Fixture table flatness

Is there anything that over time would cause the fixture table go out of flat? I may be wrong but I can see gravity being detrimental to most things we need to be flat and true. Has there been any testing of the fixture tables over time and hard use?

I come from a Automotive background and racing. I know back in the day when you were looking for cast iron engine blocks to build, the rule was find a older one that had been sitting around for along period.

Newer castings were considered green and would move around after being machined. This was along time ago and maybe does not make any difference anymore. Plus engine blocks are exposed to lots of heating and cooling cycles and I am sure that played a role in the movement.

Those were the days! Castings left in the yard for long enough to de-stress before they get machined.

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Thanks for the replies. Honestly I have heard of what you are describing Knick. I am considering buying one of the fixture tables. Jason has proven to me how accurate the tables are. However, i need to know if they stay that accurate over time before I drop that many gold coins on one.

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My current table is 3 years old now. I haven’t seen any change in flatness over the course of this time. The build design of the torsion box lends itself to remaining flat.

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In Foundations of Mechanical Accuracy they’re trying to build a ridiculously high tolerance cube.

It starts by building three flat tables out of cast iron. Their opinion is that weathering cycles don’t make a difference, but bringing parts up to a stable temperature can have a large impact when dealing with extremely small numbers.


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