On Sat, 14 Apr 2018 11:54:58 -0700, Jeff Liebermann
wrote:

On Fri, 13 Apr 2018 09:28:28 -0700, wrote:

On Thu, 12 Apr 2018 13:31:11 -0700, Jeff Liebermann
wrote:

On Thu, 12 Apr 2018 11:59:48 -0700, wrote:

I use some very fine particle size diamond lapping compounds in my
shop.

What's the grain diameter? If it's larger than the depth of the
cracks and crevasses in the aluminum extruded heat sink, then you're
taking a step backwards. The bulk of the heat is passed by metal to
metal contact.

Smallest grain size is 1 micron. Or .0000039 Inches

or 39 micro inches (one too many zeros).

My best surface plate is flat within 30 millionths of an
inch. My best set of gauge blocks, the ceramic ones, are +1 to + 3
millionths in size except for the 4 inch block which is +4 millionths.

Arctic Silver 5 uses:
http://www.arcticsilver.com/as5.htm
Average Particle Size: 0.49 micron or 0.000020 inch or 20 micro
inch. However, they use:
"Arctic Silver 5 uses three unique shapes and sizes of
pure silver particles to maximize particle-to-particle
contact area and thermal transfer."

Crystalline diamond nanoparticles have an advantage, where the flat
facet surfaces provide better thermal conduction than random, rough,
or spherical shapes.
https://www.google.com/search?q=diamond+nanoparticles&tbm=isch

Your diamond particles are twice the diameter, but considering the mix
of sizes in Arctic Silver 5, the sizes are comparable. They should
work if you decide to mix your own thermal goo. However, you can buy
diamond thermal paste:
https://www.innovationcooling.com/products/ic-diamond/
The data sheet claims:
Average Particle Size: 40 µ maximum particle diameter
40 micro what? inches or meters? Probably inches which is the same
as your lapping compound.

If we made CPU's and heat sinks with the same precision as your gauge
blocks, then we wouldn't need thermal paste or even mounting hardware.
The two surfaces would stick together by themselves.
But they sure would be spendy. I don't even wanna remember what I paid
for my ceramic gage blocks.
Eric