some machine ways have a "S" shaped groove in them to help retain the oil. I
don't know if you could create a groove simply enough. the groove seems to
help the way float on each other like a hydrodynamic spindle (I think that
the term). But some how some small groove parallel to the ways would work, I
would think if you could scrape them yourself but maybe there's a retired
person in your area who could do this for some beer and time to chat about
the old days.

"Alan Rothenbush" wrote in message
...

Can two sliding surfaces be too flat to slide nicely ?

Here's the story. I bought a little ( 4x7 ) Sanford Surface Grinder
off eBay. Got it home, did some checking and found the ways pretty
worn in the middle of the travel. ( The ways are a V way and flat way )

So I spent all of yesterday with my good friend Marcus, a tool and
die maker of what is, to me, extraordinary skill and knowledge.

I learned a WHOLE bunch about surface grinding and even more about the
use of prussian blue.

After form grinding the V way and flat of the saddle, we mounted the
little
Sanford table on the great big table of Marcus' grinder. ( His mag chuck
was
almost the size of the Sanford's table ! )

The saddle was ground first, as it had some ground surfaces obviously used
as refereneces in the initial construction.

We form ground the V of the table and then proceeded to grind the last
flat.

The problem here is that the relative heights of the V and the flat must
absolutely correct or the flats will not sit parallel to each other, but
will instead sit an at angle. The contact will then be along two lines,
as
opposed to three planes ( one side of the V, the other side of the V and
the flat ).

The first cleanup pass got us, by measurement and calculation, about .002"
high.

We spent the next 2 hours getting rid of that two thou, about .000,2" at a
time. That is, remove a tenth or so, blue, look, measure, grind another
tenth and a bit, blue look measure, and so on. We finally got to a point
where the blueing matched the measurements matched the initial
calculations.

At this point we removed the table, mounted it on the saddle and gave it a
slide. BEAUTIFUL. Absolutely fabulous.

I'd spent a week wondering if I had bought two hundred pounds of scrap
cast
iron and left wondering how I could be so lucky.

Then I got home.

First thing I did was to oil the freshly ground surfaces, something we
hadn't
done. I then slid the table along, expecting to almost glide off the end,
only
to find it .. sticking .. kind of a hydraulic sort of stick. I kept
sliding it
back and forth, getting stickier and stickier until it stuck solidly.

It took a LOT of force to break it free .. in fact, they were stuck so
firmly
together that that lifting the table also lifted the saddle.

Once apart, I examined things and found nothing but clean, nicely oiled
surfaces. The oil I used was nearly clear and it was still nearly clear,
allowing a good look at things. Nothing. Finger test showed .. nothing.

Tried again and found the same thing. Cleaned all the (light) oil off and
tried some heavier oil. Same thing. Cleaned the heavier oil off and
tried
the lightest oil I could find. Same effect.

It's like the back and forth slide acts like a pump, and a hydraulic
"lock"
is generated.

All of this is absolutely foreign to me. Two flat things with oil between
them has always slid smoothly, but I've never had any two things THIS
flat.

Can something be TOO flat to slide properly ?


Thanks for any thoughts.


Alan

--
Alan Rothenbush | The Spartans do not ask the number of the
Academic Computing Services | enemy, only where they are.
Simon Fraser University |
Burnaby, B.C., Canada | Agix of Sparta