Components needed for heat treat oven?

A

Andy Johnston

Joined
Feb 10, 2014
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Hey guys. I am planning on building a heat treat oven this summer. I have found a few plans such as this one http://www.freewebs.com/knifemaking/HT FURNACE.pdf and several others over on british blades. The problem I have is that none of these plans tell me what I need for electrical components. I know that pretty much every pid controller will run on 100-250 volts, which is good because I have no way to do 220 right now. I know that the element needs to be rated to 2300 and that the thermocouple will need to be for a kiln also rated to 2300. Other than that I have not seen any mention of the other parts I will need. If I could get any advice on what electrical components I will need for a 120V oven that would be awesome. As far as the physical construction of the oven goes I am pretty much set. I even recently found a local store where I can get refractory bricks for 2 bucks a piece, which cuts my build cost by at least 60 bucks if not more. Thanks again for all the help guys.
 
I've looked through the thread that steelslaver did and I downloaded the schematic that jtdesigns drew up, but everythings for 220-240. I also have not seen anything talking about a power supply or anything on how to power it, just the wiring of the controls its self. I have another window open right now with the following links based on what other threads have suggested.

http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=4

http://auberins.com/index.php?main_page=product_info&cPath=3&products_id=39

http://www.auberins.com/index.php?main_page=product_info&cPath=3&products_id=40&zenid=52501b8d6a7f7a3ad3287bd500a87dd8

http://auberins.com/index.php?main_page=product_info&cPath=3&products_id=119

http://auberins.com/index.php?main_page=product_info&cPath=2&products_id=9

http://auberins.com/index.php?main_page=product_info&cPath=2&products_id=45

I know I must be missing stuff and I am still unsure of exactly what I need for a 120V build. I have read several places that 120V ovens only need one element, but I am unsure of that now. I am also unsure of if I would need 2 ssr's for a 120V build.
 
If you're running the elements in series there'd be no need for 2 relays. You can get the same wattage (power) out of a 110v and 220v elements, you just have to run twice as much current through them (elements would need half as much resistance).
 
The first electrical thing you need is electrical knowledge.



It is critical that you fully understand how the oven works before you get any parts.....not just a general idea of how it works. The most common error is getting the wrong elements because you were just going by some plans downloaded from the internet. You HAVE to be able to calculate the resistance of the elements needed for your particular build to get the right ones. This is a product of length, diameter, and resistance per inch. If Ohm's law isn't part of your mental toolkit, either get very familiar with it or get someone to help you who is.

Many people say, "I can build anything with a good set of plans and a parts list."...... and they may be right. BUT, building a HT oven can be a tragic waste of time and money if you make even one accidental calculation or connection. We have a thread on this forum regularly where either the oven only heats up to 1600°F, takes an hour to heat up, or burns out the elements in seconds. Do yourself a favor and get fully familiar with all the details before cutting the first piece of metal or ordering the first part.

Be aware of the fact that changes and re-calculations are needed on any British Build, as electricity is run differently there.
You said 220 was not possible. Is there no 220 dryer or air conditioner in your house or apartment? A 120VAC HT oven will have to give up something to run on a 20 amp circuit. Think the operating voltage over fully before you decide to go with 120VAC unless it is truly impossible.
 
I know that ohms is the resistance that electricity faces when going through a wire and the most basic formulas used to calculate it. Voltage = Amps*Ohms, or to find the ohms Ohms= Voltage/amps. If it was as simple as that then I would need 6 ohm resistance, but I know I need to keep my wire gauge (smaller the number bigger the wire) and length in mind. I have not found a good source to teach me how to calculate that. I have been trying to research as much as I can as I know I am not good with electrical things. My father is as he and my grandfather did all of the wiring in our house after they and my uncle built it years ago, it is just not something that was passed on. I am willing to learn and take any and all advice I can get here. As far as my choice of 120V I know thats what I need to use. I have a washer and dryer in my apartment, but no possible way to access the outlet. I would have to move the washer dryer combo out to far and it would break the dryer exhaust. The air conditioning made me laugh a little bit because we have just had some of our warmest days in the 20's up here. If it were possible at all I would of course use 220, but for now its just not.
 
After doing all the research I could and Looking at the circuits I have in the apartment I don't think that I will be able to make the build work right now. The majority of the fuses are 15 amp other than the plugs that I know I cant use. The plugs outside by the porch are not even labeled on the breaker box so I don't know what they are. I can only assume they are 15 amps also. I just don't think I would be able to get the power I would need. Thanks for the help anyways guys :/
 
I currently have 1095 as I bought it before I really knew anything about knife making, heat treating, or really anything about this whole process. Now that I know more (didn't know Id know so much about electricity) Im probably not going to use 1095 again for a while, but I would like to. From what I've seen on the forums a lot of guys like 1095 and is a great steel. If I had a ht oven I would for sure keep using it and invest in some parks. As for blade size Im only going to be making small hunters/skinners for now so I'd say 10 inches over all would be the biggest knife I'd have.
 
There are many places which will do the heat treat for you once the blades is ready, I would really recommend that and wait until later to take on a kiln,
 
If the bulk of your blades will be carbon steel, a forge with HT capabilities is a good option. It can be on a rolling cart and rolled out in the driveway or patio for use. Even if you never forge a blade, it will be good for HT and annealing/normalizing. All you need is PID control and it can hold a very good temperature control. The stickies have a section on it. Such a build will cost about the same as a home made HT oven. You can easily sell it if you get an oven later on.

Sending them out in the beginning is a good idea, as it will eliminate one part of the problems encountered in getting started. As your blade grinding and finishing improve, then consider adding HT to your skills.
 
I know a guy back home that has told me to come by and he could show me some stuff and heat treat what ever knives I have that are ready. His names Delbert Ealy. Problem is I am at college 4 hours away. I hope to get home next weekend since it is spring break, but the fiancee doesn't know her work schedule. Hopefully everything works out and I can get my 1095 treated and then buy a different steel.
 
If Delbert invited me to his shop, I would make it a priority to find a reason to go. File and sand up a bunch of blades and go home on a weekend.
 
+1 to Stacy there, if Delbert Ealy invited you to his shop that's what I believe they call an opportunity. Do it!
 
Andy Johnston said:
After doing all the research I could and Looking at the circuits I have in the apartment I don't think that I will be able to make the build work right now. The majority of the fuses are 15 amp other than the plugs that I know I cant use. The plugs outside by the porch are not even labeled on the breaker box so I don't know what they are. I can only assume they are 15 amps also. I just don't think I would be able to get the power I would need. Thanks for the help anyways guys :/
Click to expand...

15 amps should be more than enough for a 1500W oven running on 120VAC. You might even get away with a little bigger, depending on what else is on the circuit.
You should be able to find an applicable element here: http://www.duralite.com/store/scripts/prodView.asp?idproduct=108

Another thing that's fairly easy to do (assuming the elements in the circuit can support it) is to swap out one of your 15 amp breakers with a 20 amp breaker. Remember, however, that a circuit's protection is only as good as it's weakest element. Also, the NEC requires that 20 amp breakers have 12AWG wire (or heavier) for the conductor. It's possible that you only have 14AWG wire running to your outlet.

All that being said, I fully agree with Stacy: You need to understand exactly what you're doing and how the oven works, before you do anything. You are working with some potentially lethal voltages, as well as some very high temperatures. It's very easy to get severely injured (or even killed) or to burn your shop down if everything isn't done correctly, or if short cuts are taken.
 
P=U*I, so 15amps at 120V would be 1800W. I would definitely not recommend replacing any breakers with a higher value, if you are not absolutely sure the wiring can take it. A lot of factors play into this. Is the wiring laid directly into the wall, or wall insulation or is it inside a cable shaft etc etc.

There are tables were you can just read off the max. amp value for a certain wire gauge depending on how its installed, but the ones I have are all in 230V and mm² instead of AWG.

I am also not familiar with the law in the US, but I assume that your insurance wouldn't pay if something happened because you changed the fuses.
 
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