Howdy,
On Mon, 2 Nov 2009, Arvid Jedlicka wrote:
> We will agree to disagree on the "is junk" part.
>
> And I believe I did think about it. I came to the "accurate measurements
> party" pretty late and therefore everything I have is digital. A
> mechanical vernier caliper may not have any way to set the zero datum
> but all of my digital ones do. So I have naively set the zero as needed
> and gone about the business of getting what appear to be accurate
> measurements - i.e. things fit together when I am done - without any
> problems.
I think the issue here is mostly related to something you touched on...
There's no way to zero the ID measuring jaws, like you can with the OD
measuring jaws. Because of that, if the jaws aren't machined such that
the ID is zero when the OD is zero, if you're trying to transfer
measurements (i.e. measuring the inside of a bore and the od of a part
that is supposed to fit in the bore), you're pretty well hosed.
Bore guages and the like get around that by "zero-ing" to a known
dimension with a guage block or a micrometer or something. I suppose you
could do something similar with a regular caliper, but I'd tend to think
that if you're getting down to the point where it matters and the caliper
isn't junk, a caliper isn't the right tool for either measurement.
But I'm just a hobbiest, not a pro.
Mark
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