Page 105 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 2 Common processes and techniques

Off-set measurement 1
Fixed point
1
To find the correct off-set angle, the size of the off-set should
be deducted from the 600 mm and the 600 mm folding rule
opened to the measurement, i.e. off-set 50 mm. 600 – 50 = 550 Fixed point to centre of obstruction
The bench mark on the first bend is determined by
Off-set measurement Angle required adding 1 /4 of the diameter of the obstruction to the
measurement from the fixed point to the centre of the
50 mm
obstruction
Bending mark
Fixed point to centre
of obstruction Add 1 /4 dia
600 mm rule
2 of obstruction
Bend tube to the angle set by the rule
2
To find the correct angle for the first bend, multiply the
diameter of the obstacle by 3 and close the folding rule by
this amount then position the tube in the machine so that
the bending mark and the centre of the angle align

Then form the
first bend to the
angle of the rule

3 Remove tube from machine and mark for the second
bend measuring from inside edge of tube using a
straight edge

Bending mark
3 Making sure that the bend clears the obstruction, place a straight
Straight edge Off-set edge over the tube and mark the bending marks on both sides
measurement

Bending mark

Bending marks
4 Re-position tube in the machine so that the
mark forms a tangent to the former
4
Position tube in the machine so that
the bending mark touches the former edge

5 Re-position the rule to give the correct 5 Bend until the top of the
angle for the second bend tube is level and in line
with the former mark
Re-position tube in the
machine so that mark
forms a tangent

Reverse tube in the former
and position as before then
bend until the top edges
are in line

p Figure 2.11 Off-set bends p Figure 2.12 Passover bends
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