In part 1 of this series, I shared a couple of images of a DMT Fine (600) diamond plate before and after “break-in.”
In this article, I present a few images from a Coarse (325) and an Extra-Fine (1200) diamond plate. These images provide insight into the surprising results of The Diamond Plate Progression.
The Coarse plate is very similar to the Fine, with a relatively uniform size distribution of diamond particles embedded in a nickel plating.
In this example, the hone was “broken-in” by rubbing on a hardened steel surface for approximately ten minutes and then used to lap a Shapton 16k hone for a few minutes. The results are consistent with those observed in the case of the Fine hone. The diamonds that sit higher are removed or broken off, evening out the variation in the height of the exposed diamonds and smoothing the diamonds that contact the surface being honed.
The Extra-Fine (1200 grit) is of similar construction, with appropriate-sized diamonds embedded in nickel plating.
Surprisingly, this plate is “contaminated” with over-sized diamond particles. These coarse-sized diamonds are approximately twenty microns higher than the nominal-sized (9 micron) diamonds. Such over-sized particles are likely responsible for the anomalously deep scratches created by the EF and EEF hones in The Diamond Plate Progression.
This plate was then broken-in with the usual process of rubbing a piece of hardened steel across the surface for approximately ten minutes.
Closer inspection of the remaining over-sized diamonds reveals several outcomes.
The break-in procedure affects the extra-fine (9 micron) particles as well. The less well adhered diamonds fall out, and many are broken.
The before and after images presented here demonstrate that significant changes occur in the surface of the plates occur within the first few minutes of use. The depth of scratches created by these hones will depend on the shape of the exposed tips and on the applied pressure.
Noting that pressure is inversely proportional to contact area, when honing on the extra fine plate with its few tall coarse diamonds, the pressure will be very high with the force spread over those few contact points, resulting in anomalously deep scratches. Successful break-in will require complete removal of the over-sized diamonds. The challenge is to find a break-in procedure that will remove the over-sized particles while minimizing the loss of nominal-sized abrasive.