Stone Surfaces & How They Effect Sharpening

Over the years I've come to learn a few things with regards to how the condition of the sharpening stone's surface effects the sharpening process.


1. Flatten your stones

Many people I've talked to are shocked to find out that new stones aren't flat out of the box. I know this sucks but it's the truth, you need to flatten all of your stones before using them.

Some new stones can come with stickers on the surface (which when removed leave glue behind) or they have ink embedded into the face due to fancy markings, we want to remove these things before use.

All stones come with high edges/corners and some will even have a sort of surface crust on them that needs removing before the stone actually works correctly.

My advice is to soak (if required) the stone first and then follow with rounding the edges, corners, and ends - then flatten - then round the edges, corners, and ends (again). The order that you do this procedure is the same that you do for flattening a stone each and every time you do so although it's much more important to do the edge rounding at the pre-flattening stage when the stone is new because these high edges won't allow for you to flatten the stone correctly since the flattening stone/plate will be lifted off of the stone's surface. Sounds crazy I know - but trust me - this is key to getting your new stone(s) really flat.

Flatten your stones often if you want good/fast sharpening results - this also prolongs the life of your stones as well!




2. Coarse stones cut better when coarse & fine stones cut better when fine

So what does that mean? It means that if you want a coarse stone to cut fast - make the surface coarse and if you want a fine stone to cut fast then make it's surface fine (smooth).

I've found that to really get a coarse stone cranking I lap it on 36x silicon carbide (SiC) abrasive on a cinder block. Most times just a pass from a 140x diamond plate can help a hell of a lot too. The idea here is that the coarse abrasive creates tiny peaks that are sharp and grab onto the steel to move it.

To make a polishing (or fine - 5k+) stone really do it's thing I like to smooth the surface texture through the use of a 600x nagura stone. The idea here is to expose a greater surface area of the stone's abrasive to the steel being polished. There are a lot of polishing stones that simply don't work all that great unless their surface is smoothed out before use.