Figure 3-47.Finding the cutback.
distance along the bottom quarter line. Make punch
marks with the center punch on each side of the line,
along the side quarter lines. These marks will make it
easy to align the pipe for welding after the joint is cut.
Use the spring steel wraparound and pull the loop to
the cutback point. Next, draw a chalk line over the top
half of the pipe through the first cutback point.
(NOTE: Do not allow the wraparound to twist or
kink, and hold the chalk at a right angle to the
wraparound while marking the pipe.) Now roll the
pipe one-half turn and mark a chalk line in the same
way around the bottom half of the pipe.
If a template is not available, you may determine
the dimensions and markings for the cut necessary for
a two-piece welded turn of any angle between 1 degree
and 90 degrees by making a full-sized drawing, as
shown in figure 3-48.
Draw the center lines intersecting at b by using the
angle of turn T and then draw the outlines of the pipes
by using the center lines and the diameter D. These
will intersect at a and c. By laying the pipe over the
drawing so that point b will coincide with that
determined by construction details, you can draw the
lines a-b and c-b in preparation for miter cutting and
After being prepared for welding, one section of
pipe should be rotated through 180 degrees to form the
desired angle, and then it should be tack-welded.
Figure 3-48.To locate cut on a pipe for any angle two-piece
Spacing should be slightly greater at the inside of the
To lay out the template for cutting the branch and
header for a 90-degree tee with header and branch of
equal diameter, draw the side and end view, as shown
in figure 3-49, views A and B.
In making the template for the branch in figure
3-49, view A, draw lines 1-5 at 45 degrees to the center
line. Lay off distance 1-P equal to twice the thickness
of the pipe wall and draw the smooth curve s-P-s. Now,
project point P from view A to view B and draw the
lines P-t radially. At a distance above point t equal to
the thickness of the header wall, draw a-t horizontally,
and vertical lines a-a and t-t. With lower points a as
center, swing arcs r-s. Using the intersections of these
arcs as centers and with the same radius, draw the
curved lines a-be-d-e arid e d-c-b-a.
Divide the outside circumference of the branch
top into equal parts and draw the vertical lines b-b, c-c,
and so forth. Also, draw the horizontal base line a-a.
Lay off the unwrapped circumference (fig. 3-49,
view D), and divide each half of it into the same
n u m b e r o f e q u a l p a r ts
a s t h e b r a n ch
semicircumference. In view D, you should plot the
distances a-a, b-b, and so forth, from view B. This
gives the distances from the base line to the branch
curve of the intersection and determines the location
of the branch template.