Quenching in sawdust

Speaking as an engineer; it is always best to use the heat treat specified by the steel manufacturer.
 
AlaskanHunter said:
Not intentionally burning the sawdust, but rather making charcoal of it in a way. Some of the dust will burn, taking the oxygen in the muffle with it. This is the oxygen that will cause scale and decarburization on the surface of the knife. If the oxygen is used up before the metal is hot enough for this to happen, you should in theory get no scale or decarb. Obviously this doesn't work perfectly, because oxygen is free to enter the open end of the muffle, so you will get some scale/decarb, but it seems to help. You will still have to grind/sand some scale and decarburized metal off of your blade post heat treat, however from my humble experiments it appears to reduce it a bit.
As for carbon migrating into your metal during the process, in theory it's possible, but you won't get any noticeable results, much less ones of value to the finished blade.
This is the only legitimate use of sawdust in the heat treating process that I'm aware of. Any other use of it, especially as some sort of quenching medium is likely a tall tale. Those who understand the heat treating process better than I - feel free to correct me.
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Thanks alot:)
 
tacticalrescue said:
Thanks alot:)
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Keep in mind that I am referring to wood "sawdust" not the dust byproduct of cutting metal. Small chips like those from a chainsaw seem to produce better results for me than the dust you get from a table saw or skill saw. Pack a plug of the stuff in one end of the pipe and leave a layer of it on the bottom of the pipe. Set pipe in forge, and bring up to temp. Insert blade into pipe and carefully move back and forth with your tongs to bring it to an even heat. You don't want the tip on your knife to get too hot. Bring up to temp, and quench. Your temp and quenching medium will vary with the type of steel you are using. Starting with a simple high carbon steel will make your job much easier. I use primarily 1084, as it is very forgiving in the HT. Easy to tell when it's at the right temp, no soak time, and quenches very well in warm canola oil.
I have only used this method in a charcoal forge, so it may not perform as well if used in a gas or coal forge... then again it might. The chemistry shouldn't change too much by swapping fuel sources.
Good luck.
 
tacticalrescue said:
does anyone have some insight into quenching with sawdust? ive done it where i am and noticed significantly less scaling. ive read some "more superstitious" claims and insights that it is better for the steel and carbon?....
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It's a good idea. In our region some knifemakers do it. But wood sawdust with blade need to be closed into a stainless steel box with lid. Sawdust will burn oxygen from box and will keep blade away from it.
 
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Jesenius said:
It's a good idea. In our region some knifemakers do it. But wood sawdust with blade need to be closed into a stainless steel box with lid. Sawdust will burn oxygen from box and will keep blade away from it.
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Interesting. Im up in lapland in sweden and where i caught wind of the idea and tried it. I just dunkd it in a bucket of sawdust and there was noticable less scaling. But i could see where in a box would be great for the theory. Any tips on how long to dunk it in? Or time left? Is the saw dust wet?
 
You will read/hear a multitude of ideas about quenching ands other HT things. Most are based on someone's misunderstanding of a real thing.


Sawdust is an industrial waste product. It is made literally by the ton in the lumber industry, and they have to find ways to get rid of it. It is light weight, non-toxic, easy to dispose of when not needed anymore, and basically free.


If a carbon bearing object is placed in the muffle of a HT oven or forge, it will burn and give off CO2. This reduces the available oxygen in the immediate area and retards scale and decarb somewhat. Some people use a small piece of wood or a piece of charcoal. I have heard of sawdust, but never actually knew anyone using t. Sawdust would burn too fast. There are people who put the wood/charcoal in a regular HT oven for the same reason. Mostly, these procedures just make you feel good and also make a lot of smoke.

A common use of sawdust was taking a metal container or iron "case" of fine dry sawdust ( later replaced by bone meal) and packing a piece of low to medium carbon steel in it. Seal this up tight, and place in an oven or forge to carburize the steel surface. This is called "case hardening". In older days, steel with high carbon was harder to make and hard to get. It was also expensive. Case hardening allowed tools surfaces to wear longer for very little extra expense.

Another common use for sawdust is an old annealing technique. After heating a piece of steel or iron to red hot and holding it there for a short while, the object was allowed to cool to dull red or black heat and then plunged deep into a box of dry sawdust. It was left there for many hours as it slowly cooled. This was called "box annealing". If a red hot item was plunged into the sawdust and the box covered tightly, the cooling process would take even longer. This was a softening, not a hardening process.

The list goes on -
Hardwood saw dust is an excellent drying and oil absorption agent. In many industries, parts were cleaned and oiled, then dropped in a box of fine dry sawdust to dry them and remove the excess oil. Jewelers and watchmakers always had a metal can of "drying sawdust" on the bench. Many old-timers still use this technique today.

In industry, barrels of sawdust were kept around every work bay and shop to soak up spills , especially oil and chemical spills.

Before kitty litter, sawdust was used for animal cages, too. When I was a kid all pet shops smelled like a wood shop.

Sawdust bags were also kept in car trunks for traction on slippery places. It was kept in a bin near steps and entryways when the weather was icy.

Ice was packed in ship holds filled with sawdust and shipped to the tropics. Sawdust is an excellent insulator.
 
Thank you very much! The bigbred moderator font is very powerful:) that was perfect and informative. Enough that i will continue my interest testing and curiosity.
 
tacticalrescue said:
Interesting. Im up in lapland in sweden and where i caught wind of the idea and tried it. I just dunkd it in a bucket of sawdust and there was noticable less scaling. But i could see where in a box would be great for the theory. Any tips on how long to dunk it in? Or time left? Is the saw dust wet?
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Dry sawdust, wood pieces or charcoal as Stacy wrote. Put blade in a box, fill in by dust or coal, tight close with lid. Add about 5-15 min on temperature depending on size and mass of the box. Box should be from austenitizing steel. It will last longer.
 
Jesenius said:
Dry sawdust, wood pieces or charcoal as Stacy wrote. Put blade in a box, fill in by dust or coal, tight close with lid. Add about 5-15 min on temperature depending on size and mass of the box. Box should be from austenitizing steel. It will last longer.
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oh okie. so your using a box with saw dust like steel foil.... not quenching in the sawdust?
 
Yes but not exactly. You need pull blade out from the box before quenching. Quenching in the media depending on type of the steel of course.
 
Quench in oil, air or water depending on what is best for the blade

Sawdust belongs on the floor of the butchers shop.
 
This thread isn't any less funny even after clarification. :D
 
Greenberg Woods said:
Oh my god. Please never get near fire again.
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This made me laugh out loud.

As for quenching/hardening a piece of steel in sawdust, I can't say I've heard of that one. I can see where it could be used for annealing under the right conditions.

At any rate, if you want hard steel, there's plenty more proven and effective methods out there.
 
thank you everyone for your input into my curiosity in the multitude of possibilities with heat treatments. best wishes and your time is appreciated..
 
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