FAQ: Why do certain razors require more honing than others?

Why certain razors require more or less honing than others

The material that your razor is made from will determine how much hand honing is required and how long your edge will remain sharp. Stainless steel for instance takes more work to achieve the same sharpness as carbon steel, but will also stay sharper longer. Also it has been mentioned that if a razor has more of a wedge shape (less hollowing) it will generally require more honing to achieve the same sharpness as a razor that has been partially or fully hollowed. This is due to the amount of metal that must be removed to achieve that perfect edge.


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This thread is incomplete. If you feel any information here is incorrect or incomplete then please post what you feel is wrong or missing. If you agree with what is written here, you can write that too ^^

Please try though to keep replies focused on these tasks. A thread to discuss these FAQ threads in any other way is available here.

Many thanks.

Sandy

Also dull is a very relative term in that there are many different levels of dullness just as there are many different levels of sharpness. If a razor has no edge then it will take a LOT of work just to set a bevel and get the razor to a level of knife sharpness. Many razors will also have chips in the edge and/or corroded steel which could take a lot of work to work through before you even reach the good steel that will take a quality edge.

Another factor is that some razors are "hardened" more than others. This process is called "heat treating" and involves putting the razor into a forge or molten lead ( which is used at Dovo and TI), raising the temperature of the steel to a certain high temp, generally more than 1400 F, then rapidly cooling the steel in a "quenching fluid", typically a high speed oil. Following that the blade is then put into a tempering oven at over 400 F for an hour or more. This will result in a hardness rating measured on the Rockwell C scale. The temperature's are determined by the type of steel used with each type of steel having its own "as quenched" hardness. The tempering then further "soften's" the steel. Each manufacturer will decide the level of "hardness" that they want.

Oh, and it is just speculation on my part but I think that some razors inadvertantly miss the tempering step which leaves them really hard!

Clear as mud?:)

Are these last two posts discussion or are they suggestions of text to put in? I am confused. :thinking:

Also, they both seem very elaborate and I didnt quite understand them. Maybe they could be simplified some? :shrug:

Or perhaps I need to read them again later when i've woken up properly. ;)

I think both are a suggestion of text to be added to the FAQ.

Perhaps I can simplify/rewrite mine in a day or two. I am short of time today.

OK i'll watch for your post and save the edit for when it comes. :)

OK, I have edited my post. Here it is. I would suggest that you PM Robert Williams, Mike Blue, Joe Chandler and any other knife makers in SRP to review and modify this post.
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Another factor is that some razors are "hardened" more than others. This process is called "heat treating" and involves putting the razor into a coal or gas fired forge, molten lead bath( which is used at Dovo and TI) or molten high temperature salts, raising the temperature of the steel to a specific high temperature, generally more than 1400 F, then rapidly cooling the steel in a "quenching fluid bath", typically a high speed oil which rapidly absorbs the heat from the steel.This leaves the steel so hard that it is almost impossible to sharpen. Following that the blade is then put into a tempering oven at over 400 F for an hour or more to soften the steel and make it less brittle. This will result in a hardness rating measured on the Rockwell C scale, look that up in the Wikipedia if you wish. The temperature's for each step are determined by the type of steel used with each type of steel having its own "as quenched" hardness. The tempering then further "soften's" the steel. Each manufacturer will decide the level of "hardness" that they want.



The harder the steel then the more difficult it is to hone.

Clear as mud?

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Thank you randy I understand that better now. I think leaving out the speculation part at the end might be one possible edit but other than that i'll add it to the next update.

If you think it would benefit from anyone elses input would you be able to contact them and encourage them to comment? I'd really appreciate it.

Many thanks :tu

Sandy

The ability to take an edge and keep it is the result of the type of alloy used, and the hardening and tempering. Simple steels with few alloying elements rely solely on the formation of iron carbides for their hardness. Steels with more alloying elements such as vanadium, cobalt, manganese, chromium, tungsten, etc. require a more complicated hardening process at different heats for different amounts of time because the carbon forming the vanadium carbides, cobalt carbides, tungsten carbides, etc. form at different temperatures.

Hardening temperatures are usually in excess of 1000 deg. F and are often in the 1200 - 1400 degree range. The temperature has to be closely and accurately monitored so that the steel can be quenched to low temperatures ranging from room temperature to maybe 150 deg. F very quickly. This is what gets the bladesmith the optimal performance from any alloy. The phase change in the steel (at quenching) has to happen very quickly and often within seconds or it won't work right. This is one explanation for a blade failing to perform.

Quenching liquids include water, various oils, air, or salt brine. A2 tool steel, for instance, is air-hardening and tends to warp less on cooling. 01 is an oil hardening tool steel. 1095 tool steel is best quenched in a salt brine.

Tempering temperatures range from 430 - 600 deg F and tempering is actually a softening process which also makes the metal tougher. Hardened steel that is not tempered is very brittle and not tough at all. Tempering should follow hardening fairly soon or the steel could ultimately end up not performing as expected. Tempering can be done in a toaster oven, a low temperature kiln, or in a forge - be it gas or coal.

Tempering can be done in a lead bath, as someone noted, as the temperature of molten lead is 600 deg. F. Hardening has to be done at much higher temperatures in an electric kiln, gas or coal forge, or even using a cherry tip on an oxy-acetylene torch rig (I've done this).

The end result of all this is an edge that can take an edge and keep sharp due to a variety of factors that interplay and include number of carbides present, size of carbides, grain size, zone of hardened steel along the edge, etc. It's all quite complicated and people devote lifetimes to mastering the art of heat treating. At least one prominent heat treater in the knife industry says that you can do everything right and still not get the results you expect! It's an art as well as a science.

So why do some blades fail to perform?

Alloy, heat treating, grinding (get a thin blade too hot while grinding and it will lose the heat treat), and type of grind. There are steels that don't do as well in a hollow grind as they do in a more angular, beveled grind.

That's it in a nutshell! There's a whole lot more to it if you're inclined to engage the topic.

I should leave this alone. But errors are errors. Please allow me to supplement some of this. Randy made a fine start...

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Originally Posted by Howard

...Hardening temperatures are usually in excess of 1000 deg. F and are often in the 1200 - 1400 degree range. The temperature has to be closely and accurately monitored so that the steel can be quenched to low temperatures ranging from room temperature to maybe 150 deg. F very quickly. This is what gets the bladesmith the optimal performance from any alloy. The phase change in the steel (at quenching) has to happen very quickly and often within seconds or it won't work right. This is one explanation for a blade failing to perform.

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Then leave out 1000 deg F, it's redundant information. Most steels A1c is much higher than that and more likely to be greater than 1450 deg F up to 1900 deg F anyway. That's not to say I (and several others I know) couldn't harden a steel below those temperature, but the equipment investment and patience is beyond most knifemakers or smiths. I agree that some steels require a faster quench than others.

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Quenching liquids include water, various oils, air, or salt brine. A2 tool steel, for instance, is air-hardening and tends to warp less on cooling. 01 is an oil hardening tool steel. 1095 tool steel is best quenched in a salt brine.

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How much A2 have you worked with? Depending on the grain structure from the steel mill, it can be a miserable warping material. 1095 will tolerate water "sometimes" but brine will crack it to hell everytime. 1095 will get acceptably hard in oil, even poor old veggie oil, everytime. Guys and gals, there are no absolutes in this business.

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Tempering temperatures range from 430 - 600 deg F and tempering is actually a softening process which also makes the metal tougher. Hardened steel that is not tempered is very brittle and not tough at all. Tempering should follow hardening fairly soon or the steel could ultimately end up not performing as expected.

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The steel don't care when it's tempered. But a good tool will get tempered. Rather than explain tempering as a softening process (although the relative Rockwell hardness will be less), think of it as relaxing the tension between the crystals of iron/carbon. More of a de-stressing the material. The range quoted could be expanded and depends completely on the type of steel. 10xx, plain carbon-iron steels, can be tempered as low as 350 deg F. Stainless steels may require up to 1000 deg F depending. The key word is "depending." Each steel has it's particular recipe for success. Some methods of austenitizing (the name for bring the steel up beyond its critical temperature where all the steel forms martensite) will not succeed with some steels, likewise some methods of tempering will not succeed with some steels.

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Tempering can be done in a lead bath, as someone noted, as the temperature of molten lead is 600 deg. F. Hardening has to be done at much higher temperatures in an electric kiln, gas or coal forge, or even using a cherry tip on an oxy-acetylene torch rig (I've done this).

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Randy correctly pointed out molten salts will work too and are much safer than lead. Molten salts will work for austenitizing and tempering. Tempering can be done in oil too. Peanut oil works really well.

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The end result of all this is an edge that can take an edge and keep sharp due to a variety of factors that interplay and include number of carbides present, size of carbides, grain size, zone of hardened steel along the edge, etc. It's all quite complicated and people devote lifetimes to mastering the art of heat treating. At least one prominent heat treater in the knife industry says that you can do everything right and still not get the results you expect! It's an art as well as a science.

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I'd agree with all this. And, I know the fellow in the quote well enough.

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So why do some blades fail to perform?

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As noted previously, there are so many variables that have to be controlled. Sometimes a blade performs exceedingly well and you don't know why. Sometimes you do everything exactly right and the blade sucks. Sometimes it's operator error. The maker could start with a piece of steel that was not the type he thought it was. But, you left out abuse, improper use, intent, foolishness, attempting to get a blade to perform outside its envelope. Etc.

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...and type of grind. There are steels that don't do as well in a hollow grind as they do in a more angular, beveled grind.

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Which steels are those? I'd interject that those steels were badly heat treated, or badly used. Subject to variable control that Randy began to explain well, and your other illuminations, the type of grind should not make much difference unless the blade is being expected to perform outside the limitations of the particular grind. I.e. using a straight razors to chop kindling for instance.

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That's it in a nutshell! There's a whole lot more to it if you're inclined to engage the topic.

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That's a wholly true statement. :D

Suggestions for discussion only:

The honing medium will also determine how much honing is required, I believe. Or are we making the assumption that a Norton waterstone is being used?

Also, I'd question whether, for a newbie FAQ, there's a need to get into the gory matallurgic details. If people are interested in alloys, temperatures, etc. they can start a new thread somewhere to get the technical details.

James.

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Originally Posted by Jimbo

Suggestions for discussion only:

The honing medium will also determine how much honing is required, I believe. Or are we making the assumption that a Norton waterstone is being used?

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I dont think assumptions should be made at any point in these FAQs

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Originally Posted by Jimbo

Also, I'd question whether, for a newbie FAQ, there's a need to get into the gory matallurgic details. If people are interested in alloys, temperatures, etc. they can start a new thread somewhere to get the technical details.

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I cant second this idea enough.

If you guys think the technical stuff is not appropriate then go ahead without it.:) I do not feel it is absolutely necessary, just informative. But you guys can make that decision. I am biased in the matter so I will step aside on that point.

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Originally Posted by randydance062449

If you guys think the technical stuff is not appropriate then go ahead without it.:) I do not feel it is absolutely necessary, just informative. But you guys can make that decision. I am biased in the matter so I will step aside on that point.

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I think it depends on who the target audience is... if it's a newbie then I'd think the less technical the better. If it's a veteran member, then I'd think they would almost demand the technical detail. So, where is this FAQ going to be... if it's the newbie forum, then I'd vote for low tech content. If it's going to be in the Razor or restoration forum, then perhaps more technical detail would be appropriate. :shrug:

I am updating the info that will appear in this FAQ.

Please bear in mind I am trying to find a balance here between telling a newbie enough to answer their question but not going into too much technical detail to confuse them.

I am looking for a specific type of input on this post. I suspect I may have misunderstood some things so I need to know if there is any incorrect information here.

If there is anything that I have not said here that has been mentioned in previous posts it may mean I have taken it out for reasons spoken of above. If you still STRONGLY FEEL that it should go back in then please post and let me know.

I think this answer is very comprehensive with all the input its had and i'm pleased with the responses. Thanks to all you guys! :tu I think joe its maybe time to close this one down? Bear in mind all that this is not the be all and end all of it. If needs be it can be changed at a later date. We're just looking to get something down for now.

So without further ado....


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Why certain razors require more or less honing than others

There are a number of reasons this why some razors require more honing than others:

1. The material that your razor is made from will determine how much hand honing is required and how long your edge will remain sharp. Stainless steel for instance takes more work to achieve the same sharpness as carbon steel, but will also stay sharper longer.

2. Also it has been mentioned that if a razor has more of a wedge shape (less hollowing) it will generally require more honing to achieve the same sharpness as a razor that has been partially or fully hollowed. This is due to the amount of metal that must be removed to achieve that perfect edge.

3. If a razor has a dull edge then it will take a LOT of work just to set a bevel and get the razor to a level of knife sharpness. Razors with chips in the edge and/or corroded steel could take a lot of work before you even reach the good steel that will take a quality edge

What other factors influence the edge of the blade?

The ability to take an edge and keep it is the result of the type of metal used to make the blade and the process used in manufacture. Simple steels with few alloying elements rely solely on the formation of iron carbides for their hardness. Steels with more alloying elements require a more complicated hardening process at different heats for different amounts of time.

So it can be down to the quality and care taken with the manufacture of my blade?

Yes. The temperatures at which the blade is tempered range from 430 - 600 degrees Fahrenheit. Tempering is a softening process which also makes the metal tougher. Hardened steel that is not tempered is very brittle and not tough at all. Tempering can be done in a toaster oven, a low temperature kiln, or in a forge - be it gas or coal. Tempering can also be done in a lead bath as the temperature of molten lead is 600 degrees Fahrenheit. The end result of all this is a blade that can take an edge and stay sharp due to a variety of factors.

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The following terms appear in this post and are unexplained to a newbie. Whilst they may know what they are thay may equally not and NOT knowing the meaning makes the post harder to understand.

- Bevel
- Iron Carbides


I know I cut out huge chunks out but I had to try and strike a balance. Please dont be offended if your bit isnt in there.

Your opinions gents?

Looks good to me.

Regarding the terms "bevel" and "carbides". The Razor central document explains the "bevel" somewhat and it is a term that newbs need to know, it is a foundation term in understanding sharpness.

"Carbides" is a very technical term but also central to understanding steel. If they have a question about it then we can refer them to the Wikipedia or a book on steel.

We do not help ourselves or others by writing for the lowest common denominator. We all need to learn and thus understand.

I think you have hit a pretty good balance. Nice job!:)

Thank you randy :)

My $.02 would be to go with what you have. Faqs do not need to define/describe all the ancillary terms used in their answers. Other faqs will certainly evolve which cover most of these terms. I would be pretty confident that faqs will appear that describe the various parts of the razor, the various grinds, the geometry of the edge, etc. Probably not for carbides... at least in the newbie forum... and any newbie that thinks they need to know about carbides to get started in str8 shaving might want to rethink their priorities ;). It would be useful to have a good faq/discussion on carbides, etc. (ie, metallurgy) in the restoration forum.

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Originally Posted by azjoe

My $.02 would be to go with what you have.

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If thats the case joe then just go with it as we have it. If you could post it as a sticky and make a link to the post so people can see what they are commenting on in this thread.

Thanks everyone for your help on this one.

Ok... the FAQ thread was created and this (the first) FAQ has been posted there.