[Scott]

Part 4 Hardening

While the blade is still in the handle, hone it as sharp as possible. Wrap a sheet of 600 grit wet/dry sand paper around a piece of dowel (eg.30.5cm (12”)of broomstick) to clean off the burr in the hook. If there is any damage to the edge and for sharpening the hook after it is hard, make two more dowel sanding sticks with 360 and 240 grit.
Use dowel sanding sticks for the inside of the hook and straight sanding sticks for the back. Once the hook is hardened and tempered it will be sharpened from the inside and only the burr would be removed from the back.
For the hardening process you will need a coffee can (or something that holds at least 750ml) 2/3’s filled with olive or canola oil warmed to body temperature, a propane torch set into a small bucket of sand for stability and safety, and a pair of vise grips,
Have the can with oil and the torch in sand beside each other on a table free of any obstacles. If you’re right handed have the torch on the left. If you’re a lefty do it with the torch to the right of the oil. This way when you have your hook at the right colour you can quickly douse it in the oil without burning yourself.
Take the blade out of the handle and place the end of the tang securely in the pair of vise grips. Always be aware of the razor sharp, thin, soft edge. Warm the oil in the can to body temperature. Japanese sword smiths apparently achieved this temperature in the stomachs of slaves. An old timer told me his father would use fresh urine… from a cow. I prefer canola for the deep fried chicken aroma after dousing.
Now you have the vise grip in hand, blade in vise grip, torch on med. high and secured so it will not move. Do a practice run smoothly and quickly from the flame to where it would land into the centre of the can, like a perfect dive, not touching the sides or bottom of the can with the blade (and don’t go into the oil yet). Start passing the blade over the flame. The cutting edges are thin and so is the tip, so when passing the blade over the flame spend more time on the thick section. Move quickly through the flame but keep the steel in the flame. Parts will begin to turn blue, spend a little more time in the areas that aren’t yet blue. Keep passing the blade through smoothly, constantly evening out the colour. At this time shadows will start passing over the blade, then it will start to glow. At this point the tip and thin edges are vulnerable, letting it get to hot and glowing orange your burning out carbon, at yellow your ruining the metal and its distorting.. This situation happens very quickly. The damage can be repaired, if you get out quickly. You can regulate the temperature by keeping an even glow over the whole blade (not including the tang). Again watch that tip closely. When it passes into a pie-cherry red evenly across and from tip to tang, get ready, and in one smooth motion douse it into the oil. Wiggle the blade, stir (the best way is tapping the vise grips against the sides of the can), always keeping the blade submerged. Slow down, gently stirring until the blade can be handled. If you don’t get it don’t worry. Wipe your blade and do this process again.
The blade right now is as brittle as glass. Now it is ready to be tempered. Wipe off the blade and clean the tang bright.
I'll post on tempering soon.


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[Irish]

Scott, this tutorial is great, thank you!

I don't want to interrupt the flow of your tutorial but may I ask a question here???

I have 'heard' that the steel in older tools is somehow different than the steel in new tools. And as you are going into tempering, is this true? Are the steel mixes different today than yesteryear's tools or does the steel mature somehow as it gets older? Or it this just a myth?

Hope I have asked this correctly!

Thank you, Susan

[Hi_Ho_Sliver]

I have always had a problem getting an even color throughout the piece of steel, between the thicker areas and the very thin edge? Not enough movement over the fire? thanks, great tutorial. Dave

[AlArchie]

Susan, this is just my opinion, but it is my opinion backed by a lot of observation, both of materials and of the craftsmen who utilize these materials.

Steel is a term that encompasses a wide variety of alloys.....there are inumerable alloys that have varying qualities that adapt each to specific uses.

One of the benefits of "old steel" is that it generally was alloyed for a specific purpose by extremely skilled craftsmen who developed their craft either through loads of experimentation or from very thorough tutelage.

There were also some old time "junk tools", too. Charlatans have abounded in all eras

I doubt if there are very many, or ANY modern toolmakers that alloy their own materials.

On the PLUS side to the use of modern steels, there is a much higher degree of quality control in the manufacture of high-end, specific use steels. A modern tool maker has access to a myriad of different steels each designed to meet his individual needs.

Given, that, let's move on to one of our current well meaning concepts. RECYCLING! Steel is a material that is very easily recycled. That can be a huge negative in the quality of the material being produced, as there is no way of controlling the alloy content of re-smeltered steel.
All the impurities and alloying materials of all the scraps are smelted into one batch of "general use" steel.

Quality tool steel is generally produced from virgin sources, and alloyed to produce specific qualities. However these steels are more expensive than the recycled stuff, so unless a manufacturer is willing to purchase the higer priced first run, stuff, his product is apt to have uncertain qualities of tensile strength, ductility, final hardness, and adaptability to tempering.

There are of course exceptions to these concepts.

So, if you find a QUALITY old tool, it will be a fine piece of work, and if you find a junky old tool, that is what you will have.

If you buy a quality NEW tool from a reputable manufacturer, odds are you will have a fine tool, and if you find one made with "junk steel", you will have a piece of junk.

Al

[Irish]

Al, Thank you! That makes sense!!!

Susan

[whitecree]

Oil quenching... darn, I knew there was something I'd forgotten! Thanks for the reminder, Scott!

[Scott]

If you find a good source of recoverable tool steel you can test it for carbon content and alloy content easily with spark tests on your grinder. I don't spend a dime on steel but do spend time testing and experimenting, or should I say I have. I got a stash that will last 25 years and there is enough good knife steel out there to keep many full time toolmakers busy. As Al wrote there are some incredible steels and there is junk as far as steel for tools.
As far as aged (75yrs. or more) high carbon steel recovered fom saws and saw blades, every piece that I've come across has been good. Old swede saws are excellent. Old timers tell me that the more a saw was used the better the temper and quality became. There could be something to this and it would have to do with molecular structure changing over time, but I don't know. Are there any metallurgests out there?
While on the subject of recycling, if we don't try to use all the stuff that can be re-used I suppose the human race deserves everything nature can throw at it. Except, those of us that do try to be responsible ,not to mention our children and other life, will go down with those who do not.

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