On Jan 15, 5:19*pm, "Maxwell" #$$9#@%%%.^^^ wrote:
"cavedweller" wrote in message

...
On Jan 13, 9:31 am, "Dick Meade" wrote:

Tooling cost for permanent mold is prohibitive.

What I don't know about foundry practive would fill large volumes, but
a relatively simple single cavity that would last a while and some
appropriate finish machining still might (!) be worth looking
at....unless, of course, for some reason machining a head out of sound
billet stock isn't a solution.

Nice link.

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Machining a head from billet would be an excellent solution, just a lot more
expensive.

Cold finish aluminum billet is usually about 3 times the price per pound
than T-0 ingots, and you have to pay the same price for all the machine
shavings you do for the finished machine part. Considering something like a
VW head, you are probably tossing as much as 50% of your billet, purchased
at three times the price. Then you have to add the machining time. All worth
it if you can afford it for sure, but usually much more expensive.

That's why I suggested casting a head, including ports, combustion chambers,
rocker tub, etc, and leaving the fined area solid to be machined by CNC or
tracer. You get the ultimate detail in your cooling fins for maximum
efficiency, but save the cost of the alloy and all the extra metal discarded
when machining from billet.

So, how many actual dollars does the price difference between billet
and ingot represent as a percentage of the overall cost of an
airplane...after you sell the chips as scrap.

Presumably you are looking at at least 4 heads which fits well with
CNC. CNC milled heads made from billet will be exactly alike, which
is more than can be said for castings.