Need help installing my new thermocouple to my forge!

C

coldsteelburns

Joined
Aug 2, 2010
Messages
1,611
Hey, I just recieved an order I made from Auber Instruments about a week ago for a pyrometer, thermocouple, ceramic covered probe, along with a ceramic sheath for the probe. I had no idea that the probe and ceramic sheath would be as big and long as they are, I expected something about 1/4" in diameter, but this is about 3/8" dia (the ceramic covered probe istself) and the ceramic sheath is 3/4" dia and they are both a foot long :o .. Anyway, I took a few pictures of everything I recieved as well as a couple pics of my forge so I could hopefully get some help and advice as to how to install this to my forge and where would be the best place for it to go. I should add that I ordered this mainly for heat treating my blades (1095, 1084, W2, 52100 etc.) and not so much for forging, so I can adjust my burner etc. to get a good HT temp in my forge, not for automatic selenoid controlled forge heating or w/e it's called lol.

So first, here is what I ordered (I chose the ceramic probe with the ceramic sheath option) : http://www.auberins.com/index.php?main_page=product_info&cPath=17&products_id=199

And here is a serperate page on the ceramic probe and wire and ceramic block it came with (I also got the ceramic sheath but that will be self explanitory in the pics I will provide of everything below) : http://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=39

Ok so here are a couple pictures I took of it all together :



And another....




And here are a couple pictures of my forge so I can get some help as to where and how I should attach it...



And another view to get an idea of it's size and length...




Alright so there ya have it, I really need some help as to how I should go about hooking it up to my forge, like should I drill a big 3/4" hole in the side of my forge to fit the ceramic sheath or should I just lay in it through the small back opening of my forge etc. ? I really appreciate any and all help I can get for this, I wanna hook it up ASAP! But I want to do it right so I don't ruin the thermocouple etc. or ruin my forge by drilling large holes in the sides of it. BTW This was what was recommended to me by the guy I emailed who works there, I told him I was lookin for something I could use in my propane forge for heat treating knives. Thanks! :)

-Paul
 
Last edited by a moderator:
First, you can shorten the TC leads and sheath as needed.

The normal spot for the TC in a forge like yours is on the top about 2-3" forward of the burner entry.
If that spot seems good, drill a 1/4" pilot hole at the top. Be gentle as it passes through the lining, as it may try and wrap up the wool. Enlarge it in the metal shell until the sheath will go in. Open up the hole in the satanite to let the sheath go all the way through until it sticks out about 1-2". Trim your sheath with a diamond saw, cut off disc, or other method. Practice near the end first and when you have the cutting figured out, cut at the desired length to allow it to stick out about 1-2" inside and 2-3"outside. You can use satanite to mount the sheath in the forge permanently. Don't cover any more of the exposed sheath in the chamber than needed to get a seal. Don't put ITC-100 on the sheath. Place the TC in the sheath and cut the leads so they stick out about 1" when the TC is bottomed in the sheath ( remove spacers as needed). Mount the TC terminal block on the TC leads so it sits right against the sheath. Tighten down the screws snug.

Attach the TC wires and plug, paying attention to the polarity on both. If needed put some sort of support next to the forge to keep the TC wire from laying against the forge outside. When all is hooked up, plug into the reader and turn on the forge. Check that the start temp was about room temp and that the reading goes up as the forge heats.

That should do it.

Plan "B" would be to hook it all up at full length and set it on the forge floor sticking in from the back. That will read the temp right next to the blade. This can be done as a temporary or permanent setup. If you go with this method, take a firebrick and drill a hole through it to fit the sheath so the brick can sit behind the forge like the one in your photo. This will hold the TC sheath and TC in place, but allow removal when forging or doing work where the TC is not needed.
If you decide to install it in the top later, just cut the sheath and TC as needed and install as above. There will be no problem from using it full length first.
 
I don't know what he paid, but those packages usually run about $100.

You can get the TC, Sheath, Terminal Block, and Wire kit on eBay for $30-50.
A $30-40 PID makes a good reading device and can later be easily converted to PID control for the forge for another $100 or so.
If I was going to do it, I would go with the PID and a component kit.
 
Wow, Perfect! I could not have asked for better instructions! Thanks a lot Stacy, I really appreciate that you took the time to type it all out like that! :) You answered everything I can think of. Well there is one small question. I was reading in an older thread on here about TCs etc. and a guy suggested that he trim the TC leads as you did , but he sounded just a little "ify" as to whether or not it "might" somehow mess with the readings. Would there be any reason it could cause any trouble with the read out as long as I make sure the tip of the TC doesn't get messed with? Thanks again man, gread info! :thumbup:

Don, I purchased it all as the single package it shows in the first link I posted (with the option of the ceramic probe with ceramic sheath) for $79.51 plus the $13.50 in shipping, so a total of $93.01 :D But I'm sure Stacy has got ya covered by now :)

-Paul
 
Last edited by a moderator:
The TC reads only at the junction. That is the point where the two dissimilar wires are fused. This junction creates a small voltage when heated. The amount of heat is directly proportional to the voltage created. The reading unit merely reads the millivolts and displays the voltage as a number that we see as temperature. Shortening the leads will not change the voltage created. However, you want enough lead length for the insulation on the wiring at the terminal block not to melt. Most folks stuff a bit of kaowool in or around the end of the sheath to keep the heat in.

For best results, the TC tip should be in direct contact with the sleeve, thus you stick it all the way in. The closer to the blade the junction is, the more accurate the readings are, but practicality dictates that as being not always possible. In most forges, somewhere near the center of the forge is close enough for our purposes.

Fun romp down memory lane:
Back in my youth, if someone wanted to build an accurate temperature reader, they often fused the chromel and alumel wires themselves and connected them to a very accurate milivoltmeter. You took a reading and looked the correlating temperature up on a conversion chart. If you were fancy, you made a paper dial for your meter and marked it by hand with the temperature readings you calculated. Somewhere, I still have one of those lab grade milivoltmeters in a beautiful wooden box. It has a diamond pivoted needle indicator.
Here is a link to the charts used to calibrate TCs or to convert readings from a milivoltmeter.
http://instrumentation-central.com/pages/thermocouple_reference_table.htm
 
Awesome, more great info! Haha, I'm glad I don't have ta mess around with trying to convert things myself, it'd be one more headache I don't need at the moment, plus that's why I spent my money on something that would do it for me :D lol

I was thinking about making a muffle for my forge that I could use to better distribute the heat on the blade when heat treating, and while doing so, welding a piece of steel on the back of the pipe then drill a hole in that to accept the sheath, or probably a tube just a bit larger in diameter than the sheath that it can slide into without putting undue stress on it. I saw all of this on a thread from a differrent forum and thought it was an excellent idea, at least for my type of forge. Here is a link to the thread that shows it. It's about 2/3rds of the way down the page and posted by a user named "Kentucky" http://knifedogs.com/showthread.php?27466-quot-The-Alaskan-quot-WIP/page4
I may try this but it if becomes cumbersome to deal with due to the ceramic covered TC as well as the big ol' ceramic sheath, I will deffinitly go the route that you've instructed me.

Do you have any thoughts on this setup? Maybe if I went that route I wouldn't even need the sheath? Sorry for all the questions, as you have more than idealiy answered my original post! I just figured it would be worth sharing to get any opions on that method as it's not further discussed on the original forum/thread it came from. I really appreciate you're help and input Stacy, thanks again man! :)

-Paul
www.youtube.com/Lsubslimed
 
You are correct, if the TC is placed in a muffle, it won't be in the direct flame, and the sheath will be unnecessary in that use. The sheath would slow down the reading time as well as take up valuable space. For best reading, the TC tip and blade should be close to each other in the muffle. It won't hurt anything if the TC lays right on the blade ( with its insulators on the leads, of course).

I wouldn't bother with a closed end muffle, but it won't really hurt, either. Make sure the ceramic insulators on the TC go all the way out the muffle to avoid shorting out the signal. The tip can touch the blade or the muffle, but the leads need to be isolated from each other. Bend the TC lead ends down as needed to keep the block/connectors and wires out of the blast. This type application is when leaving the leads at full length helps.

While a muffle and TC is great for accurate HT, the forge top TC and sheath installation is still a good idea, too. It would be best to have two TCs ( They don't like to be moved after they have been heated several times), both with wire leads and a plug. Just switch the plug at the reader to use one or the other. Some readers/pyrometers have multiple sockets/inputs and can be switched back and forth between two or more TCs.
 
You must log in or register to reply here.
Back
Top