Infrared Thermometer

[GRapp]

Do they work very good on steel around 1500-1700F? We have one at work that claims to read accurate up to 1920F.

 

[Stacy E. Apelt - Bladesmith]

A $15 HF laser thermometer says it is good to 2400°F ... but the truth is none of the ones you can afford are any good above 900°F.

I was watching a damascus video the other day and the fellow pointed his HF thermometer in the forge at an angle through the slit between two firebricks and stated his billet was at 1900°F and needed a little more time before welding it up. While the video was pretty good otherwise, that was just not right.

The reason they don't work for our purposes is they stop being accurate once the steel starts to glow. They can be calibrated for emissivity, but that would vary for every knife and situation. The EMS knob is how it is done. Cheaper units do not even have this adjustment. As said, even adjusting one won't guarantee it is accurate.

I have a very expensive lab unit (surplus auction steal) that I use for checking the grill, pans in cooking, tempering ovens, wall temperatures, etc. But I don't use it for HT because it isn't really accurate on knives.

 

[GRapp]

Copy that and thanks.

 

[ScarFoot]

Stacy pretty much nailed it. The one you have access to might well be accurate to 1920 degrees in certain conditions with known variables but outside of that won’t be trustworthy enough to get an accurate temp. Most people that have them don’t really understand their limitations. Emissivity, spot size/distance from target, ambient conditions/external light sources, surface conditions, material type and a host of other things can affect the reading they give. That’s true for the $15 HF “temp gun” and the IR cameras approaching six figures and more. They all work on the same principles. Very useful tools but generally misunderstood at the same time.