I could use some help with sharpening stones ... lapping information and identifying

[FortyTwoBlades]

Grading finer than about 240-ish grit is usually done via sedimentation rather than screening, for reference. The mesh rating is a "simulated" value only since a screen isn't used at that point.

 

[Gritomatic]

Washington Mills is a huge SiC manufacturer in the US, but I'm not sure if foreign sourced materials would be inferior, the manufacture of SIC is pretty well understood.

Thank you for info and reference! It would be interesting to get datasheets from Washington Mills and compare. At a glance they offer expensive green SiC and cheap black SiC. As far as I know, green SiC does not suffer from described "jelly bean" problem because grains tend to expose new sharp edges during disintegrating.

 

[HeavyHanded]

Thank you for info and reference! It would be interesting to get datasheets from Washington Mills and compare. At a glance they offer expensive green SiC and cheap black SiC. As far as I know, green SiC does not suffer from described "jelly bean" problem because grains tend to expose new sharp edges during disintegrating.

That's definitely a subject for further research. AFAIK the black SiC breaks down to sharp edges just like the green, just a question of how it breaks down - how much shear force is needed to bust it.

When the grit is passed through subsequent screens to grade it, or is contacted through some manner of sedimentation, the contact with other particles is going to be very gentle, like a tumbling action. Hard enough to knock the corners off but not enough to fracture the grain at least that's my theory.

It can still work well but needs some extra attention to the binder or it will work well for a polish and not so well for a honing compound, as most stropping isn't going to exert the force needed to break it further.

 

[FortyTwoBlades]

All silicon carbide is graded in some shape or form. If what you were describing was at all typical of the process, all silicon carbide abrasives would exhibit it.

 

[HeavyHanded]

All silicon carbide is graded in some shape or form. If what you were describing was at all typical of the process, all silicon carbide abrasives would exhibit it.

You'd only ever notice when you first started using the stone in that case - once you started using it the grains would bust out sharp. Most if no tall new SIC stones are somewhat glazed out of the box.

Admittedly that doesn't explain the nice qualities of a fresh sheet of wet/dry...

I base my observations on what I get from the lapidary supply houses. Those are probably the most carefully graded samples of this mineral (maybe) and every sample I've looked at under the microscope was none too sharp edged.