16 Nov
2003
16 Nov
'03
2:24 p.m.
On Sun, 16 Nov 2003, Jay West wrote:
Wizard wrote....
If it did, the readings would likely be erratic. More likely,
that 'lever' that you referred in a prior message is to retract
the ball from the surface while the disk is rotated by hand.
- don
Runout is side to side oscillation (off center)
Think of the stick
on sanding disk not perfectly centered on the rubber base.
Aha! This makes
sense... that's why they would put the ball touching the
"vertical" edge of the platter.
Flatness is how perfect it is (90 deg to the
axle) with very little
or no wobble. Think of a spinning top slowing down and it get wobbly
by the second. Also checks for bow-ness.
I thought so, which leads to...
I agree having that steel ball touching media is
BAD day. :-)
The platter is turned by hand less than one revolution during the
test, it's
not at 3600 rpm when the ball is on it. But it sure LOOKS like they put the
ball right on the media surface. Specifically "Place the ball so that it
rests on the top outer circumferance of the fixed disk within 1/4 inch of
the outer edge". This would be outside the head loading zone... but still.
The manual doesn't mention it, but I wonder if the dial gauge from them is
special because it has a rubber tip or something. Still not good on the
media I wouldn't think. Odd.