Salutations to Stone Sharpeners!

[Mark Reich]

Hello Mr Me2, I’ve been reading your very astute posts, and find them quite intriguing. It’s great to hear you are sharpening on stones, as that is my preferred method as well.

I’m sure there are more than a couple of us, so we’ll see who signs in. Sharpening and maintaining high quality kitchen knives on stones and leather hones is a subject of high interest to me. 

I’ve spent enough time with Murray Carter to have been his first apprentice, several years ago. I just got back from visiting him in his new shop, and had a swell time with him. He truly is amazing, and I’m forever humbled to know him as a Grand Master Bladesmith and friend.

I am pretty familiar with kitchen knives, especially Japanese carbon steel. I’m well connected with many friends who highly prefer Japanese carbon steel kitchen knives, and I have well over $10k worth of laminated Aogomi Super Blue, with which to appease them, ASAP. The only thing I lack is time to focus on it, which is mandatory. I’m not interested with anything that wouldn’t make Mr Murray proud.

So anyway, I’m really happy you’re here, and I apologize for not speaking up sooner. Please allow a late Welcome to the forum. I’m really looking forward to visiting with you. Hopefully we’ll have company.

[me2]

Thanks. I wouldn't worry about the delayed welcome. I'm pretty sure we've talked before. I think I remember seeing you on the KnifetalkOnline forum, which seems fairly slow lately. I have not tried SB steel, and regret missing out on the Spyderco models using it. I am not terribly familiar with Murray, other than his sharpening videos on YT and his time on Forged in Fire. Perhaps you can provide some insights into his methods and theory if questions arise.

Do you use a guide when using bench stones? I've had a couple for years that I use, though I've retaught myself to freehand sharpen as well. It's not too bad as long as you don't care what the edge looks like when you're done.

My focus lately has been on speeding up stone based sharpening with simple steels used in inexpensive kitchen and field knives and using as little equipment as possible to get as high a sharpness as possible. It's a small portion of knife users that have higher end steels that respond to sharpening like Super Blue or White #1, #2 or similar.

I have most of my kitchen knives sharpened on a Norton Economy stone coarse/fine, and only recently added in a ceramic rod. I also use a DMT Aligner clamp set as low as possible with the Norton. These cheap steels get tricky sometimes, but I can usually get an edge tree topping sharp with just that set up. This set up was about $8 for the stone and $15 for the clamp. It still suffers from the long sharpening session for the initial rebevel, but subsequent sessions are very quick from the repeatability. I had so much trouble from power sharpening I've abandoned it in all but the root cutting blades and setting initial bevels on thick knives. I've even begun to prefer steels that can be filed easily for certain uses.

[Mark Reich]

I could certainly give some insight to Mr Murray's methods, although it would probably be better to read his book. That way you don't get mixed up between my words and his, because they could differ in areas, I'm sure.

Interesting that you've been to Mr Ed Fowler's sight! He is Friend and Mentor. He is one of very few, if not the only person I've seen Murray credit. I'm not sure why that is, but possibly because Mr Ed is very gracious and open minded, because their methods differ to the point of infinity.

I have virtually all the guided stuff, with an inch of dust on it. It's simply easier for me to use stones. I do use 2x72s to profile edges, and I've been known to use a fleet of 1x42 Kallys, and (my newest machine) a Gen III.

All you need to increase your productivity are the right stones. I can't recommend the 140 Atoma enough, for sharpening and lapping the rest of your stones.

[me2]

I've been a member there for a while. My username there is ChrisAnders. I forgot the space in my name when setting up the account. I watched Murray Carter's video of forging a Nakiri, and it was quite entertaining.

I used to sharpen a lot on a belt sander, but after years of thinking it was working fine, I found out my edges were being softened considerably, so I stopped for the most part. Until I get a cooled version or a variable speed machine, final sharpening will have to be on stones. I only use power equipment for edge thinning or blade grinding now. A properly thinned edge doesn't take that long on stones, and even if it does, I only have to rebevel it once. I have reground a couple of knives down to around 0.005" at the top of the bevel, and they sharpen in no time.

I use a guide block for sharpening, similar to a one sided Spyderco Sharpmaker with a cedar 4x4 supporting a bench stone. It allows me the control to form a burr on a dull edge in as few as 15 passes per side following rope or cardboard cutting tests, and to remove an average of 0.0005" of width with each sharpening. This is on knives I've rebeveled to match my sharpening methods. I can sharpen free hand a bit faster, but the edges are just a bit less sharp, and I'd bet I'm removing more metal. The edges aren't as even either, and the scratches along the bevel have swirls and such in them. Sharpening isn't hard if you don't care what the knife looks like when you're done.

I read here you prefer a toothy edge. Have you tried one off a coarse Norton India stone? I think they're in the 100 grit range. I often use the fine side of my Norton Economy stone, which is similar to a Norton India fine. If you want a toothy edge, give it a go with you're coarsest stone. Rips right through stuff. I have a knife I carried that was my dad's, a spey and clip blade trapper. I sharpened the clip blade at 7 degrees per side with a Norton 220 grit water stone final finish. Nearly wore the knife out, but it cut like nothing else.

[EOU]

Our apologies Me2 for bouncing in and seizing on just a couple of sentences from one of your posts again but you have plucked a string once more on a subject we've been curious about for some time. " I used to sharpen a lot on a belt sander, but after years of thinking it was working fine, I found out my edges were being softened considerably, so I stopped for the most part. " It's not difficult at all to create a little warmth in the body of the blade while using many powered sharpening methods . Better sharpeners than us would tell you that they create no thermal transfer of heat from the edge to the bulk of the blade but still we wonder. Just how hot does the bevel and the tiny sliver of metal at the very apex of the edge have to get before it can transfer enough heat to warm a substantial portion of the entire blade even a very imperceptible 1 degree? We don't expect an answer to that question here. We certainly can't answer it. It's just food for thought. We don't hope or plan to derail the topic of this thread but Me2's observation and statement gave life to our question and as every Bladesmith knows "you gotta strike while the iron is hot".

[Jan]

It may be good to briefly recollect the heat transfer concept. Heat conduction means that heat is transferred from high temperature to low temperature by molecular agitation within a material without any motion of the material as a whole.

Heat conductivity describes this material property. In metals, heat conductivity is quite high and is primarily due to free electrons. The same mobile electrons which participate in electrical conduction also take part in the transfer of heat.

Heat conductivity in non-metals is much smaller than in metals and is mainly due to lattice vibrations. Such heat transfer is often described in terms of "phonons", quanta of lattice vibrations. (Do not confuse with "photons", which are quanta of electromagnetic radiation.)

The rate of heat transfer is proportional to the heat conductivity and also to the temperature difference between the spots with different temperatures.

Jan

P.S.: An example:
Assume that the edge was heated up during sharpening from the room temperature 70°F to 470°F (yellow colour).
The mass of the heated edge was 0.1% of the total mass of the whole blade. How large will be the equilibrium temperature when we neglect blade cooling by the air?
Answer: Equilibrium temperature caused by the heat transfer within the blade will be 70.4°F. Really an imperceptible difference.

[Ken S]

Our apologies Me2 for bouncing in and seizing on just a couple of sentences from one of your posts again but you have plucked a string once more on a subject we've been curious about for some time. " I used to sharpen a lot on a belt sander, but after years of thinking it was working fine, I found out my edges were being softened considerably, so I stopped for the most part. " It's not difficult at all to create a little warmth in the body of the blade while using many powered sharpening methods . Better sharpeners than us would tell you that they create no thermal transfer of heat from the edge to the bulk of the blade but still we wonder. Just how hot does the bevel and the tiny sliver of metal at the very apex of the edge have to get before it can transfer enough heat to warm a substantial portion of the entire blade even a very imperceptible 1 degree? We don't expect an answer to that question here. We certainly can't answer it. It's just food for thought. We don't hope or plan to derail the topic of this thread but Me2's observation and statement gave life to our question and as every Bladesmith knows "you gotta strike while the iron is hot".

The statement about the edges being softened by the belt grinder struck me. Recently I have been spending a lot of time converting a Viel and a Kally to variable speed. With the Viel, I also converted it to a smaller drive pulley, thereby decreasing the surface feet per minute even further. With careful technique, this should solve the overheating/softening issue. With variable speed and a coarse belt, the initial roughing could be done at a faster speed, slowing to cooler grinding as the blade stock became thinner.

Ken

[Mark Reich]

I have great plenty of experience grinding blades and heat treating to pay any attention to overheating steel by sharpening. You have to get a blade 350°F to even come close to tempering it down a point.

I think this is fact- Tool steel must change color to affect the heat treat at all. The color it turns is a very precise temperature gauge.

I have kilns and Rockwell machines, so that is ancient HT history myth busted.

If you're blades are even getting warm, either change to a new belt, or use less pressure.

[Jan]

Mr. Mark, in my example above I have considered a temperature of 470°F which corresponds to deep straw-yellow colour.

What is the colour of the steel at the temperature of 350°F you are mentioning? Is the down tempering stronger at high carbon steels compared with lower carbon steels?

Jan

[Mark Reich]

I agree that softening during grinding the edge is an interesting and important topic, but how do I know if you're talking about a new 120 grit or an old 220 grit? That makes a huge difference!

Mr Jan, I'm sure you know different types of steel use different temps. I haven't heat treated many types of steels. In fact, I have been very single minded about maximizing 52100, but I think all simple tool steels are fairly similar.

Adding carbon and other alloys means slightly higher temps, with longer soaks before quenching. It's more important (and difficult) to harden perfectly. Tempering is easy. 

Tempering is two pronged. You manage time at temp. Most bladesmiths temper for two hours, twice, as do I. 350° barely colors the steel. You almost have to see it next to un-tempered steel to see that 350° is very light straw, and only drops RHC 2-3 points. I use 375°, which drops RHC about 4 points, and the color change is easy to see.

That leaves the edge on the hard side- slightly chippy, but I draw everything except about 5/16" of the edge clear down to dark blue (grey is too soft for me), which makes 52100 very springy, with RHC about 47-49 on the spine. There is a video on my website that shows the color and how that HT performs.

470°F probably would be at least deep straw. I've never gone over 425°F, which I thought was fairly deep straw, but there are enough differences in kilns, not to mention opinions on color description, to make it difficult to be very precise. Guys who don't do differential HT temper at 425-450, which leaves a pretty tough blade around RHC 56-57, but the blade would be breakable. Differential tempering allows near magical qualities.

Higher carbon starts harder, but equal tempering drops the RHC about the same amount.