I have several old rasps I want to convert to knives, what is the best way to anneal , and then retemper them. I,m pretty new at this and just hope I,m asking the right questions.

Edited May 10, 200917 yr by mikeb

Search this site for annealing and heat treating There has a lot of information posted on here.

i thought the best way of annealing hardent metal is by making it about white/yellow and then letting it cool in the air, that's my way

but i'm not sure if it is the best way

Welcome aboard Mike, glad to have you.

Do NOT heat the steel above non-magnetic during heat treatment. Orange or yellow is WAY too hot and will damage it.

Gradually heat the piece and when it starts approaching bright red start testing with a magnet. Pull it from the fire and touch a magnet to it, if it sticks put it back in the fire, if it doesn't stick put it in a bucket of perlite and leave it till tomorrow. If it's real thin heat a larger piece of steel to near non-magnet to bury with it to slow cooling.

If you click "User CP" at the top of the page and edit your profile to show your location it can make a big difference. IFI is represented by members from more than 50 countries and a lot of info is location specific. Also, if local folk know you're there they can invite you to get togethers, tip you to tool deals and offer hands on help.

Frosty

Just a point about old rasps and files. After softening, get rid of the teeth by grinding or you risk cold shuts in your work.

If, like me, you don't have a bucket of pearlite just standing by, I've heard that woodash works almost as well.
my $0.02

Get them red hot and tuck them in aq material that keeps air away. Pearlite, ashes and a host of other things will work. The main thing is a slow cool down.
Finnr

If you have a well insulated forge,and you don't have pearlite or vermiculite, you can leave in the forge and just shut the thing off and block the openings with hot bricks when it is at or just below the correct temp. Adding a large mass of hot steel helps, too.

I have a forge with firebrick floor and then "wool" under the brick and under the roof, with "wool" side insulation. It is venturi type. I put whole firebricks across openings, careful not to close too much and limit airflow. This helps with reducing hot spots and getting more even heating, too.

I also place bricks just in front of opening to forge, so they get HOT. When time to anneal, I shut off forge with item inside. I then rapidly turn hot bricks so that they totally block the forge. If I had a kayowool blanket, I would put it over forge and bricks as last layer. In my forge, a knife sized cross sections cools to around 500F in about 4-5 hours. Not as good as vermiculite plus hot mass, but...

This is a really simple trick, it works for 10xx and w1 or w2 and o1. It is not good enough for many other types of steel, where vermiculite with a hot brick or large piece of hot steel would work much better. It is just a way that works easily if all you have is your gas forge and fire bricks.

You can get neat patterns on outside if you grind everything smooth but still leave the little "half moons" from the teeth. Looks like fish scale or feathers. This pattern happens if you forge to shape and then grind teeth off. If you ground teeth first, there would not be the little oxidized half moons at the base of each one. So, the surface of this knife is smooth as glass, but it has the "feather" look. If you leave the teeth during forging, don't forge the "middle" section too thin. The teeth will be nothing but a lot of cold shuts and weak spots after forging. You will need to have enough spine left between them, so that when they are 99.5% ground away the knife has sufficient stucture.

OK, I went on a long time. Sorry. I have a lot of rasps.

Kevin

ps - this was the first knife I ever sold!

Edited May 11, 200917 yr by kevin (the professor)

that knife looks like a khukri to me. it is still very cool. i have found wood ash works well (along with everyone else on this thread). good luck

Also standard Barn Lime will work....have used it myself. One tip I have though, don't put it in a plastic bucket, when a hot part tips over into the side, it will melt through the side of the bucket, and you will end up with lime all over the place.

You shoud try to keep the part as close to the center of the bucket anyways.

would wet sand work?

NO it will not. In case you have not noticed, water is a good conductor of heat. To anneal you want to insulate the heat, to slow the cooling, NOT cool it fast.

my bad... im still new to this. What about just plain old dry sand?

Not nearly as good as sifted wood ashes! (and if any was to melt to the steel a bigger pain to remove.)

ok cool thanks...what do u mean by sifted? how do u sift ash?

Window screen, hardware cloth , kitchen colandor... what evr.

I like vermiculite my self but that is just me.

Will regular dirt work as an insulator?

Hello Thomp82, welcome aboard! This is a worldwide forum, answers often depend upon where in the world you are located (but probably not in this case). Please edit your profile header and add your general location so the rest of us have an idea where in the world you are. Also if you haven't already see the "read this first" pinned topic for clues on getting the most from this forum.

To answer your question.... yes if it's dry it will insulate if you have nothing else but it's probably not the best thing to use.

Good Morning,

A bucket of Garden Lime works well. When you are finished, it can still be used as Lime.

Neil