Not sure you can get the "pipe" oven hot enough in a small forge wihtout burying it in the coals as you will continually lose heat on the top side. An end cap on one end will make it more efficient, but it still needs to be covered to maintain consistent heat.
Agree with Ray on the laser, working right at the top (or bottom) end range of an instrument is always iffy and not certifiable in industry. The T couple is a much more accurate route, however with an open coal forge, the effect of the surrounding heat outside the pipe will adversly effect the readings unless you can devise a way to attach that avoids this heat (which in turn indicates you will have a cold spot differential at one part of the chamber). Having worked on the instrumentation of industrial incenerators and heat exchangers as well as many other types of industrial equipment, I can tell you that the T-couples are much more accurate, but come with their own set of vunerabilities. You have to protect the lead wires and instrument from the heats. Industry standards require iconel stilling wells or sleeves to protect the end and leads of the T-couples. On a small muffle furnace...Paragon type HT oven, only the tip portion is exposed to the interior of the furnace heat chamber.
As you can see by the time you get all this divised to work consistantly right in a small open coal forge....you are pretty much hunting field mice with a .577 Snyder. Not to mention the bulk and set up each time you build up your heat nest. A quick check with the T-couple of your chamber to check it's interior heat (when all of it's the same color) will give you reasonably accurate results. Once you get it stable in the range you want, let your blade reach that same color (all but disappears) with no shadows or bright spots and you are ready for quenching.....provided your quench is up to the correct temp as well. Get it all correct at the same time or you are just shooting craps with your HT.
__________________
Carl Rechsteiner, Bladesmith
Georgia Custom Knifemakers Guild, Charter Member
Knifemakers Guild, voting member
Registered Master Artist - GA Council for the Arts
C Rex Custom Knives
Blade Show Table 6-H
|