testing for best temper temp

JTknives

JTknives

Joined
Jun 11, 2006
Messages
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i have been thinking about tempering temp and how many things determin the temper a knife can handle. what i have been thinking is to take the same steel as the knife that needs heat treating. give it the same grind as the knife and heat treat. then sharpen and put one end of the steel in water and heat the other end. wate to see the color run. then dunk in water. sharpen and do a brass rod test and see what color offers the best strength. what you think
 
Unless you're making very large blades, it seems like using an oven is the best route. Oxide colors aren't likely to stay consistent between blade, but if you want to use them, there's already a basic color list out there (for plain carbon steels):

400 degrees, pale straw
425 degrees, straw
490 degrees, golden yellow
500 degrees, brown
525 degrees, brown purple
570 degrees, purple
600 degrees, bright blue
650 degrees, pale blue

You just need to know what temperature your steel is supposed to temper at.

It's going to be hard to get a reasonable amount of temper time that way, so you'll be relegated to the simplest of steels. Even then you probably aren't getting an optimum temper. If you plan to do this with alloy steels, the color will not be consistent between alloys (perhaps even batches?) and you'll never be able to reach time at temp.
 
Dunking the hot piece in water will wreck any results you hope to achieve. You'll "shock" the steel by doing that, and will likely get micro fractures.

The brass rod test is a far better indicator than any color. Color is not a constant, and can vary in appearance due to many factors. A far more accurate method would be to test with the brass rod, and record the temp the blade was tempered at .
 
what i ment was testing the edge in the area of the color run. the brass rod would be run down the edge starting at the straw color and tested down past the blue. then check the edge for chips. where the chips stop look at that color and that gives you the tempering temp to set your oven.
 
You may very well find the best tempered area of the blade with this method, but the problem is knowing what temperature the color actually represents for this area to set the oven by. Colors are a rough estimate and vary by steel and even within the steel depending on multiple variables. I agree that an oven and an accurate in-oven thermometer is the best method.

--nathan
 
ok so let em get this right you want to do a test on tempering sorta like the way they do a grain growth bar
you want the blade edge to be a progression from one end of the edge to the other in say a range of 50Rc-full hard and test the blade for the sweet spot
i think it would be best done making a bar in to a straight edge with even bevels and then heat treat / quench and do your first lowest temper you want then snap the bar into say 5 2 inch long mini knives and temper then progressively hotter (in a kiln)to do your test
 
You could also start at the low end do a small section of the Brass Rod Test then move up in temp. I normally do this test and if there it chips out it goes back in at 25deg hotter.

Chuck
 
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