----- Original Message ----- 
From: Grant Saviers 
To: Robert B Garner 
Cc: Bill Flora ; 1401 Restoration Team  

All,

In my experience with precision gages and rebuilding several machine tools 
is that superficial rust as shown in the photo feels and looks worse than 
it is functionally.  Removing the debris and rust will leave small 
surface pits which are not likely to have much affect on the operation 
(except if they are in a sleeve bearing).  320 grit sandpaper 
is way too coarse, however.  

If the parts can be removed (best) then a 
very fine (000) steel wool, used way away from the mechanism and any 
electronic parts will usually clean up the part.  I sometimes use WD40 
as a cutting lubricant as it helps to cut residual grease and keeps 
the rust from clogging the steel wool.  This is messy so wear nitrile or 
neoprene gloves (WD40 eats latex quickly). 

For flat parts, some 600 grit 
wet/dry paper can be used as a coarse lap, or we can get some 3M lapping 
film in much finer grades that can ceate a polished surface finish.  
I wouldn't use any power tools for the first pass cleaning.

Oxided oils can be very tough to remove - parts look rusty but it is 
mostly oil and dirt.  I use a hot solution of water and dishwasher 
detergent in an ultrasonic cleaner.  There is probably a little etching 
of the surface, but cutting tools (end mills, slotting cutters, etc.) 
come out looking almost new and work fine after 10 minutes or so in the tank.

If the part has to be cleaned in place, try a brass brush with WD40 and 
have lots of rags/wipes to collect the debris.  Steel wool or abrasives 
used in place are very dangerous for the long haul.  Keep the WD40 out 
of bearings if at all possible as it is really not a lubricant.

If the rust is so bad that the part won't function after the above, then 
the choices are more complex and expensive - regrinding and shim to fit, 
resize and use new bearings to fit, plate nickel or chrome and grind to 
original size, plasma spray coat and grind to size, etc.

Grant

----- Original Message ----- 
From: "Paul Pierce"  
To: "Robert B Garner"  
 
All,

A very good treatment for this sort of equipment is
the maroon 3M 7447 scrubbing pads wetted with a light
lubricant and solvent such as light oil or kerosene.
These pads are made for exactly this sort of work and are
amazing on light rust such as in the photos, producing
a nice smooth surface. They will dull highly polished
surfaces such as chrome or nickel plate, but there is no
alternative that will remove rust and magically restore
the polish. They are available at industrial supply stores
such as J & L Industrial. ( http://www.jlindustrial.com )
(see http://www.jlindustrial.com/catalog/product.jsp?id=SBH-04029J 
) If there is a store in your area, you can
get advice from the clerks (or better yet, the customers.)
They do require considerable elbow grease.

Probably the card paths should not be oily when you are
done. Look in the service docs for places they say to avoid
with oil. After cleaning the rust off, such surfaces can
be degreased with a solvent such as lacquer thinner or 
a degreaser. However, its much safer to stay on the too
oily side than to degrease much, which can ruin bearings.
A little residual oil on surfaces is a good thing, it
protects from further rust.

I would clean these with a 3M pad and kerosene first, then
when everything is as clean as you like go through and
lubricate the machine according to the service docs, the
kerosene will slightly degrease things.

Find people who restore old cars etc. and see if you can
get even better advice.

Paul

From Dag Spicer

Hi folks,
 
Whenever you have material science related issues like this, 
would you mind copying Allison Akbay, (akbay@computerhistory.org)?  
She has much experience and extensive contacts 
   with subject matter experts in this area.
 
Also, she needs to approve any compounds used for restorative work 
   before any work is undertaken.  
 
Any thoughts on this one Allison?
 
Thank you,
 
d.
 

From Allison Akbay 

A great resource for finding materials that are considered safe for
restoration is the Conservation DistList Archives:


 http://palimpsest.stanford.edu/byform/mailing-lists/cdl/
 
There is a search option on the above page and when I searched for rust
a large number of messages came up.  One of interest is :


http://palimpsest.stanford.edu/byform/mailing-lists/cdl/2000/0137.html

The maroon 3M 7447 scrubbing pads may be appropriate but first it there
needs to be a check done that whatever cleaner they contain is
neutralized at the end of the process and doesn't keep eating away at
the metal in the long term.  They sound like ones that are used by
jewelers to polish metal in which case they work by abrasion and are
chemically neutral, fine as long as they are used in moderation since
they actually remove the top layer of the metal.

Allison