. Set the slide to bring 155 on
the Cl scale under the hairline. Now set the
hairline over 55 on the C scale. Read 682
under the hairline on the D scale.
To locate the decimal point solve men-
tally: 15 x 8x .5= 15x 4=60. The correct
answer, therefore, is 68.2 cubic feet.
Notice that in the above example only
one setting of the slide is necessary to solve
two multiplications simultaneously. The par-
tial answer 124, from 8 x 15.5 is on the D
scale under the left index of the C scale.
Since the second step in the problem is to
multiply by 0.55, it is necessary only to set
the hairline to 55 on the C scale and read
the answer, 68.2, on the D scale without
any regard to the partial answer.
OTHER CALCULATIONS Cubes and Cube Roots (use of the K scale)
By using the D scale and K scale in com-
bination, cubes and cube roots can be found
directly on your slide rule (the K scale does
Squares and Square Roots
Note that the relationship between the A
and the D scales is such that for numbers | not appear on the POST 4 inch rule). Note
appearing on the D scale the squares can be that the K scale is made up of three identical
found directly above on the A scale. Con- | sections placed end to end. Each section is
versely, the square roots of numbers appear- , similar in construction to the D scale except
ing on the A scale are read directly below that it is exactly one-third its length.
on the D scale. To find the cube of a number, set the
Thus, to find the square of any number, cursor hairline to that number on the D
set the cursor hairline over that number on scale, and read the answer under the hairline
the D scale. The square will be found under on the K scale.
the hairline on the A scale. To find the cube root of a number, the
To find the square root of a number, the procedure is reversed, setting the hairline
reverse precedure is followed. The hairline is first to the number on the K scale and read-
set over the number on the A scale, and the ing the cube root under the hairline on
root is found under the hairline on the D | the D scale.
scale.
Locating Numbers on the K Scale
If the A scale number has an odd number ]
of digits to the left of the decimal point, it is ,
located on the /eft-hand half of the A scale.
If it has an even number of digits to the left
of the decimal point, then it is located on
the right-hand half of the A scale. Thus, 125
would be found on the left-hand half of the
scale and 12.5 would be found on the right
half.
The three segments of the K scale cover
numbers ranging from 1 to 10 for the left-
hand section, from 10 to 100 for the center
section and from 100 to 1000 for the right-
hand section. Thus, for any number between
1 and 10 on the D scale, the cube can be
read directly off of the K scale somewhere
between 1 and 1000. Conversely, for num-
bers between 1 and 1000 on the K scale,
the cube roots will be read directly on the D
scale somewhere between 1 and 10. For
10 11
numbers less than 1 or greater than 10 on
the D scale, or less than 1 and greater than
1600 on the K scale, the decimal point may
be moved both before and after the opera-
tion to obtain a number within the range of
the scales. In such cases a definite rule may
be followed
'f the decimal point is moved n number
of places in a value set on D, it must be
moved back 3n places in the cube, which is
read on ihe K scale; or if the decimal point
is meved n number of places in a value set
on the K scale, it must be moved back 3
places in the cube root, which is read on
the D scale
For example, to find the cube of 0.456,
we move the decima! point 1 place to the
nigra. By setting the hairline at 4.56 on the
D scale, we obtain 95 at the hairline on the
K scale. According to the above rule, we
now move the decimal point to the left
three places and obtain the answer 0.095.
To find the cube of 1214, we move the
decimal point three places to the left.
Setting the hairline to 1.214 on D, we find
the cube 1.79 on K. We now move the
decimal point back nine places to the right,
giving us the answer 1,790,000,000.
To find the cube root of 0.0052, the
decimal point is moved three places to the
12
right. The hairline is now set over 5.2 on
the left hand segment of the K scale, and
the result, 1.73, is read off of the D scale.
According to the above rule, the decimal
point is now moved back one place to the
left, giving the answer 0.173.
Reciprocals
The relationship of the C and Cl scales is
such that the reciprocal of any number on
either scale can be read for that number
directly opposite on the other scale. For
1.
7 > 0.5,
To solve on the slide rule, set the cursor
hairline over 2 on the C scale. Under the
hairline on the Cl scale, read the reciprocal
0.5. The position of the decimal point in any
reciprocal can be determined by a mental
calculation using round numbers as ex-
plained in the section on multiplication. The
procedure may be reversed by setting the
hairline to 2 on the Cl scale and reading the
reciprocal 0.5 directly below on the C scale.
example: The reciprocal of 2 =
Logarithms
The L scale on the back of the slide is a
uniformly divided scale which gives the man-
tissas of logarithms of numbers read on the
D scale. Example: Find the logarithm of 2.
13
Set the left index of the C scale over 2 on
the D scale. Turn the slide rule over, and
read the mantissa 301 on the L scale under
the fixed hairline on the back of the rule.
From the principle of logarithms, it is
known that the characteristic for 2 is zero;
the logarithm, therefore, is 0.301.
TRIGONOMETRIC FUNCTIONS
The two scales on the back of the slide
marked S and T are the sine and tangent
scales respectively.
Sines
The S scale is divided ue read in degrees
and minutes from about 0°34’ to 90°. It is
designed to be used with the A and B scales.
Example: Find the sine of 21°.
Set the slide to bring 21 on the S scale
under the right-hand fixed hairline on the
back of the rule. Turn the rule over, and
read 358 on the B scale under the right
index of the A scale. Note that the values
of sines found on the right-hand half of the
A and B scales range from 0.1 to 1.0 and
those on the left-hand half range from 0.01
to 0.1. Therefore, our answer in this example
is 0.358.
When given the sine, the procedure is
reversed to find the angle.
Example: Find the angle whose sine is
0.126.
14
Since the sine is greater than 0.1, 0.126 is
located on the right-hand segment of the B
scale. Draw the slide to bring 126 on the
right half of the B scale under the right
index of the A scale. Turn the rule over, and
read the angle 7°15’ on the S scale under
the fixed hairline.
Alternate Method (Sines)
Remove the slide from the rule and re-
insert so that the S, L and T scales are face
up. With the slide centered so that the
indices of the A scale line up with the ends
of the S scale, sines can be read on the A
scale directly opposite any angle on the S
scale. Thus, to find the value of sin 7°, set
the cursor hairline over 7 on the S scale and
read the answer 0.122 under the hairline on
the A scale.
Tangents
The T scale is divided to read in degrees
and minutes from about 5°45’ to 45°, It is
designed to be used with the C and D scales.
Example: Find the value of tan 35°.
Set 35 on the T scale under the right-
hand fixed hairline on the back of the rule.
Turn the rule over and read the answer
0.700 on the C scale over the right index of
the D scale. Note that the values of tangents
of angles from 5°45’ to 45° range from
0.1 to 1.0.
15
Alternate Method (Tangents)
Turn the slide over as described in the
alternate method for using the S scale and
read directly from the T scale to the D scale °
or vice versa.
Tangents of Angles from 0°34’ to 5°45’
The values of tangents and sines of angles
smaller than 5°45’ are so nearly alike that
they may be considered identical for slide
rule computations. Consequently, for angles
from 0°34’ to 5° 45’, tangents can be read
directly using the S scale and the left half of
the A or B scales, as described in the section
on sines.
Tangents of Angles Greater Than 45° ;
Using the relationship tan x = tan (90-x),
tangents for angles greater than 45° can be
directly computed on the slide rule.
Example: Find tan 69°.
Solution: 90-69 = 21. Set 21 on the T
scale under the right-hand fixed hairline. The
answer, which is the reciprocal of tan 21, is
read directly on the D scale under the left
index of the C scale as 2.605. Note that for
angles between 45° and approximately g4°
the value of the tangent ranges from 1 to 10.
When in the above relationship 90—x is
less than 5°45’, the left half of the S scale is
16
used in making the computation. As pointed
out above, the sines and tangents of small
angles may be considered equal for slide
rule purposes.
Example: Find tan 88°.
Set 2 on the S scale (90-88) under the
right-hand fixed hairline. Turn the slide rule
over and read the answer 28.6 on the A scale
over the left index of the B scale. Using this
method, tangents of angles up to 89°25’ can
be read directly.
Sines and Tangents of Very Small Angles
For determining the sine or tangent of a
very small angle, two gauge points are pro-
vided on the S scale. The one identitied by
the symbol (‘) is called the minutes gauge
point and is found next to the 2° mark on
the S scale. The seconds gauge point marked
() is found near the 1°10’ mark on the S
scale. They represent the value of the angle
in radians. Their use is based on the fact that
for very small angles, sin x = tan x = x (in
radians), approximately.
Example: Find sin 3’.
Since sin 3’=3' (in radians), solve 3 x 1’
(in radians). The procedure when using these
gauge points is the same as the use of the Cl
and D scale combination for multiplication.
With the slide turned so that the trig scales
17
are face up, set the minutes gauge mark
under 3 on the A scale. Over the right index
of the S scale, read 0.000873 on the A scale.
Example: Find sin 3”.
Set the seconds gauge mark under 3 on
the A scale. Over the left index of the S
scale, read 0.0000145 on the A scale.
The decimal point in the above examples
is located by noting that:
1' — 0.0003 radians (approximately)
1” — 0.000005 radians (approximately)
18
THE FINEST IN
ENGINEERING
SUPPLIES
AND DRAFTING
EQUIPMENT
Teledyne Frederick Post carries a full
complement of drafting, engineering and
art supplies.
The Post Consumer Buying Guide gives
dealers, students, engineers and do-it-
yourself fans easy access to a complete
line of products carrying the POST name
and traditional quality.
The merchandise shown in the catalog is
the same, nationally advertised merchan-
dise used and respected by professionals
all over the world.
Send for the 32-page Post Consumer Buy-
ing Guide now, and stock-up on those
items you’ve been “meaning to get” for
some time. Post has drafting supplies to
fit every budget. Write to:
“4 TELEDYNE POST
P.O. BOX 803, CHICAGO, ILL. 60690
ALL NUMBERS HAVING SAME DIGITS ARE LOCATED ON SAME
POINT ON SCALE REGARDLESS OF POSITION OF DECIMAL POINT.
~
1165 27.400
FIG. 1 105 (5 ESE) 2055 0.00774 406
»
D SCALE ON Lil 15 2 [21 si ch SW a 505 BUZZ ESL) 925
PICAL 10” RULE tr
LEFT INDEX RIGHT INDEX
10? 108 205 = 750
295
295 3/8 | 6/% (5 EST)
FIG. 2
D SCALE ON
PICAL POCKET
RULE
LEFT INDEX RIGHT INDEX
A AND B SCALE SETTING FOR 4x 9= 36 OR 36-9=4
BODY 4 36
[mmo By 9 Equals ~———_. |
FIG. 3
EXAMPLE OF
LTIPLICATION
D DIVISION ON
B,C &D SCALES
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