View Full Version : Heat Treating Railroad Spikes...


gunnut_69
05-15-2006, 03:33 PM
Does anyone know how to temper a "soft" blade made from a railroad spike?
I inherited a roughed out blade made with a gas-fired kiln at 1,800 degrees,
and he said I could "re-temper" at home using nothing but my oven. Any
suggestions? Thanks...

Take #2- Guess the above is a little confusing...what I want to do is "harden"
the blade following all grinding and finishing. I was told this was possible with
a regular electric cook oven found in one's home?

TexasJack
05-15-2006, 05:48 PM
The answer is no. To "harden" the blade, you need to heat it up to non-magnetic and quench it. That's quite a bit higher temp than your oven will reach.

Now, after a blade has been quenched, it can be tempered in an oven at around 350 degrees. That's probably what the guy was thinking about.

After re-reading your question, it looks like the blade has been quenched and the maker is telling you that it can be tempered after you finish the blade.

gunnut_69
05-15-2006, 05:53 PM
TXJK-

Thanks for the reply. By "quenched" you refer to the method of cooling after being heated in the kiln and shaped into the rough outline for detail work? I guess I'm confused. He said verbatim- "Once you have the final shape and finish you want, you can temper at home for the strength you desire." Did I misunderstand or was he referring to another process I'm not clear about?

-Troy

blacksmith101
05-15-2006, 07:46 PM
I dont usually answer, just read but here is my 2 cents worth. Get a sharp file with single cut teeth. Try and file/ sharpen the edge. If it slides over without cutting the blade then it has enough carbon to do something with. If it cuts the blade easily then the blade needs to be hardened. Try heating the blade with a torch or in a forge untill a magnet will not stick to it. Quickly plunge into water. Now try the file again. If it is still soft, sharpen it and use it for a letter opener/ conversation piece. If it is hard then come back and let me know and i'll give you the remaining steps. Railroad spikes arent known for having much over .35% carbon. (they wont harden enough to make a good blade)

TexasJack
05-15-2006, 11:57 PM
Reading between the lines, gunnut doesn't have a means to heat the spike to non-mag.

There are some great descriptions of heat treating around this place - some written by metallurgists who actually understand this stuff pretty deeply. But here's a short version of it: When you forge a piece of steel to make a knife, the first thing that you need to do is anneal it. To do that, the steel is heated to a critical temperature and then allowed to cool slowly. Annealed steel is 'soft' and can be forged and worked into it's primary shape.

The steel is then 'normalized' by heating it and allowing it to air cool a few times so that stresses are relieved and the grain structure is finer. Then it is heated to critical - at which point it becomes non-magnetic - and quenched quickly. In the case of plain carbon steel like a RR spike, this would be done in water, brine, or oil. That maximizes the 'hardness' of the steel, but it leaves a lot of stresses in it. So it is then tempered by holding it at 300 or 400 degrees for a couple hours, then letting it cool to room temperature. (This is usually repeated a few times.) The blade will lose some hardness, but will be less brittle.

All that leaves the surface pretty cruddy. At that point you can - carefully - finish the blade and polish it. (I say carefully because you don't want to overheat it.)

Now different bladesmiths have different ways they do these steps and different steels are treated other ways. What I've said so far is an over-simplification that contains almost none of the technical details. If you want that, you'll need to do a bit of searching around here. For now, let's just stick to the simple case for RR spikes.

Straight carbon steel can dissolve up to about .84% carbon. (It can contain more carbon, but let's avoid that case for the moment.) These are referred to as the 10xx steels, where 1080 contains 0.80% carbon. High carbon is good, low carbon is bad. RR spikes usually run around 0.3% carbon. To a knifemaker, that's way too low and the steel just won't harden well enough to make a quality knife. There may be other things in a RR spike (like copper) that affect the hardness, but again, that's a case for another search.

The thing about RR spikes is that they are cheap and the knives you make from them are interesting conversation pieces. They are never going to be really tough blades, but that's OK; They're still neat. Some REALLY cool knifemakers (e.g., Tai Goo) make some really cool knives from RR spikes. They sharpen easily and make decent letter openers.

It sounds like your knife has been forged and quenched. I say go a head and clean it up and make the nicest knife you can out of it. When you're finished, use a little wax on the blade to deter rust. I sometimes spray clear acrylic on the handle to keep it from rusting, too.

Drunkenduck
05-16-2006, 01:07 PM
Somewhere on this board is a rather in depth discusssion on railroad spikes. What it boils down to is that what is wanted of a railroad spike is just the opposite of what is wanted of a knife blade. Railroads, actually the government, want maximum toughness out of the spikes and care nothing about wear resistance (read edge holding ability). RR spikes have to be able to almost bend double without cracking. Steel for knive blades have to have a balance between toughness and wear resistance, which are generally at the opposite ends of the spectrum form each other. We want something that has enough toughness not to break, chip, or crack but have enough wear resistance (hardness) to hold an edge for a reasonable amount of time and be reasonably easy to sharpen.

Doug Lester

gunnut_69
05-19-2006, 02:34 PM
Fellas,

Thanks for the informative discussion- guess I'm trying to make a cadillac out of a pinto when it comes to having everything in this one type of steel. I'll stick with what I have and just work it the way I know how and hope someone buys it! If I can finish it like I want, I'll post a pic and let you critique! Anyone know any websites with blades fashioned from spikes? I would love some inspiration...

-Gunnut

blacksmith101
05-19-2006, 06:10 PM
4136Don't sell the lowly spike short. Last year I was in southern Indiana at a large flea market and there was a gentleman that had retired and found himself short of funds to get by on. He had a simple coal forge and a railroad rail anvil and was fashioning spike knives for sale. In fact he had quite a crowd most of the day as he was making noise and smoke. I talked at length with him, about his knives as they were quite nice. He stated that this was how he was supporting himself and his wife. Said that he wasn't rich but all the bills were paid and they had food. Makes the rest of us think of our station in life. Back to a picture: here is a knife I beat out of a spike years ago at a demonstration. Hope it helps with your quest.

TexasJack
05-20-2006, 01:03 AM
gunnut, how could you possibly miss the spikes that Tai Goo ('Misternatural') has posted here? He turns them into a real work of art!! Do a search and you'll see what the lowly RR spike can become!