machine accuracy (was Resolution and surface finish)

This talk of shank size and toolholder runout, especially the idea
that an endmill may be cutting on only one flute, got me thinking
about overall machine tool accuracy and alignments that we don't
often question. I'm sure the bigboys have their machines' various
axes aligned deadnuts (we hope), but what kind of alignments are
we seeing in the world of Sherlines, Taigs, MaxNCs, mill-drills,
old Bridgeports, etc? Exactly how orthogonal are the x-y-z axes
to each other? Is there a standard, such as .0005"/ft, which is
acceptable? I'm especially curious because I'd like to know what
to shoot for when I finally assemble my own ground-up machine.

Thanks in advance,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Marcus & Eva [mailto:implmex@...]
Sent: Saturday, December 30, 2000 12:13 AM
To: CAD_CAM_EDM_DRO@egroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Resolution and surface finish

(snip)
If you use shitty quality import cutters you will often find that
they cut
only on one flute, even when the shanks are running pretty
concentric.
Another big problem is the use of endmill holders together with
undersize
shank cutters.
Clarkson cutters were often 0.001" undersize, about 10 years ago,
and ran
out horribly in endmill holders with nominal or +0.0002 bores.
They could only be run successfully in collet chucks.
I have come across Polish cutters that had so little flute relief
that they
were unuseable without a regrind.
I won't even talk about some of the Pakistani cutters I have
seen!!
I now use only 2 brands of cutters: Niagara for HSS, and Garr for
carbide.
Both are excellent quality material, and stand up well enough to
justify the
difference in price, and they have consistent shanks ( good for
endmill
holders) and nice flute geometry. They cut beautifully!!