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Want to make a leather working knife like I saw a couple weeks ago and need info. and how to's about annealing a circular saw blade and then retempering it back to original after it's shaped.
I would think there would be instructions as to how an item is make in the listings but I can't seem to find any ???
Here's what I do:Quote:
Originally Posted by Ron
1).Go to Google and type in "Annealing and Retempering Sheet Metals","How to do I do annealing for sheet metal?"
2). Try this link: http://www.forgottenbooks.com/downlo...1000774468.pdf PASTE THIS LINK IN YOUR BROWSER
I don't remember how I found this book site,but I'm really glad I did.The link above is for a specific book okay.
The actual link is:"http://www.forgottenbooks.com"
So put the link into your browser and check out this book,now as your going through the book you probably come to a page that says this page is missing become a paid member or something like that.
Because I'm really strapped for cash I take the title and author and I go into a browser and paste title and author and look for the book that way.
You can also go to abebooks.com you can buy new and used books I use this site and I have gotten a couple of used books and one new one. vary good site for books.
Also Google has EBOOKS check that out.
Rich.
Here's what I do:Quote:
Originally Posted by Ron
1).Go to Google and type in "Annealing and Retempering Sheet Metals","How to do I do annealing for sheet metal?"
2). Try this link: http://www.forgottenbooks.com/downlo...1000774468.pdf PASTE THIS LINK IN YOUR BROWSER
I don't remember how I found this book site,but I'm really glad I did.The link above is for a specific book okay.
The actual link is:"http://www.forgottenbooks.com"
So put the link into your browser and check out this book,now as your going through the book you probably come to a page that says this page is missing become a paid member or something like that.
Because I'm really strapped for cash I take the title and author and I go into a browser and paste title and author and look for the book that way.
You can also go to abebooks.com you can buy new and used books I use this site and I have gotten a couple of used books and one new one. vary good site for books.
Also Google has EBOOKS check that out.
Rich.
First rule, plan each step making sure that no animals, children or people will get hurt or cause problems. This includes you.
Second rule, make sure you have a really good plan for putting out all possible fires. Plans that don't include stupid things like throwing water at flaming oil.
Third rule, make sure you are rested, alert and sober.
Fourth rule, have fun this is blazing hot steel and blacksmithing, how cool is that!
To anneal carbon steel, Heat it up until a magnet will not stick to it. Cherry red usually, don't heat till it starts sparking, sparking is welding temperature and can drive out the carbon that makes the blade steel. Then let it cool slowly. Putting the blade in perlite, the white stuff available at garden centers can insulate and help slow down the cooling. Annealed steel is softer and much easier to work.
To harden carbon steel you need to quench it. Some steel likes a really fast salt water quench. Some steel likes a more even oil quench. Your guess. Oil quench can light the oil, water quench can crack the steel. Either way you need long tongs or you might not enjoy the rest of your day. To quench, heat up to where the magnet does not work on the metal (cherry red glow) and then plunge it into the quench and stir vigorously. Now you have really hard brittle steel. It needs to be tempered so that it can hold up.
Clean the steel and make it shiny again without fracturing it. If you have a lot of a particular steel it is worth testing color to temper on a test piece. As you heat the shiny steel it will change color like a rainbow. This is not a glow it is the tint of the metal. By heating a long thin evenly sized test piece to a range of color in a sort of metal rainbow, you can then try scratching it with a good sharp knife tip from the most heated up area to the least. At the point where the scratching stops, usually past purple and into straw colored, the metal is about as hard as the good knife you are testing with. Then put the test steel in a hole and start bending it. Start from the most heated end. At the point where you can bend it and it returns to original, usually blueish, you have a spring steel hardness. This is good for the body of the blade but not the edge. At the point where it breaks before it flexes you have file hardness. The parts you want to be tough but will not be sharpened you want to heat to spring consistency. This is why file tangs are purple, so they won't just snap off. The area that will be sharpened, including all the area that will ever be sharpened you want to be hardened probably to straw color or whatever matched your good knife with the scratch test.
If you know the metal and want a uniform quench, then you can do it by temperature. The easiest way to temper is to us a home frying unit like a FryDaddy so that you can quench by temperature and let the blade soak at that temperature a long time. Afterward you can heat the handle and spine to a higher temperature to make the knife tougher.
Another hint to may your life easier, and the job you do better. When annealing and hardening steel, I put borax on the metal the second it is hot enough to melt borax. This gives a weak glass coating that protects the steel from oxygen and makes it much easier to clean up later.
Bob
Thanks all, This is just what I was looking for. Will update with results.
Ron Frost
Quote:
Originally Posted by CedarSlayer
Hi Ken and Jon,
I do vote for a best tutorial award : well written, fully secured, pleasant to read, and perfectly described for Bob above !
I recognize the great teacher he is !
I will print that, even translate and keep it in my shop !
Thank you very much !
Christophe
(Bob, do you authorize me to quote this on my website and translate it into French ?)
Christophe, how could I deny you? You have Carte Blanche.
Looking it over, I should add a few notes. First, wear safety glasses. Second, on the oil vs water quench, The most reliable test is to do both if the difference is not dramatic, the real test is to see how well the best spring tempered section will handle extreme bending and how well the blade tempered section will sharpen and hold an edge. Cutting pine end grain is a classic test for edge retention.
When testing scrap I also check to see if spring tempered steel can be made into a scraper with a burr. If it can it is work hardening. Work hardening can be an indicator that it's life as a spring may be short. The best sythe blades I have used are work hardening.
Bob
Great post, CedarSlayer! Quite informative.
Actually, non-magnetic is the Curie Point, not the Critical Temperature.
Critical Temp for most simple steels is a bit above non-magnetic. You
have to reach critical to get the steel to harden properly. That's when the
carbon in the steel enters into a solid solution with the iron and can form
Martensite.
Thanks Bill for that precision.
And is this Critical temp far above the Curie Point ?
I mean is the Curie point a good enough approximation, or maybe saying we can continue to heat up during X minutes after the Curie Point ?
Thanks, I'm learning a lot of things hre
Christophe
Generally, CP is in the 1400's F, and CT is in the 1500's F. If I'm forge heat treating, I go to CP,
note the color and let the steel sit until the color is a LITTLE more to the orange side.
You can also see the recalescence/decalescence shadows pass across the steel as the carbon
enters/leaves solution. The shop should be pretty dark to see this well, but after you've seen
it once you won't miss it again.
I generally quench in Parks 50 oil for hardening, and temper oven is a gas grill with multiple thermometers.
Temper about an hour, let cool to room temp, 3 times. Most of my heat treating is done on
knife blades.
The Critical temperature is often below the Curie point. The Curie point is used by blacksmiths when they don't know the ideal temperature, cannot precisely control the temperature or cannot measure the temperature precisely. If you purchased the metal knowing what it was, you may have the first, but unless you have a good steel working furnace, the second two are unlikely. Since the loss of magnetism is related to the loss of structure, in general a blacksmith can count on the magnet test. In cases where the loss of structure that allows for magnetism to happen is reached and the carbides are not dissolved, the blacksmith might or might not have better luck going with a longer wait at temperature or a bit higher temperature.
In the end a blacksmith's final judgment is based on results. If it does not work out, the metal is not considered useable. In some cases a blacksmith will go for a longer hold temperature. In an old fashioned or more primative environment, where the metal is not wrapped in stainless foil and put in a furnace capable of multiple hold times at a range of temperatures, the odds are that the curie point will be exceeded by a bit anyway.
There are a lot of odd metals used in knives, but apart from top end rather expensive steel knives and pretty much all stainless steel knives, knife steel can be handled by a blacksmith using the magnet test.
Really good read ... Congratulations to the teachers. :bow:
Hotz :hattip:
Here is an odd tip that some metallurgists and machinists know but few blacksmiths. Hot oil quenches faster than cold oil does. The reason is that low viscosity gives better circulation than high viscosity. Since the oil immediately vaporizes and forms a gas envelop around the steel, the gas is replaced faster when the oil flows more easily. A rapid stir and moving oil will help collapse/replace the envelope, but the advantage of fluid oil outweighs the advantage of cooler oil.
On the downside, if you don't have enough oil, hot oil can quickly be brought to a temperature that will allow an oil fire. I used to use a small long container to quench and not waste oil. Now I want a large enough volume so the oil temperature will not be raised too much as the metal transfers heat.
Bob
I very respectfully disagree. I've never heard of a common high carbon steel which has a CT
below the Curie Point. Now that I've stuck my neck out, I'm only familiar with blade steels.
Some hi-tec stainless steels may be different, but I've never heard of one.
What I've learned from 50+ years of making knives is that without a carefully temp controlled
heat treat oven, mine's a Paragon, you need to refer to the calescent shade change to insure
that the carbon has entered into the iron matrix to form Martensite from the lower temperature
Austenite. The magnet test will get you into the ballpark, but the transition is somewhat
higher than the Curie Point. The Japanese bladesmiths have for centuries used the "shade" test
to determine when the steel is ready for quench.
You may get some hardening if you quench from Curie Point or below, but it will not be the max
the steel is capable of.
This is great. Civil discourse of an issue from which we all can learn. If I'm wrong, then
apologies all around.
Bill
ABS Apprentice
I love a good discussion and I tend to learn more when I am wrong than when I am right. :) As a confession, my actual education is in the area of physics, but electronics and light are more of my area of mastery. Furthermore, I have used a magnet to test the concept, but I go by eye and use a cherry red glow in dim light to judge temperature. So my experience with using magnets to test has been limited to 01 steel.
That said there are a lot of rather amazing blacksmiths that will look at you with a blank stare if you start this discussion with them. A lot the old timers consider pounding hot steel to be important in the formation of a good blade and steel temperature charts rarely take that into effect.
The critical temperature, is a term that moves depending on what you are referring to. For magnetism, the Curie Point is the critical temperature. For carbon to be made available for producing carbides the critical temperature is where austenite is forming. Since the question of where austenite forms is so important, those who know that there is a difference in Curie Point and carbon being made available tend to label this the Critical point. At this critical point in the discussion, we lose most of our audience. For those who are persistent, austenite is one of the many crystaline forms that carbon steel can take. This form is particularly good for forming carbide crystals during a quench.
You are correct that in simple carbon steel, the temperature for austenite formation is above the critical point after the carbon content goes over 0.77%. This is however not the entire story.
Alloys of carbon steel can lower the temperature where austenite forms. O1 steel is typically held at 1400 in order to anneal. The Curie point for o1 is 1420 F. So for a steel with 0.95% carbon, the Curie point is a pretty good temperature for annealing.
Since I personally use a cherry red glow, this is hardly an issue. Cherry red is just bit below 1500 so I am typically am way over. I try to not get much further into the red orange zone, since a lot of steels such as o1 can develop retained austenite with over heating.
In any case, better blacksmiths that I will ever be regularly use magnets to test temperature and seem to manage quite well.
This thread has been moved to the Must Read subforum. Congrats (and thanks) to Ron for making such a valuable contribution!