RE: ATM Abrasives uniformity (PSD)

["Tony Cecce" <tonycc@exotrope.net>]

Here is an example of an optical quality alumina oxide abrasive that I have.  I
had this powder run through an instrument (Microtrac) which characterizes the
particle size distribution (PSD).  If you look at the summary, this supports
what Mel stated about median size +/- 50% out to the 10% tails.  Note that the
summary shows that this is a 15 (15.85 actually) micron grit with 10% of the
particles smaller than 10.54 microns and 10% of the particles larger than 24.62
microns.  Additionally, if you look at the detailed distribution below you will
see there is a small percentage of particles larger than 40 microns.  This
matches the distribution you saw under the microscope.  I believe at this grit
size sorting is done through an air blowing process.  It is physically
impossible to get grits with no particle size variation.  I would be interested
to see the PSD for Microgrit abrasives.

Material: Alumina Oxide Powder
Summary:  10%=10.54
                     50%=15.85
                     90%=24.62
Particle Size Distribution (PSD):
Size (Micron)  %(In size range)
48                    .37
40                    .80
34                  1.93
28.5               4.37
24                  8.87
20                15.18
17                20.78
14                20.84
12                14.51
10                  7.29
8.5                 2.97
7                    1.21
6                      .56
5                      .32

Tony Cecce