I tried to find a good .html picture for you but couldn't. If you go here
to the Barden site and look at page 13 of their "Machine Tool Catalogue"
you'll see a very good diagram of the different arrangements:

http://www.bardenbearings.com/literatr.htm

Look closely at the diagrams and you'll see the bearings have an open side
on the outer race, your bearings should have this too. In back to back the
open sides face out.

Also found info that says "The DB arrangement requires the inner rings to be
clamped whereas the DF arrangement requires the outer rings to be clamped".
It's on the NTN site here at the bottom of the page:

http://www.ntnamerica.com/Knowledge/Product_FAQs.htm

With the 8520 the lock nut bears down on the inner rings so "back to back"
should be right.

After sifting through the Yahoo posts and getting more confusion from reps
at the manufacturers I figured it would make a good topic here, thanks!

BTW I went with a pair of Barden 205HCDUL which are 15 degree contact,
duplex mounting with a light pre-load

More pix of my restoration here, getting ready to paint soon...

http://gallery.intlwaters.com/thumbn...bum=323&page=1


"Mike Henry" wrote in message
...

"Terry Keeley" tkee(no spam)@(or mail)rogers.com wrote in message
.. .
Here's a good diagram of the different arrangemenats and their
symbology:

http://www.nhbb.com/engineering/precision/preload.cfm


Can anyone describe which face is the "" and which is the ""?

The Fafnir 7205WN SU bearings that Clausing sold me don't have any
circles,
dots, or "" marks that I can see. I'm guessing that the marked edge is
the
face - would that make sense?

I suspect that my 8520 still has the original bearings, so it may be
possible to check that way, but it would be better to know this ahead of
time.

Mike

PS: Terry - this has been a great thread!