Razor Sharp Knives, Chisels, and Plane Irons

My 2 cents on how to sharpen kitchen knives and workshop tools like chisels and planes. There is so much information out there for some reason, and it’s as confusing as hell. It really doesn’t have to be. I imagine there are plenty like me who grew up with blunt knives kicking about in a draw, with perhaps one “good knife” kept aside or in a holder. And forget being taught this is “shop class”. I did every woodworking class on offer at my old high school, but we just didn’t go to this sort of detail.

Keep It Simple

Remember we are talking chopping wood or veggies, not performing brain surgery, so we don’t need to be molecule sharp! You just need an edge sharp enough to do the job, and it’d be a bonus if it didn’t cost the earth or take until earth’s end to finish. So don’t be distracted by too many advanced techniques; they may technically be right, but you can do well with a simple approach too.

Knife “Steels”

So firstly let’s talk “steels”. Those rods you see on TV in the hands of a chef cris-crossing with a big knife. I always presumed this was how knives were sharpened and spent a lot of time fruitlessly waving knives about imitating what I saw with minimal improvements.

Really these are to maintain your edges (straightening up the edge as it gets knocked about), and honestly I think you can largely ignore them for domestic use. Now you can sharpen with some steels, and I use them for sharpening odd shaped blades like on a blender, but that’s not what I’m talking about here. If you really want to get a proper edge back into your knife, it’s all about “whetstones”. 

Whetstones

A whetstone is fundamentally just a flat abrasive block that works a bit like sandpaper.  So just like sanding up a rough block of wood, you move between finer “grits” to progressively get something smooth (and for knives smooth at the edge equates to sharp!).  You use oil or water to stop the bits of steel you are removing from clogging up the stone.

The modern marvel of Ebay has given easy access to a heap  of affordable stones if you are prepared to wait for shipping. But what to buy? There are so many options it’s a bit daunting. But my pick of the crop currently are these  $20-30 “water stones”, i.e. stones designed to just use water as a lubricant. You need at least 2 different grits, but 3 grits will save you some trouble.

My set up is a combination stone with  3000 grit one side and 8000 on the other, plus one more really fine 10,000 grit stone. The 10,0000 stone is a bit of an indulgence as my friends were already cautious using my knives with the 8,000 grit, and it did the jobs just fine for chisels and planes irons. 

My whet stones. (Left) 3000/8000 (Right) 10000. They come with handy rubber holders to protect the corners and keep them nice and still while using them.

I personally would avoid the cheaper “combination oil stones”, and anything which doesn’t give you some sort of grit number (E.g. skip the generic “coarse”, “fine”, “extra fine” labels). The even lower price is of course tempting, but I think you’ll be disappointed. While yes you’ll get things sharp enough I suppose, I would not call them good enough to get that real razor finish needed for that satisfying glide through a tomato, or that wafer thin shaving from a chisel or hand plane. 

Example of the typical combination oil stone, and something I’d not bother with if I were you.

Method

Water stones, unsurprisingly, use water to lubricate them (oil stones use oil, diamond stones use… water! Dang, something went wrong with the naming convention). So soak them in water for a few minutes before you start, and keep a little water ready to add to the stone to keep things lubricated. But be careful not to use too much water while sharpening.  As you work the stone, a paste will form, which is really what does a lot of the sharpening.  If you wash this paste off you are just making life hard for yourself. (Edit- this only applies for water stones. For oil and diamond you wont get a paste but just metal contaminate which will clog those stones)

With a little bit of water a paste forms. Don’t wash it all off as this helps the sharpening.

The other key tip is to work your stone evenly. Water stones are soft and wear out over time, so make sure you don’t wear grooves into them. Work all around the stone to keep wear even as you can. Eventually you may need to flatten the stone, but that’s another story.

Apart from that it’s really pretty easy. start with the most coarse stone first and work the edge keeping the angle consistent  (just use the existing edge as a guide and try to keep your hands steady. Play with different positions of your body until you are conformable). The general method is to keep working the edge with a light pressure until a small burr forms on the other side.  Carefully feel the edge with your finger until you feel a little burr forming along the full edge. That tells you that you’ve fully ground down one side and can move onto the other. It can be a little hard to feel but it’s an important step so do look out for it. Repeat on the other side. Then repeat both sides again on your next finner stone and so on.

Finding the right angle is pretty easy. Start the blade flat then rotate until the gap disappears.

At the end of using the last stone, it can help to remove the final burr by just running the edge flat on some timber like a chopping board. Not super important by my thinking as it’s very small at that stage.

Testing the Edge

As you’ve gone to this effort you really want to have some sort of test that you haven’t wasted you time. But “how sharp is sharp?” About the most reliable method I’ve seen to test your edges is the “paper test”. Grab any old sheet of paper and try slicing off some slithers off at an angle away from yoy. Do this before and after sharpening to really see the difference. If you are catching or tearing the paper, you still need to work on the edge.

Testing the edge of a freshly sharpened chisel

Guides and Jigs

I have bought some sharpening guides for both chisels/planes and kitchen knives but I’m not going to recommend them as such. Now there is nothing wrong with them, but after a bit of practice I’ve found you don’t really need them. The key thing is to keep the angle of the blade consistent, and provided you are careful, doing this just by hand is quite practical and accurate enough if you ask me. Without a guide it’s also much easier to evenly work the stone all the way to the edges, avoiding uneven wear. So if I had my time over I would have saved my money and gone without. But look, you can get them from Ebay for about the cost of a stone, so if it gives you some confidence it certainly can’t hurt, but don’t treat them as a must have.

(Left) knife sharpening guide (Right) chisel / plane iron guide
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2 comments

  1. Really useful info there Dan! I have one of those combination stones, maybe need to get a better set 🙂

    Also I didn’t realise the thing about the paste building up, I always thought it was “clogging” the stone and stopping the sharpening from happening, so I was washing it off. Easy mistake I guess, but thanks for the clarification!

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    • Thanks! 🙂 If it’s a hard “oil stone” you are right, wash it off with some excess oil as it will clog and not been as good. But if it’s a soft water stone them yep, it works best if you leave a bit on. Or at least that’s what I’ve found.

      Like

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