A good bend has the same diameter in the bend as in the remainder of the tube (1, Fig. 41). It is rather difficult to make because the tube tends to cave in on the inside of the bend (2) or flatten on the outside (3), or both.
Make the bend as follows: Heat a piece of No. 2 tube about 2 inches from one end in the lamp flame, turn it constantly and move it back and forth endwise to heat a length of about 2 1/2 inches. When soft, take the tube out of the flame, and bend the ends upward until the angle is 90°.
If the bend is flat on the inside or outside, close one end of the tube in the blowpipe flame, smooth the other end and allow them to cool, then heat the flat side of the bend in the blowpipe flame and blow it out slightly. This makes the diameter of the tube at the bend equal to that of the remainder of the tube. Cut off the closed end, smooth the edge, and your bend is complete.
Make bends with No. 4 tube.
Fig. 41. Bends