Vintage engine guys want to do a run of brake drums.

They spent a while on Sunday trying to cast Ally in the drum to make a pattern, but it didn't work out. Then they come to me yesterday asking for plywood to layer together to make a pattern.

So, I scrounge for plywood, then find some of Dad's old 8" x 3" pine. (Dad was a patternmaker)

Cut two squares, lop the corners off, mount onto a faceplate:
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and start to machine round. Wasn't easy to get the tool far enough out:
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so in the end I used a cheaper cutter half way out of the holder for roughing down:
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Then clean up with a sharper tool:
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(ground positive rake Aluminium cutting insert, small cuts).


Now, measuring shows this is a little small for the outside of the drum, because the drum has a lip at the back. So we can use it for the inside mould, right?

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Spend an hour tapering, radiusing the inside corners (fillets), replicating the inside core/negative shape...



until I realise I am being an idiot!
The sand mould needs to be that shape, not the pattern to make the mould!!!




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So, here is the brake drum, on top of a much larger bit of old timber (Jelutong), ready to chop the corners off, and bore a CAVITY into.


Might get lazy, and with a quick trip to a foundry with the drum, cast the cavity in Alloy instead, to machine out into the cavity pattern.
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