Page 4 - June 2014
P. 4

MAKING THE PATTERN FORA NEW CAS

   THOUGHT I HAD DONE ENOUGH weakness which could be the start of a crack

   when I took my wooden model of                 and give way under pressure, like Ɵghtening

   a chase to the foundry. I hadn't. The          up the quoins. So a small rounding of the

   manager said that most of the paƩerns internal corners would be a good idea. (3 & 4)

   they used were made of hardwood                They wanted to cast a prototype to see what

   whereas mine was ordinary old soŌwood, was involved. The bill for this was £68.08.
however he went on to say that it would
                                                  The MD, who had given me the esƟmate, was
probably work if I didn't need too many of them. away so I paid up and took it home to balance
They apparently get a bit of a baƩering when it and make it fit my press by filing down the
making the sand moulds.
                                                  small bumps I had included on my paƩern for

How much would it cost to cast? About £30-£40 this purpose.

each was the answer. On that basis I adverƟsed    Did I realize that cast iron shrinks a liƩle on
for customers. There were condiƟonal              seƫng? Yes, I did, I told him, but by how
customers for 16 chases, which would have         much? I though he said 0.3%. Only when my
been enough for a "full heat" (a crucible full).  prototype had finally been cast and I found it

Then he said everything had to have a "relief" about 3mm too small did I discover that it was

angle on it so that it could be liŌed out of the  more like 1.3%.

sand without damaging the edges of the mould;     The prototype took ages to appear because
about 2 degrees would do, and to make the         they wanted to wait unƟl they could fit it in
inside of the chase perpendicular to the base of  to a batch of cast iron work (they also cast in
the bed there had to be a separate paƩern for     bronze, aluminium and ducƟle steel, all much
the space where the type would go. (1 &2)         more expensive).

This paƩern had to come apart without liŌing      The ProducƟon Manager told me that my
it off the sand. Oh, and by the way, sharp         paƩern for the inside of the mould had "been
right angle corners in a casƟng could create a    a bugger" for the chap who had made it. My

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