Otis College of Art and Design
presents ...
with me
Making accurate measurements is the first step in any successful building project.
All the subsequent steps of cutting and assembly of the various parts of your project
will be affected for better or worse by the accuracy of your initial measurements.
So it is important to build precision from the very start,
being certain every step of the way you are preserving the accuracy of your work.
We will be measuring using United States customary units.
The 32nd of an inch is the smallest unit of measure that will be using.
To demonstrate these techniques l'll be using an Xacto knife,
a 36 inch metal ruler, a tape measure,
a framing square, a sheet of corrugated cardboard,
self-healing cutting mat,
and sharp pencil. The pieces that you cut out for your projects
should be measured to the nearest 32nd of an inch
and they should not deviate from their plan size by any more than plus or minus
1/32.
This range of unintended but acceptable deviation from a design
is called tolerance. In this demonstration
I will cut a set of 6 inch by 6 inch squares from a sheet of corrugated cardboard.
Lay your material down on top of your cutting mat with the rippled side up
place your 36 inch ruler on the left hand edge of your material
and measure its height from the bottom left corner. Mine
is 22 and a 1/2 inches. Now move your ruler to the bottom edge
of your material. I will mark point at the exact same distance
out from the bottom left hand corner 22 and a 1/2 inches.
Lay your ruler diagonally across your cardboard and strike a line between
the two points.
This diagonal line runs at a 45 degree angle to the corrugation of the board.
Cutting the cardboard in the bias insures that all four edges of our piece
will be identical in appearance and all equally supported by the corrugated.
From this point on we will refer to this diagonal line
as our baseline. The factory cut edges of the cardboard
are no longer relevant in our process. Align your framing square
so that one leg runs along the baseline and the corner
is a little over six inches from the top left corner
of the cardboard. Mark a point along the top edge of your square
exactly 6 inches from the baseline. Lift your square over
and repeat this process.
This time start 1 or 2 inches from the bottom edge of the cardboard.
To save material, remember to draw your perpendicular line
along the outside edge of your framing square.
Each of these new lines is at a 90 degree angle
from our baseline. Use your 36 inch straight edge to draw a line connecting
these two points.
This new line should be parallel to the original baseline.
Next, we'll cut along these two lines to produce a consistent 6-inch strip
that we can later divide into squares. Lay your 36 inch metal straight edge down
and line it up against the baseline.
Now we'll cut.
Hold the ruler firmly against the material with your sub dominant hand
spreading your fingers wide enough to evenly distribute pressure
along as much of the ruler's length as possible. Stand with one foot forward
and lean over the cardboard. Take the knife in your dominant hand
hold it like a pencil, not like a dagger, make certain that the tips of your
fingers do not protrude beyond the edge of the ruler.
Align your body so that the line to be cut points to the center of your torso.
Do not try to cut through the material all in one pass.
Use a three pass cutting technique. Be sure that the ruler does not get moved
between passes.
Hold the knife against edge of the ruler.
Site down the blade making sure that it is not leaning to the left or to the right
otherwise you will cut a bevel into your cardboard.
Draw the blade back toward you by rocking backward from the hip.
Keep your elbow, wrist, and shoulder joints
immobilized.
Before picking up the ruler,
check to make sure that both pieces of material are free from each other.
Make additional passes with the knife as needed.
Next use the same technique to cut along
the parallel line you have drawn six-inches over from the baseline.
Make sure to reposition your material as needed
so that the cutting mat remains under the length of your cut.
Just as before,
hold the Xacto knife like a pencil, slide the blade along the edge of the ruler.
Walk your fingers down the ruler to keep constant pressure on your material as you cut.
Use multiple passes to create your cut.
Draw the blade back toward you by rocking backward from the hip.
Remember to keep your elbow, wrist, and shoulder joints
immobilized. If your ruler gets accidentally moved
don't work. Simply stop and realign it before continuing with your cut.
You should now have a 6 inch wide strip of
cardboard. Set all the other materials aside,
and lay the strip down so that it's length runs parallel to the front edge of the table.
We will now cut out or 6 inch squares.
Place your ruler along the perpendicular lines
at the end of the strip.
Cut the line using the technique that I have just demonstrated.
Use the inside corner of a framing square to check that the cut
is 90 degrees from the baseline, which is a right angle.
If it is within our tolerance then proceed to your next cut.
Use your square to mark a point 6 inches from the perpendicular cut
along the top line
and baseline.
Now use your ruler to create a line between these two new points.
This line will be at a right angle 90 degrees from our baseline.
Using your Xacto knife, cut the line.
Spread your fingers so that you have even pressure along the ruler.
You should now have a precise 6 inch by 6 inch square.
By cutting the cardboard on the bias now
all four edges of our peice are identical in appearance and all these edges are
equally supported by the corrugated structure of the board.
Use the inside of your framing square to make sure that all the corners are 90 degrees
Repeat this process down the line
to create a set of identical squares.
Place your framing square along the baseline to measure the distance
to your next cut.
Repeat this process along the top parallel-line.
Now use your ruler to cut the line.
Accuracy - not speed - is important at this stage.
Check each corner against the inside of your framing square
to make sure that all the corners are 90 degrees.
Press your cut squares together back to back and make sure they're all the same.
Continue on to your next cut.
Check your work as you go along.
Continue to press your cut squares together back to back and make sure
they're all the same.
Once you have you cut squares to construct your object,
press all the squares together back to back
to make sure that they're all the same.
Discard any pieces that deviate from the 6-inch design specifications
by any more than a 32 of an inch in any direction.
Once you have the required squares,
it is a good strategy to double check all your pieces before you proceed to
gluing them together.
Checked them with your ruler to make sure that their heights and widths
are 6 inches. You can also do this with a tape measure.
Discard any pieces that deviate from the 6-inch design specifications
by any more than a 32 of an inch in any direction.
If necessary cut additional pieces using the methodology I demonstrated in this video.
Continue cutting and checking your results until you have produced 6
perfect 6 inch squares.
Accurate measuring, precise cutting are fundamental to producing more effective
and professional work.