On Tue, 26 Feb 2008 03:31:55 -0800 (PST), wrote:

I need to get some parts made, and am going to approach a few of the
local and online cnc machine shops. I need 300 tubes made, and up to
now I have been doing these on my manual lathe in lower, "as I need
them" quantities.

On my lathe, I was able to hold a .0005 tolerance, which I think would
be called +/- .00025.

Is asking for +/- .00015 too much to ask for a cnc job? Would this be
deemed extreme, or add to normal costs?

Please, only helpful and productive replys.

thanks!

In my outdated opinion, the tolerance should meet the demand of the
part and should have nothing to do with the machine it's made on. If
..0005 tolerance is what is required for the part's performance, that
is the tolerance. The machinist needs to be able to meet that
tolerance.
If you've been making them at .0005, and that has been acceptable,
that should be good enough.