On Sunday, April 25, 2004, at 04:14 PM, MJSUKEY@cs.com wrote:
>
> I know when a shop mills a head or decks a block it is "cut, as in
> milling
> cutter". The question I have is... is there any reason that the head
> and or
> block could NOT be ground? Would this prevent the gasket from sealing
> properly?
> Any negatives?
Marty,
Good question, the answer is, I think,: it depends, When a block or
head is machined there are 3 things you are working to accomplish: 1)
establish a deck height (block) or a combustion chamber volume (head);
2) establish a flat plane surface within some spec, 3) establish a
surface roughness in order to enable the gasket to remain clamped in
position. The first two do not care if you plane (push a cutter over
the surface), mill (pass the item under a circular cutter, blanchard
(sp?) grind (a misnomer as this is a milling/cutting action) which
moves the workpiece in a non -linear motion under a rotating cutter, or
grind. But the surface finish / roughness can vary a lot between
these. True grinding will give you a pretty smooth surface, I expect.
I think different types of gasket designs and materials have different
requirements for optimal holding, but I am no expert. I expect
grinding would not give the desired surface finish. This is where you
count on the experience of the machinist to know how to establish the
feed rates and cutting tools to give you a good finish.
Some race engine prep from a few decades ago (don't know if it is still
done) would use a lapping plate. This allowed a very controlled
surface finish. One could use 220 grit and create a cross hatch
pattern.
-Roger
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