Whetstones - Accuracy of grading?

[LancsRick]

Right, whetstones. They're wet, they sharpen, and they conveniently get identified by their grit so that you work from low to high and end up with a mirror, right? Nope...

I have a set of 3 whetstones from Rutlands (600,1000,3000), and another 8000 grit from Amazon which seems to get good reviews all over the place. From the 3000, I can start getting a mirror finish on my edges, and after a bit of use the stone surface feels extremely smooth. For the 8000 though, it seems to cut faster and doesn't get surface clogged.

Which is the oddball in this scenario? Have I got a 3000 that clogs too quickly, therefore smoothing out and allowing a higher effective grit? Or have I got an 8000 that is actually coarser and should perform differently?

I realise I could spend £80 per stone and get some excellent ones, however, this is a temporary solution until I pick up a good rotary wet grind system like Tormek, so I just want to do something sensible but effective in the meantime.

Cheers.

 

[lurker]

I have been dabbling with sharpening tools for at least 40 years.
I doubt I have spent a total of 80 quid on abrasives in all that time.
Hopefully Jacob will be along soon to put the world to rights

By the way....... Whetstone :wink:

 

[D_W]

Let the 8k run a little dry at the end of a hone if you want it to bring up a polish. Generally, it's cosmetic at that particle size and only matters for razors and skiving knives .

 

[AndyT]

I think there may be on or two other sharpening threads somewhere which will probably cover this better, but I believe it's safe to say that grit size and cutting speed are two separate characteristics of a whetstone. They do not necessarily stay in step across the range from coarse to fine, so it's no surprise that your 8000 grit stone seems to cut faster than your 3000.

There are many other factors which make one stone different from another, including, in no particular order:

• - The shape of each particle - does it have naturally angular corners or are they rounded over? (Think of river gravel compared to beach sand, but on a smaller scale.)
  
  - The degree to which each particle is held in the background 'binder' or is released to roll around in a slurry. (Some natural stones hold tight on their grains; waterstones let go of them much more readily.)
  
  - The hardness of each particle.
  
  - The consistency of behaviour within a single cut piece and from one piece to another.
  
  - The purchase price
  
  - The sizes available.

There are probably more, but I expect you get the point that there are a whole bunch of factors to consider.

Bear in mind too that there is no single grading system applicable to all types of abrasive.

Some woodworkers react to this by wanting to explore all the possible permutations of these factors in pursuit of the "best" sharpening system. (Doing this can apparently take a while and cost a lot.)

Others think "coarse/medium/fine, that will do - " and get on with woodworking.

 

[essexalan]

Important thing is that each stone in the progression should remove the scratch pattern left by the previous stone and your 8k should leave you with a finished edge but not necessarily mirror finished. Your 3k should cut faster than your 8k, if it is clogging easily then it could just be that it needs running in a bit, sometimes new stones are like this, or it needs more water or it's no good. Refresh the surface with whatever flattening method you are using and try again. You should get lots of black swarf off a good 3k with any normal steel and if you don't wash this off it can clog the stone. Of course you could jump straight from the 1K to the 8K.

 

[LancsRick]

Thanks all. I've just had another go with a scrap blade I had around the place. The 3k Rutlands stone feels slick and will put a mirror shine on something. My other 3K stone will remove material but leave a scratch pattern, and the 8K leaves a fine scratch pattern.

I assume therefore that the 3K from Rutlands is out of whack and needs moving up the progression? I'm surprised the 8K doesn't put a mirror finish, but as mentioned above, I'm not fussed about cosmetics really.

I've also corrected my phone's autocorrect from earlier, thanks!

 

[Phil Pascoe]

I assume you mean water stones? Whetstones to me are oilstones. :?

 

[murrmac]

There is no historical justification, AFAIK, for restricting the term "whetstone" to oilstones.

"Whet" is an ancient word meaning to sharpen , and whetstone is just a synonym for a sharpening stone.

Oilstones or waterstones, they are both whetstones.