< SAND VENTING WITH BLIND RISERS
DRAINS
Drains are small stubs of wax, similar to BLIND RISERS. Drain stubs are positioned on the wax pattern and the end of the stub kept exposed by scraping as the investment mould is built up. This later allows melting wax to escape the mould via the drains during the kiln burnout. Residual drain holes are then blocked off with a refractory paste before casting, unless they fulfil a secondary function such as for SAND VENTING (see previous page). Most ceramic shell mould designs allow the inverted pouring cup to be used as a main drain, though supplemental holes are sometimes drilled through the investment walls with a small masonry bit for additional relief. Like drain stubs, these relief holes are sealed with a refractory cement before the mould is filled with metal.
CORE VENT >
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