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  #1  
Old 10-23-2016, 09:56 PM
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Grundsau Grundsau is offline
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Just got a free kiln and have questions

So I finally got started working with high carbon steel making herb choppers.
Have been using my kitchen oven for tempering and need something better.

Today I was given a small kiln from a local pottery and the interior is 13" deep and 15" wide.
It is a 230v, 13amp unit.
The bricks and coils appear to be ok and it will need some electronics.

I've been reading through a number of threads about pottery kilns and not sure what to do.
Usually I forge 8 herb choppers at a time and this top loading kiln may pose a problem during hardening.
If I understand correctly, the heat loss when opening the lid may cause the internal heat to fluctuate and a person could get a snootful of hot air.

I've had my eye on the Evenheat KF18 w/Tap Control or the Evenheat KF 27 w/Tap Control.

During my search on here I've read that two ovens are better because of the long cooling time for a single oven from hardening temps down to tempering temps.

Would it be better to set up this kiln for tempering and buy an Evenheat for hardening?
If I could use the kiln for tempering, could someone point me to sources for the electronics?

Could the Evenheat models I listed handle 8 or 10 herb choppers?
The herb choppers are usually 4.5" tall x 6" long.
Not sure how close an object can be placed to the sides before the heating elements create hot spots in the steel.
Attached Images
File Type: jpg Photo Oct 23, 15 21 17.jpg (373.5 KB, 8 views)
File Type: jpg Photo Oct 23, 15 21 45.jpg (327.7 KB, 9 views)
File Type: jpg Photo Oct 23, 15 21 40.jpg (346.6 KB, 7 views)

Last edited by Grundsau; 10-23-2016 at 10:46 PM.
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  #2  
Old 10-24-2016, 08:33 AM
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Ray Rogers Ray Rogers is offline
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You would definitely be better off with an Evenheat for heat treating but kilns have been used successfully by numerous makers. The big problem is your desire to manufacture batches of blades. You didn't say what steel you use. If you use an air cooling steel then you can pull all 8 blades at one time and let them cool. But, if your steel requires oil quenching you can't do that so easily. Even if you rig a big oil tank you probably won't get enough space between the blades to allow them to properly cool. It will work but the HT won't be the best it could be. And, there's no way you can pull the blades from the oven one at a time and quench them without having some effect on the remaining blades no matter which oven you use.

If you want a separate and cheap tempering oven just get a toaster oven. Put a good thermometer in it.

To add temperature control to your kiln look for a PID controller, preferably one with ramping ability. These are inexpensive and easily found on eBay ...


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Old 10-24-2016, 08:58 AM
Doug Lester Doug Lester is offline
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It would be a good to get some infra-red goggles to work with that kiln. If you just need glasses just make sure that they are IR resistant. They would probably be a good idea around that Evenheat oven you're looking at.

Another thing, if that kiln doesn't have a disconnect switch to the door make sure that you always unplug it before opening it. If you touch one of those coils with tongs with the power on you could be shorted out.

Doug


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Old 10-24-2016, 09:29 AM
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Grundsau Grundsau is offline
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Thanks for the replies.
Have been thinking of IR protection and will be looking into it.
Sorry about not mentioning the steel.
Am using 1084 and worn out hoof rasps.

Currently, I use my gas forge to harden one blade at a time.
I wait till its dark outside and hold each one by the handle with a pair of tongs while moving it around to get a uniform color on the blade and quench in pre-heated veg oil.

While hardening one at a time, could I do 4 herb choppers in an Evenheat oven using 1084?
Not sure how much soak time that steel can take before it becomes an issue before quenching.

If they are placed near the back of the oven, there may be minimal heat fluctuation as the door is opened and closed quickly.
But, if each blade has to be hardened separately then that's ok.

Last edited by Grundsau; 10-24-2016 at 09:34 AM.
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Old 10-24-2016, 11:29 AM
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Ray Rogers Ray Rogers is offline
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Heat treating by color as you are currently doing is a subjective crap shoot as far as getting the most desirable results are concerned. Your results will improve greatly with an Evenheat due to the improved accuracy of your temperature control. You can do batches of blades in an oven if you wish but there are always trade offs. If 'close enough' is OK for you then batches are doable but you will add wear and tear to your oven. You may not cool the blades much while they sit at the back of the oven but you will definitely lose significant heat from the oven. That means the heating coils and the brick liner get a blast of cold air which will take a toll over time. And, each successive blade you quench will add more heat to your oil causing the results to vary on each additional blade. Honestly, it's hard to imagine that these things I'm pointing out would make a lot of difference to an herb chopper - which is a knife that isn't likely to be pushed to the limits of performance - but being able to take the time to do the little extra steps and attend to the little details of heat treating is what makes a custom knife significantly better than one from a bulk manufacturer. Which category you want your knives to be in will depend on your customers and what they want and what you want your customers to expect from you. It usually boils down to a choice of making a lot of knives that will sell for very modest prices or fewer knives made to higher standards that will sell for prices that reflect the attention to detail that went into them ...


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Old 10-24-2016, 11:44 AM
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Grundsau Grundsau is offline
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Thank you Ray, just what I was looking for.
I'm going to try a meat cleaver sometime soon and that would be done one at a time.
Not sure if it matters, I'm using about 3+ gals of veg oil in a steel 8"ID x 22" pipe as a quench tank.
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  #7  
Old 10-24-2016, 03:26 PM
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Ray Rogers Ray Rogers is offline
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It does matter. That's very similar to what I use. Three gallons is considered minimum. From experience, I would say the oil will be too hot after two or three blades at most and each successive blade of those three will be a little different from the one before. That might not be bad but it's hard to be sure since we set up our HT and test the results usually with just one blade. Sounds like you are basically going in the right direction but need to come to a decision about exactly what you want from your knives when all is said and done ...


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Old 10-24-2016, 05:16 PM
jimmontg jimmontg is offline
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Is there any reason that the Kiln can't be set on it's side and you can build a metal holder to make the front even with the back? Also make a tray with ceramic legs to hold a knife tray made by some of the oven makers? a knife tray like this?
http://www.knifemaking.com/product-p/kf688.htm
On blocks like these.
http://www.knifemaking.com/product-p/kf631.htm
It would be safer and easier to put the blades in and out seems to me than doing it from the top.
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Old 10-24-2016, 05:55 PM
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Grundsau Grundsau is offline
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Jim, had been reading about some other knifemakers that wanted to do that.
The kiln is so old the sides will probably sag under its own weight and the lid hinge barely supports the lid in the upright position.

I had been looking at those holders and thanks for the suggestions.
Am probably going to go with an EvenHeat and then turn this kiln into a tempering oven later on. The heat blast won't be so bad at those low temps.
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Old 10-24-2016, 07:48 PM
jimmontg jimmontg is offline
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Understand, be sure and get some good gloves and get a cheap welders helmet to protect your face from the heat blast or a good face shield, they make them tinted now too. A welder's supply should have both items. If you use this to heat treat, a 1500 degree blast is something else. My brother and I made a forge that could melt steel and you had to put a welder's helmet on to get near the front and look in. Used Mapp gas and pure O2, scared the daylights out of us.LOL
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Old 10-24-2016, 09:24 PM
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Grundsau Grundsau is offline
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Wow, I can imagine how hot that was.
A bladesmith friend stopped by the smithy and we welded up some billets under the little giant.
Pushed my 3-burner gasser so hard that day and will never do it again till I build a dedicated forge for damascus.

I've got a MIG so I'm set with protective gear, thanks for the tips.
The kiln will be used for tempering and the Evenheat for hardening and that heat will be a piece of cake.
The gas forge runs much hotter than that and it's not bad.
Here are some shots of the quench tank, herb chopper, the smithy after the last January snowstorm, and the gasser while making pizza cutters.
Attached Images
File Type: jpg Quench Tank.jpg (342.8 KB, 11 views)
File Type: jpg Herb Chopper.jpg (303.6 KB, 13 views)
File Type: jpg 1-16 Snowstorm.jpg (263.8 KB, 13 views)
File Type: jpg Gas Forge.jpg (316.6 KB, 13 views)

Last edited by Grundsau; 10-24-2016 at 09:33 PM.
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  #12  
Old 10-24-2016, 11:34 PM
Doug Lester Doug Lester is offline
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Temperature is much more important than soak time. If you soak at 1475? then you could hold it there for over an hour without significant grain growth. This has been tested at least with 52100. Something like 1084 doesn't need anything more than a soak long enough to make sure that it's heated through. If it's the steel that Aldo Bruno carries then it has a little vanadium in it which will put a drag on grain growth. Also keep in mind that not only will the oven cool slightly when you take one blade out so will the other blades that you leave in the oven so as you quench one blade you will have to be re-heating the ones left in the oven.

As far as you plan to use the Evenheat oven to thermal cycle and harden with and then letting it cool and then using it to temper you could run into some problems. You really need to be able to get the hardened blade into a tempering oven just as about as soon as it cools to where you can hold it in your bare hand. Letting them sit on a bench as you wait for the oven to reduce around 1000? could leave you with some broken blades.

Doug


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  #13  
Old 10-25-2016, 08:56 AM
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Grundsau Grundsau is offline
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Hi Doug, the 1084 is from Aldo and glad to hear the soak time won't be an issue.

I plan to use the Evenheat for hardening.
Tempering was being done in our kitchen oven and I added some 3/8" thick plates to the wire racks for the herb choppers to lay on.
Picked up a $20 infrared heat gun for my cast iron cooking awhile back and used it to check the plates and choppers.
The temp is consistent.

After hearing from Ray about using a toaster oven, maybe it'd be better to skip trying to use the kiln for tempering.
We have an extra toaster oven and will test it with a 3/8" thick plate inside.

I understand about the metal being fragile after hardening.
My smithy is not heated so that will be more of a problem this winter.

Somewhere I read about flash tempering.
What about a toaster oven right next to the hardening oven at 200 or 300 to keep the choppers warm till its time to do the tempering cycle?
Soon as the chopper comes out of the quench it can go right into a low-heat toaster oven.
The temps can be raised when I get four choppers into the toaster oven and the tempering cycle can be started.

After all of the good info you folks have shared, are there any steels that can be hardened and then tempered using a single Evenheat?
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Old 10-25-2016, 11:43 AM
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Ray Rogers Ray Rogers is offline
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You plan for the toaster oven sounds good.

Yes, some steels can wait for tempering under some conditions but it really is never a great idea. And why bother? You have a toaster oven right there so use it . The exception would be for certain stainless steels that temper around 900F. The oven can cool that far while the steel stays in the quench tank. The downside is that some of those steels give more desirable results when tempered in the more common 400 F range. Read the spec sheet on each steel you use to eliminate the guess work ...


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Old 10-25-2016, 12:02 PM
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Grundsau Grundsau is offline
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Great!
Just to clarify, once I start attempting to make meat cleavers, knives, etc, they will be done one at a time.
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