1095 Heat Treat NightMare !!*Update*

[Remyrw]

Every exposed surface. Generally it's a very shallow layer though, so when folks grind the secondary bevels in for the edge it tends to remove enough metal at the edge to do the job. If you've got bad decarb though... Remember, usually it's only a few thousandths of an inch. It's only when there's something causing excess decarb that it becomes a major headache.

 

[stevomiller]

I recently built an oven and had trouble getting knives to harden consistently at first........ I used an infrared thermometer to measure the controller temperature and the thermocouple to copper junction temperature.......found that the temp of the thermocouple connection to the copper wire was directly related to the error in indicated temperature and that temperature was almost directly related to outside air temperature....... my oven will read about 30 degrees hotter than it really is because the thermocouple only tells the DIFFERENCE between its two ends......

Great experiment and use of intuition ;~)

Couple quick comments that might apply in your case (or not if I misunderstood):

1) Is your IR thermometer adjusted/calibrated for the emissivity of the materials you were checking? Different surface textures, colors, etc will greatly impact the reading. Another way to determine the temp at this junction is to use a cheap thermocouple of the same type (if your controller has two inputs that is),

2) Are you running a copper extension wire from the thermocouple to the controller? It's best to use TC type specific extension wire and not copper. You will reduce the offset, and it is also guaranteed as far as accuracy.

Best,
Steve

 

[Jason Magruder]

Stevomiller, I tried to calibrate the infrared thermometer to the emissivity by measuring pieces of steel in boiling and freezing water. I checked with both clean and heavily scaled steel and there was a difference of a few degrees between the two. Plastic, wood, and micarta all had vastly different readings though. I checked both of my thermometers this way, a $15 dollar cheapie from Amazon and a $30 one from Harbor Freight. The Harbor Freight one read within one degree of boiling and freezing points of water on the scaled steel while the Amazon one consistently read 5 degrees lower.

I ran copper wire to the thermocouple. Yeah, I know I should use thermocouple extension wire but I didn't learn about any of that until I had already put the thing together. :foot: