Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
- Joined
- Aug 20, 2004
- Messages
- 38,477
I was posting this morning and used a reference from a course syllabus. I got to thinking that that particular info is the plain and simple explanation of about 60% of the questions asked here. I decided to refine the info into a simple tool for those trying to understand, and learn, the metallurgical processes used to make a knife.
SADLY, THE FARMINGDALE COURSE INFO IS NO LONGER AVAILABLE WTHOUT A LOG-IN.
The information is from a course taught a few years ago at Farmingdale University
http://info.lu.farmingdale.edu/
It is in Farmingdale,New York.
The course index is here:
http://info.lu.farmingdale.edu/depts/met/met205/index.html
There are lots of good topics to glean information about other than knife related areas. I recommend you read it all. The Lab projects can be good learning tools,too.
General info on CPM steels and HT by Seamount Knifeworks:
http://www.seamountknifeworks.com/articles.htm
Annealing:
http://info.lu.farmingdale.edu/depts/met/met205/annealingstages.html
http://info.lu.farmingdale.edu/depts/met/met205/ANNEALING.html
Normalizing:
http://info.lu.farmingdale.edu/depts/met/met205/normalizing.html
Understanding a TTT chart:
http://info.lu.farmingdale.edu/depts/met/met205/tttdiagram.html
Heat Treatment:
http://info.lu.farmingdale.edu/depts/met/met205/heattreating.html
Quenching and Tempering:
http://info.lu.farmingdale.edu/depts/met/met205/tempering.html
Cryo:
http://info.lu.farmingdale.edu/depts/met/met205/cryogenictreatment.html
Steel types:
http://info.lu.farmingdale.edu/depts/met/met205/fe3cdiagram.html
http://info.lu.farmingdale.edu/depts/met/met205/stainless-steels.html
http://info.lu.farmingdale.edu/depts/met/met205/toolsteels.html
Iron, Carbides, and Alloys:
http://info.lu.farmingdale.edu/depts/met/met205/fe3cdiagram.html
http://info.lu.farmingdale.edu/depts/met/met205/carboneffect.html
http://info.lu.farmingdale.edu/depts/met/met205/alloyingeffect.html
The internet is wonderful. It is great to take a quick look at something you want to know about and say, "OK, I get it.", but the best way to learn it is to teach the skill to yourself. Read the entire article. Read it again if needed. Print out the charts and post them on the wall or bulletin board. Without the text in front of you, explain the topic displayed to yourself. If there are any spots where you are weak or unsure, go back to the text and refresh yourself. Once you have the information down where you can explain it clearly and concisely,you will have it committed to memory. If possible teach it to someone else, using all the text and charts. The standard method for training is 1) Learn the skill; 2) Practice the skill; 3) Teach the skill.
Print out the things that are important to you. Nothing sucks like going to your stored favorites and finding out that a site is no longer available. The stickies are full of those by now, and it can be frustrating. Get an accordion file and stick all the pages that you think you will ever need in there.
There is something different about holding a page, or reading a chart, that is in your hand. The parts of the brain involved in viewing information on a computer screen are not the same as viewing a printed page in real time. Your brain stores everything it sees around you in a 3D format. It is much different than the 2D storage of a monitor or TV screen. Internet info is a short term storage, and not the best way to learn. Reading printed text, looking at charts on a wall, etc., will lead to much better retention. Dumb as it sounds, speaking the words out loud as you explain to yourself what you are reading will increase retention even farther. This is why you teach the skill to yourself. Do it verbally, as that is also a separate part of the brain. The more pathways used, the more available the information is for recall.
Verhoeven's work on the metallurgy of knife steel
http://www.hybridburners.com/documents/verhoeven.pdf
Heat Treatment - The Process and Principals of Quenching - by Kevin Cashen
http://www.bladeforums.com/forums/threads/639019-The-process-and-priciples-of-quenching
Working with Three types of Steel - by kevin Cashen
http://www.bladeforums.com/forums/threads/673173-Working-the-three-steel-types.
HT for complex stainless steels
http://www.bladeforums.com/forums/showthread.php/896982-HT-Regimen-for-High-Alloy-Stainless-Steels.
HT for 1095
http://www.bladeforums.com/forums/showthread.php/379832-How-the-hell-do-you-heat-treat-1095-!
Dry Ice vs Cryo
http://www.bladeforums.com/forums/s...-and-Some-Explanations?highlight=dry+ice+cryo
http://www.bladeforums.com/forums/showthread.php/1015501-Dry-Ice-and?
Info from a discussion on 1084 HT and tip geometry:
First - 1084 austenitizes at 1500°F. The eutectiod point is when the ingredients go into solution. The austenitization point is when they are ready for quench....not the same. Some steels have a lower austenitization temp than 1084. What makes 1084 a great steel for minimal HT methods is that it does not require time for excess carbon or alloy ingredients to form carbides. Thus it needs no soak time.
Second - When using a torch, the metal is the only place that gets heated. In a forge, or even a row of firebricks like Pat mentioned, the refractory will get heated and try and retain and/or reflect a bit of the heat back into the blade. With a blade held in the air, and a torch played up and down it, the blade radiates the heat back into the air. In the thick places of the blade, the mass holds some heat, which helps keep that area hot a bit longer. However, the thin sections like the edge have no mass, so they cool down faster. The tip is the extreme, as it has no mass, and no spine ( which has mass) to send some heat to it. The tip will cool off faster than any part of the blade. (It will also overheat faster than any part of the blade for the same reason)
Third - In a small blade, less than 3" , you can play the flame over most of the blade at one time. In a bowie, you can never be heating more than a small percentage of the blade at any one time. Heating from the spine is the best method, but success is unlikely with a large blade unless you are fairly well skilled at torch HT. Most folks make the mistake of using a hot flame, not a large flame. A rosebud tip in a welding torch or any large flame tip is far better than a hot pencil flame. You only want the blade to get to 1500°, so having a flame running at 5000° is a problem, not an asset. The flame should be evenly blue....and as large as possible. When using a forge, the same rule exists. The forge flame/heat should be just high/hot enough to get the blade to 1500°, not hot enough to weld with.
Forth - You are not exactly clear in your description of the tip "bending". Do you mean it bends and stays bent...or does it "flex" and return to straight by itself when it is pulled out of the wood.
A poor ( insufficient) HT will bend and stay bent. No good knife should do this.
A proper HT and good blade geometry will flex a small amount and return to straight. Most hunting knives and general use kitchen knives need this type of tip.
A proper HT with too thin geometry will bend greatly, and also snap off easily. Only thin slicers should have this tip.
A robust tip with proper HT will not flex, or break. Bowies need a robust tip.
It is a bit hard to describe how a robust tip is shaped in words, but I'll try.
1) If you taper the blade from ricasso to tip as a continuous taper ( distal taper), the tip will be thin. This will make it very weak when the edge is added.
If you don't taper the entire blade much or any, the tip will be nearly as thick as the spine is. This will make it strong, but rather blunt for piercing. Machetes are made with this geometry.
If you taper the blade to a degree where the tip end is about 1/2 to 1/3 as thick as the ricasso, you will have a starting point for a robust tip. The final tip will be thin enough to puncture things in a stabbing cut, but strong enough to resist breaking. The distal taper will allow the blade to slide into the hole made by the stab.
On a bowie from .250" stock, the tip should be about .080-.100" thick after the distal taper.
2) After the distal taper is established, add the primary ( main) bevel. This will taper the blade from spine to edge. It also should stop with a bit of meat on the edge for a bowie. I would go to about .030" on a bowie pre-HT. As you approach the tip, you need to change the angle of the bevel grind a bit to maintain the .080-.100" end thickness at the tip. It is a matter of "blending" the two into a smooth transition. Remember that you can always take a bit more off after HT, but can't put any back on.
3) After HT, the bevels are re-sanded, and then the secondary ( edge) bevel is added. This should carry up the main bevel about 1/8-1/4" to allow a good slicing edge. The exact amount of height is determined by how thick the blade edge was before HT and the edge angle. On a bowie, slicing tomatoes and such isn't what you will be doing, so a fairly thick edge is the norm. This is usually referred to as "meat" behind the edge. This is to allow the edge to survive the chopping and hacking a bowie will encounter, but still have a sharp edge. The tip should have more of this "meat" , as it gets far higher degree of stress. The trick is to roll the edge up into the tip , maintaining the width of the secondary bevel as you go. If the edge bevel is 1/4" wide, carry that 1/4" up to the tip. As you go closer, the angle you sharpen at will increase greatly. You may have been sharpening at 20° on the .030" thick edge, but as you go up to the .080" thick tip, the angle will become close to 45°. This will still pierce things, but will resist breaking or bending far greater. If you get this to all blend together, the knife will have perfectly even looking bevels, but will have a thicker tip than the edge. You have now made a Robust Tip.
SADLY, THE FARMINGDALE COURSE INFO IS NO LONGER AVAILABLE WTHOUT A LOG-IN.
The information is from a course taught a few years ago at Farmingdale University
http://info.lu.farmingdale.edu/
It is in Farmingdale,New York.
The course index is here:
http://info.lu.farmingdale.edu/depts/met/met205/index.html
There are lots of good topics to glean information about other than knife related areas. I recommend you read it all. The Lab projects can be good learning tools,too.
General info on CPM steels and HT by Seamount Knifeworks:
http://www.seamountknifeworks.com/articles.htm
Annealing:
http://info.lu.farmingdale.edu/depts/met/met205/annealingstages.html
http://info.lu.farmingdale.edu/depts/met/met205/ANNEALING.html
Normalizing:
http://info.lu.farmingdale.edu/depts/met/met205/normalizing.html
Understanding a TTT chart:
http://info.lu.farmingdale.edu/depts/met/met205/tttdiagram.html
Heat Treatment:
http://info.lu.farmingdale.edu/depts/met/met205/heattreating.html
Quenching and Tempering:
http://info.lu.farmingdale.edu/depts/met/met205/tempering.html
Cryo:
http://info.lu.farmingdale.edu/depts/met/met205/cryogenictreatment.html
Steel types:
http://info.lu.farmingdale.edu/depts/met/met205/fe3cdiagram.html
http://info.lu.farmingdale.edu/depts/met/met205/stainless-steels.html
http://info.lu.farmingdale.edu/depts/met/met205/toolsteels.html
Iron, Carbides, and Alloys:
http://info.lu.farmingdale.edu/depts/met/met205/fe3cdiagram.html
http://info.lu.farmingdale.edu/depts/met/met205/carboneffect.html
http://info.lu.farmingdale.edu/depts/met/met205/alloyingeffect.html
The internet is wonderful. It is great to take a quick look at something you want to know about and say, "OK, I get it.", but the best way to learn it is to teach the skill to yourself. Read the entire article. Read it again if needed. Print out the charts and post them on the wall or bulletin board. Without the text in front of you, explain the topic displayed to yourself. If there are any spots where you are weak or unsure, go back to the text and refresh yourself. Once you have the information down where you can explain it clearly and concisely,you will have it committed to memory. If possible teach it to someone else, using all the text and charts. The standard method for training is 1) Learn the skill; 2) Practice the skill; 3) Teach the skill.
Print out the things that are important to you. Nothing sucks like going to your stored favorites and finding out that a site is no longer available. The stickies are full of those by now, and it can be frustrating. Get an accordion file and stick all the pages that you think you will ever need in there.
There is something different about holding a page, or reading a chart, that is in your hand. The parts of the brain involved in viewing information on a computer screen are not the same as viewing a printed page in real time. Your brain stores everything it sees around you in a 3D format. It is much different than the 2D storage of a monitor or TV screen. Internet info is a short term storage, and not the best way to learn. Reading printed text, looking at charts on a wall, etc., will lead to much better retention. Dumb as it sounds, speaking the words out loud as you explain to yourself what you are reading will increase retention even farther. This is why you teach the skill to yourself. Do it verbally, as that is also a separate part of the brain. The more pathways used, the more available the information is for recall.
Verhoeven's work on the metallurgy of knife steel
http://www.hybridburners.com/documents/verhoeven.pdf
Heat Treatment - The Process and Principals of Quenching - by Kevin Cashen
http://www.bladeforums.com/forums/threads/639019-The-process-and-priciples-of-quenching
Working with Three types of Steel - by kevin Cashen
http://www.bladeforums.com/forums/threads/673173-Working-the-three-steel-types.
HT for complex stainless steels
http://www.bladeforums.com/forums/showthread.php/896982-HT-Regimen-for-High-Alloy-Stainless-Steels.
HT for 1095
http://www.bladeforums.com/forums/showthread.php/379832-How-the-hell-do-you-heat-treat-1095-!
Dry Ice vs Cryo
http://www.bladeforums.com/forums/s...-and-Some-Explanations?highlight=dry+ice+cryo
http://www.bladeforums.com/forums/showthread.php/1015501-Dry-Ice-and?
Info from a discussion on 1084 HT and tip geometry:
First - 1084 austenitizes at 1500°F. The eutectiod point is when the ingredients go into solution. The austenitization point is when they are ready for quench....not the same. Some steels have a lower austenitization temp than 1084. What makes 1084 a great steel for minimal HT methods is that it does not require time for excess carbon or alloy ingredients to form carbides. Thus it needs no soak time.
Second - When using a torch, the metal is the only place that gets heated. In a forge, or even a row of firebricks like Pat mentioned, the refractory will get heated and try and retain and/or reflect a bit of the heat back into the blade. With a blade held in the air, and a torch played up and down it, the blade radiates the heat back into the air. In the thick places of the blade, the mass holds some heat, which helps keep that area hot a bit longer. However, the thin sections like the edge have no mass, so they cool down faster. The tip is the extreme, as it has no mass, and no spine ( which has mass) to send some heat to it. The tip will cool off faster than any part of the blade. (It will also overheat faster than any part of the blade for the same reason)
Third - In a small blade, less than 3" , you can play the flame over most of the blade at one time. In a bowie, you can never be heating more than a small percentage of the blade at any one time. Heating from the spine is the best method, but success is unlikely with a large blade unless you are fairly well skilled at torch HT. Most folks make the mistake of using a hot flame, not a large flame. A rosebud tip in a welding torch or any large flame tip is far better than a hot pencil flame. You only want the blade to get to 1500°, so having a flame running at 5000° is a problem, not an asset. The flame should be evenly blue....and as large as possible. When using a forge, the same rule exists. The forge flame/heat should be just high/hot enough to get the blade to 1500°, not hot enough to weld with.
Forth - You are not exactly clear in your description of the tip "bending". Do you mean it bends and stays bent...or does it "flex" and return to straight by itself when it is pulled out of the wood.
A poor ( insufficient) HT will bend and stay bent. No good knife should do this.
A proper HT and good blade geometry will flex a small amount and return to straight. Most hunting knives and general use kitchen knives need this type of tip.
A proper HT with too thin geometry will bend greatly, and also snap off easily. Only thin slicers should have this tip.
A robust tip with proper HT will not flex, or break. Bowies need a robust tip.
It is a bit hard to describe how a robust tip is shaped in words, but I'll try.
1) If you taper the blade from ricasso to tip as a continuous taper ( distal taper), the tip will be thin. This will make it very weak when the edge is added.
If you don't taper the entire blade much or any, the tip will be nearly as thick as the spine is. This will make it strong, but rather blunt for piercing. Machetes are made with this geometry.
If you taper the blade to a degree where the tip end is about 1/2 to 1/3 as thick as the ricasso, you will have a starting point for a robust tip. The final tip will be thin enough to puncture things in a stabbing cut, but strong enough to resist breaking. The distal taper will allow the blade to slide into the hole made by the stab.
On a bowie from .250" stock, the tip should be about .080-.100" thick after the distal taper.
2) After the distal taper is established, add the primary ( main) bevel. This will taper the blade from spine to edge. It also should stop with a bit of meat on the edge for a bowie. I would go to about .030" on a bowie pre-HT. As you approach the tip, you need to change the angle of the bevel grind a bit to maintain the .080-.100" end thickness at the tip. It is a matter of "blending" the two into a smooth transition. Remember that you can always take a bit more off after HT, but can't put any back on.
3) After HT, the bevels are re-sanded, and then the secondary ( edge) bevel is added. This should carry up the main bevel about 1/8-1/4" to allow a good slicing edge. The exact amount of height is determined by how thick the blade edge was before HT and the edge angle. On a bowie, slicing tomatoes and such isn't what you will be doing, so a fairly thick edge is the norm. This is usually referred to as "meat" behind the edge. This is to allow the edge to survive the chopping and hacking a bowie will encounter, but still have a sharp edge. The tip should have more of this "meat" , as it gets far higher degree of stress. The trick is to roll the edge up into the tip , maintaining the width of the secondary bevel as you go. If the edge bevel is 1/4" wide, carry that 1/4" up to the tip. As you go closer, the angle you sharpen at will increase greatly. You may have been sharpening at 20° on the .030" thick edge, but as you go up to the .080" thick tip, the angle will become close to 45°. This will still pierce things, but will resist breaking or bending far greater. If you get this to all blend together, the knife will have perfectly even looking bevels, but will have a thicker tip than the edge. You have now made a Robust Tip.
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Now all I have to do is get the time to sit down and digest it all. My favorites file grows by leap and bounds once again! :thumbup:
