Installing high temp thermometer in forge

[Mohillbilly]

This is the forge I'm running.  I use primarily 5160 and want to better control my temps.  I know this is probably a can of worms, but want to know what the internal temp of my forge is and work on adjusting so that I can better harden.  what type of thermometer, where to get, and how to install in a forge like this.
Thanks,
Bret


 

[Mohillbilly]

p.s.

I have been away from the forge for about 3 years.  My first knife back is close to finish and will be posted shortly.  YAY!!!! :-)

[Lin Rhea]

I used a "K" type from Omega. Just drilled a hole in the side of the forge and stuck it in.

I would like to make a comment if I may. I also wanted to find out what temperatures my forge would reach and this allowed me to do just that. Found out that the forge would reach a given temperature. Right where the probe is.  

But after I found out, that's about all I needed it for. A forge is not an oven and your workpiece may or may not be as hot as the probe is reading. The forge will have hotter areas and cooler areas. The blade cant be exactly where the probe is and the presence of a blade in the swirling atmosphere of the forge will influence the reading of the probe.

Some might object to this observation, but I have one and I have fiddled with it some and that's what I have noticed.  

Unless you know what the actual temperature of the blade is, it dont do much good, in my opinion. You would have to be able to read the temperature directly by means of a lazer gun or know the temperatures by the color, or use an oven.

[Mohillbilly]

Lin, thank you for the information.  I guess I will try to work on my color recognition and try to work on my heat sequence that way for now.  

Bret

[gables]

I support what Lin wrote. I spent about a $125 on a probe and unit. I now know I can run my particular set up between 1600-1900. My best forge investments have been a 4" diameter stainless steel tube and a laser thermometer. I built my forge and it has uneven heat issues. I bought the tube longer than I needed and cut it into two pieces. The first piece runs the full length and sticks out the forge about an inch. I stuffed kaowool scraps in the far end to seal it. I also added a couple of stainless bolts inside so I can keep my blades upright. I use this longer tube for only heat treating cycles. The shorter tube I cut off is used for forging. I also stuffed small kaowool scraps in this piece. I use this to protect the points of my blade from overheating and I can block off the heat from certain areas to target the spot I want to heat. Again, this is a band aid fix to my forges issues but I like the results. I can insert the point into the wool and have the thicker spine up to help protect the thinner areas from over heating.

[Doug Campbell]

Morning Bret, I've had a pyrometer in my forge for years and while it's sure like Lin said there can still be temp variations inside your forge I'd hate to go back to not having mine. Like any tool you have it can take a while to learn to get the most out of it.

I'm assuming your wanting to control/know the heat for heat treating purposes mostly. I don't have a heat treat oven either so here is what I've done for several years and I feel I have very precise control with this set up.

Your looking at a piece of 2" stainless tubing capped on one end, that I put in my forge, (the "deflector" keeps the burners from blowing directly on the tubing). I put my "K" type thermocouple in the tubing with the blades I'm heat treating. I'll also put a piece of ceramic wool over the end of the pipe to make a fairly still attmosphere inside the pipe. By paying attention and turning the gas off and on I can control the temp within 20º or so while I allow the 5160 to "soak".
 
 

[Mohillbilly]

Doug,
I like the look of that set-up.  Where did you purchase your pyrometer and thermocouple.  Can you also describe your heat treating cycle for the 5160 roughly? Also, what is the thickness of your stainless 2" tubing?  Does it matter for durability in the forge environment?
Thanks,
Bret

[gables]

Thanks for the post Doug. I'm going to get me a longer probe from the popular auction site and and run it from the back of my forge into my stainless tube.

Mohillbilly- I got my probe and reader off of the popular auction site. I got a, 8 gauge kiln probe with the ceramic protectors. Get a long probe because you can always cut it down to length. The protective ceramic discs are 1" thick and can be added or removed to fit the best length. I got my stainless tube online found through a google search. I got the thickest wall thickness they had. I also got a small piece of stainless angle to use a a deflector as Doug described.

here is a good heat treating resource.

 http://www.cashenblades.com/heattreatment.html

[Mohillbilly]

Gables,
Thanks for the info and link....great stuff.  

I will check the site and see what I can find.
Bret

[Lin Rhea]

Doug, That looks like a good set up. You certainly can get a more consistant temperature like that. You basically made a small oven out of the pipe.

[Doug Campbell]

Yea it works real well for me, you've got to really pay attention to keep in the correct temp range though. If you get to day dreaming things can get out of control in a hurry.  

I got my original pyrometer from Baily's Ceramic but there are lots of options if you look around.

I fire the forge and bring things up to temp then put my blades in the pipe and put the ceramic wool over the end. Once the temp gets back up to where I want, (1525ish on 5160) I will turn the gas off and on as needed to hold it where I want. You'll have to play with it tp find what works best for your forge.

This is assuming you've already normalized your blade it is ready for heat-treat. After a 20 min soak I'll quench the blade in Park AAA, most times I edge quench 5160. I'll let the blade cool completely inspect it to assure averything is good then repeat the whole process at least one more time.