Annealing

[doug]

     A question which I don't think has been asked before.  When annealing steel, particularly high carbon steel such as drill rod, does it matter how long you hold the metal at red hot before putting it in wood ash or similar to begin cooling.  Another way of putting it is; part of the annealing is allowing the carbon molecules to reorientate in the crystaline structure, but do they do so in seconds or minutes?   I am sure that someone is going to jump in and say use a heat treating furnace, but I suspect there are more than a few of us who don't have the space and don't want to spend the money

thanks Doug

[D. Taylor Sapergia]

I have recently had the occasion to anneal a tumbler so that I could cut a recess for a detent.  I tried everything I could think of - wood ash, sand, lime - no go.  So I phoned Cody and Tom Curran, and they both suggested a good soak at critical temperature, then a long cool down period.
So I built a little fire with yew for kindling and birch for fuel until I had a nice bed of coals.  Then I used my oxy/acetylene torch to heat the tumbler to critical temperature, and dropped it into the red coals.  When the fire was dead, I plucked the tumbler out of the ash, and found it to be as soft as mild steel.  There  were no hard spots.  I am very grateful for their wonderful advice.
I did not sustain the red heat with the torch for more than fifteen seconds I suppose, before I threw it into the fire.  So, I don't think it was at critical heat for more than perhaps twenty seconds.

[northmn]

Generally I have been told that it is best to anneal by heating in a furnace and then turning the furnace off and letting it stay in the furnace until everything cools down.  There is also the issue of "normalizing" that is recommended for things like forming springs where that sort of heating process is recommended before tempering.  I have tried to make knives out of files and had the same result as Taylor.  There are now so many different alloys out there that one system may not be universal as you have to know the steel you are working with.  Most of the "rules" are for straight carbon steels.

DP

[LRB]

  Northmm has a valid point. In annealing common steels you want the steel to be a little above critical, if you are calling non-magnetic critical temp, then very slowly cooled, but with steels that contain more than .85% carbon, such as 1095, 01, ect., you may need to do a different anneal called a spheroidized anneal. This just about requires an oven to get done well. When high carbon steel is slow annealed, the carbon and iron form layers. When the carbon is near, or above .85%, these carbon layers can dull drill bits, even though the steel seems relatively soft. If this .85% or above steel is heated below non-magnetic, then air cooled in multiple cycles, the carbon forms spheres which sorta/kinda roll and shift out of the way of cutting tools, rather than being a layered hinderance. This can be done with any steel, but is most useful with the higher carbon types.

[jmforge]

Don't mess with wood ashes.  If you are trying to anneal simple carbon steel without a lot of alloying elements, go to Home Depot and buy a big bag of vermiculite an use that.  This only applies to simple steels like the 10xx steels and W1.  It will not work as well on O1 drill rod.  The other thing you have to worry about with steel that contains certain percentages of stuff like chromium is air hardening.  O1 is known for doing this on occasion as is 52100.  When that happens, it ALWAYs seems to happen in the one spot that you want to drill...lol.

[Stophel]

Siler parts....O1 steel.  I find these often difficult to anneal.  Usually, I have to heat them, hold them at heat for a minute or so, then I put them in a sack of lime, and cover it up so that it cools as slowly as possible.  Occasionally, I have to do it again...

[Dave B]

I had a bad experience with a Bridger hammer for a California rifle I built. I needed to stretch the hammer just a little to get the best alignment and was able to heat it up and using a cross peen hammer got it just right but when I went to soften it up  for engraving it had a hard spot in it that I could'nt  engrave or file. I had a friend take it to work and heat soak it for a couple hours wrapped in a stainless foil envelope. The furnace was turned off an allowed to cool down on its own.
This gave a perfect softness through out the piece and I was able to engrave it with out any trouble.

[FL-Flintlock]

I have recently had the occasion to anneal a tumbler so that I could cut a recess for a detent. 

Get some diamond files and rifflers, no need to anneal.

[ottawa]

I make a lot of my knives out of old files and other tool steels I work them to shape in the forge then set them off too the side on the forge to soak if its a real hard piece i will work it then set it in the fire pot and let every thing cool together soaking seems to be the best way to anneal

[doug]

     For small pieces, once or twice I have annealed them by increasing the thermal mass; ie buried them in an iron box filled with dry sand and then heated the sand red hot in the forge.  You have to be careful not to keep the sand red hot for too long or it will turn to glass :>(   Drill rod is mostly what I work with for making springs and have had mixed results with annealing it, perhaps because of different alloys in different batches or different suppliers.

cheers Doug

[Dphariss]

I have recently had the occasion to anneal a tumbler so that I could cut a recess for a detent.  I tried everything I could think of - wood ash, sand, lime - no go.  So I phoned Cody and Tom Curran, and they both suggested a good soak at critical temperature, then a long cool down period.
So I built a little fire with yew for kindling and birch for fuel until I had a nice bed of coals.  Then I used my oxy/acetylene torch to heat the tumbler to critical temperature, and dropped it into the red coals.  When the fire was dead, I plucked the tumbler out of the ash, and found it to be as soft as mild steel.  There  were no hard spots.  I am very grateful for their wonderful advice.
I did not sustain the red heat with the torch for more than fifteen seconds I suppose, before I threw it into the fire.  So, I don't think it was at critical heat for more than perhaps twenty seconds.

Hi Taylor

I have gone to using miniature carbide endmills and drills for this. I put a fly into an original TD Springfield tumbler that was case hardened and the carbide cut it like butter. But a pretty good mill is needed, the carbide is brittle and will break easily if things are not pretty tight and the small mills need high speed as well.
I have used a wood stove to anneal, works very well.
Dan

[bob in the woods]

My woodstove is great for this. I put the parts in the stove when I go in for the day [ stove is hot ] and take them out in the morning. [ stove is barely warm ]