How Do You Read a Grade Rule?
By Elizabeth White, [TC]2
Whenever someone is first exposed to grade rule tables, there is some confusion
on how to read the grade rules. Most of that confusion can be easily removed by
knowing a few terms and conventions. There are several different ways to set up
grade rule tables that will be covered in a later article so I will focus on one of the
most common ways that uses x,y coordinate pairs for distance away from the
sample size.
First, it is helpful to know the location of the grade rule on the pattern. I will
primarily use corner grade rules to clarify the principle. Grade rule tables usually
are numbered so that individual rule numbers relate to particular locations on
pattern pieces. In the following illustration, there are 5 grade rule numbers, each
at a different corner on the rectangle or on a notch.
Notice that the grade rule numbers are not consecutive when reading the
numbers in any direction around the boundary of the piece. Sometimes, when
first setting up grade rule tables, the original pattern pieces may have
consecutive numbers but that is a personal preference. Other systems may
incorporate a numbering convention such that the grade rule numbers
correspond to particular pattern piece locations.
In this example, there are only five grade rules to be considered. The grade rule
table associated with this piece includes these five grade rules.
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S
1
8
12
17
25
X
0
0.5
0.5
-1
-1
M
Y
0
-2
0
-2
0
X
0
0
0
0
0
L
Y
0
0
0
0
0
X
0
-0.5
-0.5
1
1
XL
Y
0
2
0
2
0
X
0
-1
-1
2
2
Y
0
4
0
4
0
When reviewing the grade rule table, notice that four size labels head columns of
x,y coordinate pairs: S, M, L, XL.
Next, the pattern piece size needs to be identified. In the grade rule table, a
sample size is often used for reference when compared to the other graded
sizes. If the pattern piece is the sample size, it is fairly simple to grade to the
other sizes. See this article for information on sample sizes and conventions for
sizing charts. For this example, size M is the sample size since the coordinate
pairs are 0,0. The pattern piece is also labeled with size M.
But how do we read the individual grade rule values in relation to the pattern
piece and the rule’s location on the piece? In the next illustration, I have
enlarged the corner that uses the grade rule number 8.
The sample size is M, so since the pattern is already size M, there is no change
to the pattern piece. For size L, the piece needs to change using the x,y
coordinate pair under the heading L for grade rule 8: (-.5,2). However, in order to
make this change to the corner, the orientation of the pattern piece to the grade
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rule table is needed. The illustration shows how the corner would look based on
different orientations to the table.
Once we know the correct orientation of the pattern piece, we can see how the
corner would grade. By following the x,y coordinate pair, we can change the
corner correctly. The x coordinate denotes how many measurement increments
the corner would move, in either the positive or negative horizontal direction.
The y coordinate denotes the number of measurement increments for vertical
movements. The corner moves to the intersection of the x,y coordinates for the L
size as shown below using the correct piece orientation.
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The following illustration shows how the other sizes would grade at this corner
using the x,y coordinate pairs for S and XL in comparison to sizes M and L.
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Once the orientation of the pattern piece is known for one grade rule, the other
grade rules on the piece should also grade correctly as illustrated below.
Of course, it is helpful to know the units of the grade rule table so that the correct
scale of grade is applied to the pattern pieces. In this example, the rectangle
was 12 x 7 so the grade rules significantly affected the height more than the
width. It is also important to understand that negative grade rule values only
affect the direction of the point movement and not whether the grade rule is
making the piece larger or smaller. For some people, it is difficult to understand
how negative values can make a piece larger. There is also a notch on this
piece with grade rule 1 holding the position of this notch in the same place with
no grading.
Elizabeth White assists and instructs companies in the use of product
development tools through [TC]² seminars and consulting services. Grade rules
and sizing are integral topics within the Pattern Development, Grading for Fit,
and How to Build a Tech Pack seminars.
July 2012
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