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Heat Treating and Metallurgy Discussion of heat treatment and metallurgy in knife making.

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  #16  
Old 03-05-2011, 07:52 AM
The Tourist The Tourist is offline
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Agreed. I was only offering this as a contribution to a debate, and to help voice a differing opinion.

For example, I think that some modern cutlers just assume that slurry and folded steel are a product of history. That is, a quaint method that died about 1870 with the demise of the samurai.

The stuff still exists and represents some of the finest alloys (and ancillary construction methods) in our time, as well.

One modern cutler, Rick Barrett, makes blade blanks as well as finished knives and swords.

Most of you know Mcusta, a current company that uses folded steel in present folding knives.

I'm also a consumer. I use a Ishikawa folding santoku when I eat at my favorite Japanese restaurant. Folded in the traditional manner it has a core of VG-10.

Obviously, the members here are more than hobbyists and collectors. The professionals know all of this data. I don't think most end-users are aware of this however. Also it might evoke some further research here--and a fun debate.
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  #17  
Old 03-05-2011, 11:14 AM
Doug Lester Doug Lester is offline
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I assume that by modern cutlers you mean commercial makers. I really doubt that they think that differential hardening and pattern welded damascus is a thing of the past, it's more that they cannot be ecconomically utilized with modern manufacturing techniques. Yes there are a few cutlers who utilize pattern welded steel but they are supplying a niche market. Most manufactures are supplying the average buyer, which means postley stainless steel and some carbon steel blades. They are just making what sells.

You also have to keep in mind that modern steels, even the 10XX and W series, are superior to, by way of composition and consistancy, than what was made in the past. Welded damascus, especially mosaic damascus, has a visual appeal that just can't be matched by monosteel but the best damascus made is no better by nature than a monosteel blade. All that folding and forge welding opens up the possiblily of there being hidden cold shuts and occlusions (hopefully any knife maker who makes a blade with obsurvable defects would scrap it).

A hamon, even though attractive to some, contributes nothing to the blade. It is just evidence that the blade is of shallow harding steel and has been differentially hardened by some technique. A blade with a hamon is no better or worse than a blade of the same steel that has been differentially hardened but does not, by way of surface preparation, show a hamon. It could be worse, admittedly a highly subjection term, than a differentially hardened blade that, due to the steel used, cannot desplay a hamon. For that matter, the comparitive qualities of differentially heat treated, which includes differentially hardening, is a matter open to debate.

Doug Lester


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  #18  
Old 03-05-2011, 04:09 PM
The Tourist The Tourist is offline
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Quote:
Originally Posted by Doug Lester View Post
I assume that by modern cutlers you mean commercial makers.
Overall, yes. But there are guys like Rick Barrett who are more like the members here than any commercial venture. In the end, there are many paths to the same goal.

Quote:
A hamon, even though attractive to some, contributes nothing to the blade. It is just evidence that the blade is of shallow harding steel and has been differentially hardened by some technique.
Hmmm. True, but that is the history of the process. Even modern togishi (one of them is interviewed on YouTube) state that when the hardened outer layer is polished off the sword loses its intended function. Still, considering the successful span of 800 years, that's not too shabby for a peasant washing iron filings out of river mud and rubbing metal with a wet rock.

I admit to being prejudiced here. I had no idea just how stupid sharp folded steel could get until I studied the process and polished Japanese laminate steel.

http://www.authenticjapaneseswords.c...s.php?CatID=25
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  #19  
Old 03-05-2011, 06:12 PM
Doug Lester Doug Lester is offline
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That has to do with the martinsetic steel being abraided away. The old tamahange steel was very shallow hardening with not much martinsite on the blade after quenching. The initial grind would remove much of it, not leaving much for subsiquent sharpenings and polishings. That is probably the one place where a hamon is funtional; when it's gone so is all the hard steel.

Doug Lester


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  #20  
Old 03-06-2011, 12:53 AM
The Tourist The Tourist is offline
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Taken in context, I think that the togishi are referring not to one or two polishings done by a single craftsman, but repairs done over centuries. They make mention of the fact that 800 year old examples were swords that had not seen much use or combat.

When I get done sharpening (more properly, polishing) my hands are covered with swarf and the container I use to soak stones has a grayish silt on the bottom. And that's after polishing only a few knives in an afternoon. If, theoretically, you collected the swarf from all of my relatives going back several hundred years it amounts to quite a bit of metal.

I have also noticed that softer metals "bleed through" the decorative surfaces of modern kitchen gyuto knives. In fact, I used to keep a small bottle of soft soap and canola oil in my kit. When a knife showed telltale orange spots, I would slice off a piece of a carrot and polish off the spots. I was trying to stay ahead of severe rust problems on knives that were used for long shifts and usually always wet.

But my point is this. Folded steel isn't uniform in its layers. It's hammered, it wears, I polish it. Even on new knives I find spots of "foil" along the edge from delaminating. The numerous layers are very thin. The one thing I do know from not only my daily work but also from study is that folded steel knives were always being repaired and "appraised." In short, it appears that all who value this type of cutting implement are very worried about its care.

Admittedly, my observations are anecdotal. But even I notice the wear and the ever changing complexion of individual knives. And I use very fine grit waterstones and I'm known for having a soft or very 'slow' hand. (Below is an example of a knife made from 1095.)

I believe that the sharpest knife this world has ever seen is the yanagiba. Traditional 'blue' or 'white' steel can show rust in a matter of hours. The rust is always being removed and the edges need to be polished. Literally, I'm grinding away the very thing I respect.

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  #21  
Old 03-16-2011, 12:33 AM
Kevin R. Cashen Kevin R. Cashen is offline
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To the original topic, there are several properties that are often confused in knife production- toughness, strength and ductility. Strength is resistance to deformation (not bending or soft), toughness is most often referred to as the ability to withstand sudden loading, such as impact, without failure, ductility is the ability of steel to bend or deform easily without brittle type failure and is somewhat the opposite of strength. A fully hardened blade will have the most strength, an edge quenched or clay quenched (differentially hardened in either case) will deal with marginal edge strength and mostly ductility, while a differentially tempered blade, or a blade of certain alloying will deal with toughness.

I must admit that I have a hard time with the idea that 800 year old swords can rival what we can do now, as this is mostly only in Hollywood as opposed to the real world. I regularly work with both modern steels and ancient steels (quite similar to those from a tatara) and much of the heat treat developed for swords both in the east and west was due to the severe limitations of simple iron/carbon alloys compared to modern steels. I am delighted to see one of my best friends in the whole blade making world, Rick Barrett, cited in the conversation, however, since Rick has one of the most down to earth and realistic approaches to the Japanese sword genre that I have encountered, and because of this I believe he is producing some of the best Japanese style blades here in the states.

The whole topic gets VERY complicated if one is not careful to keep the three properties I mentioned at the beginning of this post in perspective. How much force it takes to flex a blade is of course nothing more than a matter of its thickness or cross section regardless of heat treatment, but how much force it will take to bend it depends on the method of heat treatment. Where the bend happens, at 75 foot pounds or 500 foot pounds depends on how you heat treat. The differential hardening will only take the lower end while the differential tempering will take the higher end, one will bend and stretch quite a ways with no added force while one will reach its ultimate strength (snap!) shortly after bending under more force than one mans arm can produce.
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  #22  
Old 04-10-2017, 08:05 PM
PeterTheWolf PeterTheWolf is offline
 
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I know this is a very old thread; however, I have to ask you Ed....
How far, in degrees, would these "soft back draw" tempers make it before they broke in the 90? test? Would they typically make it at least 30 degrees?
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Thanks for the feedback. ...
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Quote:
Originally Posted by Ed Caffrey View Post
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When I really started to notice this was during testing folks for their JS.....those who chose to differentially harden generally had no problems getting through the tests. Those who fully hardened their blade(s), and then tried to soft back draw, often failed. After questioning those individual who had failed, the common theme was that they would heat the spine of the fully hardened blade "until it was blue", and when their blades broke, the tempered "skin" that I mentioned previously was evident.

Last edited by PeterTheWolf; 04-11-2017 at 07:36 PM.
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  #23  
Old 04-14-2017, 06:56 AM
PeterTheWolf PeterTheWolf is offline
 
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Ok.... how about anybody on the answer to this question?
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Quote:
Originally Posted by PeterTheWolf View Post
I know this is a very old thread; however, I have to ask you Ed....
How far, in degrees, would these "soft back draw" tempers make it before they broke in the 90? test? Would they typically make it at least 30 degrees?
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Thanks for the feedback. ...
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  #24  
Old 04-15-2017, 07:21 PM
PeterTheWolf PeterTheWolf is offline
 
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All right then ... I will assume this is something nobody knows on this forum ... thanks anyways ... will look else where ....
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Quote:
Originally Posted by PeterTheWolf View Post
Ok.... how about anybody on the answer to this question?
......

Last edited by PeterTheWolf; 04-16-2017 at 12:33 PM.
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  #25  
Old 04-16-2017, 07:18 AM
jmccustomknives jmccustomknives is offline
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Quote:
Originally Posted by PeterTheWolf View Post
All right then ... I will assume this is something nobody body knows on this forum ... thanks anyways ... will look else where ....
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Your question was originally directed at Ed so I didn't answer. But depending on the steel and design, yes you can get a 30deg flex or more from a blade with a soft back draw. The difference? The soft back draw blade will return to strait.

I used to do the edge quench but found by experience that the soft back draw makes a better blade. One I tested, a 8" Bowie, was able to pull my 65lb vice out of its anchors. It flexed about 30 deg. That test followed chopping through a 2x4 3 times then slicing cleanly through a rope. I still carry that knife with me.
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  #26  
Old 04-16-2017, 12:28 PM
PeterTheWolf PeterTheWolf is offline
 
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Thank you for the timely reply. I am working on / foring a 24? Machete from 5160 steel. I really do not want to put this blade through a destructive testing to prove this process. I have done that already on a 12? blade from 5160 (basically the same process) ? forged at 2000? F ? 2100? F. Then first thermal cycle with the last forge working (at 1900? F) allowed to cool in still ambient temperature. Then I brought the Heat-Treat Oven up to temp with the PID Program for the Thermal Cycling. I made three 20 minutes soaks at 1350?F and then remove from the over to air cool in still air until about 250?F. Then repeated the Thermal Cycle. After the three Thermal Cycles, I programed the PID with the Annealing Program and annealed the steel accordingly. The Rockwell check after annealing was 21-24 HRC. This allowed me to grind the blade thickness in to about .140"-.150" with 40 grit belts. There was a lot of DeCarb on this blade coming from the Annealing process above. This DeCarb really uses the belts up. Marked the Center of the blade on the edge and then ground the bevels in on the edge. Starting with 40 grit belt to about .040"-.050" thick cutting edge. Then ground with 120 grit (A160 [120 grit] 3M Trizact CF-337 DC-$7.25) blade to about .030"-.040" cutting edge. Then finished the grind with a 280 grit belt (A65 [280 grit] 3M Trizact CF-337 DC-$7.25) with the cutting edge ending up at .030"-.040" (with a short area of it at .025") thick. The spine ended up at about .130"-.140" thick with the handle area ending up at .160"-.190" at the end ... this will give weight to the handle end of the blade to help balance this long 24" blade.
I have used this process on a previous 12? blade from 5160 (Forged) with, what I thought, was good results. However, I did do a ?Soft Draw on the spine with an O/A torch) while keeping most the edge in water to ensure the heat did not draw down into the edge and affect my 58HRC. I did put that blade through the destruction testing of bending it and found that at 30? is where it failed. The grain of the steel after it broke looked very fine and I, being an amateur, was happy with the grain results from the heat-treat/thermal process I used.
I just wanted confirmation from an experienced Blade Smith to verify results of what they have seen when a ?Soft Draw? spine process was used.
I am not looking for the ABS JS test to pass here as I only wanted a Machete for use in my back yard clearing brush, one that would handle the abuse I intent to give it and still hold an edge. As I am sure I would be paying over $400 or more for one of these blades made by a Master Blade Smith.
Below is a picture of my destructive test made on the first 12? blade I made. Which was Heat treated with the heat-treat oven using a PID program. Then I had a full dip quench (tip down) in Duratherm "G" Quench Oil at room temp at about 65-70 degress F. No warpage and very little de-carb.
Quench Oil Note: Maxim compounds and blends a line of paraffin based, fast quench oils for the heat treating industry. Our "benchmark " and most popular product in this line is Duratherm "G". Duratherm G is a premium quality high speed quench oil that exhibits a GM Quenchometer speed of 10-12 seconds( Ni ball).
I do have a new design of keeping the Blade Edge cool, since it has curvature, while ?Soft Drawing? the spine after the heat-treat process on this 24? blade. Which is almost impossible to do with a pan of water on curved blades. If this works I will share with my experience/design. Not that any of the Master Blade Smiths would consider it ? since I am only an amateur.
Once again, thanks for your timely reply as I was going to heat-treat this 25? blade today and having your feedback really helps me in the direction I am choosing to go with this process.
Sorry to get so long winded ?

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  #27  
Old 04-16-2017, 07:59 PM
PeterTheWolf PeterTheWolf is offline
 
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Posts: 5
Thank you for the timely reply. I am working on / foring a 24? Machete from 5160 steel. I really do not want to put this blade through a destructive testing to prove this process. I have done that already on a 12? blade from 5160 (basically the same process) ? forged at 2000? F ? 2100? F. Then first thermal cycle with the last forge working (at 1900? F) allowed to cool in still ambient temperature. Then I brought the Heat-Treat Oven up to temp with the PID Program for the Thermal Cycling. I made three 20 minutes soaks at 1350?F and then remove from the over to air cool in still air until about 250?F. Then repeated the Thermal Cycle. After the three Thermal Cycles, I programed the PID with the Annealing Program and annealed the steel accordingly. The Rockwell check after annealing was 21-24 HRC. This allowed me to grind the blade thickness in to about .140"-.150" with 40 grit belts. There was a lot of DeCarb on this blade coming from the Annealing process above. This DeCarb really uses the belts up. Marked the Center of the blade on the edge and then ground the bevels in on the edge. Starting with 40 grit belt to about .040"-.050" thick cutting edge. Then ground with 120 grit (A160 [120 grit] 3M Trizact CF-337 DC-$7.25) blade to about .030"-.040" cutting edge. Then finished the grind with a 280 grit belt (A65 [280 grit] 3M Trizact CF-337 DC-$7.25) with the cutting edge ending up at .030"-.040" (with a short area of it at .025") thick. The spine ended up at about .130"-.140" thick with the handle area ending up at .160"-.190" at the end ... this will give weight to the handle end of the blade to help balance this long 24" blade.
I have used this process on a previous 12? blade from 5160 (Forged) with, what I thought, was good results. However, I did do a ?Soft Draw on the spine with an O/A torch) while keeping most the edge in water to ensure the heat did not draw down into the edge and affect my 58HRC. I did put that blade through the destruction testing of bending it and found that at 30? is where it failed. The grain of the steel after it broke looked very fine and I, being an amateur, was happy with the grain results from the heat-treat/thermal process I used.
I just wanted confirmation from an experienced Blade Smith to verify results of what they have seen when a ?Soft Draw? spine process was used.
I am not looking for the ABS JS test to pass here as I only wanted a Machete for use in my back yard clearing brush, one that would handle the abuse I intent to give it and still hold an edge. As I am sure I would be paying over $400 or more for one of these blades made by a Master Blade Smith.
Below is a picture of my destructive test made on the first 12? blade I made. Which was Heat treated with the heat-treat oven using a PID program. Then I had a full dip quench (tip down) in Duratherm "G" Quench Oil at room temp at about 65-70 degress F. No warpage and very little de-carb.
Quench Oil Note: Maxim compounds and blends a line of paraffin based, fast quench oils for the heat treating industry. Our "benchmark " and most popular product in this line is Duratherm "G". Duratherm G is a premium quality high speed quench oil that exhibits a GM Quenchometer speed of 10-12 seconds( Ni ball).
I do have a new design of keeping the Blade Edge cool, since it has curvature, while ?Soft Drawing? the spine after the heat-treat process on this 24? blade. Which is almost impossible to do with a pan of water on curved blades. If this works I will share with my experience/design. Not that any of the Master Blade Smiths would consider it ? since I am only an amateur.
Once again, thanks for your timely reply as I was going to heat-treat this 24? blade today and having your feedback really helps me in the direction I am choosing to go with this process.
Sorry to get so long winded ?

Picture of my first test knife can be viewed at: http://www.ontimetooldesign.com/RJ/B...iled_30deg.jpg

Picture of my current 24" blade project can be viewed at: http://www.ontimetooldesign.com/RJ/2...d_BeforeHT.jpg

I just finished the heat-treating process of this 24" blade. Results turned out excellent ... my rockwell checks on the spine in three places (that are parallel) produced 62-63 HRC. No warpage
and very little DeCarb (Scale).

Picture of HRC check: www.ontimetooldesign.com/RJ/RockwellCheck.jpg

Tried getting these pictures posted here; however, the moderator must not approved the post.
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Last edited by PeterTheWolf; 04-16-2017 at 08:55 PM.
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  #28  
Old 04-18-2017, 05:34 AM
jmccustomknives jmccustomknives is offline
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Peter, I would expect a blade as thin as a machete to go past 30 Deg easily. You really don't need to anneal your steel as that invites grain growth, normalization followed by a 1200F temper should soften it enough to do any drilling without grain growth. If you do anneal thermocycle before heat treat.

Take your soft back draw to 2/3rds of the blades height leaving 1/3 hardened and you should get better results in the strength test.
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