Heat treat help

[Hot sauce 2884]

Hi, I’m a relatively new knifemaker. I’ve been progressing from kits to full builds and have recently begun heat treating my own knives using a propane torch and a small block forge.

I don’t have the money for ovens or tons of fancy tools. I use a magnet to test and see if my metal has heated enough. My question is, after the quench, if I file test it and it still seems to bite: will there be any damage done to the blade to throw it back into the forge and try again?

I am always indecisive on if the file is biting on the blade or if it’s biting on the scale from the quench. Sometimes it is very obvious it’s not biting at all and sometimes it seems to glide but also tugs a little.

Can anyone give me any advice? If I have question should I throw it back in and attempt again? If I’m over thinking and it is hardened will this damage the metal? Any assistance help.

 

[R.C.Reichert]

The guys might be able to help you better if you gave a little more detail. What kind of steel? What is your quench medium?

 

[JTknives]

You should know instantly if the blade is hard. There will be decarb on the surface but Normaly it’s not to thick. If the file keeps biting and you have removed .010-.020 then putit back in the forge and go alittle hotter. You will not damage it be doing multable quench’s. In fact back in the day that was the magic formula to make super knives. Mostly joking but it was a common practice.

 

[Hot sauce 2884]

I use mostly 1095 and o1 steels. My quench oil is usually canola oil.

 

[John mc c]

Canola is not really fast enough for 1095
That explains a file kind of biting like you describe,it's hardened but not as it should
Get some parks' 50
Canola is great for o1 tho
Just make sure you have enough oil to really agitate it and practice in a darkened room how to pump the blade in and out of the forge and keep it hovering around critical temp,when the magnet starts to want to stick to blade again give blade another couple of ins and outs of the forge and check again with magnet.10 mins soak time essential.practice and practice this and you will be able to make a great blade with tools you have and o1

 

[Stacy E. Apelt - Bladesmith]

Canola will harden a blade thickness in 1095.

You need at least a gallon of it .. preferably 2 gallons.

I listen for the sound of the file more than look to see if it made marks. It should "sing" like you were filing a piece of glass. If it digs in and removes steel, the blade is unhardened. If it just leaves a streak with hash marks, if may be just the decarb being filed off. As JT said, if you keep removing metal, it isn't hard.

You want the blade a little hotter than non magnetic, too. About one shade brighter red tan when the magnet stops sticking.

Few propane torches will HT a knife blade. You need a high output torch like the BrenzoMatic JT800 or equivalent.