Do you measure metal temperature and how ?

I guess I should have been more clear. I'm planning on getting a piece of conduit just like you're using and more or less doing the same construction.

I'm going to see if I can connect the wires from the thermocouple directly to the plug I got from Clay-King. Assuming I can get that sorted, I plan on working out some way of attaching the pyrometer unit to the end of the conduit.

 

BTW, thermocouple wires are always colour coded, on K-type thermocouples, the wires are red and yellow, it's a little counter-intuitive but the red wire is negative and the yellow wire is positive

 

If none of your kit instructions says which wire goes to which spade on the connector, just google k-type pyrometer and you'll easily find the info. I already had an attachment provision setup on my conduit as described previously, but HT1's method of just slitting the end of the conduit and hose-clamping it will work fine.
I bought the $20 multimeter from harbor freight that has the k-type setting and outlet on it. It came with a little probe and connector so I just used that connector with a little of the provided wire and attached to the new probe leads.
My old setup usually showed about 35C ambient so I know it was off. My new probe shows around 25 so. I'm in Buffalo, not Tucson.
I try to creep up on my temp. Shooting for around 710C in aluminum, I preheat the tip till it shows around 550 and climbing. Then I shut off the furnace and dip the pyrometer. I try to get a feel for the rate of climb as the reading increases. I wait until the reading stops increasing and then bounces back a degree or two. If I've stopped at 690, I'll turn the furnace back on for 2 or 3 minutes and then pour. If it has gone over 700 and rising, I know I'm too hot and I'll remove the crucible and wait for it to cool down. It's easy to get fooled and overheat the metal. It takes awhile to finally get all melted, but once it does the temp shoots up fast.

Pete

 

slit the end of the conduit with a hacksaw, and use a small hose clamp to hold the thermocouple into the conduit. QED

V/r HT1

 

I don't know if anyone is interested in this, and haven't even gotten everything together yet, so I don't know if I like this idea...but I put together a mounting bracket for the UT302A thermometer unit.

The idea is to clamp it onto the end of the conduit, so the whole thing becomes a single assembly.

I put this together in Fusion 360. The model is here: https://a360.co/3CQUve1

It's not perfect, but it's close enough for now.

 

Got it put together. Much appreciation for the information I got here. This forum really is fantastic!

 

Nice build and video. At 1000 feet elevation in Omaha water should boil at 211. A precision deviation of .5% for a TC is not bad at all. Given the TC read you ambient temp prior to immersion at 82, I assume it does compensate for cold junction temp.

You may have folks lining up to buy the printed bracket!

Denis

 

LOL!

I'm not going into the bracket business! Hopefully others find the 3D model useful.

FWIW, I didn't put much effort into refining it. The print I ended up using was just the second run from that file. Initially, I had some of the parameters a little large, and the thermometer had a loose fit. With the second one, I reduced those parameters and it's a tight fit.

I should also mention that the nuts and bolts I used are 1/4"-20.

 

Just finished my first pour (Everdur) using the new pyrometer.

Everything went as expected. With the foundry running, I hung the probe over the exhaust vent (the hose clamp proved handy...just hang it on the edge of the hole) until it got up to 2kF or so, then dunk it in. Plenty of reach with this design to get into the metal with the foundry running.

The immediate lesson learned here is that I've been pouring at way too low of temperatures. I waited to test the temperature until I figured I was probably a little high. Then I'd let it cool down to casting temp.

(I was targeting 2150F for this).

Turns out not. My first measurement was barely 2kF.

Took a while, but eventually got it up to the 2150 I wanted.

I'm letting the flask cool right now. Really interested to see how this one comes out.

Thanks again to everyone here with the ideas/design/etc on that. I think this is going to be a very useful tool!

 

Great! Thats how I do it too. Overshoot then turn off flame and let it cool to 2,150 and pour. Works well. Post updates on casting quality!

 

Guess I should update.

Bottom line: I think I've got the surface finish stuff pretty well sorted.

The "big three", as near as I can tell, are:

1) Using the pyrometer to ensure adequate temp. I've found that if I overshoot a little (like into the low 2200's) it doesn't hurt anything, but you really want to be over 2150.

2) I started adding boron copper shot right before the pour. 1% by weight, so it's just a couple of ounces for my pours. The guys at Belmont advised me that this will have degassing results, and it seems to work. What I do is get the melt up to temperature, get the flask set for the pour, then the very last step is to de-dross the crucible, add the boron copper shot, give it a quick stir, then pour.

3) I re-engineered my vacuum table. I added an 11 gal air tank to the system. Before I pour, I close the valve on the tank, then turn on the compressor, allowing the tank to build a full charge of vacuum. Immediately after the pour (and I mean as fast as I can manage), I hit the valve and release the vacuum. That seems to be working really well, so well in fact that the flask ends up well and truly sealed to the vacuum table for a while. I use high temperature silicone sheet to create the seal, and that stuff has proven to be tough as nails.

All that adds up to getting some pretty good results.

 

Has anyone had success with any of the enclosed Tyke K probes off Amazon? I already have the HF multimeter with the K type hookup.

 

amazon is fine for a kiln, just not for dipping in metal. Go mifco, it's worth it.

 

Thanks Kelly, I am looking for entry-level contact pyrometry for molten aluminum, crucibles are smallish about 8" tall. I get asked what my temps were for my pours and I cannot answer.

Thanks Jason.

PS: just saw this: https://forums.thehomefoundry.org/index.php?threads/cheap-pyrometer-parts-list.33/

 

Ya mifco's probe is the way to go its only around $50 if I remember right.

 

Just called, ordered, SKU 004041, 62$US

PS: Shipping is less expensive to a business address.

 

Solid. I still have my original probe working well after 7 years.