Paragon Oven Questions

Michael J. Spangler

Michael J. Spangler

Joined
Oct 8, 2003
Messages
2,181
Hey guys i've done some reading on the ovens. they seem like the way to go over the evenheat. I've worked very limited time with both of the brands and i do like the paragon a lot more.

but will the 110V 14" deep model cut it for stainless steels? has anyone timed how long they take to egt up to temp?

I would really like something about 18" deep and if i needed to i would step up to the 24"

proably not worth having them custom buold an 18 for me right?

i would prefer the 220 model, but at 24" would i just be wasting a lot of energy heating up that chamber whn i normall do knives under 10"

and i over thinking this?

and any suggestion on where to purchase them would be great. seems like there were a few place online that were pretty good, but it can't hurt to ask again.

thanks ain advance guys you all rock
 
In general I'd say get a longer oven than you think you need. It sucks a lot to have something that won't fit in...

-d
 
From what I've read in other recent posts, it seems 110VAC ovens can take up to an hour to get to stainless temperatures, maybe 20 minutes for carbon steels. My home built 220V gets to 1500 in 5 minutes flat. You may be using a bit more energy to heat up a 24" chamber, but you'll have more coil, and it will take considerably less time with a 220V. Plus, if you ever do a massive bowie, it would be nice to have the space. :)

--nathan
 
220V does not mean that it costs TWICE as much as 110V. What makes that meter spin around is amperage draw as measured in Kilowatt hours, which is what you are billed for (kwh).
As far as time, don't be concerened about how fast it gets up to temp! You want that entire oven up to your target temp, NOT just the interior air mass.
I use an 220 Evenheat 18", and when I do spherodizing anneals, which take most of the night, or long soaks on 5160, I set the ramp to take the oven up to my target temp in 2 hours, so that the entire oven comes up with the internal mass. Then, I often let it soak at that temp for 30-45 minutes before introducing my work-of-the-day.
As well, I have placed a 1/2" thick piece of plate steel the size of the bottom of my oven to hold and evenly distribute the heat throughout the oven during work time. This keeps the oven from cycling to maintain temp.
Whether I have a month where I use the oven a lot, or if it's a month of forge heat treating and assembly, I can never tell by my electric bill.
 
Karl is pointing out a common misunderstanding on HT ovens. The pyrometer may well read 1500F in 5 minutes, but the whole interior must be fully at 1500F before a HT begins. It is penny wise and pound foolish to rush this . A HT program should start with a fully soaked oven. One hour startup is not too much to ask to make a stainless blade come out right.

As for which to get....get the 220V and get at least an 18" deep oven. You will regret it at some point in time if you don't.

The average rate for electricity in MA is 15.32 cents per KWH. At 1800 watts, a 220V oven will cost about 28 cents an hour to run.
Stacy
 
Interesting.... Would you guys mind expanding on that a bit? I can understand that the entire oven mass would take longer to heat to a give temperature than the TC tip, but I'm having a hard time putting it together beyond that. My blades are placed on their spine on a small refractory holder so that 90% of the blade is in open air. If the air is a steady 1500, wouldn't the blade be heated to the same? BTW, the 1500 in 5 minutes remark was from initial testing not involving blades, as I've seen ovens take 10-15 minutes to get the same pyrometer readout.

I place my blades in a cool oven and ramp up to 1200 followed by a 5 minute hold to let everything (I thought) come up to temperature and then push up to 1475 (for O-1 blades) and hold for 12 minutes before quench. All those temps based on the reading of the pyrometer. Is that satisfactory for heat treating O-1, or do I need to pre-heat the oven first? If so, how long do you let your blade have to come up to temperature before you start your soak period?

And if you're working with stainless, if you let the oven come to temp for a time period first and then place your blade in, how long do you give the stainless to come up to temp before starting the soak?

Just trying to put it together.

Thanks!

--nathan
 
With stainless you ramp up to a pre-heat, and soak at that temp for the prescribed time ( from 10min. to 1 hour) then you ramp up to the soak temp and soak for from 15min. to 45min.. The oven will be fully heated before it gets to those temps. You can start with a cold oven and the blade in it.
In a carbon steel HT the oven needs to warm up a while (30 min should be plenty) to get evenly heated. Then you put in the steel and soak for the desired time after the temp returns to the set point!. If you are doing a pre-heat ,say with O-1, then you can put the steel in the cold oven and heat the oven to 1200F and hold for 15 min to get the oven and the steel heated throughout. Then ramp to 1500F and soak 10 min.,once the set point has been reached. All times in HT are once the temperature has been reached.
Stacy
 
After the initial drop in temp after inserting blade into oven, and then the oven rebounds to the set temp, my blades in my setup, are three minutes behind the oven rebound. I've determined this with a high temp digital laser thermometer.
You could use one of those weak pocket-type, clip, telescoping magnets. After the oven rebounds to set temp, wait about two minutes, open the door and quickly check magnetism on the blade. I suggest using a small pocket type magnet so it's not strong enough to drag the blade out of the oven! Then, check it every miunute or so until you reach non-magnetic. This will give you ball park idea of rebound time.
I suggested the steel plate in the bottom of the oven and the long soak time for several reasons.
With a LOT of playing around with that digital laser thermometer I determined #1.) that simply by raising the blade off the bottom of the oven I changed its temp by as much as 30 degrees - yes, 30 degrees! There is NO moving air in that oven and things tend to stratify. Relatively speaking, it's cool on the bottom floor as compared to the ceiling where your temp sensor is! The temp at the bottom is NOT what your controller reads. Each oven needs a lot of testing.
#2.) The large plate I place in the bottom helps to not only raise the blade up, but it helps to even out the oven's temp with as long a soak as you have the patience for!
Thses things alone made the difference between getting a 5160 blade hard, and NOT getting it hard, even with the same soak time.
 
Good info guys. The tip of my TC extends into the oven (fairly shallow oven) to the same level as my blade's edge (near the middle of the oven). I need to check the rebound times for my blade temps to get a better idea how long things are taking. I've had good success with O-1 with a 12 minute soak after steady state, but perhaps a longer soak could be even better to take into account the lag of the blade temp.

--nathan
 
I have the paragon 110v kmd 14 and have had no problems doing stainless in it. At full ramp I will reach 2000 degrees in about forty minutes. I like Karl normally set to ramp to the desired temp in one hour. I program in the ramp to the soak temp and the hold time then ramp to the hardening temp at full power and program the hold timeand set the alarm. when the alarm sounds I take the blade out and air oil or plate quench depending on what steel I am using. I let the steel rest at room temp while the oven cools to the desired tempering temp then put the blade into liquid nitrogen and soak for the apropriate amount of time remove it and then temper. I have had no cracking problems with this method not even once.
 
sweet guys thanks for the info.

still don't know what to do. but i think i just might go with the 24 for the fact that i can HT a larger blade if needed.
 
Damn RJ your shop rocks. Thanks for the invite man. I really appreciate everything.

except the fact that you have me pricing up the cress kilns...:D

you know they do make a smaller model avaiable in 220... man those things are nice
 
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