Re: [CAD_CAM_EDM_DRO] Re:Lead screws

On Wed, 14 May 2003 21:03:02 -0700, you wrote:

>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?

Lapping.

Harvey

>
>With that, nite nite
>
>Don
>
>