I managed to pick up a small oven at NAMES. Brand in Temco and it seems to be pretty old. Runs on 110V 50/60 cycle and draws 18 amps. It has a built in pyrometer that goes up to 2000 deg F. The interior is about
4x5x8 (give or take). I figure it will be useful for heat treating small things like the punchs and dies I plan on making for my roper whitney bench punch.
What are the odds the old pyrometer is accurate or even close?
I pluged it in and the relay in the bottom very slowly kicks in and out. After a bit (maybe 10 minutes) the pyrometer showed 500 degrees. I decided it was working at this point and deferred additional testing so I could check out the other things I bought.
Can't make an intelligent comment on the function, but, in my opinion, you did fine with the price. Burnout ovens aren't cheap, although they used to be a lot more affordable. I also recall 25 cent gasoline, though. Sigh.
Now that I think about it, I'm not sure I can make an intelligent comment about anything, but I'm having a damned good time trying!
There's a few guys on the group that will likely recommend a solid state controller for the oven, which could be a very good idea. I have an old, but virtually unused, burnout oven that jewelers use, slightly larger than yours, which I bought new years and years ago for eventual use in investment casting. I've used it for heat treat only thus far. I'd like to go the solid state control route eventually. The right unit allows for programmed temperature cycles, which is important for burning out flasks and having them ready for casting. You need not tend the furnace that way. May not be as important if all you intend to do is heat treat. A simple calibration may be all you'd need if that be the case.
Probably reasonable, as long as the thermocouple is still intact. (Assuming that this has a meter as part of it.) If it is just a duty-cycle type of timer, it will take longer to reach temperature, and will be subject to changes in the insulation quality and outside temperature to some extent.
That sounds like the duty-cycle type, I would replace it if I were you.
It sounds good to me. About what I paid for one of similar size which I controlled with an electronic controller from Omega which I had picked up earlier. (And a solid-state relay to handle the current, since the contacts in the tiny Omega would never handle that current.
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I can be numbered in that list. The Omega controller sells for something like $200.00 new -- and I got one for $100.00 unused from a project overpurchase that someone was getting rid of on here a few years back.
One of the benefits for the Omega controller is that it will run the header full time most of the way up --- and when it gets to something like 80% of the set-point, it will turn off the heater for a while, and observe the behavior as it overshoots, to adjust the approach to the final temperature. As a result, I can aim for 1800F and it will go no more than one degree F above that set point. Other systems without this feature will tend to overshoot a bit, and then coast back down to the set point. Depending on what you are doing, this may not matter, or may be very important.
While I was about it -- I added a tiny toggle switch in the wired between the controller and the solid-state relay, so I could turn off the heating element, and use the readout to watch it slowly cool down. IIRC, it takes about an hour to reach a full 2000F (which I think is near the top of the capability of that oven.)
This one sounds a bit small for that purpose. I know that I consider mine too small for that. The overall size of the chamber is about that of a single building brick.
That may depend on *what* you are heat treating. Some things, like HSS among others, likes to go through cycles of heat to this, hold for this long, then down to this, hold for this long, then heat back to this, and hold this long. For that - a programmable control is advantageous.
I also have a Old Temco, it came with a tube type pyrometer/controller. I got it for $10 at a yard sale, I bought a solid state controller for about $50 from Dwyer Instruments for it. Mine needed some minor repair on the door mechanism. I think you got a good deal, as mine did not work. Alan
I turned the oven on last night and let it heat up to about 1000 deg F according to the built in pyrometer. At that temp the inside of the oven was glowing a nice red. I placed a small piece of drill rod inside the chamber fairly close to the door. I suspect the temp is a lot cooler next to the door because the drill rod only glowed a slight red when observed in a poor lite room. At this temp I had the dial set pretty close to max. I looked at some Starret 01 and I need to get it to 1450. Not sure this oven will go that high. What will steel look like at 1400? Orange?
I was also very surprised to find I could put my hand on the top of the oven even when the internal temp is 1000 degrees. (yea I was damn careful to make sure it wasn't hot before touching it!)
I believe that some long reach tongs are on my list because a short pair of pliers isn't going to work very well. A friend of mine said he has seen blocks that are for setting things on. Should I make some from some fire bricks so that I am not setting things on the bottom of the oven?
How long was it on? Even after near an hour of melt time, my reverb. furnace is still touchable on top. Some of insulating refractory in the lid seperating 1500 to 2000°F and the room-temp world. If your oven uses kaowool (like fiberglass insulation but doesn't melt) I would expect it to be very nice indeed.
It has a nice bit of warmth after I'm done and bring it back indoors though. :)
Tim
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