Question about temper

txmm10

txmm10

Joined
Mar 14, 2015
Messages
41
Hey guys,

I picked up a toaster oven the other day thinking that it would be nice to start the temper on some blades as I was hardening the next batch in stead of waiting until they are all hardened and temper them all at once. My ht oven only holds 8 knives at once so I thought this would save some time but I can't get it to hold a steady temp.

Question is will a fluctuation in temp during the temper change the end results dramatically? I set it at 400 and monitor the temps and get 370-440. It never stays at one temp for extended amount of time so I really don't know if it's going to hurt the temper or not. I don't have a Rockwell tester.
 
I guess if your blades come out swearing and throwing a tantrum you will know they have a bad temper. :grumpy:
 
From my own research:
Yes, it will impact the temper, but not dramatically. Basically, you'll get closer to the effect of the higher temperature, maybe dropping the steel one Rc point.

Two ways to mitigate this effect:
1) Put a big radiating source in the oven, like a lead block. This will absorb heat and re-radiate at a slightly more consistent temp.
2) Put your blades in a bed of material, like brass shavings or salt. This will protect the blades from the direct heat of the source, and even out differences over time.

Personally, I would shield the blades from the heating elements in some way, but not worry about it beyond that.
 
FunkCoaster said:
From my own research:
Yes, it will impact the temper, but not dramatically. Basically, you'll get closer to the effect of the higher temperature, maybe dropping the steel one Rc point.

Two ways to mitigate this effect:
1) Put a big radiating source in the oven, like a lead block. This will absorb heat and re-radiate at a slightly more consistent temp.
2) Put your blades in a bed of material, like brass shavings or salt. This will protect the blades from the direct heat of the source, and even out differences over time.

Personally, I would shield the blades from the heating elements in some way, but not worry about it beyond that.
Click to expand...



Lead and brass shavings are not the best idea. Pack the blade is salt !!! - a really bad idea.



Use a 1/4" sheet of steel, or even better aluminum, to lay the blades on. What you want is a thermal mass to regulate the temperature somewhat. The best setup is a plate above and below the blades.

Along with the plates, you can convert the oven to PID control very cheaply and get more accurate control. The instructions are in the Stickys.
 
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