temp accuracy in evenheat kiln

rustyrazor

rustyrazor

Joined
Oct 13, 2011
Messages
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just wondering if anyone knows how accurate the evenheat furnace heat control is from the factory? I have had one for about a year now and have only played with it about 10 times... until I can afford a RC tester, it's a real pain in the can, so my question is, if I follow the HT recipes I find online or get from a friend with more experience in HT, how can I be sure that my thermocoupler is accurate? I have had a couple HTs not turn out the way I had expected and I was trying to rule out anything in the oven itself

any help would be much appreciated
 
The only way to determine the accuracy of your kiln is to use another - calibrated - thermocouple. Not the answer you want, probably, but the right one.

Also, consider taking a few measurements from various areas of the kiln, you'll probably be surprised by how much disparity there is.
 
there was a topic here with good detail on even heat oven (i think its a few pages in) http://www.bladeforums.com/forums/s...s-Quenched-with-Parks-50-and-9-Brine-Solution

Its a good question, ive got a paragon 24 inch oven (km24d) where the majority of the oven was 130F hotter than the thermocouple was showing (not fault of thermocouple, fault in oven design and overheating)

Best thing is use your own thermocouple and check the temperature in the oven (drill hole, or insert wire though door). Currently compensating in my oven until i can get a new element.

I think rockwell is a good indicator but from my understanding its not going to tell you everything, even getting good hardness might still have non-optimal properties in your blade.
 
rustyrazor said:
just wondering if anyone knows how accurate the evenheat furnace heat control is from the factory? I have had one for about a year now and have only played with it about 10 times... until I can afford a RC tester, it's a real pain in the can, so my question is, if I follow the HT recipes I find online or get from a friend with more experience in HT, how can I be sure that my thermocoupler is accurate? I have had a couple HTs not turn out the way I had expected and I was trying to rule out anything in the oven itself

any help would be much appreciated
Click to expand...

http://www.bladeforums.com/forums/s...-and-9-Brine-Solution?p=16567013#post16567013
 
I have a freind that works for a company that has an FLIR camera. I had him check my oven 2 different times by shooting a pic
next to the thermocouple,- first time dead nuts on same temp as showing on my controller. Second time (2 years later) he shot another
pic and it was within 2 degrees. Long story short I'm happy.
Ken.
 
Man there are a lot of things to deal with... I just read the better part of that thread Natlek posted and that was a lot more work than I'm prepared to do at this point. I am just paranoid that my oven is off... perhaps normalizing of some of the steels I have had an issue with might solve it but time will tell.
 
I'm curious as to where the thermocouple is located on that oven. On my home built unit, I came straight down from the top, half way from front to back. This is right where my blades go so it is maybe 2" above them. I have had no issues. I did just do an auto tune after tweaking some things and it holds temps like a champ now.
 
I also use Tempilstiks (one slightly below my target temp and one just above it). If one melts and the other doesn't, I feel fairly confident.
 
thanks ken and Tenebr0s... that will have to do for now. here's hoping i get the same warm and fuzzy from the sticks
 
rustyrazor said:
just wondering if anyone knows how accurate the evenheat furnace heat control is from the factory
Click to expand...
My measurements:
- 14 degree cyclic while holding ( empty oven, thin naked tc). This is worst case at tempering temperatures. At higher temps is about 2 d.
- 30 degree offset. This will vary from oven to oven, and drift with time.
- 20 degree back to front, 2 inches from the extremes.
 
Last edited:
gammarad said:
My measurements:
- 14 degree cyclic while holding ( empty oven, thin naked tc). This is worst case at tempering temperatures. At higher temps is about 2 d.
- 30 degree offset. This will vary from oven to oven, and drift with time.
- 20 degree back to front, 2 inches from the extremes.
Click to expand...

and how did you measure those results? just saying for me, I think the only option is to go with the sticks and ballpark within a set number of degrees, then play around with coupons until I feel like the results are what I expect and repeatable. thanks everyone for your imput
 
rustyrazor said:
and how did you measure those results?
Click to expand...
I bought a high end tc meter and tc's from omega, and I did a single point calibration using fine silver wire. I expect my measurements to be +- 6 degrees.

Accurate temperatures are important to share with other people, or to translate to different setups. But you should expect the oven to be reasonably precise, even if not accurate. Then you can run coupons. With hyper eutectic steels you will notice a drop in hardness due to RA. Dial your temperature back from that point.
 
rustyrazor said:
and how did you measure those results? just saying for me, I think the only option is to go with the sticks and ballpark within a set number of degrees, then play around with coupons until I feel like the results are what I expect and repeatable. thanks everyone for your imput
Click to expand...

I've mentioned in another topic , but I will say once again here . Sometimes I use to HT some blade in HT oven in my friend work shop / CNC machine , waterjet ,laser cut....... /. It is a professional/industrial kiln in witch they HT far more expensive steel parts than knive blade .And that oven from inside was covered with the insulation ,you can not see heat element when inside is cold .When oven is ready for work , say on 800 celcius you can see behind that insulation HT element /wire . I do not know how important it is for equal temperature inside.............. just to let you know that detail :thumbup:
 
Not a method to make the kiln heat more evenly, but a solution to the problem. I gave found lisding my kiln with several long pieces of steel helps to even out the temps. I put sone extra short pieces in the front by the door to increase the thermal mass there. Also letting it equalize temperature before putting blades in it.
I hope that helps and makes sense.
 
You Evenheat will work just fine.
Always let it soak at your target temp for at least a 1/2 hour for the oven's entire mass to equalize.
Use a fire brick with a slot shaped in it to rest your blade(s) upon. The extra mass of the brick will help regulate thermal oscillation.
Place your blade in the oven and also account for the time it takes for your blade to get to the target temp before beginning any timing cycle.
Once my oven has normalized at temp, it has a <2 degree window.
 
I put a half thickness fire brick in the end of my 24 inch Paragon shielding the elements to combat overheating the tips.
 
just ordered two tempil sticks 50deg apart to check their melting points against my thermo reading... will be putting fire bricks in as well and let it all soak before trying the next blades... just have to go to a friend to check the RC so it's a pain in the arse until I get my own.
 
jdm61 said:
I put a half thickness fire brick in the end of my 24 inch Paragon shielding the elements to combat overheating the tips.
Click to expand...

Do you have the KM24 D?

I tried this in mine, it does nothing to the temperature difference! :( after soaking the oven for several hours temps were still variable ( at thermocouple + 0 , 8 inches into the over +70f, 16 inches in +110f, 20 inches in +120f) the least temp variation being the last 2/3 of the oven.
Recently aquired a new element to unwind the back wall section and see how that goes. Long electric ovens are a trick to heat evenly IMO, air doesnt move at high temps so temperature differences form very easily
 
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