Runout vs. Flatness and Dial test indicators

From: Jay West <jwest_at_classiccmp.org>
Date: Sun Nov 16 22:48:33 2003

Andrew wrote...
>(if I remember correctly) you were supposed to position the ball at extreme
edge of the
> upper surface, right where the bevel is, and there is a picture in the
> service manual showing it.
Yup, they say to make sure it is in the outer 1/4 inch of the media surface.
However, they also specify to make sure it is not on the "extreme edge" or
what I mean is, it must be in from the chamfered area. The picture doesn't
quite do it justice :) Sure, there's never going to be any data there, but I
would worry about microscopic particles coming off the platter where the
ball rests (the media is coated to the very edge, no uncoated area visible)
and flying particles of oxide are definitely not a good thing. But, it
appears that is ok for this operation, and the way they specify to do it.

> There was a hole specifically placed in the
> chassis, back by the card cage I think, that you placed the post
> attached to the dial indicator into
Just to the left of the heads actually, mirror image from the card cage.

> The dial indicator had a little
> switch to change from measuring runout and flatness.
Yeah, now see, that's the part I can't figure out. Exactly what does that
switch accomplish? I know one position is for measuring runout and one for
flatness, but what does it actually cause to happen? The lever tony refers
to is the joint in the guage, what I was referring to is this "switch" on
the guage. Could it be that the older dial indicator wasn't auto reversing
while newer ones are, hence, the switch?

More specifically, I'm sure I'll never find the original HP dial indicator
and holder bracket. So, I'm hoping to use "any old" dial test indicator (I
know these terms aren't interchangeable). Harbor freight has a cheap one.
The trick is the mounting bracket. As long as the dial indicator from harbor
freight could be attached to the drive in a stationary way, I would think it
would work for either test and that the HP dial indicator wasn't a "special"
one.

So Andrew, any idea why the dial test indicator on harbor freights website
wouldn't work or easily be made to work?

> It was a special dial indicator. I did a google search and I think it's
 Thanks much!!

Jay
Received on Sun Nov 16 2003 - 22:48:33 GMT