Sharpening/sanding grit chart.
Denotes calculated value. Not defined in the standard. * Colours representing Shapton & DMT are appromximate. This list of 'grit sizes' is as complete as I can make it with the available information at the present moment in time and from the information provided by manufacturers and standards associations. At the time of this compilation, to the best of my knowledge, there is no other table of abrasives and their relative sizes as complete and broad ranging as the one presented above. While it is as all encompassing as is possible, there are limitations to what can be presented in such a table with respect to the amount of data, the way it can be presented and even avoiding "information overload". I have tried to make it as easy to understand as possible, and to try and explain the difference in the abrasive particle sizes in most of the commonly found materials as pertains to 'sharpening'. The common denominator in this table is the "stated 'grit' size", which does make labelling easy, but the problem is that grits aint grits! As you will see, for any given grit size, there is no commonality based on the only unchanging measure available to us, abrasive particle size in microns* *micron, also expressed as μm or micrometre (micro-metre) is one-one millionth of a metre, 0.0000001m, 1.000×10−6 m, 1/1000mm, 39.37 x 10−6 inch, 0.000039" or in terms we might be able to comprehend, a piece of standard, good quality copy paper is 100 microns thick, human head hair is said to be between 17-150 microns in diameter. Or, really really small. The way in which 'grit' is defined is typically as a 'specification', not an absolute measure. We know these particles are very small, and it's not possible to measure each one individually, so a specification is used to ensure that the abrasive in question 'generally conforms' to a set of dimensions. In most cases, a set size or range of sizes is said to match a grit number, and there is a tolerance in size and percentage of particles above and below this size/range that is accepted as conforming to the standard. As an example of
this ‘specification’, in the case of JIS R6001 the specification is that for
any given grit, there is a maximum size, a range of sizes where 50% or more of the
abrasive particle sizes must conform, and 'bookend' dimensions where greater than 94% of the
particles must be larger than and 94% of the
particles must be smaller than. Sounds complicated, but for example; 100% of #1000 grit
must be smaller than 32.0μm, >50%
at 11.5 μm +-1.0 μm, >3% <22.0 μm, >3%>7.0 μm. Or as a visual representation;
To be contnued. 23/11/2011 |
