Re:Lead screws

At 12:18 AM 5/15/03 +0000, you wrote:

>It comes in different levels of linear precision and it is fairly inexpensive.

And

>Ball screws are quite expensive but offer less turning resistance and more
>accuracy than acme rod

This brings up a "which came first, the chicken or the egg" question.

Some 40 years back, while I was an apprentice machine repairman, I
marveled at the huge machines that I worked on whose purpose was to make
smaller machines. The question came up in my mind, how can you machine a
40 ft bed on a planer when the biggest machine you have is a 30 ft machine,
an to boot, to get a 40 ft bed, you need at least 80 ft of travel? If you
have a large machine, you can make a smaller one, but how do you make a
bigger one?

Now, we are talking about lead screw accuracy, how do we get 0.001" per
foot accuracy when the best lead screw we have is 0.006" per foot? And how
did we come up with one that accurate when a machine that accurate didn't
exist yet?

With that, nite nite

Don






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