Hand Tools

Subject:
How diamond abrasive is graded/sized

Bill Tindall, E.Tn.
Historically, and for the places that reveal how the product is sized that I know about(limited) what follows is how it is done and the product results. (There are other possibilities but I do not know if they are used for diamond sizing. )

Suspend stuff in a liquid and the rate that a particle settles depends on its size, all other variables held constant (in this case we are talking about just diamonds and some viscous liquid, historically olive oil).

Grind up some diamonds. Suspend in liquid and allow to settle. After XX amount of time decant liquid with suspended diamonds from what has settled. (Often the first that settles is reground). Allow the liquid with suspended diamonds to settle YY time. After YY time decant liquid with suspended diamonds and recover what has settled to be sold as some size range. Repeat this settling- decant many times to generate many ever smaller size ranges.

It follows that the more settle-decant steps are included the more narrow the size range of each product recovered. And, in the end there is a size fraction that does not settle in the time allowed that will be "0-ZZ" size range. The larger number in this range depends on how long the manufacturer allowed the preceding settling to occur.

The more steps are included, the more narrow the product range and the higher the manufacturing cost. Pay more, get a more narrow range. Someone selling a 0-2 micron range chose to quit the separation at 2 micron. Someone else could sell a 0-1 micron range by doing a preceding 2 micron decant step.

It should be added that the amount of the actual particle sizes in the range will be biased to the larger sizes. Something labeled 2 micron with a range of 1-3 will not be the weight average 1 micron. This value will be greater than 1 micron.

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