Standards relating to Diamond and CBN Powders

Product Standards

Micron Powder Standards

A frequently asked question is: Why is there no international micron diamond powder standard, like there is a standard for almost any other product, including diamond mesh sizes. The answer is quite simple: No dimensional standard can exist without a common, reliable and repeatable measurement method.

Here is a history of some attempts to design a micron diamond powder standard:

In 1976, FEPA had organised comparative microscopic measurement tests between 6 different laboratories on a single, coarse micron size. For a 40µ median size, the results varied between 36.54 and 41.11µ, i.e. 11.3%. On a 90% size span basis, a distribution width including 90% of all measured particles, the maximum variance was 25.0%.

In 1979, FEPA nevertheless designed a micron diamond powder standard that was in fact rarely used, mainly because of the lack of a common measurement method, but also because the standardised micron sizes did not match the industry’s ever increasing demand for accuracy and diversity in micron diamond powders. It had the virtue, however, to define some optical measurement procedures and the 'circumscribed circle' measurement method. Since that time, most manufacturers abandoned microscopic powder measurement anyway, to concentrate on easier and less time consuming measurement procedures.

In 1998, in an attempt to revise the FEPA micron diamond powder standard, another test was organised between 6 major companies, on 5 samples of approx. 2, 8, 20, 35 and 80µ median sizes. By then, due to the many different instrument types used (optical, electrozone, laser diffraction), the variances had grown considerably, to 23.5% on Median Sizes and 82.4% on the d95-d10 span. The correlation had not improved, it had become significantly worse. It was then decided to repeat the exercise on all samples except 2µ, in considerably more detail and using optical instruments only. This choice was made in the assumption that a product standard should be capable of being used not only by the manufacturers, but also by the major users, with a reasonable investment.

In 1999, the variances between measurements were found to be 21.5% on Median Sizes and 124% on the d95-d10 span! The study included various other analyses, such as operator variances within a single company, or variances between different slides of the same product, etc. The standardisation project was there­fore abandoned, on the following grounds:
  • No dimensional standard can exist without a reliable and repeatable measurement method. The current variances cover approximately 2 micron sizes, which is enormous compared to the grading consistency expected by the users.
  • The skills of optical measurement are no longer available in most of the companies concerned and no other instrument can at this stage be expected to produce matching results in different locations, by lack of common measurement methods and calibration.
  • Most users now require grading accuracies and batch-to-batch con­sis­tency far greater than could be granted by any such standard. Many of them showed little interest in a new standard anyway. In addition to the basic measurement problem, no standard could probably go into the accuracy and detail that is now required by the industry.
In 2002 a project for a DIN/ISO standard was abandoned for the same reasons. Simultaneously, a Japanese project was also aborted.

ANSI B74.20-1997
This US standard covers 'Specifications for Grading of Diamond Powder in Sub-Sieve Sizes', using the Coulter Multisizer (electrozone type) in the coarse range and the Horiba LA910 (laser diffraction) below 3µ. It cannot really be regarded as a product standard, but rather as a recommended inspection method. On the Coulter Multisizer, spherical calibration is prescribed, which causes the measured values not to match the product denominations. Example: On a nominal grade 6.00µ, with a 4-8µ size range, the prescribed d50 (median size) tolerance is set at 4.20µ±8%. The underlying 1.43 mean multiplying factor between the two figures reflects the difference between spherical and length measurement.

Mesh Size Standards

Micron powders are produced by sedimentation methods, in which the size distribution is guided by particle mass. Mesh sizes are sieved and the sieve apertures determine the maximum particle dimension allowed to pass. Their distribution is therefore roughly based on the smallest particle dimension. Mesh size quality inspection was ruled by the FEPA Standard, first published in 1972 and revised 1997 and now by the internationally accepted ISO 6106 Standard, first published in 1979 and revised in 2006, which are both based on a sieving method.

There is an overlap between micron sizes 45-70 to 70-120 and mesh sizes D46 (325/400) to D76 (200/230). This subject is further discussed under Technical Information/Micron-Mesh Overlap.

Other Standards

It is worth mentioning a number of other standards, which relate to the superabrasives micron and mesh sizes:

ISO 565 and ISO 3310-3
These standards define the test sieves, metal wire sieves, perforated and electroformed sieves that are used in sieving and testing sieve sizes.

ISO 9284
This defines the sieving machines.

FEPA, in 1994, published some further standards relating to:
-Measuring the relative strengths of saw diamond grits.
-Measuring the metal coating weight on coated diamond and CBN grit.

ISO 13322-1:2004)
This standard describes the static image analysis theory in great detail.

ISO 13320-1 and 13319
ISO 13320 describes the principles of laser diffraction methods for particle size analysis. It is worth reading, as it adequately describes the many problems encountered with laser diffraction instruments. ISO 13319 describes the electrozone measurement methods.

ISO 4287
This describes the Geometrical Product Specifications, i.e. surface texture or surface roughness, a subject frequently referred to in diamond lapping and polishing applications.

Comparison of Grit Denominations in International Standards

ISO 6106-2006
Grit Size Standard
ISO 565 Stan-
dard Sieves

(for ISO 6106)
Old German Standard DIN 848-1965
(replaced by DIN 6106)
GOST 9206-80
Russian Standard
Sieve sizes Aperture
in µm
Fine Coarse Denom-
Aperture µm
16/18 D1181 16/18 1180/1000   D1100    
18/20 D1001 18/20 1000/850   D900    
20/25 D851 20/25 850/710   D700    
25/30 D711 25/30 710/600   D700    
30/35 D601 30/35 600/500 D550 D500 630/500 630/500
35/40 D501 35/40 500/425 D450 D500 500/400 500/400
40/45 D426 40/45 425/355   D350 400/315 400/315
45/50 D356 45/50 355/300   D350    
50/60 D301 50/60 300/250 D280 D250 315/250 315/250
60/70 D251 60/70 250/212 D220 D250 250/200 250/200
70/80 D213 70/80 212/180 D180 D150 200/160 200/160
80/100 D181 80/100 180/150 D180 D150    
100/120 D151 100/120 150/125 D140 D150 160/125 160/125
120/140 D126 120/140 125/106 D110 D100 125/100 125/100
140/170 D107 140/170 106/90 D90 D100 100/80 100/80
170/200 D91 170/200 90/75 D90 D70 80/63 80/63
200/230 D76 200/230 75/63 D65 D70    
230/270 D64 230/270 63/53 D55 D50 63/50 63/50
270/325 D54 270/325 53/45 D45 D50 50/40 50/40
325/400 D46 325/400 45/38 D45 D50    
  Wide Range          
16/20 D1182 16/20 1180/850        
20/30 D852 20/30 850/600   D700    
30/40 D602 30/40 600/425   D500    
40/50 D427 40/50 425/300   D350    
60/80 D252 60/80 250/180