---------------------- multipart/alternative attachment If you want/like to make your own steel tools, get this book: "The Complete Modern Blacksmith" by Alexander G. Weygers, published by Ten Speed Press for about $20. Check Amazon or the other big book dealers. It is perfect for people who are handy, but don't have a degree in metallurgy. Warning: you will want to start pounding metal after reading this book. The short version: Soften high carbon steel by heating to a red glow and cooling very slowly (hours). Make your tool. Harden to brittle hardness by heating to light cherry red (1275 to 1450 degrees F) and quenching very fast in water, brine, or oil. Heat treat to specific tempering temperature to control final hardness vs toughness (400 to 640 degrees F). Think of this process as going over a hill. You have to go all the way up to brittle hardness, then come back down to the moderate hardness you want. You can't go up from soft to medium. A very hard steel will shatter like glass. A soft steel will bend. The art of tool making is selecting the point in the middle which is hard enough to do the job without bending or shattering. (Shouldn't all piano tools be well-tempered? :-) The long version: Quoting from Weygers, in Chapter 2: Tempering Steel "Only high-carbon steels are temperable and can be hardened in the process called tempering. Mild, or low-carbon, steel cannot be tempered but may be case-hardened (a chemical process on and just below the surface). Hardened tool edges must cut, shear, punch, emboss, and do many other tasks demanding both hardness and toughness. Such tools must not break or bend in normal use. The aim should be that tool edges, in well-designed and well-tempered tools, should stand up, even under momentary extra strain." .... Tests for Temperability: Test 1: From the scrap pile, choose a steel rod that you suspect may be of a high-carbon quality (auto axle, leaf spring, metal file, drill bits). Hold it on the power grinder an examine the sparks. .... The rule of thumb in the shop is that a dull spark is mild steel, and a brilliant, sharply exploding spark is high-carbon steel. .... If you are still not certain, you can resort to the following sure and final test. Test 2: Build a medium-hot "clean" fire (not emiting smoke or yellow flame. Combustible gases remain which may damage hot steel.) It should resemble a glowing charcoal fire. Place an inch of the rod horizontally in the fire, making sure that hot coals are always underneath the steel, as well as around and above it, to prevent fresh air from hitting it directly and thus oxidizing its surface. As soon as it heats up to a light cherry red glow (as judged in a semi-dark room), pull out the rod and immediately quench it completely in water at room temperature. It should emerge pearl gray in color. Next, clamp the steel rod in the vise and, using the tip of a sharp file, pick on the gray quenched end. If the file tip slides off, like a needle on glass, it means that this steel is of high-carbon quality and thus temperable." Tempering a tool blade: I will paraphrase Weygers: Soften (anneal) the steel by heating to red heat and cooling very slowly, covered in ashes. Once a tool blank made from softened, tested steel is finished, the blade can be tempered. Heat to light cherry red and immediately quench, fully submerged and motionless in one of the following coolants: Water, if the blade is fairly thick. Brine, if the blade is fairly thin. Oil, if the blade is very thin. Steel cools, through conductivity, at a pace dictated by the boiling temperature of the liquid. In water, the core becomes only a little less hard (fast cooling). In brine, the core is a little softer (slower cooling). In oil, the core is softer still (slowest cooling). Polish the area most critical (usually the cutting edge) to a mirror finish so you can see the slightest change in oxidation colors during the tempering. Drawing Temper Colors To "draw" color is the term used for the process of reheating a brittle, hard steel in order to tember it for a specific hardness. As steel heats, its shiny surface changes color, and each color change indicates a change in steel hardness. Use a propane torch. Heat the tool, holding the thicker shank toward the handle end in the blue flame. Keep the mirror smooth, brittle blade safely outside the flame. Soon, as the gradually increasing heat of the shank is conducted toward the blade, the first oxidation color appears - a faint straw yellow (400 degrees F). (This is an oxide on the surface, not a glow). As you heat the steel further, you will see the whole color spectrum appear as a full color band: blue, nearest the flame, followed by other colors, to, finally, the original sheen. When this full color band moves down the shank to the beginning of the blade part, now hold that part quite high above the visible flame, in the invisible column of heat rising from it. Manipulate the tool over the heat to spread the desired color (and thus hardness) over the working areas, then quench at the moment the color is correct. Oil quenching is less likely to crack and weaken the steel. Oxidation colors: "Light straw" for blunt-edged, sturdy tools. (400 degrees) HARDEST "Dark straw" for center punches, cold chisels (475 degrees) "Peacock" for thin, delicate tools, or spring-action parts (540 degrees) "Full blue" to "light blue" is the last color to appear (640 degrees) SOFTEST Get the book for 300 pages of low-tech tool-making how-to and other practical shop tips for metal maniacs. I purchased my copy in 1997, but I'm sure it is still available. Originally issued in 1973. Good stuff. (No, I don't have any relationship with the publisher.) Greg Graham Graham Piano Service Brodheadsville, PA __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/e4/79/aa/eb/attachment.htm ---------------------- multipart/alternative attachment--
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