Tempering swing?

Daniel Macina

Daniel Macina

Well-Known Member
How much swing is to much on a tempering oven? I can get my current oven to swing between 393 at it’s lowest and 407 at it highest with a set point of 400. Is that good enough or does it need improvement? Going to add some more thermal mass and see if that helps even more.

Happy New Years guys!
 
Need more details. :) Oven type, control type, etc.

Mine will stay within a degree or two once warmed up good.
 
It is a convection oven. No control yet just the oven dial and a thermo couple. I was planning a adding a PID but wanted to see how Accurate it was out of the box. Just trying to see if that 7 degree +\- is acceptable or if I should do the pid.
 
That's super accurate for a non PID control. I think I'd adjust my temp so my target temp is the high end of the swing, and give it a try.
 
That's a ±7 degree swing, should be ok. Even with a PID controlled oven with a ±1°F swing at the tip of the TC, I expect if a check was made from one end of the blade to the other the swing might come close to that 7 degree swing. Not sure, but would be a good test sometime.
 
DON'T TOUCH THAT OVEN!!! :) That's pretty darn good for just about any type of oven.

Tempering "changes" in steels take place every 25 degrees F, starting at 350F. Generally when talking about "swings" in oven temps, the downward swing is not nearly as pertinent as the Upward swing. In other words, as long as the upward swing does not exceed about 20degrees F, you're OK.

Now, why is the downward swing not so important?? Well, let me explain it this way.....when experimenting to figure out the tempering temp you need/want for a given steel/grind combo, it's always better to err on the low side..... that way when you test, if the steel is too hard, you simply put the blade back into the oven, at 25F higher then the previous temper, then test again....until you find your "sweet spot". IF you temper too high, and the steel ends up being too soft.....you're usually hosed.... because then you must go through the hardening AND tempering processes again....and usually, the edge is too thin to endure the hardening process without badly warping or burning.
 
If you can find a pizza stone or ceramic tile to fit in the oven, that will help to regulate temperature quite a bit. It will take the oven longer to warm up, but adding that thermal mass is a pretty effective way to stabilize things, so long as the blade isn't so close to the elements that that the blade gets all the direct heat.
 
EdCaffreyMS said:
DON'T TOUCH THAT OVEN!!! :) That's pretty darn good for just about any type of oven.

Tempering "changes" in steels take place every 25 degrees F, starting at 350F. Generally when talking about "swings" in oven temps, the downward swing is not nearly as pertinent as the Upward swing. In other words, as long as the upward swing does not exceed about 20degrees F, you're OK.

Now, why is the downward swing not so important?? Well, let me explain it this way.....when experimenting to figure out the tempering temp you need/want for a given steel/grind combo, it's always better to err on the low side..... that way when you test, if the steel is too hard, you simply put the blade back into the oven, at 25F higher then the previous temper, then test again....until you find your "sweet spot". IF you temper too high, and the steel ends up being too soft.....you're usually hosed.... because then you must go through the hardening AND tempering processes again....and usually, the edge is too thin to endure the hardening process without badly warping or burning.
Click to expand...

This is a very helpful post, Ed! It makes perfect sense having read this- but I've never heard it explained this way before. Thanks for sharing this.
 
EdCaffreyMS said:
DON'T TOUCH THAT OVEN!!! :) That's pretty darn good for just about any type of oven.

Tempering "changes" in steels take place every 25 degrees F, starting at 350F. Generally when talking about "swings" in oven temps, the downward swing is not nearly as pertinent as the Upward swing. In other words, as long as the upward swing does not exceed about 20degrees F, you're OK.

Now, why is the downward swing not so important?? Well, let me explain it this way.....when experimenting to figure out the tempering temp you need/want for a given steel/grind combo, it's always better to err on the low side..... that way when you test, if the steel is too hard, you simply put the blade back into the oven, at 25F higher then the previous temper, then test again....until you find your "sweet spot". IF you temper too high, and the steel ends up being too soft.....you're usually hosed.... because then you must go through the hardening AND tempering processes again....and usually, the edge is too thin to endure the hardening process without badly warping or burning.
Click to expand...
Thank you! That was very helpful.

Thank you everybody!
 
If you have a thermocouple for measurement, stick it in the oven on its own and watch the swing (this is what you've already done), then without changing the oven setting, take out the thermocouple, bury it in the middle of 2" depth of dry sand in a tray, put it back in and watch the swing again. It'll take much longer to reach temperature, but the effect on the swing will probably convince you.

If you are using an analog meat thermometer, you might need to drill a hole in the side of the sand tray to get the thermometer in the middle and see it though the door.

If doing this in the domestic oven, it's worth buying in a bag of kids playpit sand specifically for the job (it's washed, dried and doesn't smell like a feline latrine when heated).
 
I discovered this weekend that after adding a couple of firebricks to my toaster oven that it's temperature is more stable than our kitchen oven. Go figure.
 
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