Evenheat questions/concerns

C

Chant

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Jan 27, 2006
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I just got my new evenheat oven set up, and began testing its accuracy with an external pyrometer.

I'm just testing at lower temps for now. I've found that the evenheat's temp reading overshoots the target temp by up to 18 degrees when ramping to 550. That is probably OK, as it is a 22.5 inch oven and there will be more variance than with the shorter ovens.

I'm more concerned about the external pyrometer readings, though. I enclosed the k type thermocouple in a stainless tube, and layed the tube on the firebrick I'll be using to hold my blades. During ramp, the external pyrometer lagged by about 30 degrees until the oven reached about 300, then it sped past the oven's pyrometer reading by up to 60 degrees. I assume this is largely due to the fact that the external thermocouple is encased by stainless steel, and the evenheat pyrometer is encased in ceramic. The steel will absorb the radiant heat faster (I assume) than the ceramic.

However, once the oven reached hold temp (550), the external pyrometer dropped back by as much as 50 degrees (~500). The oven fluctuated +- 7 degrees while holding the temp, but the external pyrometer ranged between 493 and 505, which is a big difference. I held the temp for 10 minutes, and temps stayed within these ranges the whole time.

The oven's pyrometer is about 3 inches higher than the external one, and the external is sitting on a soft firebrick, which will be a heat sink, I guess, so I'm not sure if this is cause for concern or not -- perhaps a blade, with only the spine touching the soft firebrick, would more closely match the oven temp?

The differences cause me concern for hitting target temp and soaking. I'm planning on treating O1 at about 1425, halfway between the recommended 1400 to 1450 range. If the discrepancies are the same at those temps, then in attemping to heat to 1425, I would end up hitting 1485 at the high end, but during the soak time it would drop to as low as 1375.

I'm also concerned about tempering temps -- if I try to temper at 400, the high end would hit 460, and the low end 350.

If I wait until even target temp is hit (i.e. don't ramp the blade), then I avoid some of the fluctuation, and this is fine for tempering, but the specs for O1 say to equalize at 1200, and then bring to 1400-1450. They also warn not to bring temp up to quickly for fear of cracking, but I'm not sure how necessary this is with a blade.

Has anyone else had these problems with the evenheat? Or are my testing methods not valid because the external pyrometer's thermocouple is sitting on a firebrick?
 
what did you have the "ramp" set at when you programed the controller? If you programed to ramp at 999 then the controller would certaintl over shoot the set temp. I was having the same problem with my paragon when I first got it. I now set my oven to ramp at my set temp or slightly below. It takes longer to heat the oven up but I don't miss by more than a few degrees.
 
Thanks, I did have at 9999. I'll try at lower ramp speed. I'm going to try raising the external thermocouple into the air, to, so it is not touching the firebrick, and see if it ends up matching the ovens temp more.
 
I have the same model you do, and i always bring it up to temp before putting the blades in. When tempering, I preheat the oven for a half hour before putting the blades in. When hardening, i put the blade in as soon as the oven reaches temp.
It's definitely wise to check the temp with a seperate pyrometer. My oven, due to a faulty connection between the thermocouple and the controller, was reading higher than actual temp. Aside from that, i love my oven. :)
 
I have the Paragon, but it overshoots at max ramp. I set it lower and its dead on now. I do not have an external to test, so i did a makeshift test using the exact nonmagentic temp and soaking at just below that, verifying a magnet stuck, then ramping a tiny bit above, and seeing it go nonmagnetic.

Don't they calibrate the ovens before they ship? Mine came with a stamped form with calibration and testing specs....

What always amazes me is how much temp you drop opening that door.....
 
I've found the ramp speed and the firebrick are what was causing the problems. With a ramp of 450/hr, and the thermocouple raised up off the firebrick, the external pyrometer is within about 5 degrees of the oven as it ramps (so far, it is still running). I think, with the firebrick as blade support, I'll have to give it lots of time to come up to temp. I think I'll order a stainless rack to get around this. Also, I'll avoid ramping the blades (I'd avoid that, anyway -- too much carberization (or however it's spelled)).

Brian - You are an undisputed master of hammon on O1 (a lot of people say it can't be done, but you do it anyway!). If I remember correctly, you get the hammon by painting the blade with a torch, and then doing your special etching. I'm wondering how you're planning to do hammons with your evenheat. Edge quench? Clay? (I hear clay doesn't work on O1 either, but I'm hoping you'll prove us wrong). Torching the spine? I expect you'll be doing a lot of experimenting to figure a new process out -- I'd love to hear about your results -- I really like the hammon and finish you get on your blades.
 
Ive gotten hamons with 01 but never with clay...its always been an edge quench. O1 seems to harden too deeply or too easilly to allow the clay to mask off that part of the blade from the quench. Even with the clay, the steel underneath seems to cool fast enough to harden and wipe away that line for the most part. Now that you have the oven, experiment away!
 
With the oven I think I'll be going for full harened blades or a LARGE tempering oven :) The torch is just too nice of a temper line to mess with :)

If it works.....I aint messin with it :) :thumbup: ;)
 
Jeff
I don't know about the others with Evenheats, but I never use mine to temper in, unless the blade is way too long..
"mine is custom made at 27" inside,," I just don't want to heat all that up,,, $$$
I use a toaster oven with a separate thermometer and if I want to do bigger stuff, it goes in the house in the kitchen oven with a thermometer.
I have two thermometers of the same type to watch the other..
it's like wearing two watches, you'll never know the exact time using them both:D .
I also pre-heat before I put a blade in for hardening heats..
you'll find that you will find your own way that your set up's will work for you..
 
TikTock said:
Ive gotten hamons with 01 but never with clay...its always been an edge quench. O1 seems to harden too deeply or too easilly to allow the clay to mask off that part of the blade from the quench. Even with the clay, the steel underneath seems to cool fast enough to harden and wipe away that line for the most part. Now that you have the oven, experiment away!
Click to expand...
O 1 was made to harden evenly hence the trouble with it as far as Hamons. trying to get a Hamon like with the 10XX steels in O1 you're trying to undo what the manufactures did to it..it was made as tool steel made for tools:) I should say tool and die work
 
I can only fit about 5 smaller knives in my toaster at once, so I'll be making more larger ones at a time and hope that by making more at one time....I counter act the extra power $$ to heat the oven :)
 
blgoode said:
I can only fit about 5 smaller knives in my toaster at once, so I'll be making more larger ones at a time and hope that by making more at one time....I counter act the extra power $$ to heat the oven :)
Click to expand...
a turu home grown knife maker to the bone:D :thumbup:
 
Well, letting the oven heat more slowly, and avoiding the fire-brick as heat-sink problem, my external pyrometer is pretty much consitantly 10 degrees over the evenheat pyrometer once target temp is reached. Both are brand new, so I don't know which is wrong, though I suspect it is the evenheat, as it would be far harder to calibrate given that the thermocouple runs through the firebrick. Also, the external pyrometer says it is accurate to .1 degree.

Ten degrees is OK to deal with, but it is annoying -- I have the same problem when I heat my quenchant -- I have three kitchen thermometers - a meat thermometer, a candy thermometer, and a digital oven thermometer - they always give different readings, often by 10 degrees, as well (and thats with me rigorously stiring the quenchant).
 
do you think this will work?
Have the D2 in th eback of the oven and the 0-1 in the front. When the 0-1 has soaked long enough take those blades out and ramp up to the D2 temp?

Think that will be a way to save on power also?

B~
 
blgoode said:
do you think this will work?
Have the D2 in th eback of the oven and the 0-1 in the front. When the 0-1 has soaked long enough take those blades out and ramp up to the D2 temp?

Think that will be a way to save on power also?

B~
Click to expand...

I would think so. You could just consider the time that D2 spent soaking at o1 temp it's equalizing time. You'd probably want that stainless foil to protect it though (I'm going to order some of that scale-preventing powder from brownings to try out).

Also, I found the oven takes quite a while to cools down, and waiting for it to cool for tempering would take a while. I'm going to follow Dan's advice and get a toaster oven for tempering. The other thing I found re: cooldown, is that the oven temp, with the door open, may say 350, but if turn the oven on to 410 and close the door, the retained heat in the brick will quickly drive it up to 460 or so. I think I'd have to wait a long time to be able to temper in it.
 
I've had two toaster ovens and neither one would hold ther temp I wanted it at. It would vary as much as forty degrees and my wife was tired of me using her stove to temper in, so I bought an oven.
 
any thoughts on dooing you tempering in an oil bath like ysing a frydady or something like it that should keep temps nice and even right
 
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