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Chapter 2 Layout and Fabrication of Metal and Fiber-Glass Duct | Up
Steelworker Volume 02 - Building manual for how to work with steel | Next
TrammelPoints |
Complete the line by scribing from the other prick
punch mark in the opposite direction.
Flat Steel Square
The FLAT STEEL SQUARE is a desirable tool for
constructing perpendicular or parallel lines. In the
method of layout, known as parallel line development,
the flat steel square is used to construct lines that are
parallel to each other as well as perpendicular to the
base line. This procedure is shown in figure 2-2.
Simply clamp the straightedge firmly to the base line.
Slide the body of the square along the straightedge,
and then draw perpendicular lines through the desired
points.
Before using the flat steel square or at least at
periodic intervals, depending on usage, see that you
check it for accuracy, as shown in figure 2-3. When
the square is off, your work will be off
correspondingly no matter how careful you are.
Combination Square
The COMBINATION SQUARE can be used to
draw a similar set of lines, as shown in figure 2-4. An
edge of the metal upon which you are working is used
as the base line, as shown in the figure. One edge of
the head of the combination square is 90 degrees and
the other edge is 45 degrees. Combination squares are
Figure 2-2.—Using a swuare to cinstruct perpendicular and
parallel lines.
Figure 2-3.—Checking a square for accuracy.
Figure 2-4.—Using the combination square
delicate instruments and are of little value if you
handle them roughly. Store your squares properly
when you have finished using them. Keep them clean
and in tiptop shape, and you will be able to construct
90-degree angles, 45-degree angles, and parallel lines
without error.
Protractor
To construct angles other than 45 degrees or 90
degrees, you will need a PROTRACTOR. Mark the
vertex of the angle of your base line with a prick
punch. Set the vertex of your protractor on the mark
and then scribe a V at the desired angle (assume 700).
Scribe the line between the vertex and the point
located by the V, and you have constructed an angle
of 70 degrees.
Prick Punch
When you locate a point and mark it with the PRICK
PUNCH, be sure to use alight tap with a small ball peen
hammer, ensuring it is on the precise spot intended to
mark. The smaller the mark you make (so long as it is
visible), the more accurate that mark becomes.
Dividers
You should use DIVIDERS to scribe arcs and
circles, to transfer measurements from a scale to your
layout, and to transfer measurements from one part of
the layout to another. Careful setting of the dividers is
of utmost importance. When you transfer a
2-2
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