tempering color question.

R

redd1981

Joined
Oct 4, 2011
Messages
251
I just heat treated a couple knives from aldos 1084 and used a brand new oven thermometer to find 450 in my toaster oven (kinda tricky) I covered them with a thick folded sheet of aluminum foil and set the thermometer on top just to make sure I was keeping a consistent temp.

My question is this, after the first 2 hr cycle Im seeing a little bit of straw brown on the thick parts but its a bluish color along the thinner edge and tip. Is this ok or did I ruin the cutting edge by making it to soft? the edge is about the thickness of a dime btw.

Thanks.

EDit: I realize color is not the best indication of results but Im under the impression that it has SOME merit in giving a general idea of things. please correct me if I am wrong.
 
With oxide coloring its hard to get an accurate read. Light blue is 475, 500 or so. the golden straw color is 400 or so. Just a guess but I think your ok. See if a new file skids over the edge.

Fred
 
if you mean the hardening process yes paint can forge to non magnetic given another 20 count quenched in 130-140 deg vegetable oil quick scrub with dawn and straight into preheated toaster oven for a tad over 2 hrs quenched in running water and thats when I noticed the color and figured I would ask before the second cycle.
 
I've read that the colors coming out of an oven can vary a lot. The oxide colors that you might be thinking about are used when doing a temper using a torch or red hot piece of metal to soften from the spine to the edge of the blade. If your thermometer is acurate then your temper should be good.
 
The problem with many toaster ovens is getting the blade too close to an element. The blade can get much hotter than the thermal setting. I would much rather use a kitchen range with the blade buried in clean sand and have an oven thermometer right there beside it.
 
Unless there isn't a kitchen oven within a days drive, a toaster oven is not the best thing to use for tempering.

There are several threads for making a PID controlled toaster oven and how to try and make the temps more even. Putting the blade between two plates of aluminum ( 1/8" thick) will be a lot better than using folded foil.

The standard gas or electric kitchen oven works fairly well as is. Putting the blade between two sheets of metal helps here, too.

You are smart to use a thermometer rather than trust the dial on the oven, as these can be far off. The best method is to use a digital oven thermometer, and place the probe under the blade between the plates of metal so it is reading the actual blade metal temp.
 
I've noticed when blades are tempered while wrapped in foil the oxide colors make it appear the blades were tempered at a higher temperature than they actually were. Even a 400 degree temper results in blue oxides. I don't know why, I just know it happens consistently.
 
You must log in or register to reply here.
Back
Top