Hey David, I have a related question about pressure on diamond stones. You know from other threads that I have pressed "too hard" on mine in the past, which has impacted my sharpening results. Trying to learn and remedy that now. But.....I've also read here that pressing too hard on diamond stones can wreck them. Since I used the stones for several years, presumably pressing too hard the whole time, I wonder if I damaged them.
Is there some kind of straightforward way to test my interrupted surface DMT stones to see if they have been damaged? They still seem to sharpen ok, although it takes longer than I'd expect to get good edges.
Testing for 'damage' is sort of subject to interpretation (where's the threshold for 'damaged' versus for 'normal wear'?). It comes down to figuring out if they've slowed down too much to be useful at all. And the slowing down of them could also be due to other factors, like loading or clogging with swarf. If used dry, and if some lower-alloy stainless blades have been ground heavily on them, they can clog very fast, and will appear to quit working almost entirely. To make sure they're not clogged, a thorough cleaning with Bar Keepers Friend powder and water, with a good, stiff brush, should clean them up.
I thought I'd ruined one of my Dia-Folds a few years ago, after I used it to lap a ceramic hone. I had obviously scrubbed a fair amount of diamond off the hone as I could see the bare spots, and wrote it off for a while as unusable without actually trying it. I dug it out of storage a year or two later, and gave it a few passes on one of my knives. It still worked, although to a somewhat finer, less aggressive degree. But still good enough to be useable for a touch-up hone. It takes quite a lot to completely kill them.
You can test for effective metal removal by scrubbing one of your blades on the hone, as if grinding new bevels, then wiping down the hone with a clean cloth/towel and some Windex. A microfiber towel wetted with Windex will lift the vast majority of swarf from the surface, if there's any there at all. If the towel comes away clean, I'd be concerned about the effectiveness of the hone.
I've noticed, when using my diamond hones with mineral oil, it becomes obvious if/when metal is removed from the blade. The oil does a good job 'floating' the swarf as it's generated, and it'll be easy to see it in darkened 'puddles' of oil on the hone, and even easier to see in the recesses on the interrupted-surface hones. And, as with the Windex, if you wipe that oil from the hone with a rag or towel, the 'dirty' swarf will easily be seen on the towel.
You can also test by scrubbing some clear, smooth glass on a diamond hone. If the diamond is still there, it'll scratch the glass pretty obviously.
David
