3M Lapping Film
3M lapping film is a kind of ultra-fine sandpaper, although the backing
is actually a polyester film rather than paper. I had some sheets
in 15 micron, 5 micron, and 0.3 micron grades (a kit for "scary
sharpening," available from http://www.toolsforworkingwood.com).
(Actually,
I discovered the "scary sharp" system by way of Brent's
Sharpening Pages, which also introduced me to the QX3
microscope.)
I cut some small (1/4" wide) strips of lapping film and applied them to
the axles using
some honing oil. After each application I wiped the axle with a
cotton cloth, just as I did with the wet sandpaper. For these
pictures I started with the axle that had previously been prepared by
nail file and then polished with 2000 grit sandpaper. The first
picture shows
that axle again, just before application of the lapping film.
To my eye, it looks to me like the 15µ film makes a worse finish
than that left by the 2000 grit wet-or-dry. Getting down the the
0.3µ film improves the surface compared to 15µ (as you'd
expect), but overall it's hard for me to say the surface ends up any
better than what the 2000 grit sandpaper left.
The best reference for grit sizes I have is wikipedia's entry on
Sandpaper, but it doesn't seem to describe 2000 grit
sandpaper. That article refers to a sizes.com page
that suggests 2000 grit sandpaper has a roughly 1µ particle size
already. So maybe this result is unsurprising.
Next to try – lapping film with water rather than oil.
