Ultra fine ceramic stone produces sharper edge than 6000 grit water stone

[george wilson]

Actually,it was to say:"Don't waste your money on a 6000 grit stone if you have a ceramic UF,which will produce a sharper edge." Just a simple statement.

[Stewie Simpson]

George; if you cant manage that King stone, post it to me and I will use it.

regards Stewie.

[Pat Barry]

With regard to the manmade stones there are two basic approaches required for fabrication. One is to create a bunch of particles and use the sieving process to sort the particles into the desired range. This will be limited by the mesh size of the sieve. It will also be limited by the shape of the particles - ie: a long but skinny particle will fall through a small mesh size and these can therefore lead to larger than planned particle sizes (in one dimension ~~ length for example) in the finished stone. The other approach, one used for very small particles, is based on process control and sample testing. This might employ high powered microscopes or even SEM tools to measure particle sizes produced by the process and to develop a statistically valid model for the range of sizes produced by the process. One such process is called ball milling (there are others). Controlling the time and agitation of the ball milling process as well as the media used and other factors produces particles that are then measured and graded. Milling for a longer time can produce finer particles as the batch is further refined by the longer process. Once a given process batch has been measured and tested it can then be dispostioned for its ultimate purpose - for example a fine or UF stone. No matter, there can still be outliers present in even the UF stone (large particles that escaped detection). I would suppose that you can get more uniformity of particle sizes in th man made stones by paying the estra cost for better process controls or inspection and sorting.

[Patrick Chase]

Patrick; the main lesson from this discussion, is that from a buyers perspective, we will continue to be at the mercy of the retailer, and manufacturer, to accurately describe the range of micron sizing contained within these polishing compounds.

Stewie;

Another main lesson is "you get what you pay for".

Engineers (and more to the point machinists/technicians) would never accept the sort of variability discussed here for serious work, and there are plenty of abrasives out there with tightly specified and controlled composition and particle size distributions. As a simple example, quality diamond compounds (the sort that cost $3-$7 per gram depending on source and grit, from Norton, Sandvik, PSI, etc) conform to ANSI B74.20-81, which specifies both testing methods and distribution constraints. That's one of the big differences between those expensive compounds and stuff like this that costs a tenth as much.

If you buy lapping compound that costs $13 for 6 oz of compound ($0.07/g) then you're not paying enough to reasonably expect a tightly specified or controlled particle size distribution about a sub-micron nominal (tight-ish distributions around larger nominals are inexpensively achieved via sieving as Pat described). It's that simple.

EDIT: Note that the stuff you bought from workshop heaven is ~7X as expensive as the LV compound at $24 for 50 g ($0.48/g). Even at that price you're not getting a guaranteed size distribution, though given that it's pure chromium oxide it's likely tighter than the LV compound.

[Patrick Chase]

With regard to the manmade stones there are two basic approaches required for fabrication. One is to create a bunch of particles and use the sieving process to sort the particles into the desired range. This will be limited by the mesh size of the sieve. It will also be limited by the shape of the particles - ie: a long but skinny particle will fall through a small mesh size and these can therefore lead to larger than planned particle sizes (in one dimension ~~ length for example) in the finished stone.

Those long-but-skinny particles are described as "slivers" in the relevant specifications. Similarly, a particle that's large on 2 axes but small on the third is called a "plate".

The other approach, one used for very small particles, is based on process control and sample testing. This might employ high powered microscopes or even SEM tools to measure particle sizes produced by the process and to develop a statistically valid model for the range of sizes produced by the process.

Yep, that's what I was referring to in a reply to your previous post where I said that Stewie's 12K stone is in the "sub-sieve" range. If you wanted to make an equivalent synthetic stone then you'd have to use this second approach to grade the abrasive. One advantage is that you can specify and control slivers.

[bridger berdel]

Particle grading for diamond at least used to be done by weight rather than size. The ungraded grit would be suspended in a fluid moving slowly along a sluice. The larger particles settle out fastest and so forth. I assume this process will work for any mineral heavier than water.

[Patrick Chase]

Particle grading for diamond at least used to be done by weight rather than size. The ungraded grit would be suspended in a fluid moving slowly along a sluice. The larger particles settle out fastest and so forth. I assume this process will work for any mineral heavier than water.

I think that to meet ANSI B74.20 that way you'd need a pretty tightly controlled grinding process such as Pat described before the grading and/or a multi-stage cascade of grading steps to weed out problem particles with acceptably high probability.

While it's very hard to find the current version of the spec without paying, it's basically identical to this previous revision. Note in particular the fairly tight ranges in the higher (but still too-low-to-sieve) diameters, and also the constraints on slivers and shales in sections 3.4-3.5. I doubt that grinding diamonds up willy nilly and then doing a one-pass suspension-based sort as you describe would be sufficient.

EDIT: You can do minerals lighter than water the way you describe, because there's no reason why you have to use water as the fluid medium. You could get down to ~70% of water density with mineral spirits for example.

[Stewie Simpson]

Hones - comparison table

The table below offers a quick overview of different hones, their specific features, typical uses, and comparable hones.
It should be noted that since natural rocks of the same kind can vary widely between one another (unlike synthetic hones), it is difficult to assign grit ratings to them in whole groups. Also, different synthetics (brands, makes) of a given grit rating should not be expected to have precisely the same distribution/range of particle sizes, as they may be made or graded to differing standards. In addition to differences in size, abrasive particles will cut differently depending on their material and shape and the matrix in which they are embedded, or surface to which they are applied.

http://straightrazorplace.com/srpwik...mparison_table