Wednesday, February 13, 2008

Sharpening a Plane Blade

At last count, there were exactly 3, 970, 000 ways to sharpen a plane iron. Well, maybe it just seems like that many. The point is, you have lots of techniques from which to choose, and all produce the same result—a sharp blade.

Here are photos showing how I sharpen a newly-made plane iron using a grinder and 800 and 8,000 grit waterstones. Make sure your stones are flat. I flatten mine sometimes twice during a job like this.

Flatten the back of the blade on an 800 grit stone. By gripping a piece of wood on top of the blade, you can apply greater downward pressure than you can with just your fingers. Keep the blade flat as you move it forward and backward on the stone and just concentrate on the 1/2" or 1" that is closest to the cutting edge. Once you have uniform flatness, do the same thing on an 8,000 grit stone until you achieve a mirror polish.

I hadn't sharpened the bevel on this blade completely before heat treating, so it's back to the grinder to finish sharpening before using the waterstones. Here is where you'll want to be sure to dunk the blade in water as you sharpen at the grinder so that you don't overheat the blade. Keep your fingers close to the cutting edge because if it's too hot for you, it's too hot for the blade, and you'll know to quench it.

For safety precautions, always wear a facemask at the grinder and let it run for a minute to warm up before grinding. You should also check to make sure your grinding wheel is not cracked. Do this by removing the wheel, slide a pencil through the center hole so it's suspended without you touching it, and tap it lightly with a plastic handle. It should ring like china. If you hear "thunk", throw it out.

You are finished with the grinder once you can no longer see light reflecting on the cutting edge. Next, secure the blade in a sharpening jig at the same angle you established at the grinder. In this case, 25 degrees. Start with the 800 grit stone and only sharpen on the pull stroke. When you have two flat surfaces on the bevel, move to the 8,000 grit stone without removing it from the jig. Once polished to a mirror finish, angle the blade up about 3 degrees in the jig (with some jigs, you don't have to reposition the blade; you can just turn a knob and it will steepen the angle for you) and create a micro bevel using the 8,000 grit stone only. A micro bevel is not necessary; it's just my preference.

You will now have a small burr on the back of the blade which can be removed with a few laps on the 8,000 grit stone.

You're done! That blade will now shave endgrain, hairy legs, and your neighbor's cat.


Adam Aronson said...

Bravo! Thank you for demystifying in 3,472,102 words or less the black art of sharpening. I'm anxious to try your method -- a simpler version of the one I've been using for too long.

Kari Hultman said...

Great! Glad it helped. :o)

Kari Hultman said...

I forgot to mention that the nagura stone is used with the 8,000 grit stone only. Spritz the 8,000 stone with water and rub it with the nagura stone in circles to create a slurry. (You can see it in the one photo) This produces the grit you need to achieve the mirror finish.

Nick Brygidyr said...

Do you NEED to use a negura stone with the 8000 grit stone? wouldn't you still get a mirror finish without it?

Kari Hultman said...

Good question, Amish. You could always try it without first. The 8,000 stone is very hard and I believe your blade might just skid across it.

The slurry created with the nagura stone gives a little more grip. I can't remember how much I paid for the nagura stone, maybe $12? It will last you forever.

Adam Aronson said...

How do you store your water stones; specifically the 8000 and nagura. I keep both in a tupperware container with 1/2" of water in it (along with a drop or two of beach to keep mildew at a minimum). The stone (a 6000 in my case) rests stone side down in the water.

The reason I ask... I used my 6000 this afternoon to flatten the back of the blade from a low angle jack plane. During the sharpening I noticed the edges of the stone were crumbling away. I've never seen this before... you? I also store my 120 and 800 submerged in a tub of water. No problems there.


Kari Hultman said...

Hey Adam, I store my 800 stone submerged in water, like you, but do not store my 8,000 or nagura in any water. The stones are so hard, that the water rests on top when in use (which is what you want), so it's not necessary to submerge them. You submerge the 800 stone so it's saturated when you use it and any water you spritz will stay on top of the stone.

Another thing you can do so that the edges don't break is when you flatten them, chamfer the edges while you're at it to knock those sharp corners off.

Anonymous said...


just one question: Why do you polish the bevel before establishing the micro bevel?

With the micro bevel, you just remove the polished surface at the cutting edge and replace it with an other. In my experience, honing only the micro bevel is enought.

Kari Hultman said...

That's a good point, Marcus, and would make for a good experiment—to see which way is better or if sharpening the bevel makes a difference at all.

I sharpen this way because it's the way I was taught by David Finck (Making and Mastering Wood Handplanes) and now it's just habit.

Thanks for the comment!

Kari Hultman said...

Marcus, I might have misunderstood meant, why not stop with the 800 grit stone on the primary bevel before adding a microbevel, right?

The 800 grit stone beefs up the primary bevel where it has been hollow ground from the grinder. It seems to me that at least is necessary before adding a micro bevel. Whether or not it's necessary to progress to the 8,000 grit stone with the primary bevel, I'm not sure.

If you meant that you go straight from the grinder to the micro bevel, let me know. I am curious to hear how long the cutting edge stays sharp (and if it chips) before you have to resharpen.

AKnox said...

I've been trying a very similar procedure to this, only using diamond stones for the rough work and then switching to a 1k grit and then 8k grit waterstones for honing.

When I switch over to the waterstones the steel becomes opaque/cloudy and generally not as reflective as the coarser stones. I can't figure out if I'm pressing too hard or not hard enough. Or is this just a step and I'm not honing for long enough?

Thanks for any advice

Kari Hultman said...

AK, are you using a nagura stone and water to create a slurry on your waterstones? If not, then the steel will become lodged in the stone and can create scratches on the surface of your blade. The nagura and water carry the bits of steel away so they don't become lodged.

Have you tried going from your coarse diamond stone straight to the 8,000 grit waterstone (skipping the 1,000 grit)?

Do you leave your stones out in the open where sawdust and other particles can light on the surface? You'll want to clean them before you use them, if so, and keep them covered in future.

You want to press pretty hard on the iron when you're sharpening, so I would not lighten up your touch.

I hope this helps!

AKnox said...

I go from a 320 grit diamond to a 1k grit waterstone and this is where the steel becomes less reflective.

I haven't tried going to the 8k after that, it seemed like a waste. I true the stones and try and keep the surface clean, but I do get mucky lines after a little while that don't wash off (they come off with flattening)

I keep them clean (they are pretty new still)

I haven't tried using nagura before.

As a note, i've tried honing a micro-bevel on the edge with the 1k and 8k and I do get a mirror finish within a few strokes. Perhaps I lapping the flat side of the blade too many times... About how man passes do you make on the medium grit stone 4/10/20/50+ ?

Kari Hultman said...

AK, you only want to use the nagura stone on the 8,000 grit, not the 1,000, so that must not be the problem. I'm guessing you need to keep working at it with the 1,000 grit. I don't know how many times I lap the blade, but I definitely spend several minutes, especially with a blade that's in bad shape. So it would most certainly be more than 50 strokes.

The micro bevel hones quickly because you're only sharpening a little sliver and are putting all of the pressure on that one thin area.

I suggest pressing harder and lapping for a longer period. Feel free to send me an email if you're still having trouble. Good luck!

Anonymous said...

Thanks very much for the explanation with nice pictures.

Every time I learn something.

May I ask what is the purpose of a microbevel? If your plane is 25 degrees and you make a microbevel a few degrees higher, why not just make the plane 28 degrees?

A few weeks ago I bought a Stanley sharpening set which includes oil, a jig, and oil stone.

I started sharpening my blade and then noticed that certain parts were getting a different look. This is when I realised that the shape of the stone was changing and that I need to keep the stone flat as well. What is the best(cheap!) method of keeping the stones flat?

Another question. The higher the grit one uses for honing the blade, the sharper the blade gets?

I still don't understand the differences between diamond, water and oil stones. Does one need to keep all of these stones flat? Or is the diamond stone so hard, the shape never changes? Also if I spray water on an oil or oil on a water stone, what happens then?

I do get the blade at 25 degrees with my jig and sharpening stone,
but it never really gets sharp.

Does the back of the blade need to be completely flat? I have seen some vids on youtube where they are putting a thin ruler under the blade while flattening the blade. I assume this changes the angel of the back slightly.

Sorry for so many questions. I have only recently started using
a jack plane. The Jack plane fell on the ground a few times and the shape of the blade changed and it lost it sharpness. Since then I have been trying to get a sharp blade without much succes.

Thank you again.



Kari Hultman said...

Yalcin, you have some excellent questions and I'm going to answer what I can in a new blog post, so that others can chime in with their thoughts. Sharpening is such a huge topic, it's no wonder there are so many books written on the subject. Hope that's okay with you. I should be able to post this very soon.

Yalcin said...

Dear Kari,

Thanks for answering. I will
be waiting for your new blog post with great interest.

Just a quick question. I found this sharpening set on ebay:

It's 3 diamond sharpening stones and a jig. Here is the description of this product:
''Contains three grades of stone, coarse for swift material removal, fine for shaping, and extra fine for the perfect cutting edge.

Easily lubricated with water, these stone will find numerous uses for planes, chilsel, and knives.Generous dimensions (6" x 2") make the stones particularly easy to use.Sharpening guide ensures consistant edge profile.
Just wash off with a little soapy water after use, and dry before storing away''.

What is your opinion on this? Seems like an easy and cheap way of keeping my jack plane and spoke shave sharp.

I am very interested in your opinion.

Thanks again.



AKnox said...

The short answer, from my experience:

The 25 degrees is a guide, trying to polish the whole bevel is unnecessary.

The back does need to be polished, the blade is an intersection of two planes.

Honing causes small scratches on the surface of the blade. The higher the grit the smaller the scratches. The smaller the scratches the smoother the surface becomes.

David Charlesworth's ruler trick is to establish a highly polished surface on the back of the blade. I personally think this is only necessary on finishing planes. You still polish the back side (un-beveled) so that you don't have to do David's trick everytime.
Though, because polishing the whole back side is tough, the ruler trick is a handy crutch.

My preference for keeping my waterstones flat is coarse diamond stone (blue from dmt).

Diamond stones have diamonds embedded in them and stay flat (you can use oil or water with them).
Waterstones should only be used with water. From what I have read these give better feedback on how flush you are holding the metal to the surface of the stone.
Oilstones should only be used with oil.
Getting oil on waterstones, or vise versa causes the stone to degrade in a way that it was not meant to.

I think diamond stones are best suited for rough work. Thus I think it worthwhile to get a coarse/extra coarse dmt diamond stone. Chris Schwarz and David Charlesworth then both recommend (in latest articles) a 1000 and 8000 grit Norton water stone (you can get them seperate or combined). Schwarz likes this little Eclips sharpening guide, but for the novice (me) I think the Veritas MK2 is a better choice (except for cambering the iron, as a cambered roller for it is another 60$ or so)

here is a link to a really good article.

(sorry to take up so much room on your blog, ps I solved my polishing problem. I just need more pressure. whoever said less was wrong. It ended up being pretty quick work once I figured that out. Thanks for the help)

Kari Hultman said...

Thanks, AK--feel free to repost this on my latest entry in response to Yalcin.

Kari Hultman said...

Yalcin,I don't know how effective that jig would be at holding your blade. It seems to me that, even with finger pressure the blade might want to lift off or slip as you pull if back along the stone. I see that the jaws are beveled to grip the blade, but I'm not sure that would work well. I use the Veritas jig which securely clamps your blade in place. The jig in your photo also limits the width of the blade you can sharpen--there would be no way to to sharpen a chisel this is thinner than the minimum width of the jig's jaws when they are closed. The roller is also small in width, which might make it tippy in use. The Veritas has a wider roller so it's stable.

I have never used diamond stones, so I can't comment on whether or not these are a good choice. I would want to know what the exact grits are, though, since I hone to 8,000. You don't have to go that high, though. Some people stop at 4,000 (and probably less).

If you're looking for an inexpensive sharpening method, have you considered the "Scary Sharp" technique?

Yalcin said...

AK, thank you for your explanation.

Dear Kari,you are righ that jig
does not look very good for a wide
blade. Luckily I have the jig from my Stanley sharpening set.

I emailed the seller of the diamond stones+ jig. He told me the grits are 400,3500 and 6000. That seems great I think. The set
is only about 30 dollars.

I have seen the regular diamond stones which have many holes in them so the dirt can go away. Problem is that then the when your honing those holes are not touching the blade.

Kari yesterday I bought sandpaper and started doing the scary sharp technique. It works, but I did not have very high grit sandpaper. The finest was I think 400 or so. It's probaby the easiest technique.

I see many people like the wetstones. I read that these are made of aluminium oxide. Does not seem very healthy to me especially somebody who uses them a lot. It might not be a big problem since one sprays water on the stones which makes it near impossible for the aluminium oxide to be breathed in, but I choose not to use the wetstones with aluminium oxide.

Sorry too long post again.



Yalcin said...

I just emailed another seller of
the diamond stones I mentioned in
my previouse message and he told me
the grit is 300-900. Don't know why the other seller wrote 300-6000.

Kari Hultman said...

Yalcin, I use 80/1000/8000 grits. But you can use other combinations. Some people only hone to 2000 or so. 300-900 is not necessary. You would only need one of those, like 600 or 900.

Kari Hultman said...

Yalcin, you can buy higher grit sandpaper at automotive stores. I believe up to 12,000 grit. I don't know if there is a danger in using aluminum oxide and I don't know if the ones I use are made of that or not. Mine are King brand, which you can buy from

Yalcin said...

Dear Kari,

Thanks for your advise.

I was wondering at what grit
does the blade get sharp
enough to cut easy?

I know you go to 8000 grit, but
what if you would stop at 1000 grit? Would it still be sharp?

All most all synthetic waterstones are made of aluminium oxide as far as I know. I don't know about the natural stones..

Thank you in advance for any advise.

AKnox said...

sharp is a pretty relative term. If you ever plan on using a handplane you own for finishing I would go up to the 8thou grit.

Since I have these stones laying around, it really isn't that much extra work to go up to 8thou on all of my hand planes.

The sharper your blade is the easier it will be to plane wood... it seems intuitive, but there it is. plane and simple (ha!)

Kari Hultman said...

Yalcin, I have witnessed Steve Latta, who makes gorgeous Federal style furniture, sharpen chisels on a belt sander.

What happens, though, when you continue to sharpen and hone to progressively finer grits is you make the scratches left by the previous grit smaller and shallower. As these scratches are diminished, there is less resistance when you cut through wood--there are less scratches to get hung up on wood and therefore, less tearout. The cutting edge leaves a smoother finish.

So, yes, you can stop at 1,000 grit, but you will probably not get as nice a finish/as smooth a finish and you would if you went to 8,000. And the tool might not move through the wood as easily.

If you hollow grind your chisels and plane blades and create a micro bevel, then you only need to touch up the micro bevel when your tool becomes dull. You can do this a few times before you need to go back and reestablish the primary bevel.

Yalcin said...

Dear Kari,

A few weeks ago I purchased a
1000/6000 waterstone and the
veritas jig.

The jig is really good.

Just a few days ago I got my
stones really flat. I sharpened
my blade on the 1000 grit stone
and it become quite sharp. Sharp
enough to shave the hairs on my arm.

I have not been able to sharpen correctly on the 6000 stone as I can't create the slurry. I think
I need that nagura stone?

The veritas jig is great for sharpening the blade of the jack
plane. I sharpen at 25 degrees. The back bevel I do something between 5 and 10 degrees. Is this
ok? I have not yet done the microbevel thing.

If you create a microbevel at 30 degrees, then the blade is good for hardwood. What about soft wood?

I can't use the veritas jig for sharpening the back bevel of my spokeshave blade unfortunately.
The blade is too short and therefore the angle becomes too high(english steep?).

Maybe I should flatten the back
on a piece of sandpaper or try
the ruler trick.



Kari Hultman said...

Yalcin, glad to hear that the sharpening is going well. Yes, you need a nagura stone for the 6,000 grit. They are pretty cheap and will last you a lifetime. Spritz water on the stone's surface and rub the nagura stone all over the surface to create the slurry.

I do not put a back bevel on any of my blades; I sharpen and hone them dead flat. I sharpen the bevel on all my blades to about 25º and then put a 3º microbevel on them. There is a lot of information on the web about bevel up and bevel down irons and the pitch of the plane's bed in relation to the type of wood you are cutting. I am not very knowledgeable on this, so I suggest you look into some other resources. I use the same bevel angle regardless of type of wood or whether or not I'm planing face or end grain. If my blades are sharp, they cut everything very well except for really gnarly wood. In that case, I'll use a scraper.

Yalcin said...

Hi Kari,

Did you take some shavings with those nice planes?

I thought I know this woman from
somewhere.Took some time to figure out it was you my internet sharpening teacher!

Take care,


Kari Hultman said...

Haha! Yes, that's me. I wasn't aware that Shannon had posted this. Obviously, I'd rather be behind, rather than in front of, the camera.

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