Michael Kellough Posted September 12, 2009 Share Posted September 12, 2009 (edited) I'm totally new to this craft but I want to make some small marking/utility knives for some of my woodworking friends. The form will be similar to the German chip carving knives. Like this The blades will be about 3 inches long including 2" of tang. I've ordered some annealed 0.1 steel, 1/32" thick x 1/2" wide, from McMaster-Carr and I plan to simply grind the shape, drill holes for pins, and then try to heat treat. Heat treating is the part I'm worried about. Since these blades are so small do you think I could simply use an ordinary propane torch? I've been pondering making a tiny "forge" from a plumbing Tee fitting and feed the flame in the side. Is that stupid? Edited September 14, 2009 by mod07 Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted September 12, 2009 Share Posted September 12, 2009 I have used a MAPP gas torch at work for some small O1 parts. You do not have to get the entire knife hot as the tang can stay soft. You can use a small toaster oven for the tempering. You may want to put some brazing flux on the blade to keep it from oxidizing too bad. Do not grind to size, as when you polish after heat treating you will be removing more material. Quote Link to comment Share on other sites More sharing options...
Michael Kellough Posted September 12, 2009 Author Share Posted September 12, 2009 "Do not grind to size," Do you mean don't grind the edge sharp? Surely I should grind the drop point and bevel to the approximate edge. ? Quote Link to comment Share on other sites More sharing options...
junker Posted September 12, 2009 Share Posted September 12, 2009 he means that when you grind the blade... leave it sligtly too big... that way when you polish the blade it won't end up smaller than you want Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 12, 2009 Share Posted September 12, 2009 You can make a bean can forge quite easily Michael. Simply roll some 1" kaowool and slip it into a bean can. (approx 1lb coffee can size) Then put a hole in the side and through the refractory large enough to take the tip from a propane torch like a Bernzomatic soldering torch. Bed up a couple old coat hangers to make legs and whatever else it needs. To use, just slip the torch tip just into the can, don't put it far into the refractory or it'll melt. Toss a bit of lit paper in and open the valve. Frosty Quote Link to comment Share on other sites More sharing options...
Michael Kellough Posted September 12, 2009 Author Share Posted September 12, 2009 I get it Junker, thanks. Frosty, that sounds just right for this little project, thank you. Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 12, 2009 Share Posted September 12, 2009 My pleasure Michael. Just don't try using it for tempering it's way too hot too fast. Temper it in the oven. Frosty Quote Link to comment Share on other sites More sharing options...
Michael Kellough Posted September 12, 2009 Author Share Posted September 12, 2009 So I should do this in order, 1. Cut stock to length 2. Grind to form (slightly oversized) 3. Harden (in bean can forge) 4. Temper (in toaster oven) 5. Fine grind and polish to final form Is that about right? Any corrections or additional details will be greatly appreciated. Quote Link to comment Share on other sites More sharing options...
jimmy seale Posted September 12, 2009 Share Posted September 12, 2009 may want to heat up the quinch oil to 150 degrees,but other than that your on your way...be well,jimmy Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted September 12, 2009 Share Posted September 12, 2009 That sounds like a good plan. Although with that small of a blade you could harden the end and grind the entire blade afterwards, then temper it. Watch your heat while hardening, as the thinner edges, and point will heat faster than the other parts. Quote Link to comment Share on other sites More sharing options...
Frosty Posted September 12, 2009 Share Posted September 12, 2009 You might want to draw the tang to blue, there's no reason for it to be hard and every reason to want it tough. Using the torch without the bean can. Frosty Quote Link to comment Share on other sites More sharing options...
Michael Kellough Posted September 12, 2009 Author Share Posted September 12, 2009 That sounds like a good plan. Although with that small of a blade you could harden the end and grind the entire blade afterwards, then temper it. Watch your heat while hardening, as the thinner edges, and point will heat faster than the other parts. This is the kind of stuff that worries me because I don't even know why this is a problem in the hardening stage. The fine edge can't get harder than hard can it? :confused: After hardening and polishing, if I temper in the toaster oven the difference in thickness of the different areas of the blade won't matter? Another question, why should I polish before tempering and does polish mean what it sounds like? As a woodworker I might polish a blade (on a buffing wheel) as the last step following the finest sharpening stone but I get the feeling polish is a little different in this context. Quote Link to comment Share on other sites More sharing options...
pkrankow Posted September 13, 2009 Share Posted September 13, 2009 Heat treatment likes to crack things. Expect to loose half your work till you get the heat treat process down, then should be more like 10% or less fail in heat treat. I'm still at 50%, but I haven't done any heat treat in quite a while. Phil Quote Link to comment Share on other sites More sharing options...
BIGGUNDOCTOR Posted September 17, 2009 Share Posted September 17, 2009 The thinner edges and points do not get harder, but they can burn. In other words your knife will be ruined, and look like a 4th of July sparkler. Polish the blade after hardening to remove scale, and make it look nice. Tempering will not be at a high enough temperature to cause scale to form, just the colored oxides. Since the entire part is brought up to temp slowly, and evenly in the oven, thickness isn't a factor. Personally I might just harden the blade, and the top inch of the tang, and leave the remainder soft. The only place that design would bend at is right at the junction of the handle to the blade. Quote Link to comment Share on other sites More sharing options...
Michael Kellough Posted September 17, 2009 Author Share Posted September 17, 2009 Thanks for the extra notes on heat treating. I agree about trying to just harden the business end and I have been worried about the thin edge of the blade getting too hot to fast. I wonder about putting another piece of stock in close to the thin edge as a sink to slow the heating of the edge? Another thought, what about heating a piece of angle and letting the blade draw heat from the inside of the angle with the thick edge close to the inside corner and the thin edge much farther from the hot angle. Had a similar thought using pipe instead of angle. Finally, I wonder if I can just use a propane torch (or two from opposite sides) directly on the thick edge of the blade? A slot in some sheet metal could shield the thin edge from the flame. You may know the answer to these speculative questions but I know I have to just try it to learn. Still, it's great to hear what experienced people have to say. Quote Link to comment Share on other sites More sharing options...
Michael Kellough Posted September 17, 2009 Author Share Posted September 17, 2009 (edited) Maybe I don't need a forge for this? I ground out two test blades. I heated one using an ordinary propane torch and it got to bright orange. Even though the blade is very small it was still difficult to get the whole business end of the blank to maintain the same brightness but I quenched it in oil and tested the hardness with a couple of tools. A good sharp screwdriver blade skated across but the corner of a file scratched the surface a little. At first I thought it might only be scratching the scale but I cleaned the scale off and the scratch remained. One problem I noticed is that the blade warps away from the side I ground. I ground only one side so that one side is coplanar with the center of the handle and one side is a long flat bevel. If I can't keep it from warping I'll have to do a different grind/shape I guess. Since the blade was warped I decided to test the hardness a little farther and bent the blade back towards flat and a half inch snapped off. I have no idea how hard the blade needs to be prior to tempering. Is bright orange hot enough? I suppose yellow is the next hotter color. Do I need to go there? Is there a minimum time for the heat to be held at a certain temp/color? To treat the second blade I used two identical propane torches (in air like the first blade) and they created a larger hot spot so it was easy to get the whole blade section of the blank to bright orange very quickly, like under ten seconds. I kept it at that color for about twenty seconds and immediately quenched in oil as before. The blades are now cooling in the oven after baking at 375F for an hour. I hope I wasn't supposed to quench them Any comments are welcome, even virtual dope slaps as long as they're accompanied by explanation :) Edited September 18, 2009 by Michael Kellough Quote Link to comment Share on other sites More sharing options...
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