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I have never tried this, but I have heard other people speak of it.

When steel is tempered, it can be heated to a temperature at less than the tempering temperature without harming the steel.

For example, if your blade was tempered at 500 degrees F, you could safely heat it to 200 to 300 degrees without doing any permanent damage. At the 200 to 300 degrees, the heat would soften the steel a few Rockwell points, but after cooling off, the blade would return to it's original hardness.

Back to the topic. I have heard of people heating their blades in boiling water (212 F) and sharpening them. Supposedly, it makes the blade easier to sharpen because it is somewhat softer.

Even holding it under the hot water spigot in the kitchen sink for a few minutes would probably accompolish the same thing, although the temperature would be less than 212 F.

I am posting this because of the recent posts from people who are having difficulty sharpening the high Rockwell hardness blades. This might be something you can try, but I can make no guarentees that it will work.

Boise, thats for the "Commercial," but it looks like my knife making days are over, for reasons we talked about in the past.

In my opinion, a certain person had no right to come in and hijack your post.

Robert, you've always been a straight shooter in my book, I've enjoyed our discussions and am sorry to learn you'll no longer be making knives. You're always welcome at my campfire.

Tim, mrk, has been helping me with my sharpening and I've learned to establish my cutting angle more "vigorously" prior to polishing the edge. Looking under a microscope I've learned I didn't go far enough cutting the bevel and some of the old, dull edge was still in play. My Edge Pro works great, I just need more practice and not fear removing too much material.

This knife forum is one of my favorites, I hope we can all get along even when we disagree.

Thanks, Boise. I wish that person hadn't come to this site.

I would like to start back, but if you live long enough, eventually you will get old.

Hopefully, someday I might get to make a few. I am obsessed with owning an S30V blade, one that I made myself.

This forum is my favorite, also, and I hope we can all get along.

Are you going to try that hint about heating the blade?

Forgive me but heating a blade in order to sharpen it has got to be one of the WORST idea's I've ever heard of. Why in the world would you want to potentialy ruin a blade just because you don't want to take to time to learn to sharpen properly? Why risk burning your hands! Several different sharpening systems (like the Edge-Pro) will superbly sharpen any knife steel without such nonsense.

S-30V does take a little longer to sharpen than some other steels but no more time than it would take to heat it up!

Sorry if I'm being blunt here but this idea is NUTS!................DJ

I do like my Chris Reeves hollow ground S30V on my everyday carry. Seems to hold up better than anyothers but I'm fairly new to the use of quality steel bladed knives.

I don't image I'll try warming the blade prior to sharpening. The Apex hones cut the steel very nicely as is and without the need for me to wear gloves. I have enough trouble as it is holding the blade flat with my gloveless hand.

"Sorry if I'm being blunt here but this idea is NUTS!................DJ"

You think the idea is nuts because you don't understand what I am talking about.

Re-read the post. I didn't say stick it into a furnace until it is half melted. I said heat it with hot water, just the blade you don't have to stick your entire hand in the can of boiling water. You can hold onto the handle.

If you do not heat the steel above it's tempering temperature, it will not damage the steel, but it will (might, I don't know this for a fact) make it a few Rc points softer. You still have to know how to sharpen it. This will just allow you to do it quicker. When it cools off, it regains it's hardness, and it's sharp edge you put on it.

If you are using a steel which has a tempering temperature less than the boiling point of water, then yes you could possibly ruin it. Not really ruin it, because it probably wouldn't be much good, anyway.

You think getting a blade as hot as water will harm it? Go watch a knifemaker work, either stock removal or forging. Then watch someone heat treat and temper the blade. Hot? You don't even know hot.

Watch the knifemaker hold the blade to the grinder until it gets hot enough to burn a blister on his fingers, then pitch it into a bucket of water, along with his blistered finger, to cool it off.

Watch a forger heat the steel way past red hot to forge weld it, and you think hot water will ruin it?

High speed steel can get up to red hot and hold it's temper. You can heat 154 CM up to about 800 degrees and when it cools it will still have it's original hardness.

Actually, my blades are heated up to about 800 degrees F, twice, during tempering and they test Rc61 when they cool to room temperature. But first, they are heated to about 1800 F, soaked about 30 minutes, cooled to room temperature, then quenched in liquid Nitrogen to about -320 F.

And you think boiling water will harm one of them? Gads.

You still have to use all the correct steps, like the correct angle and all the rest, and after making several hundred blades, I KNOW how to sharpen. I just don't like to spend a lot of time doing it.

Sorry about being blunt, but you need to get your facts straight before you start calling someone's ideas NUTS.

Anyone on here got a Rockwell tester, or access to one? I would like to know if heating a piece of hardened and tempered tool steel in boiling water will soften it, until it cools off. It doesn't have to be a knife blade. A scrap piece of steel will do, as long as it is heat treated.

I have heard of this, but never tried it. The point I was trying to make is that boiling water will not harm a blade that has been tempered at 800 F.

1234567

"Watch the knifemaker hold the blade to the grinder until it gets hot enough to burn a blister on his fingers, then pitch it into a bucket of water, along with his blistered finger, to cool it off."

Brought out a smile and small silent laugh reading this line. Thought as a amature maybe I was doing something wrong.

I do have access to a Rockweel tester. I will put a hardened blade or two in a small oven set at 200 then 300 and compare to room temperature reading at Rc scale. I won't be able to do this till next week though. I am curious to see the results myself.
I think I will try 52100 and 1545CM steels.

Tim

I'm quite familiar with the proper tempering of metals.

The reason that the idea is NUTS is that it's completely unnecessary. Lowering the Rockwell hardness a point or two isn't going to make enough difference in the hardness of metals to make it worth messing with. ZDP-189 at RC 64-67 is easier to sharpen than S-30V at RC 57-59. It's not the RC point that makes it harder to sharpen it's the composition of the steel. And in case you're wondering I have Rockwell tested ZDP-189 (our shop has a Rockwell tester), it really is that hard..............................DJ

Given ZDP-189 is easier to sharpen can one conclude it will also dull faster? To me, being easier to sharpen means it doesn't resist the cutting action of the hone as much. I'm betting I'm wrong but have seen a fairly reasonable correlation between hardness and edge durability but also understand the metal alloy is a major factor.

I've learned to resist displelling the old wives tails because many times it is an action, unrelated to the stated action, that results in a positive affect. I too don't see how increasing the blade temp a couple hundred degrees is going to help but I've been wrong so many times in the past. Rick

Here is what I found -- hardness (Rc) vs temperature (degrees F)

steel 70 200 300 400 70 (degress F)
_________________________________________________________________
52100 55.5 55.5 55.5 54.5 55.5
A2 60.5 60.5 59.5 59.0 60.5
154CM 56.8 57.0 57.0 55.5 56.5
S3V 60.0 60.5 59.5 59.0 60.3


This was not a real tight and statistically sound experiment, but it is enough to show us something.

I checked the blades at room temp, worked up thru 400 degrees, and then again at room temp. Note--not a lot of change.

I personally agree with djpaintless that a couple points would not make a noticeable difference to the sharpening process.

I also don't think the blade edge would hold the higher temp long enough to matter.

I am sure that at 400 degrees (where Rc started to change) you would damage your fingers and the handle material depending on what it is.

Just my findings and honest opinions.
Tim

"Given ZDP-189 is easier to sharpen can one conclude it will also dull faster?"

I don't understand all I know about it, but it has something to do with carbides, such as chromium carbides and vandium carbides, and other things as well.

Abrasive resistance is not the only thing that enters into edge holding, but it has a lot to do with ease of sharpening.

Supposidly, a knife gets dull because the sharp, keen edge wears away. I think, but cannot prove that an edge gets dull because when put into use, microscopic chips break out of the very keen edge, causing it to get dull.

Therefore, if this is true, and before I am called nuts again, I don't know if it is, a steel that would be very strong, even with a fine, keen edge, like the edge on a razor blade, would last longer than an edge that was't as strong, and suseptable to chipping.

I do know that an edge that is very keen and very sharp will have a tendency for the very thinnest part of the edge to roll over, getting very dull very fast. This roll over looks a lot like the wire edge you get when sharpening a blade on a stone, before honing it. It sounds reasonable, to me, at least, that a steel that would be very strong and resist rolling over would be the best for edge holding.

There is a way to test this, but again I haven't done it very much. Take several very sharp knives made from different steels, and use them for scrapers. Scrape something like an old, seasoned hickory axe handle and scrape it smooth, then, after a few minutes of scraping, test it by shaving your arm or attempting to slice a page of newspaper with it. The one that would hold up to doing the most scraping and staying the sharpest is the one I would consider the one that would hold a sharp edge the longest.

The other day, I needed to scrape some paint off a board, in a small area, to glue something. The only thing I had handy to scrape with was my folder with a 154CM blade. I scraped the paint with the curve of the blade, then felt the edge. The area where I had used the edge to scrape was as dull as a marble. So, I concluded that 154 CM does not make a good scraper.

Two things that do not go togather is abrasive resistance and toughness. Therefore, a fine, keen edge will not be as strong when using abrasive resistance steel. Draw die and cold work die steels are some of the most abrasive resistant steels in existince, but they are thick for strength against breaking.

D2, M2, and M4 make great shear blades, but they usually have a very blunt edge for strength.

If you look closely at a milling cutter or a lathe bit, or a drill bit, you will notice that the actual cutting edge is very blunt, and backed up by the thick steel near the cutting edge. So are scrapers used for wood turning tools.

These are made from high speed steel, which is both very wear resistant, and also resists softening from getting hot. You can imigine that one of these cutters, sharpened with a thin, keen edge would chip out quickly, in addition to the greater heat, and therefore weakening, because of the keen and thin shape.

I will try one more time. First, I do not know for a fact that heating a blade in hot water will soften it enough to matter during sharpening. I do not even know if heating it will soften it at all. I also do not know if heating it 200 F will soften it enough to make any difference. It is one of those old wives tales, but it was probably the old wive's husbands who kept the knives sharp.

That is where I first heard about it many years ago. Knives used by the older people I knew were made from steel using 20s and 30s technology, probably a steel that consisted of about 99% iron, .09% Carbon, and .01 % percent of something else, and a hardness of about 35 to 40 Rc. They might have discovered that, when heated, the knives were slightly easier, and if not easier, maybe quicker to sharpen. Then, they might not have been, but I would't refer to someone as being nuts until I could prove it one way or another.

1234567 said--

"I do not even know if heating it will soften it at all. I also do not know if heating it 200 F will soften it enough to make any difference."

Did you read my post just minutes before yours???? You had to get to 400 degrees F before moving a point down the Rc scale.

Tim

MRK

I didn't see your post. That is what I wanted to know, if heating the blade would soften it. 400 F is too hot, and not worth the slight reduction in hardness.

Good information.

If you have a piece of 01 at about 30 to 45 RC, could you try that one? That is probably similiar to what the old timers were using.

1234567
Don't think I have any 01 around. Not knowing anything about 01 I have to ask----is 30 to 45 Rc a using hardness for that steel??

Not having 01 might be a preventative measure as I am approaching the old timer status.

Tim

1234567

Thank you for the long post. I would like to point out one difference and that is end mills can be very sharp. I worked as a cutter grinder for 6 months and sent out very sharp cutters. But I will also share that in some cases it was common for the machinist to hone/dull the edge.

While working as a machinist I found the extemely sharp edge of a high speed lathe tool didn't hold up to high material removal rates. So I would use a second sharp tool for fine finishing cuts. But it wasn't long before moving to carbide insert tools with their pressuring cutting characteristics. But even when using carbide in production environments I would use the old tool for roughing and a new one for finishing, rotating the finishing tool to the roughing location and installing a new insert for finishing as the tool wore out.

I scraped some mahogany with my S30V blade yesterday and took the edge off of it. I used a file today and it worked better - just goes to show using the right tool for the job is always better but then we don't always have the best tool handy.

For a scraper I think a tougher steel would be preferred to a hard abrasive resistant one. A lot of knifes dull from the edge "rolling" over and don`t really dull from "wear".
Sharpening steels don`t work by eroding the blade and actually sharpen the edge, they straighten the blade and remove any rolling over of the edge restoring it to its sharp state.
Like everything it is all a compromise

MRK:

One of my first jobs was at an aircraft factory, and I used a Rockwell tester quite frequently. Many of us carried folders at the time, and I tested every folder I could get my hands on. Mine was a case, and I tested it. Cases at that time were made from 01, according to what I had read.

Mine tested about 35 Rc, which is actually pretty soft for a knife. I think the reason for that is the Rc 35 would be tougher than a higher hardness, with less tendency to break when someone used it for a screwdriver or prying with it. Plus, it was fairly easy to sharpen.

Most other blades I tested, commercial blades, ran 35 to 40Rc. That was Old Timer, Tree Brand, and various other factory knives of this era.

Ol Joe, I think you are correct about the tougher steel.

I read an interesting article yesterday, comparing S30V and 01. The first test was 01 at 55 Rc and the S30V at Rc 63.5. The S30V blade outperformed the 01 blade by a wide margin.

Then, the test was repeated, with an 01 blade at a hardness of 63.5 and the S30V blade at 63.5. At 63.5, the 01 blade was far superior to the S30V. The test also revealed that the S30V blade also showed many microscopic chips in the cutting edge, indicating a brittle and weak edge.

The downside, in my opinion, is that I don't believe I would want a blade of any steel that was Rc 63.5. Regardless of the steel, at that hardness, it would have to be very brittle.

Reading these articles somewhat changed my thinking about whether or not to make any blades from S30V, if I ever do make any more blades. From what reading I have done, CPM 154CM or BG 42 seems like it might be the best thing going at this time.

D2 outperformed both 440C and 154CM, when cutting abrasive material.

One thing I want to study up on is why the high vandium steels, S30V, 90V, and some of the others with very high abrasive resistance, are claimed to be easier to sharpen than other steels of the same hardness and wear resistance.

As Boise stated, it seems as if just the opposite would be true.

www.cutleryscience.com/reviews/blade_materials.html

This is a link to the site where I read about the blade testing.

There is a lot of good imformation there for anyone who wants to learn about different steels and their properities.

S-30V is brittle at RC 63-64, knowledgable knifemakers like Chris Reeves and the like ship their S-30V knives at RC 57-59.

There are many factors that contibute or detract from a knives edge holding ability including the composition of the steel, how the steel is fabricated, grain structure, how it's tempered, edge geometry etc. etc.. It's not just one or the other.

How hard knife is to sharpen also depends on several factors, though steels with the harder carbides do tend to be signifigantly harder to sharpen and polish than those of blades out of less complex steel.................DJ

If you are having trouble sharpening your blades. They are to hard. I suggest you do a Google for paper wheels for sharpening knives. They work!!