C° Temp Gauge for shop use?

[Manuel-Pagani]

Hello, I found this in the junk yard.

Someone already use one of these in a gas forge? It seems to be usefull for tempering using the forge as a oven, What do you think?

[WayneCoeArtistBlacksmith]

Looks like it will work.  One of the guys last week used one that looked like that on Forged In Fire.  And since you are in Argentina you don't even have to worry about converting C to F.

Wayne

[Latticino]

Definitely good for tempering.  At forge welding temperatures the, presumably, type K thermocouple will break down more rapidly than you want.  Not sure how accurate they are above, say, 2100 deg F, but it will still give you a general idea.  I've used on in my forge, with a ceramic thermocouple well to protect it somewhat from extremes and flux. 

[WayneCoeArtistBlacksmith]

I should have mentioned in my reply, I only use my pyrometer when I need to know more precise temps, welding and temp

[ThomasPowers]

For high temps a so rated optical pyrometer avoids the thermocouple breakdown issues

[timgunn1962]

It's probably a type K, but maybe a type J. It is quite likely to have it marked somewhere on the gauge.

The thickness of the "legs" on the thermocouple itself strongly suggests it's a base-metal type, not a Platinum-based type (R,S or B), but it's worth checking: in the (unlikely) event it is Pt-based, the scrap value of the thermocouple would certainly build (and perhaps even buy) you a new forge with temperature measurement.

I don't recognize the colour coding on the wiring. There have been lots of different standards in different places though and I'm only familiar with one or two (I am also colourblind to the point where I sometimes need to ask someone else what colour things are  when wiring up instrumentation at work).

https://www.omega.co.uk/techref/colorcodes.html 

If you really need accuracy, I'd be a bit wary of using it as-is, unless you have some way to check the calibration. 

Ice/water is the usual check for zero degC, but it's not much use with a scale that starts at 20 degC. Human body temperature at 37 degC would give a readily available fixed point for checking at low temperature and boiling water at sea level provides a fixed point at 100 degC.  It gets a bit more difficult finding usable fixed points at higher temperatures though, and it's less easy than it sounds to get reliable ice/water and boiling point fixed points. 

If your forge temperature is sufficiently adjustable, decalescence/recalescence might provide a reasonable check temperature.

Using the forge as an oven for tempering does not sound easy. The thermocouple and readout would certainly work at Austenitizing temperatures (usually somewhere in the region of 800 degC), but getting a forge to run down in the 150-450 degC range which covers most tempering operations is definitely pushing the boundaries. I certainly cannot manage it with a forge that will reach forging temperature. I can get stable temperatures from about 750 degC to about 1500 degC from a forge, using a burner based on a commercial Venturi mixer. Going much below about 750 degC (1382 degF) is difficult with my setup.

I am pretty confident I could build a purpose-designed gas oven that would do the job, but that's a whole different animal: certainly not a forge.

 

 

[Mikey98118]

On 7/28/2017 at 8:47 PM, Latticino said:

Definitely good for tempering.  At forge welding temperatures the, presumably, type K thermocouple will break down more rapidly than you want.  Not sure how accurate they are above, say, 2100 deg F, but it will still give you a general idea.  I've used on in my forge, with a ceramic thermocouple well to protect it somewhat from extremes and flux. 

Dead on. Home founders like to use them to check crucible contents for pouring temperature; some guys have set up their casting furnace with a small peep hole to run the ceramic sheiled thermocouple through, but it would be more useful to check for tempering temperatures; they consider the thermocouple to be just another consumable.

[Manuel-Pagani]

Thanks for the info, I been using it and seems to work fine. Is not high-tech but now I have an idea of how much temperature is my forge . 

 

[jcornell]

I use a thermocouple and PID style readout on my propane forge.  I'm outside, and I've learned the hard way that I can't really reliably tell temperature by color when I'm forging in my back yard.  The readout is valuable when I'm working weird steel - like S-7 which won't begin to move until you're above 2000 F and when welding.