Making woodworking hand plane irons

Greetings and salutations.

On Thu, 15 Jan 2004 03:04:54 GMT, "speedbuggy" wrote:

Well, what the heck, I may as well snap at the bait.

First off...O1 is already pretty much where you need it to be in terms of heat treatment, I think. Also, I am not really all that thrilled about a 1/4" thick chunk of steel for a blade...but, at least you REALLY will not have to worry about chatter (*smile*). I would suggest this: Grind an appropriate edge on it, being careful to keep the metal cool enough to touch with your fingers while grinding. Sharpen to Scary Sharp standards. Build a wooden plane body to fit it and see how it cuts. If it dulls too quickly...consider retempering the steel...or...running by the local WoodCraft store and picking up a Hock blade *smile*. The nice thing about making a wooden plane is that...well...it's wood. The only metal in it is the blade, so, it is a good project for a woodworker, and, when done, you WILL have a very useful tool. Wile there is (theoretically) nothing complicated about tempering steel, it actually can be quite a challenging process, requring fairly exacting timing and control of heat. Unless you have a *lot* of disposable income burning a hole in your pocket, perhaps it would be better to experiment with some smaller pieces of steel, heating them with a MAPP torch to tempering temperatures, and, annealing as necessary on the burner of your stove. I would suggest starting with a knife blade that is 1/8" thick or so... I would also suggest that you visit the local library or used book stores, and, get some books on metallurgy, to start getting an idea of what happens to the internal structure of metals when they are heated, and, how tempering and annealing changes that structure. Getting a little knowledge first will lead to a much happier and productive time. Regards Dave Mundt

Hi guys, I am a blacksmith and used to specialize in cutting tools. First thing you should know is that precision ground flat stock comes annealed, meaning as soft as it ever will be. This makes it easier to cold work (file, saw, grind) So first thing will be to shape the plane as close to finished as possible. Do not however take the edge down to a sharp edge. If you do, you risk cracking during the hardening phase of the heat treat cycle. Instead, grind a nice clean bevel but leave the very edge square and about .?" thick. Do not polish it but go to 220grit finish. I am assuming you will not be forging this blade to shape but even still the finished blade should be re-annealed before hardening. This is because stresses are imparted to the steel during heavy grinding operations. I suppose if you are careful to keep the heat down when shaping the blade you might choose to skip this step. I am not exactly sure of the hardening temperature for 0?1 but it is probably between

1450?f ?1550?f. Bring your electric furnace up to temperature then place your blade inside. It should take about 1/2 hour to get the steel to the same heat. grab blade with tongs and quickly plunge edge first into your oil bath. Drugstore mineral oil works well. Oh, warm up the oil first to about 120?f this lowers viscosity and actually is safer than cold oil. The steel should now be harder than the hubs of Hell. Test it with an old file, it should skate right off the blade and leave no scratches. If it does then you hardened at to low a heat. The steel is hard but also under a LOT of stress and must now be tempered. DO NOT WAIT as the steel will sometimes just pop apart. If you have an oil deep fat frier you can set it at about 400?f and toss the hardened blade in it for about 1 hour. You can also do this in the kitchen oven. Yer done except for the clean up and sharpening. Good luck, expect some scrap metal before you get a keeper.

Glen G.

I will not go into the heat treating cycle for O-1, that is easily obtained from the Internet or a handbook, but I did want to comment about the actually operation when you harden it. One thing to absolutely do is to get some stainless steel foil and make a foil bag just big enough for the blade to go into it, leaving enough on the opening end to make a tight double fold closure. When you are ready to do the hardening, wrap the blade in several layers of paper towel, insert it in the stainless steel bag,.and fold it tightly closed. Then do your hardening procedure, allowing extra time for the heat to get through the steel foil and the paper. The paper intercepts the oxygen as it chars, preventing the metal from getting any scale on its surface. Once you have run your hardening heat long enough, and I add about

30 minutes for the bag and paper wrap, then working very quickly (have everything ready and placed for rapid access, including a screw driver or other similar tool to help opening the bag) grab a set of tin snips and very quickly cut the end off the foil bag and dump the contents, unburned paper and all, into your oil quench. If you try to separate the paper and the blade you will lose your heat and it will fail to harden, especially so with a thin 1/4" blade. Dump it straight down in so the blade enters the oil vertically, and have the foil bag right close to the oil so there is no splash.

Then, reach in with some fine pointed tongs, so as not to cover up much of the blade with the tongs, and swish the blade around in the oil. Once it has lost most of its heat, you can just barely touch it with bare skin, then move it rapidly into your tempering oven, which was preheated to the temperature you need. If you allow the blade to go completely cold, and go off and eat lunch or something, you may find it will self destruct.

The stainless foil bag does several things for you. It prevents any fire scale from forming, which means the blade will be clean and shiny when its done, without any grinding or other treatment. It also slows the heat entry, reducing stresses, and it evens the heating so that the whole blade will come up to temperature more evenly. Doing fine blades by any other means, other than in an inert gas atmosphere, is a waste of time, and the results will be dubious at best. The stainless steel foil can be obtained through McMaster Carr, or a variety of other sources...don't try using your wife's aluminum foil.....won't work. The foil is expensive, so you may want to ask around and find someone who will sell you just what you need, not a whole roll. I am fortunate enough to have a local machine shop that makes the bags up in various dimensions and sells them to make a little extra money, so I just buy the premade bags. They generally cost between $3 and $4 each depending on size. The foil is very hard and its edges are like a razor, so if I don't have to handle it to make the bag I am happy to pay the shop for them to do it.

I will also say that the second reply you received was dead on correct. The O-1 comes in a dead soft annealed state to make grinding or machining easy. If you are going to use it without any hardening and tempering you may as well use mild steel instead, and not waste your money on tool steel.

Yours,

Ron

Golden Age Forge

E-mail: snipped-for-privacy@reil1.net Boise, Idaho

If you are really going to make a high end plane, you may be interested in making a laminated blade like the old original plane irons. It isn't hard to do, and it will be a pretty special piece of work when it's done, one that you will be proud to pass on to your son some day. Also, it will have the qualities of strength and hardness that are not available in a solid tool steel blade, although this really isn't an issue today with modern steels. I am a member of an old tools group, the vice president in fact, and am one of only three smiths in the group. All the rest are wood workers, and most collect old planes. I have made laminated plane irons several times for guys to replace badly pitted and rusted originals. If you do the forge welding in a gas forge it is very easy, in a coal forge it is very easy too...to burn the tool steel away...grin. Use gas. You could use the tool steel you have and weld a thicker back to it and draw it out to the correct thickness, certainly less than 1/4", to make your blade. If you decide to make one, I recommend 1095 for the tool steel because it forge welds easily, also I don't have any experience forge welding O-1 so can't speak about its qualities. If you have a good anvil surface, and have, or make, a good surfaced flatter, when you finish the blade you will not need to do any grinding other than the cutting edge itself, although I do take a light sanding on the faces after I remove it from the pickle tank to remove the fire scale. You do need to remove the fire scale.

Yours,

Ron

Dear Ron, Personally I think the stainless steel wrap is a pain in the butt and not worth the bother and expense. Come on Ron, fine tools were and are still made with out the foil wrap. Unless you are hardening chunky dies or something it is almost impossible to get the wrap off of a plane blade or knife before losing the critical hardening temp. Plus, if you are hardening in a forge it is next to impossible to judge hardening heat/color when the tool is wrapped in foil. I tried this stuff and did nothing but curse it. If you are careful and you are at the right heat almost all of the light scale that forms on a blade will pop off when it's quenched anyway. Another cheap and easy solution is to make a watery paste from wood ash, charcoal dust and table salt. This is painted on the blade just prior to hardening. It lessens scale formation and leaves a relatively clean surface after quenching. I learned this from a Japanese tool maker. When I asked how much salt to add he said, "till it tastes like sea water" He also said he quenched at a heat the color of a monkeys butt. Why make things complicated? It really isn't that hard to learn to judge hardening and tempering colors. There will be failures sure, but how else do you really learn anything.

Let's KIS eh? Glen

Wait a minute -- you're saying I have to go buy a monkey for a color reference and you call that keeping it simple?

Actually, It was a "Mandril" but to hard to translate from Japanese.

1382?f. Boy I got Ron steamed up.

GG