Tempering?

[Jesse]

Ok so I get the heating up to non-magnetic and quenching in oil for blade hardening.  What is the tempering process afterward that I have heard gets wives steaming mad?  Something about an oven, some questions?
Is this done immediately after the quenching process BEFORE the metal cools off.
What temperature are we talking here?
How long at that temp?
What does this step do for the steel?  The knife?
I appreciate your insight....
I only need to build a belt grinder and forge to get started.
Blessings

[tomh]

what kind of steel are you talking about. that has a bearing on how you temper.
the thing that makes the wives mad is when you temper in the kitchen oven without cleaning all the quench oil off the blade. if you clean it off, it won't smoke and she won't ever know if you do it when she is gone ;-)
after quenching leave the knife submerged in the quench until it cools down.
depending on the steel it may or may not benefit from multiple quenching.
quenching makes the blade extremely hard and brittle.
the tempering process draws the hardness down to a usable level, ideally where the blade is hard enough to hold an edge, yet is easy to sharpen.
if the edge will flex as you draw it across a brass rod, and return to true, you have a good edge.
you need to research the heat treat process for whatever steel you are using. it helps if you are using steel that you know what it is.

hope that helps a little.

[Jesse]

probably a lawn mower blade.  Hi carbon content
do you have a website with references depending on steels?
thanks

[Lewis Brookshire III]

I use mower blades and what I do is quench in the oil and let it cool till I can pick it up with my hands, then put it in the oven on 390 degrees for 50 minutes then I take it out and let it cool to air temp then go put the scales on.

[Jesse]

so mower blades files and maybe old saw mill blades should be about the same correct?

thanks for the info.

On last question, those small countertop ovens if it can go to 390 - 400 degrees should suffice right?  Keep the work outside

Blessings

[LC]

Should be. Same process for sure but may take different temps. First yes small toaster ovens work fine just put a good oven thermometer in it to verify the temps are accurate.

After hardening clean off the oil and put in your tempering oven at 375 for a hour or two. Let slowly cool to room temp and then take it out and test with a GOOD SHARP file to see if it files the blade. If not increase the temps 25 to 50 degrees and do again.Keep doing this to your sharp file cuts the blade. You can see the problem of using "junkyard steel" cause there is lots of speer menting. But once you get a forumula for one particular piece of steel it should work the same on the rest of that particular piece of steel. Change type of steel and go through the process again. One thing that helps is you can buff your steel after heat treating so you can watch the color changes during tempering. Lots of steel tempers great at a straw or golden color while some takes going clear to blue. These colors buff right off when done.  One thing to make sure your using a sharp file if your using a dull file it will throw off your file testing and get mighty agraviating.

Welcome to the world of "junk yard" steel knife making. Alot of knife makers frown heavily on anyone using this steel and recommend good steel. Good high carbon steel is actually cheap but in all honesty I like the idea of giving new life to old steel.

[Lin Rhea]

This will give you a rough idea of the carbon content of some steels. Dont trust it completely. Use LC's recommended procedure.
  Junkyard steels  
                                         Lin