annealing

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golfpin

annealing

Post by golfpin »

Good evening all,
as usual not sure of where to post this, but it is gun related.
1 Ran into a very hard and difficult spot on a job that had to be annealed or softened in order to drill, remember reading along while ago, I think in a book written buy Bill Dunlap, to use a carbon stick possibly from a flashlight battery and it hooked up to an arc welder and the carbon sharpened and then used to heat said point. Anyone perhaps know of this technique or similar or has a suggestion.
2 Must be my week for hard metals, have a piece of stainless steel 8 mm diam 30 mm long needs to be drilled and tapped 4 mm. Next to HSS or what ever is hardest metal on this planet this one has me beat. Tried to anneal from a website I found, suggested heat to yellow and hold at that temp for about 10 secs and then quench in cold water!!! needless to say it was futile destroyed a masonry/tc tipped drill sharpened correctly and any number of poor quality HSS drill bits. Job is a freebee so definitely does not qualify for a solid carbide drill. Any suggestions on how to anneal that piece of S/Steel.
With thanks
Golfpin
heisler0
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Re: annealing

Post by heisler0 »

When annealing you heat, hold temperature than cool slow. DO NOT QUENCH!! Depending on size of piece you are trying to anneal determines how long you hold temperature to make sure it heats all the way thru and not just the surface. Campfires always work good throw the piece in as it lays in the fire and heats up than as the coals slowly burn out it allows even the largest pieces to cool slow and even.
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BadDog
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Re: annealing

Post by BadDog »

Annealing, like hardening, depends on material. For instance, brass is annealed by heating and quenching. But I've never heard of quenching to anneal steel. I think all you did was make it MUCH harder (assuming you had it to critical). As suggested, you want it to cool slow. So to fully anneal carbon steel you heat it to critical (non-magnetic), then cool slowly, perhaps buried in (very) dry sand or ash. But just letting air cool (avoid drafts) may allow you to work with it. And spot annealing (like using a carbon electrode) is more like somewhat annealing because the surrounding metal draws off the heat quickly. But again, it's generally soft enough to work without carbide. In some cases they use friction in a similar manner.
Russ
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Harold_V
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Re: annealing

Post by Harold_V »

BadDog wrote: But I've never heard of quenching to anneal steel.
Common for solution annealing precipitation hardening materials. An example might be 17-4 PH stainless.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
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BadDog
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Re: annealing

Post by BadDog »

And every day I learn more. Thank you.
Russ
Master Floor Sweeper
golfpin

Re: annealing

Post by golfpin »

Hello to all,
again a big thank you to all that replied, here is what transpired. The said piece of material is stainless steel and it drives the blade of a dough/bread making machine. The blade is made from a cast alloy and is cast onto the S/S shaft. Center popped the shaft as best I could and because of the blade I could not hold in the lathe [4 jaw perhaps ? too lazy/hurry it mount fit it] used new centre drill in drill press not a mark! Googled found info heat to yellow hold it there for 10 secs [used a potato as heat sink to protect the ally blade plunged into cold water. Using new, but Chinese 3.2 tapping drill managed to drill to sufficient depth tapped but taps [chinese or blunt local not happy] did the job. So I think this what happened ... the heat seemed to anneal but possibly on the first attempt, my very bad eye sight that prohibts me sharpening drills, the drill rubbed, thereby creating the problem in the first place. Hopefully something good came out of it, I learnt something.
Thanks to all.
Cheers Golfpin
PeteH
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Re: annealing

Post by PeteH »

Couple of blacksmiths' tricks for annealing (steel only; I have no knowledge of SS):

Spot annealing, grind a flat end on a rod about the size of the area you want to anneal (a little smaller is good, larger is not so good). Heat the rod red/orange hot, and press it against the piece to be annealed. It'll likely change color, so you know when it's done. You might want to put a heat-sink around the target area, like a wad of damp clay, or a ring cut out of a potato.

Larger piece: Heat it to the appropriate temperature and then bury it overnight in a bucket of granulated limestone. (I find the powdered kind is a lot messier; the "granular" form - NOT the pelletized, timed-release kind - doesn't tend to get all over the place.)

Oh... one of the other posters alluded to "friction" for spot-annealing: Again, grind (or face) a flat end on a piece of rod about the same size as the desired annealed spot. Chuck this in the drill press, and press the rotating rod against the workpiece where you want the annealed spot. Again, check your progress by the color. This method does run the risk of gorping up the surface of the workpiece, though.
Pete in NJ
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