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Graham Gates(Ionic Muffin)

Heating source for wedding knife set

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I am familiar with most of the basics for bladesmithing and have made a few knives successfully. I am taking on a project of making a kitchen knife set for a friend's wedding. I am limited by time since the wedding is at the beginning of June. I currently have a coal/charcoal forge, and I have a gas burner that I need to fix since it isnt heating the forge properly(or maybe i just need to make a new forge body?)  I would be fine investing some money into an electric oven that could temper and heat-treat the knives, especially since I will be doing stock removal for the knives to save on time and avoid warping. I figured an electric oven would be efficent as far as time goes, since i could control the temperature precicely. I also read, that if I use a 220v power source it would be less costly for the electric bill. Then again, if its going to cost 100+$ for me to heat up the knives using electricity then I guess gas would probably be a better option. Just curious if electric would be a decent option or not.

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Electric Heat treat ovens for heat treatment and tempering are in my opinion the only way to go. You know what the temperature is and you can soak at that specific temperature for the time needed as per a certain materials HT instruction. I also use my HT oven as my Kydex oven for molding sheaths and for various other projects. 220v is the preferred voltage because as you said, it uses less electric and will heat up faster.

If you have issues with your gas forge post some pictures and maybe folks can help out.

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operational costs are the same  wither 110v  or 220v  the power used is the same. where do people come up with these ideas?

 

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With analog temperature control make sure you have a buffer between your blade and the heating elements

If the blade is close to the elements it could get uneven hot and hotter than your setting

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On the face of it, the Voltage *should* make no difference. However, when the current available is limited, which it normally is by the circuit rating, the maximum power available on the lower Voltage is reduced. This makes the time for the oven to reach temperature longer and results in more power being used over the cycle.

The difference in power cost-per-blade between 110V and 220V is usually pretty small in the real world: unless you fit a power meter to measure it specifically, you are unlikely to notice it.

The difference does get larger when higher temperatures are involved. If you are looking to HT some of the Stainless Steels that need temperatures well over 2000 degF, then 220V is most likely the way to go. If you are going to be working mostly with Carbon steels at around 1500 degF, it's much less of an issue.

It really boils down to how big and how hot you need to go (big and/or hot calls for 220V), and what power supply you have available.

I have a 3 kW, 230V, homebuilt HT oven with a chamber 7" wide, 6" high and 28" long. At the hour mark on full power, it reaches 2041 degF.

Once it reaches the temperature setpoint, it cycles power on and off to maintain the set temperature. At Carbon steel temperatures, the "on" part of the cycle is between 20% and 30%. It is considerably more for Stainless temperatures.

If we assume that a Heat-Treat cycle takes full power (3 kW) for an hour to reach temperature, half power for an hour to hold temperature and then switches off, that's 4.5 kWhr per HT cycle.

If we then throw in an arbitrary 25 cents/kWhr to get a ballpark cost, that's $1.13 per HT cycle. My oven is big and, even though it's on 230V, probably represents a worst case scenario. I don't know what you pay for power: you'll need to check your bill for the price per kWhr, but I'd expect it to be lower. 

For most makers, the energy cost for HT is likely to be insignificant compared to the cost of grinding belts.

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Timgunn said it here, as it was explained to me.

39 minutes ago, timgunn1962 said:

On the face of it, the Voltage *should* make no difference. However, when the current available is limited, which it normally is by the circuit rating, the maximum power available on the lower Voltage is reduced. This makes the time for the oven to reach temperature longer and results in more power being used over the cycle.

A 110v HT oven takes longer to come to temperature due to the available maximum wattage, and over that time some of the heat transfers out of the oven and needs to be replaced, lengthening the cycle more. Coming to temp faster with a 220v creates marginal savings in allowing less time for heat to escape, but savings none the less.

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The reason to with 220 instead of 110 is the amperage draw. 220 will pull one half of the amperage that 110 will. If a 110 kiln pulls 50 amps the same setup in 220 will only pull 25 amps. 

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9 minutes ago, BIGGUNDOCTOR said:

The reason to with 220 instead of 110 is the amperage draw. 220 will pull one half of the amperage that 110 will. If a 110 kiln pulls 50 amps the same setup in 220 will only pull 25 amps. 

for wire sizing and voltage drop loss calcs yes but for total power consumption no, In a resistive load like a heating element Amps X Volts= Watts so end cost is basically the same minus VD losses on the 240 volt circuit. You can't get around Ohms law.

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Marc1, we have 3 phase , but not in residential settings. It is out on the industrial, or rural areas. Out where I live I can have it pulled in from across the street from my property, and I can go up to 480V.

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Yes, if the wires are far away it becomes expensive. I only had to come from across the road.

400V 60a x ph and 50 hz. Keeps the Lincoln Bullet Welder happy. :)

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