Lasting time of the Magna Guide Diafold Stones

M

Mcoe01

Joined
Aug 12, 2011
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I bought my DMT Magna Guide sharpening kit around the end of the summer and have since then done a good amount of honing old blades and using the EEFine side a good amount. I was wondering if anyone had a good way on how to tell if it is worn out yet, or if they know a certain number of strokes it takes to wear out one of these Diafold stones.
 
I pretty severely abused a Coarse/Fine (blue/red) Dia-Fold a while back, using it to flatten a ceramic hone for my Lansky set. It looked pretty bad when I was done, and I just assumed it was ruined, so I stashed it away and forgot about it. Fast-forward a couple years. I just happened to stumble across it one day, so I decided to see if it'd touch up one of my pocketknives. Worked fine. In some respects, I like it better this way; the finish produced was more uniform.

These things are more durable than most give them credit for. To some extent, they'll lose some aggressiveness with heavy use. But, they still work.

IF you take care of them, they'll last a good, long time (don't press too hard, they work better with LIGHT pressure anyway). :)

By the way, if you doubt whether there's any life left in them, just rub a metal object across it (coin or anything else). If there's any diamond left on it, the scratches will tell the tale.
 
Scratches on the metal, if the surface still contains diamonds it will scratch metal it comes in contact with. DMT recommends using glass if you are really unsure. Glass will give more feedback at the finer grits.

Diamond stones will last a very long time if cared for correctly. Mainly don't use excessive pressure when sharpening and they will probably outlast you.
 
With the finer hones especially, I'd just emphasize keeping them clean. Since their grit is so small, they might be a little more prone to losing effectiveness if they get too loaded up with swarf. A little dish detergent (Ivory liquid is what I use) & water, lightly scrubbed with a fingertip & rinsed thoroughly after each sharpening session, has kept mine in good shape. Comet/ajax or Bar Keeper's Friend, mixed with water, work very well too, if they've been neglected a while.
 
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I have found that wiping them off on a paper towel or napkin or rag works well in-between sharpening tasks.

They will get rust spots if not wiped down with lubricants once in a while too.
 
The rust spots are usually leftover steel swarf on the hone. This is why I've been in the habit of washing & scrubbing mine with soap (dish detergent, specifically) or powdered cleanser & water after each sharpening session. Unless the nickel substrate on the hone has come off (exposing the steel plate underneath), they shouldn't rust on their own. I've been using mine for a few years now, and haven't had any rust issues. The cleaner they are, the less chance you'll see rust on them. Don't need to oil them, if they're kept clean. Oiling will only trap the particles & moisture, if it isn't clean.

Bar Keeper's Friend cleanser is good at removing the rust, if it's there. The oxalic acid in the cleanser actually reacts with the steel particles, effectively dissolving them. Very effective, so long as you're careful with it (read the warnings on the container). Rinse it thoroughly afterwards.
 
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While many use soap and water on their stones, I don't. As part of my job, I do finishing/refinishing of furniture and other wood and metal surfaces.

I learned about the dangers of soap remnants in an easy demonstration when we were learning about cleaning surfaces prior to finishing. Very mildly soapy water was put in a clean pane of glass, then rinsed well under warm water and allowed to dry while the rest of the demo went on.

The remaining stearates on the glass dotted it with their remains after drying. So I remembered one day when cleaning my diamond rods, and after I washed them and dried them, I tried cleaning them with lacquer thinner to see if I could remove any more dust or contaminants. A lot more steel dust came off, evidencing that the soap left its remains after rinsing. (As a sidebar, ever wonder just why you can smell soap on your hands after washing, on your hair after a shampoo, or on a towel? The stearates hold the fragrances, and when the stearates are left behind, they keep the fragrance as well.)

Sharing this piece of knowledge with the knife makers I see at out monthly gun show, the uniform response to my discovery was *duh*, and as usual, I felt like I was the last to know.

Now I do as Obsessed With Edges said, and clean them with a non scratching cleanser and a toothbrush. A couple of quick brushes and they are clean as a whistle. I allow them to air dry as a local knife maker here told me that he didn't dry his off as the diamonds would collect or cut off tiny pieces of lint that causes the diamond surface to be filled and cut less precisely.

I am not consumed with sharpening, but really like a sharp knife. With my job dulling my knives frequently, and my obsession with cooking, buy rods are used on about 3 - 4 knives a week, every week. More if I get a new knife I feel I need to reprofile. I am convinced that by keeping the surfaces clean they have lasted as well as they have. They are about 10 years old now, and while they aren't as aggressive as they once were, as pointed out above, that might not be such a bad thing.

Robert
 
I'll re-emphasize DISH detergent (previously referred to as 'soap'; I use Ivory liquid). 9 times out of 10, it's all I've used to clean my diamond hones, with hot water. Just a little bit goes a long way. I'm inclined to believe, if it can't be tasted on my dishes, or smelled/tasted in my coffee mug (guarantee I'd notice it there), it isn't leaving anything significant behind. Other soaps (hand soap, shampoo, etc.) do have other ingredients designed to remain behind & moisturize, condition, etc. Dish detergent is meant to rinse off, more or less completely, for obvious reasons. Rinsing with HOT water is all the better and more effective.

My 'order of preference', when cleaning them, is 1.) Dish detergent & hot water for light clean-up, 2. ) Comet/ajax & water, 3.) Bar Keeper's Friend & water, for rusted swarf and/or more stubborn embedded particles. In all cases, I rinse afterwards with HOT water (hones will dry more quickly & completely this way).

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I changed the word 'soap' to 'detergent' in my comments above, as there's a significant difference in meaning. Soaps (bar soap, hand soap, shampoo) contain fatty acids, which can leave residue; detergents use other 'organic' acids designed to envelop dirt & other particles and carry them away when rinsed, leaving little/no residue behind.
 
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