test18258 wrote: ↑Tue Nov 07, 2017 9:40 am Actually thats the video that inspired me to ask this question.
Since I dont have any high grit diamond stones I was wondering how much of an issue the carbide tear out is. He only finished the knife on a spyderco ultra fine.
Thats also why im trying to figure out if its worth getting some higher grit diamond stones (600 and 1200) Because I will probably be getting more knives in the future that have these super carbide laden steels.
Well this one is going to require some careful dissection to eliminate some underlying confusion.
When you say, "He only finished the knife on a spyderco ultra fine.", this is incorrect. The ultra fine stone (UF) is NOT his finishing point at all, He goes WELL past this. The UF is typically rated at 3 microns which is ~ 6k grit. The point of the video is that he tries two sequences - one all diamond and another where he uses the UF in the middle of his sequence. Indeed he takes it WELL past 6k, past 1 micron (16k) past 0.1 micron (160k) and all the way up to 0.005 microns which is 3,200k or 3.2 million grit. This rather thoroughly dispels the notion that these very abrasion resistant steels should only be used at coarser grits. Indeed because they are so abrasion resistant, it becomes worthwhile to go to much greater refinement levels - 3.2 million grit in this video.
An important point is that whether the surface being used is a stone, diamond plate or film or strop is really of little concern compared to the abrasives used. Yes there are differences, but they are minor compared to the abrasive being used.
Carbide fallout. If you abrade a steel with carbides harder than the abrasive, the only way you get to deal with the carbides is by having them fall out, with the surrounding matrix being eroded and the carbides not being eroded and eventually lacking enough support to remain in place. This really is not dependent on carbide size (or abrasive size or the ratio of the two), but by the difference in hardness between the surrounding matrix and the harder carbides in the steel. Once the abrasive carbides become smaller than the steel carbides you are now abrading the surface of the carbides and refining the geometry of the carbides to conform with the overall geometry of the edge rather than just falling out.
So if you are dealing with very abrasion resistant steels, you should use an abrasive sufficiently hard enough (on the Mohs hardness scale) to go through the carbides from start to finish. There is no disadvantage to doing this. Once you start out with coarse abrasives - eg using diamond plates like a 140 Atoma or even coarser, you just progress to finer abrasives on up as high as you wish. Plates are available from 46 grit to 3000 grit. Past that you can use diamond films (they don't last and I don't recommend them) or strops using CBN or Diamond (preferring polycrystalline diamond over monocrystalline diamond). You have available CBN down to 80 microns (coarser than 250 grit) to 0.1 microns (160k grit), providing you with the ability to go through a full sequence.
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Ken
