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I'm using diamond plates for sharpening bench chisels, and plane irons, and It's been difficult to keep them clean and performing to expectations. The instructions that come with the plates mention that only a couple passes should be necessary for honing -- which does not match at all the performance I'm getting. It seems to take longer than it should.

The manufacturer recommends water for cleaning, which for me doesn't seem to do much:

we recommend water for use with the stones. I have attached our use and care instructions for you. I have heard of some customers who use Windex with no adverse effects but we recommend the water.

The sharpeners need to be cleaned regularly. Often the fines/swarf which load onto the sharpener appear to look like rust. After a thorough cleaning, the rust look should be gone. Use Comet or Ajax and a toothbrush and give it a good scrubbing. This is the method we recommend.

Please keep in mind that with diamond sharpeners you use very little pressure. Just use the amount of pressure that you would use for shaving. Used properly and cleaned thoroughly, the stones will last for years.

My problem with using water, is that whatever I use to remove the water from the stones seems to leave lint particles of cloth or towels behind, which then roll under (or stick to) my sharpening guide's roller, or get in the way of the blade touching the stone. I've tried cloth towels, blue shop rags, J-Rags, and paper towels and they all seem to leave some sort of lint behind.

I got into the habit of misting water on the plates during sharpening, but the water layer mostly just seems to prevent friction -- it makes the blades glide on top of the surface. I then started to periodically wipe the plates with a humid cloth instead of misting. But my plates just stay gray, despite attempts to brush them with a toothbrush (and water).

I thought my planes were relatively clean, until I tried a simple pencil eraser, almost accidentally, and I realized how much swarf was stuck in them.

What else can you recommend to keep the plates relatively clean, and avoid long episodes of wet cleaning (which always seems to be the last thing I want to take time for)?

enter image description here Eraser on the plates. The cross shows before/after contrast.

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In terms of the cleanliness of the plates, I think you're worrying about nothing. Most people's plates are a bit grey, and not a few are tinged with rust from the same level of steel residue rusting sightly (reasonably common if the user is using a waterbased honing fluid or plain water). Neither seem to affect the way the plates work, it's primarily an aesthetic issue.

You can confirm whether it has any effect by carefully cleaning one half of any or all of your plates and then directly comparing cutting speed on the cleaned half versus the dingy half. My bet is that you won't be able to notice any difference.

Now that the main query you had is covered I wanted to touch on some of the incidentals.

The manufacturer recommends water for cleaning, which for me doesn't seem to do much:

Water and scrubbing with a brush using Comet or Ajax. If you're using only water that'll certainly account for some of it :-)

My problem with using water, is that whatever I use to remove the water from the stones seems to leave lint particles of cloth or towels behind, which then roll under my guide's roller or get in the way of the blade touching the stone. I've used towels, blue shop rags, J-Rags, and paper towels and they all seem to leave lint behind.

This has to be a common problem, I've certainly had it and I bet it's something that most have experienced. A few possible solutions:

  • Dab only, no wiping.
  • Blow dry using compressed air.
  • Dry off using a heat gun or hairdryer.
  • Just leave them to air dry (what I used to do when I cleaned plates under a running tap).

What I mostly do now is just brush off the swarf into a bin using a dustpan brush and stow the plates. Literally, that's it 99% of the time.

On the odd occasions I clean a plate down more thoroughly these days (and only on fine ones, never bother on my coarsest) I use a spirit-dampened wad of paper towel, wipe up with a clean paper towel and then brush off the worst of the inevitable lint with my hand. This doesn't remove everything but it removes enough that the plates work as they should.

I thought my planes were relatively clean, until I tried a simple pencil eraser, almost accidentally, and I realized how much swarf was stuck in them.

Bear in mind this residue went unnoticed because it's so fine. Even on the finest plates it could be composed of particles way smaller than the grit adhered to the surface, and as a result will have essentially zero impact on abrasion since it's just the peaks of the abrasive particles that do any work.

Only when the valleys between grit particles are completely full of swarf is cutting speed severely reduced.

The instructions that come with the plates mention that only a couple passes should be necessary for honing -- which does not match at all the performance I'm getting. It seems to take longer than it should.

I can't be sure but their instructions may be largely geared to knife sharpening, and few knives are as hard as even a half decent plane iron or chisel. A great many are significantly softer, most kitchen knives being a clear example. And the included angle at the edge may be lower as well (the edge is thinner). Combine the two factors and we're looking at two very different honing scenarios.

Anyway, I know they specifically say you should use light pressure, the quote you posted includes this advice. But IME it's perfectly fine to press harder1. Not hard (although I've done that) but certainly harder than I think they're suggesting2.

Pressing a little harder isn't just acceptable from what I've experienced using the diamond plates I have, it's the only way to get results in what I at least consider a reasonable amount of time — my goal being for day-to-day honing to take maybe three minutes and ideally less.

Obviously this means I'm not doing an excessive number of passes, but "a couple" is an exaggeration for me. Although five may be enough to raise a burr you can feel I tend to do about 10 back-and-forth passes (20 strokes total) to be sure I'm removing the entire of the wear bevel. For routine honing this is just on my finest plate. Diamonds cut fast so there's no need for anything coarser beforehand. I then strop and I'm done.

Note: if any of your tools are particularly hard or are made from a wear-resistant modern alloy like A2 you have to expect that all sharpening and honing jobs will take longer.


1 I've used diamond plates off and on for over 10 years and more recently (last couple of years) I've used them almost exclusively.

2 There's obviously some subjectivity in what constitutes reasonable and hard pressure.... just as there is with shaving pressure. I have always shaved using safety razors and I would presume this means I can press a lot harder than someone using a cut-throat can get away with!

  • I wonder if simply just not using any fluid at all is ok, as long as you brush and vacuum up the swarf. Reference stumpynubs.com/blogws13.html where he claims that "It is never a good idea to introduce water to metal unless you are absolutely sure you can get it completely dry every time". I suspect it will be next to impossible for me to habituate using a heat gun to dry the diamond stone thoroughly at the end of every single session. He also recommends using a "lapping fluid", but I'm suspicious of possible sponsor-bias there. What do you think? – bgoodr Jun 6 at 0:34
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    "I wonder if simply just not using any fluid at all is ok, as long as you brush and vacuum up the swarf." Yup. It's fairly widely stated that one of the great things about diamond plates is they can be used dry, with watery liquids or oils, whatever the user prefers. I've tried the entire gamut and I virtually exclusively use my plates dry now. Re. lapping fluid, it's the modern equivalent of honing oil, which has long been recognised to be snake oil LOL That isn't to say all are useless, some have anti-rust additives for example, but in terms of doing something specific to aid honing? Nah. – Graphus supports Monica Jun 6 at 7:15
  • Alright. This time it seems that my suspicions were warranted. Thank you, Graphus! – bgoodr Jun 8 at 16:57
  • Thanks! The half-clean half-dirty sharpening comparison experiment might be interesting. I initially just copied what I saw on Paul Seller's yt channel (he recommends automotive glass cleaner, which could be because it has more alcohol (instead of ammonia) and dries faster than water-based, but I'm unsure). I didn't have that cleaner, so I'd been using water (as the manufacturer recommended). Aside from not cleaning thoroughly, water gets trapped in the wooden holder and makes plates rust (the tools too). I might just use the eraser once in a while now -- dry messes are easier. – ww_init_js Jun 11 at 5:02
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Apart from aesthetics, why do you want them to be 'clean'?

All you need to do is remove the scarf to avoid them clogging. A rinse over the sink at the end would do that. I'd just go with a good brushing under some running water. I'm not sure what effect fine metal particles will have on the water system and pipes though.

  • Thanks. I agree that 'clean' could be rephrased. I certainly don't plan on using them as bathroom mirrors. It's more that I equate the dirt/grime with something that prevents the plates from working to their full potential. Rinsing doesn't work anymore, it's lodged. – ww_init_js Jun 11 at 4:43
  • Don't worry about the waste-water pipes. They have to be able to cope with mud and sand from peoples hands and clothes. It will be fine. – Martin Bonner supports Monica Jun 11 at 8:29

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