Holes may be drilled and tapped in the wall of fittings if the wall
thickness will provide effective thread length as shown in table 4.1
below.
Table 4.1
Table 1 and A1 Minimum Thread Length
| Size of Tapping | 3/8 | 1/2 | 3/4 | 1 |
| Length of Thread "A" | 0.41 in (10.3 mm) | 0.53 in (13.5 mm) | 0.55 in (13.9 mm) | 0.68 in (17.5 mm) |
| Size of Tapping | 1 1/4 | 1 1/2 | 2 |
| Length of Thread "A" | 0.71 in (17.9 mm) | 0.72 in (18.3 mm) | 0.76 in (19.4 mm) |
These lengths are in accordance with the effective thread length as
required in ANSI B2.1. If the tapped hole required is too large to be
accomodated by the standard fitting wall thickness, an integrally cast
boss may be required to provide the necessary thickness for tapping.
In addition, it may be necessary to integrally cast a flanged boss
to accomodate larger sized holes that are impractical to thread. In
this case a boss the size of a flange shall be integrally cast. The
hole shall be cored or drilled at the manufacturer's option. The flange
boss shall be faced and bolt holes will be drilled and tapped. The bolt
holes shall be blind tapped as to not interfere with the fitting wall
thickness (see Table 4.2).
