Thread: forge ideas

Originally Posted by mastermute

Oh.. I thought "thicker is better", so I got me some diesel engine oil Thank you for stopping me in time, will olive oil do? Or just any "fryer" oil?

No, thicker is, well, different.

It depends on the steel you're using, really. Different alloys have different requirements for how they should be quenched. Some, like 1080, 1095, and W1, need a fast quenchant to fully harden. Technically, they can be hardened in plain water, but that takes some skill and raises the likelihood of cracking the blade. Water is a very fast quenchant.

The next step down in speed is thin oil. Thin oil moves around better and disperses the heat faster than thicker oil. That's why you hear guys recommending that you preheat your quenching oil to around 130 degrees F. It seems counter-intuitive, but the preheated oil becomes even thinner.

Thick oils are for steels that work best with a slower cool. O1 is a good example. If you heat it properly, it will actually harden a bit just by air cooling it. Slow oil like motor oil will work OK for O1.

Air is the next slowest quenchant. Steels like A2 are heated and then allowed to cool in still air.

Make sense?

Josh

I think the kitty litter forge looks great, hell its made of cat litter! nice blade shape too, what is the blue all over it? Dammit if i only had the money...ive been looking to try all this stuff out for years but just cant do it..i live in a very small studio apartment and have barely any money to play with at all...do you think id be able to make a fire brick forge and operate inside?

Originally Posted by JoshEarl

Make sense?

Indeed it does!

Josh
Thanks for the input. Yes it does glow, but not on the ends. There is about a 3” section in the center of the chamber that works well the ends do not get as hot. It glows for a while after the gas is shut off. I will probably end up ordering the stuff to make a two brick forge. Considering the forge cost me nothing and kept me out of trouble for the weekend I am calling it a good experiment.

Tjiscooler,

The blue stuff is layout dye, It makes it easier to scribe lines on metal.

MidwayUSA - Starrett Kleenscribe Layout Dye 4 oz Liquid

Charlie

Find some firebricks to block up the exhaust hole and that little fire will retain a lot more heat. Really, any forge is nothing more than a collection of insulation to contain the heat in one spot long enough for the smith to get the material to the temperature they wanted to get work on the material done. All you need is a smallish hole not much bigger than the steel you're putting in there.

I know smiths whose forges are great big piles of brick that get moved around and repiled frequently depending on the size and shape of the job they are doing.

I've seen photos somewhere on the web from a guy who made his forge by stacking four to six 4x4x8" firebricks into a chamber. Like Mike mentioned, you can reposition them as needed.

I'm far from an expert on physics, but it seems like the main considerations when building a forge are: size of the chamber relative to the size of your burner, the shape of the chamber, the heat-reflecting/absorbing properties of your forge liner, and the mass of the forge liner.

- To a point, smaller is better when working with a small heat source like the JTH7 torch. A one-brick forge with a 1 1/2" round chamber will let me hit forge-welding temps on a 4" section of steel. In a two-brick forge with a 4" round chamber, I can't get it above a nice forging temperature, except maybe if I let the flame hit the steel directly for a few minutes.

- If the chamber is too small, though, it will prevent the air from moving around the steel, and you'll only get heat where the flame makes contact.

- I've heard round chambers allow for the heat to swirl around better and even things out. I haven't tried a square one, so I'm not sure from experience...

- Too much mass in the liner and it will take a long time to absorb heat and get up to temperature. That's why the hard firebricks don't work very well.

You'll probably build several forges before you get one you really like, so keep at it. Or you could do what I chose to do and get a ready-made one.

Josh

Originally Posted by spazola

The blue stuff is layout dye, It makes it easier to scribe lines on metal.

Thanks, thats what I thought after posting, haha. Why no use a sharpie?

Peter,

Thanks for the pictures of your brake drum forge. It looks like it is all business to me.

Tjiscooler,

A sharpie works, but the layout dye works better it does not rub off as easy.


Charlie

To get the most out of your blade you need to fully harden it. When hardening steel the temperature is first raised above the critical temperature (CT) this forms austenite inside the austenite are the carbon atoms. If the steel is then cooled quickly enough the carbon is trapped inside a new hard crystal structure called martensite. This has a lot of stress in it which is relieved by tempering, which turns some martensite into bainite. A steel without enough carbon in it will not harden enough, and a blade cooled too slowly (a water cooled steel in oil/ an oil cooled steel in very thick oil) will not produce the most amount of martensite it is capable of.
To heat treat efficiently you need to understand metallurgy. The better your understanding, the better you can choose a method of hardening your blades. Recipes can provide results when followed properly, but without the physics you have no explanation or starting point to understand what went wrong. Nor can you teach someone unless you know what is happening. That being said...

Simple carbon steels, and the W series tool steel harden in water. Thin sections (under 3/32) can crack. That is when you quench in something a little thicker. Too much insulation will not form martensite, which is what we are after.

O1, 51xx and others are Oil quenched because of their chemical makeup they generate too much stress in the rapid cooling water gives them.

D2 is an air hardening steel used in tools and dies, it could be considered stainless because of its high chromium content, because of its makeup even thick as hell motor oil/engine sludge could potentially crack it. quench this baby in water and it will pretty much explode.

My advice to anyone, if you are serious about making quality blades, go to the library and in the reference section dust off a copy of The American Machinery's Handbook or The Machinist's Handbook (you might be the first person to look for it in a while). Open it up to steel and read everything from simple steel's composition to the alloys you might use, then read everything regarding to heat treating it will tell you exactly what is happening in your steel and how it's doing it.

Good luck, lets see some amazing steel!

Originally Posted by Twalsh341

To get the most out of your blade you need to fully harden it. ...

Do you need to do this for every blade? The ABS spends a good deal of energy specifying a differentially hardened blade in their testing criteria. There are a lot of folks making Japanese style hamon on their blades. By definition, those are not fully hardened. Some steels do not through harden and others do. Which of those are best for razors?

... This has a lot of stress in it which is relieved by tempering, which turns some martensite into bainite. ...

I agree that you are better off understanding metallurgy when heat treating, but I want to know how tempering produces bainite. And explain the difference between tempered martensite and bainite. Why is one better or worse than the other? How does this play into the world of razors?