It is all very well to say that sandpaper is 100, 200, 600 grit etc, but what does it actually mean? When you talk about waterstones being 1000, 2000, 6000 etc, is that the same as 1000, 2000, 6000 sandpaper?
Unfortunately no! The way that I prefer to ensure I’m comparing apples with apples is to look at the size of the abrasive material itself. This at least should be a uniform way of comparing different abrasives. In other words, I may start sharpening on a diamond stone, transfer to sandpaper, and finish on waterstone. Ok, I may not jump around like this, but there is no reason why you can’t, once you understand the micron size of the abrasive.
I’ve listed here the 2 main sandpaper designations, and the actual micron size of the particles. This will then allow other mediums to be compared.
ISO/FEPA Grit designation
|
CAMI Grit designation
|
Average particle diameter (µm)
|
|
MACROGRITS | |||
Extra Coarse (Very fast removal of material) |
P12
|
1815
|
|
P16
|
1324
|
||
P20
|
1000
|
||
P24
|
764
|
||
24
|
708
|
||
P30
|
642
|
||
30
|
632
|
||
36
|
530
|
||
P36
|
538
|
||
Coarse (Rapid removal of material) |
P40
|
40
|
425
|
50
|
348
|
||
P50
|
336
|
||
Medium (sanding bare wood in preparation for finishing) |
60
|
265
|
|
P60
|
269
|
||
P80
|
201
|
||
80
|
190
|
||
Fine (sanding bare wood in preparation for finishing) |
P100
|
162
|
|
100
|
140
|
||
P120
|
125
|
||
120
|
115
|
||
Very Fine (final sanding of bare wood) |
P150
|
100
|
|
150
|
92
|
||
P180
|
180
|
82
|
|
P220
|
220
|
68
|
|
MICROGRITS | |||
Very Fine (sanding finishes between coats) |
P240
|
58.5
|
|
240
|
53.0
|
||
P280
|
52.2
|
||
P320
|
46.2
|
||
P360
|
40.5
|
||
Extra fine |
320
|
36.0
|
|
P400
|
35.0
|
||
P500
|
30.2
|
||
360
|
28.0
|
||
P600
|
25.8
|
||
Super fine (final sanding of finishes) |
400
|
23.0
|
|
P800
|
21.8
|
||
500
|
20.0
|
||
P1000
|
18.3
|
||
600
|
16.0
|
||
P1200
|
15.3
|
||
Ultra fine (final sanding of finishes) |
P1500
|
800
|
12.6
|
P2000
|
1000
|
10.3
|
|
P2500
|
8.4
|
Waterstones micron sizes are:
1000 : 14
2000 : 7.5
4000 : 3
6000 : 2
8000 : 1.2
So from this we can see that a 1000 waterstone is actually comparable to between a 1200 and 1500 grit sandpaper. And that my 6000 grit waterstones are VERY smooth!
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