course shapton stones

I just used up my norton 220 grit waterstone and was looking at replacing it with a shapton to give them a try. Looks like they have a 120, 220, and 320. I mainly use it for flattening chisel and plane iron backs and putting a good bevel back on them. Which grits have people been using? The 120 is tempting to get the job done faster but would I need the 220 or 320 before I move on to the 1000 or will going straight from the 120 to the 1000 be okay?
Thanks, MT
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Tripper wrote...

I use them all and wouldn't want to be without any of them. The jump from 120 to 1000 is big -- too big, IMO. From 220 to 1000 is ok. The key is that as the stone cuts the steel, so the steel wears the stone. The 120 removes metal quickly, but it dishes quickly as well, even when you conscientiously use the whole stone.
For your purposes, 220/1000/5000 is a good set. You could even get away with only the 1000 and 5000, if you are patient.
Generally, abrasive working time is minimized when the grit size of each grade is not very much smaller than the previous grade. When the grit size ratio between successive grades is greater than about three, it takes longer to "remove the scratches" of the previous grade than it would if an intermediate grade were inserted.
However, since the ceramic abrasive in the Shapton stones cuts so fast, even successive grit size ratios as high as five can be tolerable to a man of average patience (G). Beyond that, though, the work becomes painfully slow. Worse, the longer time spent on each stone means more dishing, which must be dealt with either A) on the next stone (ugh) or B) by more frequent dressing/flattening. Since coarser stones dish more than finer ones, (B) is usually the preferable option.
It's often convenient to think of an abrasive's grade number as a mesh size, although in practice, grains smaller than about 65 microns are usually "sorted" by a process called elutriation.
Incidentally, a Shapton stone's grade number times its average particle size in microns equals 14,700. For example, the 120 stone has an average grit size of 14,700/120, or about 122 microns.
Because a Shapton stone's grit size and grade number are inversely proportional, the grit size ratio for any pair of stones is simply the inverse of their grade ratio. That is, the 1000 stone grit particles are about five times as big as those in the 5000 stone. This handy fact is unfortunately NOT true for other abrasive grading systems, so it doesn't apply elsewhere, such as for example, to sandpaper.
Cheers!
Jim *standard disclaimers; no affiliation
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wrote...
...a most informative and enjoyable post, as seen below.
Thanks for the information Jim!
JP **************** Meliora.

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I use a 220 grit diamond to flatten an iron or chisel. I also use the 220 grit to flatten my waterstones. I then go 1,000 - 4,000 - 8,000 grit. For touchup, I use 0.5 honing compound on a leather wheel.
Preston

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