Thing of the week - Bacon and Fire part two: First Knife

Hi everybody what is going on?
I'm Roger In Technology and welcome to Thing of the Week Part Two for 30th August 2015.  This week I'd like to talk about the first knife I made from scratch.

Ferrous materials are characterised by the way iron crystallizes as it cools, and you have to master iron from the earth, air from the bellows, the blazing fire and water to quench - truly the dawn of blacksmithing represents mankind's dominance of the four elements of the ancient world.

The first step for me is to grab some one inch rolled steel stock and draw a knife on it. This is where the magic starts.

This is the steel stock I've chosen, it's about an inch wide but very thick.

This girth will give it tremendous weight and I'll have to consider that when I profile and grind it.  I'm planning a Scandinavian style grind, with about two thirds of the blade tapering to a point. Because of the thickness of the blade I might choose a convex grind instead, I'll see how it goes.

You can never have too many clamps so I clamped a clamp to a clamp.  This was an everyman project with tools you might have in your toolbox already.  Just a regular hacksaw, a file, and some clamps holding everything to a picnic table out back. I'd love to have a heavy workbench and a bolted bench vice or a leg vice, but until I get that set up it's picnic clamps all the way.

The initial cuts are all made using a regular hack saw, with a bastard file used to round it off. Its a lot easier to saw through than to file, although I found the weight of the stock was really working against me.  Lesson learned, use thin stock and you will save a lot of elbow grease.

Next step, grind the bevel. This was all done with a bastard file, clamps and some curse words that really seemed to help get the job done. The bevel isn't as deep as I'd wanted but the angle is about what I was after so that just the shape it's going to be.

Once ground, I cleaned the millscale off and polished it up with some 240 and 600 grit sandpaper. I think I might have gone finer than that just to see how much shine I could put on it, and I wanted it pretty smooth before the heat treat.

After the steel is knife shaped, Its time to heat treat the blade. First off, I'm going to pack my crucible with sugar and cap it off with clay and place the knife in it to case harden it.  Case hardening means you have to get the steel really hot and allow it to soak up additional carbon. I'm doing this because it's a low grade piece of steel stock I had that isn't really suitable for knives.
I'm going to cook the knife in sugar at about nine hundred degrees so case harden the blade a little before the quench. Since it's a soft steel, the case hardening will help it retain a really good edge. I was offered some Kasenite to harden in instead of sugar. Kasenite is a great source of carbon but it also contains Potassium Cyanide and I figured I'd stick with the non-toxic version this time.

After case hardening, the blade is back in the forge again for the heat treat. Here I'm using a graphite crucible to raise the knife to hot temperature and get it evenly cooked. I'm also cooking bacon, although the fire is a thousand degrees too hot for bacon which starts to vaporise at this sort of temperature.

OK, I said this knife was made from tools you might have lying around, and not everybody has a raging inferno to hand. But it was a very simple build and you can put one together in an afternoon with reasonable cheap materials. It's an insanely powerful fire despite its small size and can be difficult to control but if you are used to working with forge or foundry fires it isn't that bad.  For the astrophysics crowd, I've peaked at internal temperatures as hot as a Red Dwarf star and the steel bucket on the outside didn't melt. It's all about the heatproof lining.

Whole essays could be written on quenching steel, so I'll skip the details here and perhaps we'll go into those another time. The quench hardens the steel, and then the temper brings it to the exact hardness that you want. Because this is a mild steel I went with a water quench.

After the heat treat the blade is covered in scale and needs a really god grind, polish and buff so its back to the sandpaper and elbow grease for this one.

I'm hoping to get it cleaned up, tempered and get a handle on it soon. It might not be next week, just depending on how busy everything gets. But hopefully I'll have an update before long with a picture of the finished article.
This is pretty much "finished" though.  Its a knife shaped object, and its been hardened. Really it just needs handle scales pinning on.

Lessons Learned

You learn as much from your failures as you do from your successes, and while this wasn't a failure, it wasn't a complete success either and there is a lot I can do to refine the process.

Choosing such thick stock doubled the amount of work I had to do cutting and grinding and really cost me time. Its good practice on being patient but next time I'm going to choose something much thinner. It just depends on what you are trying to make.

Doing this by hand was a lot of work. Bottom line, its recreational hard graft - but still less effort and better tools that our species had for thousands of years. And I could pick them up cheaply from the local hardware store.

Next time, I'm going to want a proper height workbench and I've got to consider a belt sander too. Getting a workbench at the proper height for you is crucial else your back will ache the following day. I choose the hard way because I wasn't spending any money like this, but if I could pay sixty bucks to take away the pain right now I would consider it.  Money comes and goes but you've only got one back.

My handle pins look a little puny. I could easily have chosen 3/8 or 1/2 inch pins, and I might find something bigger when I come to do the handle. Overall I'm not that fussed - again it's about learning the process but one of the processes to learn is having an eye for what looks good, and what I like the look of.

Choosing to case harden made things more difficult. Its a way of hardening steel, which means you can start with a softer, lower grade stock. Our ancestors used to have to do it and it's not a great hardship. But I don't think I'm likely to try that again for a while. The local metal supplier didn't have any O1 steel which is what I'm after, but I found a few places I can buy one inch bar online so I'll order a few meters when I'm ready and make a few knives.

Fire! Running the fire is great fun. It gets hotter than I thought, and just for a short while I lost my nerve. Literally, it got so hot I started to get scared. So I'm going to fabricate a blast regulator to reduce the airflow.

It amazes me at every step how much mastery of the elements we have and how much power, knowledge and versatility we have within our grasp. I'm going to improve my workflow, maybe buy some more tools and have another go soon.  It's quite possible that the next few projects will be brass and bronze so it could be a while before I'm working with steel again but I want to have a few attempts until I've got something I'm happy with.

Until next time, keep your projects projecting and maintain momentum - and Clamp everything down!

Thing of the week - Bacon and Fire

Hey everybody what is going on?
This is Roger in Technology and welcome to thing of the week for the 27th of August 2015.

This week - Foundry tools!

The bucket foundry I built here is exactly what the doctor ordered, its a galvanised steel bucket and a refractory mix of about four parts plaster, four sand and three water. There are details on the construction on a previous post.

While I had to buy a steel bucket, those things are cheap enough and I knew it wouldn't break the bank. Likewise for the plaster of paris and sand and making a thrifty blast forge capable of any amount of metalwork is easier - and cheaper - than you can imagine. Here is the little fellow in action.

There are a few more materials here, a one inch steel tube and a value hair drier for an air blast. These were bought pretty cheaply. The pictured timber supports are actually my cope and drag frames for the casting flask, so I'm not counting those in the cost. The air blast does need a dedicated support, although a few blocks or timber is going to be more than sufficient for a long time yet. It also needs a regulator, because the direct blast from the blower provides too much heat.

As well as buying the materials to make the forge, next on the shopping list was a graphite crucible looking something like this.

The crucible is a precision tool, and it was important enough for me to spend the money rather than fabricating a steel cup. The thing is rated a lot hotter than steel too, by at least a thousand degrees, which is a pretty good safety margin.  Melting Aluminium and brass isn't going to take more than a thousand degrees, and neither is hardening steel so I'm very happy to have a crucible that can withstand a lot more than I'm every going to need.

The lid is the same refractory concrete as the foundry walls, with galvanised steel hooks set into it. The two hooks were bought new from the hardware store - its a needless expense when they could be beat out of steel but the wide square bases will help it hold in the concrete and I didn't want to spend any time on such a trivial item.

Once the mix was poured in, it flowed around the hook bases and the plastic cup formed a circular hole and I just had to let the thing dry before popping it out the hold. The technique was about right but I want the next lid to be thicker.

With the lid off, the crucible can be seen here glowing a bright orange at its hottest point. You can see the ash line around the edge of the lid. While its clearly more the large enough to cover the foundry I might consider an inch or so larger diameter.

It's worth mentioning that the fire at this point is running too hot - which is why I had the lid off. Actually it's running at a tad over two thousand degrees by my best guess. If that steel stays in there too long it'll start dripping. As well as being too hot for steel, that temperature is far too hot to cook bacon. As far as I can tell, bacon vaporises at two thousands degrees (3600 Farenheit) and while I tried eating what was left of it after it had been extinguished it wasn't a pleasant experience.

Cooking bacon is reasonably easy in a fire up to two or three hundred degrees, where it will sizzle well and taste delicious, but I think that anything above about a thousand degrees centigrade (1800 F) is going to do more harm than good and the direct heat of a forge fire is unlikely to yield good results.
Using nine-hundred to a thousand degrees as a maximum cooking heat is probably a good rule of thumb. If its hot enough to liquidise copper then its too hot to cook with.  Our domestic oven will reach 230 ish degrees which is just shy of the temperatures needed to temper the steel of its construction.
A discussion on cooking over the forge will have to wait for another time, while I consider some sort of heat shielding that can withstand the inferno.

Todays heat used up the last of the summer BBQ charcoal, so was the last free burn and I'll have to buy some real coal next time. The crucible was packed with sugar and sealed with my knife while it burned for a couple of hours to case harden the steel before a water quench. It was a lot of work to go through, and a better grade of steel would have skipped straight to the quench and temper.

Until next time, keep your projects moving. Finding time for recreational hard graft can be difficult but maintaining momentum is important.