Thinking about a HT oven

panch0

panch0

Joined
Jun 16, 2008
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I have been sending my knives out for HT this past year. I have spent $250 + this year in shipping and heat treating costs. That is because I was taking a really long time to make knives at first. Now I am able to make them faster and am getting more requests to have them made. I think I will it will pay for itself in a year or two. Now I am a lazy guy when it comes to being repetitive. So when I grind out 13-14 profiles then flat grind them all, then drill all the pin holes I get kind of discouraged and impatient. I know how I get and will walk away and do something else then get back to it. This of course wastes time and it ends up taking longer than a month to get the blades ready to send out to HT to save on the cost. I wonder if it would be worth while for me to invest in an oven. Is it very hard to get HT right for A2, CPM154, 1084, and 5160 since these are the ones I am going to be working with. Right now I am looking at Ht like something only the gods are capable of doing if you know what I mean. I was looking at the 18" Even Heats on Texas Knifemakers Supply. What are your opinions, advice? I think I could make knives for years and years and not get tired of it. I just want to get as efficient as possible on methods and economically. Thanks guys!
 
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Just an FYI, Tracy sells them at his store (usaknifemaker.com) and has a great price.

I honestly think a heat treating oven is indespensible unless you want to just continue to send out parts for treating.

As for the mysticism of heat treating, much of that has perpetuated from old lore. With today's steels, there is almost always an appropriate and well defined method to perform a heat treat to acheive optimum conversion in the steel. With most steels you can find the manufacturer's data sheet with hardening instructions on it.

For your air hardening steels (cpm154, A2, pretty much any stainless), you will need to pick up a couple of thick aluminum plates. I bought a single 12"x12"x1" aluminum plate and cut it in half for two 6" wide by 12" long, 1" thick plates. You use these to plate quench. The plates act as a giant heat sink and cool the blades more quickly. You'll also need the high temp stainless foil to protect your blades for the high temps and long soaks of complex alloys.

For carbon steels, an oven continues to be very handy as you can precisely control your temperature and thus increase your soak if necessary.

It is a good idea to also pick up some dedicated quenching oil like Park's 50 for fast quench steels and AAA for medium quench steels. This will make your treatments reliable and repeatable.

There's nothing mysterious about it; you just have to learn the recipes and have the proper equipment. If it were me, I'd GO FOR IT!! If I didn't just drop some change for a forge, that would be my next purchase to replace my home built oven. A tip, though...you may want to get a longer oven than you think you need. The 22.5" would be great, IMO.

--nathan
 
silver_pilate said:
A tip, though...you may want to get a longer oven than you think you need. The 22.5" would be great, IMO.

--nathan
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Why do you say this? I'm thinking of making my oven 14" long, are there any drawbacks to it?

Are there any steels that can't be plate quenched? Can plate quenching of just the edge of the blade produce hamons?
 
Tim Zowada carried them at one time. I went to Jantz and they would match any price for one so we got the info and the same price from jantz. i have the EvenHeat with Set PRO.Works for me.
 
cotdt,

The reason I say a longer oven may be a good choice is because right now, you may swear you'll never make a knife over 14" long so it's not big deal. However, I guarantee that at some point if you continue in this craft, you'll wish you had a bigger oven when you make that 15" + long blade. :) My oven if 14" long internally, and though I haven't made a blade longer than the oven yet, I could see myself outgrowing the oven eventually.

There are many steels that cannot be plate quenched. Only air hardening steels are appropriate for plate quenching. Steels such as ATS34, 440C, 154CM, A2, etc. are all air hardening steels and would benefit from plate quenching.

You will NOT be able to form a hamon by plate quenching any steel. Hamons form in steels that are termed "shallow hardening". As such, these steels typically require a fast speed of quench in an appropriate oil such as Park's 50 or even a brine or water quench combined with using a clay (unless you're really good and judging the state of the steel during heating...then you can get a hamon with no clay). Also, you can edge quench these steels in oil to get a hamon.

You will not be able to effectively get a hamon on an air cooling steel, plate quench or not. It's also a good idea in plate quenching to get as much surface area as possible in contact with the plates to draw out the heat. Edge quenching to a plate will leave a very large thermal mass in the meat of the handle and spine and heat will bleed into your edge and you will have a hell of a time hardening correctly.

--nathan
 
Pancho,
Just FYI, if you're going to go with an evenheat oven then shipping will be the same no matter where you order from. Evenheats are made to order by the facory in Michigan and ship freight to your door. I was hoping to save shipping by picking mine up at Sheffields supply but no dice so I ordered from Tracy Mickly at USAknifemakers supply. Service for the transaction couldn't have been any smoother !

-Josh
 
silver_pilate said:
There are many steels that cannot be plate quenched. Only air hardening steels are appropriate for plate quenching. Steels such as ATS34, 440C, 154CM, A2, etc. are all air hardening steels and would benefit from plate quenching.
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Thanks for the wonderful post. I have some questions.

How come only air-quenching steels can be used with plate quenching? Aluminum plate seems to be pretty fast quenchant for a lot of steels.

How much pressure should be used to clamp the plates? Should I put my weight onto it?
 
codtd,

Although it may seem fast, aluminum plates are nowhere near as fast as a good oil quench. In some steels, you have less than a second to get through the ranges of temperature in which pearlite forms. If you take longer than that, you will rapidly form pearlite throughout your blade and not acheive hardening. After that, you may form bainite if your temps to not drop quickly enought to around 500F (not desirable in most situations as well).

Remember, fast is all relative. Oil is much faster than aluminum plates. And the speed of quench needed has everything to do with what steel you are heat treating.

You may want to familiarize yourself with this thread:

http://www.bladeforums.com/forums/showthread.php?t=639019

--nathan
 
Nebulae,

You should be able to acheive 2200F in any Evenheat kiln (and any Paragon kiln if you make sure that you tell them you'll need that range).

As for being able to "go way beyond 2200F"....you won't be able to do much more than that. Most kanthal type elements max out at around 2300F no matter what type of mods you do. So unless you want to blow through a whole bunch of replacement coils, it's best to leave the oven as is.

--nathan
 
Thanks guys. Now once I get the oven I will ned saftey gear such as heat gloves, tongs, and face sheild. I will need aluminum plates also and quench oil.. Now if I want or need to cryo treat A2 do I really need nitrogen? I had some ATS 34 Hted by Don Robinson of Brownsville, TX and he cryoed the blades with dry ice. They really held a good edge. Is this a common practice and do you get similar results? What else would I need to get?
 
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Personally for the money Id go a DIY salt pot. Better heat treat than an air exposed oven.
 
nullack said:
Personally for the money Id go a DIY salt pot. Better heat treat than an air exposed oven.
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That is something definitely to consider . Atmosphere free . Have you looked at sugar creek kilns ? They all have there pros and cons .
 
A salt pot is definitely an option, but they have their dangers and downfalls as well. If you don't know what you're doing, you can be seriously injured, but it's the same with anything else.

I just use a welding gloove to get blades out of the oven and just wear safety goggles or a face sheild. I modified a set of cutters to act as temorary tongs, but I have some real tongs now to use. Before the cutters, I just used a set of really long reach needle-nose pliers with bent tips that I got at HF.

As for the LN, I was able to find a really good deal on a dewar through a BF member. You can find them used from the cattle business or dairy lots pretty easy. I'll make a run of several blades and go get the dewar filled to do them. The LN will last for several months in my dewar. You can use dry ice and acetone as well, and it's better than nothing and will help convert some of that retained austenite. You'll get somewhere around -100 with dry ice and -300 with LN.

--nathan
 
Don't forget to buy lots of SS foil. I've been without them a couple of months, it was just like a nightmare :barf:
 
Frank,

I bought an even heat oven about a year ago. I wouldn't trade it for anything.
You will be amazed at how much better your blades will preform.
before I got my oven I used my forge. I heat treated a lot of blade that way and thought I had it down pretty good. Looking back I think I was just getting by.
I know a lot of folks treat in a forge and make awesome blades.
The oven just works better for me. I sure don't want to step on any toes.
I also use my oven for tempering and have had much better results than I was getting with my toaster oven. I do still use the toaster oven at 350 deg. until the even heat cools down.

Greg
 
I understand about the hazards with salt pots, but specifically what are the downsides to it? I honestly dont see that it has any in comparison to an atmospheric oven? Thanks
 
Beyond the huge safety difference, the downsides to a salt pot are more on use ,maintenance, and storage. They require a large clear area to operate in, gas pots need proper air exchange in the shop, the salts have to be rejuvenated occasionally, the vapors are corrosive, and they take up more room than a counter top oven. In use, they may not be as suitable for ramp and hold HT formulae as a programmable oven is. Stainless HT is salt pots is a big deal, involving multiple pots and serious safety procedures.

Not to be the old curmudgeon here, but folks who are asking these kind of basic questions should not be thinking of salt pots. They are for experienced smiths with a full understanding of metallurgy and shop practices.

cotdt, and other newer smiths ( and many older smiths) should read the stickies on HT, and do some study on the subject before venturing into new territory, like stainless HT. A basic understanding of the TTT charts will show that the difference between the austenitization temps and cooling rates of 1095, O-1, A-2, 440C, and CPM M-4 put them into entirely different HT parameters.
Simple eutectoid carbon steel HT can be pretty basic. Stainless steels, hypereutectoid, and high alloy steels are a different thing altogether.

It is easy to just ask, "Can XYZ be done on ABC?", but the answer will only be good for that exact situation if you don't understand the principals involved. The use of the answer in a different situation could result in a failure. With a little reading and study, the answer will be understood ( and maybe the question not needed) and the information can perhaps be applied to other situations with good results. I'm not speaking against asking questions. I am speaking in favor of doing some study first.

OK, I'm off my soap box now.

Stacy
 
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