Metal rod, about 3mm diameter, rotating slowly inside metal tube about 25mm long and I want to reduce friction. What would be best for this purpose?
Oil?
Very fine sandpaper?
Metal Polish?
T-Cut?

 

hi,
Perhaps a Silicone.?
E
Update.
Graphite Dry Lube

Graphene being two-dimensional material, offers unique friction and wear properties that is not typically seen in conventional materials. Besides its well-established thermal, electrical, optical, and mechanical properties, graphene can serve as a solid or colloidal liquid lubricant.

 

What are the metals?

 

The rod is brass coloured and the tube is silver coloured. Neither of them is attracted by a magnet.

 

Aluminum can be difficult to deal with in close fits, particularly with itself.

Another lubricant that has not been mentioned is boron nitride (BN) (https://en.wikipedia.org/wiki/Boron_nitride ). The hexagnal form is generally used. It had advantages over graphite. Molybdenum disulfide is another, but I would want to find whether it is compatible with those metals. It is fairly reactive, beside being a mess to work with, and with water can be corrosive on steel.

 

I don't think the tube is aluminium - it is, I think, too shiny. Chrome plated brass??

 

If it's not aluminum, I would not be too concerned. I have no experience lubricating decorative chrome. A thin oil, silicone or mineral, would be my first choice. AFT fluid might be an option. It might wet chrome better.

 

For slow speed bearings i use teflon lubricant.

 

What sort of speed you rotating at ?
how long do you need this to run without "servicing"
what sort of power you transferring / what sort of pressure the bearing under.

i.e. if its a box cart, then I'd suggest something used on a bike, such as teflon lub as mentioned above.

If its a high speed bearing, then the lub will over heat,
you might need a liquid bearing,
for real high speed an air / gas bearing.
If its in a high temprature , then may be graphite,
if its in a oxygen pump, then dont use grease.

give us more of a clue as to your application,

 

Think clock not box cart!
Preferably never to be serviced again!

 

For clock is better very thin and low viscosity oil

 

The rod to tube diameter/clearance has not been specified, much depends on this.
If using a liquid lube, I second the ATF for lasting over time without drying and also if heat is an issue, no problem.
Max.