"Lloyd E. Sponenburgh" lloydspinsidemindspring.com Inscribed thus:

I'm wondering why the hell people who don't overlap one-another's
market
still have a need to "compete" with others. Mostly I'm talking about
building up one's image at the cost of belittling another's.

I had an experience. I am not a "precision machinist" by any stretch.
My primary offering to my customers is innovation, and machines that
work to improve their productivity.

Last year, I built a press and explosives composition mold for a
friend
way-far out west. When he started using it, he was using pressures
several TIMES higher than what I had designed it for (and what he
spec'd out), and the mold cavity liners were slipping a little bit on
ejection
of the product. So I made him a liner retainer plate that would hold
against that extra pressure. It has 54 cavity holes and 74
counter-sunk bolt holes in an array that will surround all the
cavities and hold the plate against the liner flanges (they look a bit
like a flanged oilite
bushing, but made of Acetal). I machined the cavity holes, and
drilled the bolt holes in a single clamp-up on CNC.

His task was to take the mold body to a local machinst (who only
normally repairs auto parts, but has a couple of general-purpose
machines), and
have matching holes drilled and tapped to fit the plate. The guy said
he could do it, and even had "CNC software" so he could match the
array exactly.

The next day, the machinist called him to say that all the holes were
"all over the place; up to 30-thousanths off-centers", and he was
going to have to take the plate to a better-equipped shop to have all
the holes
probe-plotted to make sure his holes lined up. His new price
reflected
that. He also told my friend that "next time, you need to hire
someone who knows what he's doing." (ouch!)

You have come across the "how to buck up the price and make work for a
mate" syndrome !

A common opportunist trick... Quite dishonest !

So, the liners have finally worn out. Expected by both of us. They
were made of acetal, for pressures far lower than what he is now
using. We're
going to change to a high-lubricity brass. He sent the whole mold
back for me to re-line.

I've been chasing this inaccuracy problem ever since his first phone
call
about it, and could never replicate anything remotely like it. My
only issue with my machine is poor surface finish, because I have yet
to
rebuild my spindle. But when I got the mold, the first thing I did
was
take it apart and start measuring. I deliberately did not refer to my
drawings or the CAM files. I just started manually measuring holes,
center distances, and diagonals all over the plate.

Everything is dead-on to within a half-thou in every direction (the
best
my measuring tools will do for distances larger than 2"). There are
no center-to-center variations, no cumulative changes across the
length or breadth of the plate, no out-of-square condition... nothin',
zip, nada.

Then I checked the drawings and CAM files. They exactly matched the
physical part.

He and I don't compete; we're fifteen states apart and do different
things. Maybe he thinks we do.

Why? Why do people do this crap? Is it just the bux, or is it trying
to build themselves up in their own eyes?

Damn. Well, at least I know my mill isn't misbehaving, after all.

LLoyd

--
Best Regards:
Baron.