Gunner Asch on Mon, 25 Nov 2013 15:37:40 -0800
typed in rec.crafts.metalworking the following:
On Mon, 25 Nov 2013 12:49:42 -0600, Leon lcb11211@swbelldotnet
wrote:
On 11/25/2013 12:25 PM, Gunner Asch wrote:
On Mon, 25 Nov 2013 11:00:11 -0600, Leon lcb11211@swbelldotnet
wrote:
I am a woodworker and routinely work with pieces that measure in 1/8"
resolution

Oh..you work to .125 tolerances then?

No, that is not what I said, I said I routinely work with pieces that
measure in 1/8" resolution. The tolerances have to be much greater for
a joint to disappear.

Grin

There is a difference between resolution and tolerance. They are not
the same. I simply choose to design using 1/8" as my smallest
increment. The cuts have to be as close to that measurement as
possible. A piece that calls to be 48.125" needs to be as close to that
as possible. 48.120" is way not close enough if you don't want the
joint to stick out like a sore thumb.

Then stack on top of that the wood greatly changes shape, relative to
steel, depending on the relative humidity and a project may have several
hundred pieces that interlock with each other. We wood workers work in
pretty tight tolerances too but don't draw project pieces to sizes that
include minute fractions for the sake of having odd lengths and widths.
I realize this is required in smaller sized metal working projects
where size dictates higher precision.

And in big ones too. As Pytor indicated...he turned 30' shafts that
were in .0004 tolerance. 30 Foot shafts.

Not me - that was the Experts. The parts themselves had a
tolerance of .005 iirc. That was the easy part. Anyone can turn a 3
foot diameter shaft to within 5 thou. The tricky part is making sure
that the entire piece was within 4/10ths of a thousandth of an inch at
what ever diameter you reached - over a twenty to thirty foot length.
On manual machines. Originally installed for war work (I didn't ask
"Which war") on what used to be tide flats.

OTOH, ever try to locate and measure the ridges in the bore of a
shaft, what is sixteen feet deep? Pretty smooth to look at, but
reading a dial gauge when it is more than a couple feet into the bore
gets to be a real trick. (Put a scope on a magnetic clamp and sight
through that.)
Then came honing the bore out. The hones took off about a tenth
each pass, it takes six minutes to make one pass. Some of the ridges
were 10 to 15 thou high. It was boring work, but it paid the bills.
--
pyotr filipivich
"With Age comes Wisdom. Although more often, Age travels alone."