Annealing & Grinding

[Doug Mason]

After I anneal a piece of 01 oil steel to roughly 1400 F,then quench, can I grind an edge of the softened metal without worry of the steel turning blue? Or will it still turn blue in this state?

[Zahid Naqvi]

I am not an expert on these things, but most I have read suggests that all grinding (primary bevel) be done prior to any kind of heat treatment.

[Mike K Wenzloff]

Hi Doug,

Quenching after heating will harden the metal. Heating then allowing to cool will anneal. In general, the steel most likely is annealed if purchased new unless it states otherwise.

The steel can be hardened during the grinding process, which is how it would blue the easiest. This often happens as a result of quenching during grinding in an attempt to keep it cooled down. Just watch for color change while grinding. Use a 36 grit or so wheel and it won't get too hot if you take it easy.

Take care, Mike

[Mike Henderson]

I'm not a blacksmith so I'll ask a blacksmith person to clarify, but I think that if you heat carbon steel to a high temperature and quench it, you are hardening it and not annealing it. I believe that you have to let the metal cool slowly (the slower the better) in order to anneal it.

Mike

[Jon Toebbe]

I think that if you heat carbon steel to a high temperature and quench it, you are hardening it and not annealing it. I believe that you have to let the metal cool slowly (the slower the better) in order to anneal it.
I've heard the same thing directly from an old-skool blacksmith. He uses old car springs to make tools and anneals the material by heating it up until a magnet won't stick to it any more, then burying it in dry dirt or ashes.

He's offered to give me some lessons at the local history museum's restored blacksmithing shop. Gotta get me some late 19th century working duds so I blend in, and I get to be an apprentice. :D

[Doug Mason]

I stand corrected; I meant to say if I heat it up to 1400/1500F and then let it cool in "lime" or wood ashes, then the metal will be in a softened state. It was my understanding that right after annealing, most of the edge should be ground, followed by hardening and tempering (to be done in my oven). I read somewhere that after annealing, I could grind w/out worry of bluing the metal? I have no idea if this is true (although I'll find out this weekend as I test it out)

I bought some of the 01 oil tool steel from enco (the starret version) to play around with--to make some crude cutting tools (as I have never done this). And what exactly is lime? Thx for the input

[Larry Williams]

The O-1 you've received from Enco is already in its soft state. There's no reason to heat it until you're ready to heat treat.

[John Goodridge]

Lime is a white powder (calcium carbonate, I think) and is used as part of concrete and mortar mixes as well as plaster. I believe it is also used for fertilizer. It is usually available from hardware stores in 50 lb bags. You may find it at nurseries or garden centers as well.

[Doug Mason]

Just as a follow-up; the 01 oil tool steel from Enco, as pointed out above, is already annealed. I ground a 2 inch bevel on a 10 inch long piece of it. And the result was that I got no "bluing" on it despite generating a high heat on the grinder. So I am concluding (correctly???) that most of the rough grinding should always occur after annealing but before hardening--as there is no threat of bluing the steel.

[Dave Anderson NH]

You are correct Doug. do all of your rough shaping with the steel in the annealed state. Harden, quench, temper, and then do the final sharpening and cleanup.

[Harold Beck]

Doug,

I am no placksmith by any means, but I have made my share of maring knife, plane and miscellaneous cutting blades from O-1 steel stock. As stated above, O1 steel is usually delivered annealed (in its softest state. The process is to grind to shape the initial edge, harden by heating and quenching and then toughening by tempering at a lower temperature.

Hardened steel can be softened by heating up and then cooling slowly (over hours instead of seconds).When you overheat a hardened and tempered blade (and get "bluing") you are effectively starting to anneal it (soften it again).

If you are grinding an annealed piece of steel to put an initial edge on it prior to hardening and tempering, and get some blueing you are actually hardening it a little. At this stage it is no problem as any hardening you do while grinding will be completely re-done when hardening and tempering.

If you ruin a good blade by overheating when sharpening, it can be fixed by starting over, hardening and tempering again.

Remember when hardening and tempering, the very cutting edge has a tendency to lose too much carbon and be brittle. This is why you always do the final grinding/sharpening after heat treating. This removes any metal right at the cutting edge that may have a tendency to chip.

I hope that clarifies.

HB