Oven Calibration???

Dr.Lathe

Dr.Lathe

Joined
Aug 4, 1999
Messages
2,596
I just rebuilt an old but very well made heat treat oven. It works great and has a large analog thermometer on it. It has the old style timer/switch control that turns the elements on and off to regulate the temperature. I was told that once the temp is set it holds it very accurately. I want to use this oven because it's over 24" deep!
My new oven has a digital control and I've just been using it the way it came with good results.
I'm used to picking up the phone and having someone come in to service and calibrate the ovens at work. The instrument they use costs about $1500. Having them come to my house to do mine will cost a small fortune!
The thermometer is adjustable but it is reading higher than what the temperature actually is. What would be the best way to calibrate this???? I would like to be accurate at 1830F.
Thanks,
Neil
 
How about using temperature sensitive crayons. they are availble through Centaur forge??
I'm ordering some for heat treating.
 
TJ,
In addition to the crayons, McMaster Carr has pellets that do the same thing. I was thinking of ordering 3 different temperatures to see how accurate it is between 1000-2000f degrees.
I would like to get set up with a meter and thermocouple probe that I could check my ovens against the calibrated ones at work. I'm not sure which one to buy, I have to call around today and ask some questions. Meanwhile the crayons or pellets seem to be the best idea.
Thanks,
Neil
 
Neil, I've got two older ovens on their way. May I call on you for some help in getting them going?? I sure would appreciate the help!!
Why don't ya take the oven to work the next time they're gonna have their's calibrated????? I know, dumb idea!! Take care! Michael

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"Always think of your fellow knife makers as partners in the search for the perfect blade, not as people trying to compete with you and your work!"
 
L6,
That's not a dumb idea! If they were going to have the large ovens calibrated soon, I would do this. Unless something goes wrong with one of them, they are not due to be calibrated until May. I hit a temperature that gave my A2 scraps pieces a 63Rc so I'm very close. I will only be using this oven for the larger knives that wont fit in my small one.
Once I get the blade ready, I will Email you in regards to treating the L6 camp knife I have blanked out.
Neil

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Update in process! New knives, pictures, Sheaths!!
http://www.geocities.com/Eureka/Meeting/5520/index.html


 
That is a very good idea that Michael had concering taking it to work with you. The technician does not need the whole oven, just the entire controller. What I mean by that is the electronics and the case the electronics slides into. Sometimes there is circuitry that is on the case for temperature compensation.
I work for a company, Honeywell, that manufactures these devices. About 15 years ago I did nothing but service these types of devices...before my interest in knifemaking.
Some of the devices today are accurate to within one degree!

C Wilkins
 
C. Wilkins,
I have what's called a "Muffle" oven. It has what I would call a no feedback temperature control. It has only a thermocouple and analog thermometer. The temperature is regualated by an adjustable timer that turns on and off the heating elements. Now that I have run it several times, keeping it at a given teperature is easy.
If you saw how well this oven was made, you would understand why I'm messing around with it!!! I would like to have it converted to a programable control at some point.
If you could provide me with information on how to do this I would GREATLY appreciate it!!
Thanks,
Neil Blackwood

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Update in process! New knives, pictures, Sheaths!!
http://www.geocities.com/Eureka/Meeting/5520/index.html


 
Neil,
What you have is referred to as "time proportioning" control. The relays are energized for a given amount of time. These can be a challenge to set up but once they are "on", they are "on". I will have to look into it further and will email you "off-line" on what I am able to find out. The programmable controllers tend to be relatively expensive but may be worth it in the long run.

C. Wilkins
 
I am using the oven now!! Once the temp evens out, It holds right on! The only thing I dont like is the resolution of the anolog temperature display. Being used to digital, it's hard to read,+/- 20 degrees. Replacing it with a digital readout would probably be less expensive than changing the entire controler. I think if I did that I would keep the anolog one to watch the needle sweep. It's easier to visualize the temperature variation than with the digital type.
I appreciate your help,
Neil
 
Buy a hand held digtall with a protable probe .. Betwen the digitall controller and the portable you should be in the ball . Have the protable check the oven from time to time.
They cost less that 150.00

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Web Site At www.infinet.com/~browzer/bldesmth.html
Take a look!!!




 
Neil, outstanding web site!!! I wish I could fancy mine up some. It's about as nice as a rock.

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"Always think of your fellow knife makers as partners in the search for the perfect blade, not as people trying to compete with you and your work!"
 
Darrel,
I should be getting some sort of digital temp meter and probe tomorow. I think I might be able to buy it. I have a friend that is comming over with one to check out my ovens. I just melted two 1850deg beads and set the oven for that. Those beads are damn accurate! Once the oven cooled off the 1700 deg ones melted right on 1700 degrees!!!! I am out of the beads now though!! I'm still getting used to the control on the oven. It takes a while to stabilize but it comes up to temp way faster than either of my Paragons!!!!

L6,
I still have a long way to go with my website. I have to add pricing, knife specs and a whole lot more. I am busy as hell right now with knives, I hope to do some major work to the site over the holidays!!!!
Thanks for the compliments thought, I appreciate it,
Neil

------------------
Update in process! New knives, pictures, Sheaths!!
http://www.geocities.com/Eureka/Meeting/5520/index.html


 
I've got a 40 or 50 yuear old pottery kiln that I'm converting over. This one had one adjustment for temp....open or close the lid a touch! But the walls are 6" thick, and it only cost $20!
I put in a new element, a K-type thermocouple, and a digital controller from that fellow who sells the grinder plans, Meta-Machines, out of Whitefish, Montana.
The board has 11 programs, with 7 temp settings per program & cost $200, and the project box from Radio Shack was another $12. Will fire it up this weekend, and use the cones thje ceramics workers use to calibrate it. Let you know how it does!
 
Now that I got the hang of getting mine to stabilize at a temp, it works great. I have a digital handheld unit with K type thermocouple now on "permanant" loan!! I was only off about 15 deg. using my melt point beeds. The oven is just warm to the touch when it's 1800+ deg on the inside. They don't make them like this one anymore!!
Neil

------------------
Update in process! New knives, pictures, Sheaths!!
http://www.geocities.com/Eureka/Meeting/5520/index.html


 
Dr.
You can send the meter in to the company for recalabration from time to time also if you have worries. It great that the beads work also.

Its nice to have a way of checking all the temps out to make sure all is well in the hot house ..

You may want to check different spots in the oven to make sure there are no hot cold spots ..

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Web Site At www.infinet.com/~browzer/bldesmth.html
Take a look!!!




[This message has been edited by Darrel Ralph (edited 08 December 1999).]
 
Darrel,
Now that I have the long thermocouple and meter, I can check just about anything!! It is a beautiful thing!!! Plus I got if for free, more or less....
I know what you mean about cold and hot spots. This oven is the best insulated one I have ever seen. It's also over 24" deep so if I get the smaller blades in the middle they should heat very evenly.
I want to thank you again for your compliments on my Tantos in the general discussion post!
Neil

------------------
Update in process! New knives, pictures, Sheaths!!
http://www.geocities.com/Eureka/Meeting/5520/index.html


 
A word of caution when it comes to oven or controller calibration. While it is always a good idea to have the calibration "checked", before any actual calibration is done, find out how far out the controller is. Basically what I am saying is that if the controller has NEVER been calibrated, check it first. If a baker has been baking bread for the past 25 years in the same oven and the thermostat or controller has never been calibrated, chances are the bread will either be gummy or burnt after it is "calibrated"!
Some folks may soak, for example, at 1650 degrees, while others may soak at 1680 degrees for the same steel and the results are the same. Now why is that? I am not stating not to calibrate it, I am saying just be aware of how far out it is to begin with...

C Wilkins


[This message has been edited by C L Wilkins (edited 09 December 1999).]
 
CL,
I agree with you! But this oven has not been used in years. It's a laboratory oven and was not used for heat treating steel. The reason that the anolog thermometer was off by about 300deg was from moving it all over the state of Florida!! I think the needle got bounced around. I have done 4 runs with it so far and they all have come out perfect. I will be running most of my knives in my small digital oven anyway.I just wanted to get this one working for my larger knives.
Thanks again,
Neil

------------------
Update in process! New knives, pictures, Sheaths!!
http://www.geocities.com/Eureka/Meeting/5520/index.html


 
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