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Hey metalwork guys, figured you'd like this chick's work: http://www.stumbleupon.com/su/1ySe1w/justpaste.it/26c That's some seriously amazing skill with a torch.
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Apr 13, 2010 18:54
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Hah! I've been meaning to catch up with this thread (I'm perennially 600 posts behind). I took some blacksmithing classes at the Crucible in Oakland a few years ago, and have wanted to get back into it at some point. Just bought a house in December, and I have dropped hints at my wife of my ideas for putting a forge in the garage, but I'm not sure if that'll fly (more due to regulations and/or angry neighbors really). We've also got an oxy rig that we've hardly used, and a couple years ago my stepdad and I built a big metal project table out of a 4'x4' 1/4" sheet of steel plate, stuck on to four segments of 2" schedule 40 with some bracing. It'd be perfect for some welding projects if we ever get the garage full of our packed crap cleaned up.
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Apr 13, 2010 22:16
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I actually have a whole book on making gas forges (I'd prefer to make a natural gas forge rather than deal with propane tanks). My wife got it for me for my birthday a few years ago... she was also the one who got me my first blacksmithing class. So you could say she's pro-blacksmithery? I don't actually know if I have surly neighbors or not yet; but given that we just installed bees in our back yard, it would be good to not compound things by also being noisy as gently caress. Do you guys all work outside? I've only worked with gas and indoors (at the Crucible), and was thinking that maybe if I kept the garage closed (but very well ventilated obviously) and worked during mid-day hours, it might not be too loud outside.
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Apr 13, 2010 23:20
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Hmm. Well, there's a vent at the top of my garage apparently - I can see it from outside. The previous owners for some reason stapled blue tarp all over the inside ceiling, and put up pieces of drywall in random places... we think someone must have been living in the garage for a while. (There's no leaks or anything to explain the tarp though.) I figure once we tear down the tarp and figure out what's going on under it, I could always build a hood and venting up to that vent in the roof, hook up a fan to it, and have forced-air exhaust above a forge. This is all long-term planning though. We have other projects that need to be done first.
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Apr 14, 2010 06:00
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Well, maybe, but you need room for a 100lb power hammer, right? And a couple of post vices, a big project table, a bench-mounted shear, maybe an english wheel, your anvil, a big forge and a little forge and maybe an oven for annealing... there's never too much room, right? (I'm kidding, I've been following your housebuilding thread and your tractorbuilding thread so I've got a really good idea of how much space you've got and I'm very jealous.)
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Apr 14, 2010 17:11
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Bay Area metalgoons: I got this in the e-mail this morning.some guy posted:Alco Iron & Metal is preparing to move to a new location across the street. They've lowered prices on "small stuff" to reduce moving expenses. I believe this is the San Leandro location but call to be sure.
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May 12, 2010 20:05
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Oh man. A big sturdy post vice is such a useful tool. Someday I will have one...
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May 22, 2010 19:45
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I love that vice. Almost every part of it looks hand-made, which is awesome. Making a post vice from scratch would probably be an interesting project for a very proficient blacksmith to show off his advanced skills.
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May 31, 2010 18:32
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Ugh... how did I never even notice that the two words are spelled differently?
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May 31, 2010 20:53
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Something that every household can use, is just expensive enough to be worth making, but not so expensive that few people can afford it, and is not too difficult to make. Fire irons. A set with poker, shovel, tongs, brush, and a stand. Make a bunch at a time, put some nice little flourishes in them, and you can probably sell each set for a couple hundred dollars. Most of the pieces just need basic square stock, maybe three-quarter-inch or whatever. When I look at hardware stores and home furnishing places and the like, most of the fire iron sets I see are awful; ugly, badly made, or both.
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Jun 7, 2010 18:19
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Door knockers. Candlesticks. (Other 'architectural' blacksmithing projects like door handles, hinges, railings, fences, lanterns, etc. are all probably worth a lot more, but I tend to think they have to be custom-made.)
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Jun 8, 2010 05:21
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I've used a porta-band to go through 1" square and round stock. One cut and the blade is barely warm to the touch. Given that the blade is held inside the machine basically by tension, I wouldn't want to lube it up for fear of it coming loose.
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Jul 5, 2010 20:27
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Slung Blade posted:Thinned paint is great for flowing into spaces like that. I use it all the time to paint most of my stuff. Keep in mind he wants water-safe (e.g., I think the mugs should be able to go through the dishwasher?). I don't think normal paint will handle that very well. I have applied patina using heat and wax, but I don't think that'd be a good idea on a glass piece like that either.
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Jul 14, 2010 18:59
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I have a copy of this book, and it's pretty great. Got it as a gift. If you're looking to build a gas-fired forge, I think it's not a bad $20 spent.
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Jul 16, 2010 18:16
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I've made three knives, and I took a knifemaking class at the Crucible. We used power sanding (belt/disk) for rough work after forging and shaping, on annealed soft steel. After hardening (oil quench) and tempering, everything was done by hand: first a file, for final shaping, and then hand-sanding for polishing. I would not suggest power-sanding for a polish for fear of removing too much material, although if you've got a lot of finesse I guess you could manage it. Start with 80 grit, then 120, then 200. If you're happy with a semi-gloss finish (I quite like it) you can stop there, or you can go on down to finer and finer grits for more polish. Ultimately, buff with polishing compound regardless of where you stop with the sandpaper. Edit: Of course, this was for nice carbon steel full-tang knives. For a railroad-spike letter opener, where you maybe don't care as much about getting an exact figure, and a few pits or whatever add character to the 'rough and ready' kind of look, maybe that's all way too much work. In which case I'd finish with 200 or so and not worry about it. Leperflesh fucked around with this message at 00:54 on Jul 17, 2010 |
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Jul 17, 2010 00:52
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I was wondering how something with such a huge jaw would keep the blade from deforming while cutting anything substantial. But I kept my mouth shut because I don't know jack about industrial metalworking tools.
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Aug 4, 2010 21:44
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Slung Blade posted:On an unrelated note, anyone here ever made a scythe? I think I need something to chop down my tall grass before I can cultivate the soil underneath it. No, but I've made blades. Leaf springs from a truck make excellent base stock for blades, because they're pretty cheap spring (carbon) steel. I think a spring a couple inches wide and a 3/8" or more thick would be more than enough to make a full grim-reaper scythe blade. All the normal techniques for carbon steel working apply - anneal first, don't work it cold (deep cherry red is your final blow), etc. That said, a decently-sized forge is a big plus. Depending on how big you want your blade, it can get very unwieldy working the middle bit.
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Aug 16, 2010 22:08
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Just remembered another thing about a scythe blade: it's sharp on the inside of the curve. That bears special attention. When you start with bar stock and draw out one side for the blade, the stock will curve in the opposite side. So ordinarily you'd bend the stock first, then work the inside of the curve down, and it winds up basically straight at the end. To sharpen the inside of a curved edge, you'll need to exaggerate this a bunch. So curl your stock into a u-shape, then work the inside edge, and stop when you get to the desired amount of curve.
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Aug 16, 2010 22:14
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Yup, thirding. I've forge-welded a couple times, and all we used was spoonfuls of 21-mule-team Boraxo (or however many mules it is, I can never remember). It looks totally awesome, too. Take pictures! When you first strike the work pieces together to set the weld, molten glowing flux sprays out!
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Aug 24, 2010 19:56
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I'm sure a lot of you guys hang out in AI as a matter of course, but just in case you missed it: http://forums.somethingawful.com/showthread.php?threadid=3336130 Only one page so far, some bloke in the UK restoring a camper van. Point is, he's got some really nice ironwork in there; I guess he makes ornate gates in his spare time, and he's just built a great big steel rotisserie for the van chassis so he can roll it over and work on the underneath/roof easily. Worth a gander.
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Sep 25, 2010 04:52
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Slung Blade, that carbon-steel bolt knife looks pretty good. One thing I was taught in knifemaking class is that a small detail adds a lot to a knife: try putting a ricasso on one.  In this picture, the upper blade has a nice gradually-curving ricasso. I've also done sharp little ones, just a little semi-circle cut into the knife body to separate the blade from the flat non-sharp handle part. Also in both of the shown knives, you see a sharply-defined transition from the blade to the handle and spine. Doing that requires that the flat of the blade be very very flat; if it's slightly lumpy, the transition from blade to spine will be wavy and uneven. Which means that it shows off how consistent and even your blademaking technique is. Anyway of course you're going for more of a rough, hand-finished look, so I'd never say you should or shouldn't do either of these things, but you might find it fun to try it out a bit.
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Oct 5, 2010 22:09
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Haha yeah actually I think there's a lot of 'knifemakers' out there who are doing entirely stock-removal with grinders. So I like the idea that with a forged knife, there's something to it that informs you it's forged rather than just a piece of stock you ground the poo poo out of. The knives in that picture have small tangs but you can definitely still do it with a full tang or even a fully metal handle. The key is that you want a clear transition between the handle and the blade - but not TOO sharp, because a really hard crease in the metal is a weak point where it is likely to snap if abused. So just a definite transition with a little bit of curve to it. There are of course a thousand and one different choices you can make with a blade, I find it fascinating. I don't remember if I recommended before, but I have this book, and I think it's great. Definitely one of those books-written-by-a-craftsman where the guy clearly didn't have a ghost-writer; the editing is alright but you still get a lot of dense sections, a certain amount of train-of-thought organization, etc. But it's got chapters on every step of blademaking, including handles and sheathes, loads of very clear drawings, an extensive discussion of steel alloys, basically every step from tools to finished blades. Oh and when I was talking about ricassos earlier, that little curved cut back into a ricasso is called a choil, I had to look it up because I'd forgotten the term. Here's a deceptively simple-looking full-tang blade with a very pronounced choil:  And here's a loving beautiful, simple little full-tang blade with a really small choil that I think makes the entire design really pull together:  This one doesn't have much visible transition from the sharpened edge and the spine, but that little choil transforms it from just a piece of metal with an edge ground into it, into a deliberately designed knife. It also lets you sharpen the blade all the way back, without having to pick an uncertain point where the edge stops but the narrowing of the steel keeps going back a little bit.
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Oct 6, 2010 04:41
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Sorry, what? I'm... flabbergasted. Are you saying there's some kind of steel rod that goes bad at room temperature? I mean I'm not saying you're wrong or anything, but that flies against everything I've learned about iron metallurgy, so now my interest is more than piqued.
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Oct 30, 2010 19:05
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Oh OK, I didn't realize those welding rods had flux, that makes a lot more sense then.
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Nov 1, 2010 01:29
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Is it impossible to do what he wants to do with oxy/acetylene?
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Nov 11, 2010 18:48
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Yeah fair enough. I have an oxy rig but I've never attempted to weld stainless, nor weld a round thing to a flat thing (or really do anything besides joining two pieces of flat mild steel). My wife has much more welding experience than me (mostly with aluminum!). I didn't know you could rent tanks. I got mine by going to a welding place and paying some money which includes a large deposit on tanks, which lets you keep them as long as you want, and when they're empty you go trade them for full tanks and pay the cost of their contents only. Eventually you can just give back the tanks if you want to and get your deposit, or, just keep them forever. The hardware and dials and gauges and stuff can be bought as a kit for less than $100, for a cheapo starter kit. Ours was around $150 came with goggles, too (something similar to this e. Oh yeah, in addition to the rigging and tanks, I needed a tank cart, which was probably another $60 or something. So yeah, pushing up above $300 for the lot, I'm sure. Leperflesh fucked around with this message at 20:17 on Nov 11, 2010 |
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Nov 11, 2010 20:13
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Yeah - I'm sure that the deposit I paid was probably at or above the wholesale cost of the (used) tanks, though. I don't remember exactly how much it was, but it was above $100 and I think less than $200 for the two tanks, which are like three feet tall ish?
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Nov 11, 2010 20:19
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As my stepdad explained to me: there are a huge pile of regulations about how tanks must be secured, which can be quite onerous to do in your garage. However, there is the giant loophole of the cart; an OSHA approved cart can be used to hold tanks, and there's no rule about how long they can be stored in one. So, if you have a cart, you're legal and covered. You certainly need one for transport, anyway - don't get pulled over driving around with loose tanks in your car or truck. That said I'm sure you're right in that it is better to have your tanks secured somewhere, so you don't pull one over while yanking on a hose. e. http://www.ehso.com/oshaConstruction_J.htm Note in particular (a)(10): the fact that you have to store your oxy cylinder at least 20 feet from any flammable/combustable, including the fuel gas cylinder, or with a non-combustable barrier with a 30-minute fire resistance rating, and the laundry list of rules for (a)(11). Leperflesh fucked around with this message at 21:13 on Nov 11, 2010 |
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Nov 11, 2010 21:04
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"Damascus" (actually, pattern-welded metal) is also used for art objects, and in those cases, you want contrasting metals, not necessarily hard or tough or hard & tough metals. I have seen very nice contrast between mild steel and straight nickel. I would not bother forge-welding hacksaw blades because they're so thin. I'd want a billet made from much thicker pieces, so that I could draw it out and shape it and twist it to make patterns, and also, so I'd lose less material (as a percentage of the total) to scale, while heating. With really thin metal, any kind of drawing is going to 'break through' the layers in points, leaving you with either a messy swiss cheese or just a poorly incorporated alloy.
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Nov 24, 2010 00:20
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Ambrose Burnside posted:'Nother blacksmithing question- Several good answers already but, here's another one: Go to your local flea market. Look for people selling rusty old tools. Buy them! Many are made of hardened tool steel and you can often get them for super cheap. Especially if they're damaged in some way. Sometimes you can get a whole toolbox full of ancient rusty tools with broken handles for a couple dollars. Of course, some of them are still functional and just need the rust taken off or a new handle, which is also great. Also, flea markets are just great, anyway.
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Nov 25, 2010 19:23
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dv6speed posted:The tuyere is simply the hole the burner enters the furnaces at. A tangential tuyere is one where it enters the furnace on an angle so the flames hits the side of the furnace, causing a swirling action around the crucible. That's not strictly correct (although it's not strictly wrong either). A tuyere is a hole where air enters the combustion area of a forge, crucible, furnace, or smelter of some kind. When your air is being pre-mixed with fuel and ignited, such as with a gas burner, then yes, it's a hole for the burner. But in any other design, such as with a more 'traditional' coal or charcoal burning forge, the tuyere is strictly for forced air induction. The wikipedia article is useful. Check out this image of a very pretty coal/charcoal forge using the traditional pan design. In this image, the tuyere can be seen coming up through the bottom of the pan; there is also a hole so that "clinkers" (coal slag) and ash can drop out without obstructing the airflow (it has a door at the bottom that is sealed during use). And, there's a hand-cranked turbine for forcing air up into the forge. Tuyere design and materials are dependent on the application. With a gas forge it's just a steel tube your burner can fit into, possibly insulated. In a smelter where the interior temperatures get close to the melting point of the tuyere's material, it may be a hollow affair, actively cooled with water. The exact dimensions and material used for the tuyere vary from one design to the next. So, to make a long story short; Ambrose Burnside posted:Also, where does one get a tuyere? They're referred to in most furnace designs but only in passing and I'd have no idea where to get one. Depends on what your exact design is and what you're gonna do with it. Sometimes it might be a complex, valved or cooled affair, such as the one in the image on the wikipedia page for tuyere; sometimes it's just a steel tube of the appropriate diameter to fit your burner into your gas forge. Here is one of the first hits for tuyere; it's a product page from a company that makes copper tuyeres, apparently of fairly advanced design. I think these are for industrial use. Here is a ready-made tuyere and other parts for making a traditional coal/charcoal blacksmith's forge, from Blacksmiths Depot. If you ask me, it's far more than you need to pay if you're just building your own forge; you should be able to fabricate most of those parts (albeit not from cast iron) yourself. Or maybe you just need the pan that goes over the hole in the bottom of your forge, in which case, Here's one on eBay for fifteen bucks. Leperflesh fucked around with this message at 08:28 on Dec 5, 2010 |
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Dec 5, 2010 08:22
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jovial_cynic posted:Sucks, man. I think for your purposes, inch-thick steel is overkill. At 12" x 12", half-inch would be totally rigid and impossible to flex even a little bit, just doing hand-work (hammering, etc.). Also, one foot square of inch-thick steel weighs just over 40 pounds. (Density of mild steel = 0.2836 lb/in3., times 144 square inches = 40.8384) That's a seriously expensive shipping weight for just a chunk of metal you're going to bang on. I dunno where you live, but around here there's a few places you can go to buy steel, and they generally have a 'scrap bin' of some kind you can pick chunks out of for cheapo. Failing that, if you have some sheet steel, you could just cut out several foot-square pieces and stack them up. Weld or bolt or glue them and you've got your rigid steel surface to set into your bench.
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Dec 8, 2010 08:16
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dv6speed posted:If it fits, it ships... for a low flat rate! (Up to 70 pounds) I had no idea they were so generous with the flat rate weight limit. That's awesome. jovial, yeah I guess you had more purposes than just a flat thing to bang on, so you're on the right track. Even so, definitely see if you can't find a steel supplier in your area that you can drop by and check out. The scrap bin is a goldmine. (well, OK, iron mine.)
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Dec 8, 2010 20:32
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How do you know that wheel is cast iron? It seems like an odd choice for a wheel, since cast iron is very brittle. Could it be a mold-cast of lower-carbon steel or wrought iron? It looks like a ton of really amazing stuff. Wrought iron scrap is very valuable because it hasn't been made (on an industrial level) for a century, so if some of that stuff is too far gone to be interesting to look at, by all means preserve the metal for re-use in a forge. Obviously that's not for anything that has value as an antique, e.g., you can still tell what it was/was for. Have you shown any of it to the museum staff yet? Also, are you taking photos and documenting the excavation? There is some value to doing that, even though such a recent site probably isn't an archaeologically important dig, just to preserve the arrangement of finds in case anyone in the future cares.
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Dec 9, 2010 20:34
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I dunno if it's been mentioned before, but everyone needs to check out nonentity's thread over in TFR in which he restores some firearms that were severely damaged by fire. With absolutely gorgeous photography. Oh and he also machines pens from metal. And some other cool stuff. You don't have to be interested in guns at all, to enjoy what he's doing.
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Dec 13, 2010 22:34
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Ambrose Burnside posted:I'm gonna use Christmas to actually get my foot in the door, so- what's a good blacksmithing book or two, the kind of thing you ought to start off with? Some were posted earlier in the thread, but fat loving chance of me finding them. I realize hands-on classes would be a lot more useful- and I'd like to get into one of those too- but I figure it's a decent start. Most of the blacksmithing books on Amazon have at least something to offer. I'll run through the ones I have: The Art of Blacksmithing: This is a nice book to have but will not teach you how to blacksmith. It's a reasonable introductory primer into what blacksmithing is, though, which is an important thing for someone who wants to do this stuff. And it's $10. I'd call it a decent "second book". New Edge of the Anvil The first half of this book is pretty good as a beginner's primer. The second half is pretty much useless except as nice reading (lots of stuff about really advanced technique you really can't hope to learn from a book). This is definitely a good book, don't get me wrong, but probably best as a classroom text. Worth the $25 just for the first half though, I'd say. Complete Bladesmith If you're going to make blades this is a fantastic book. Again not exactly an introduction to blacksmithing, but lots of bladesmiths who do nothing else, could get everything they need from this book. It's also got photographs as opposed to the typical line illustrations in the other books I've got, which is nice. Hrisoulas covers theory and practice, in a logical progression, and has chapters on each important area around blade-making, including making handles and sheathes, a (really excellent) bit on selecting metals, etc. I also have Hrisoulas' follow-up book on pattern-welded blades, but it is not for the beginner. Practical Blacksmithing This was my first blacksmithing book and I'll swear by it. It's absolutely a "manual on how to learn how to blacksmith" which is different than just a manual on blacksmithing, in that it's not just telling you what to do, but how to learn to do it and get better at it. Kinda dry in many places, very much a textbook like what you'd read in college, except for blacksmithing. My copy is battered and worn because I actually brought it with me to every class and lab (I took classes at The Crucible in Oakland for a couple years). For $20 I'd say this is the best book I've come across to be your "first blacksmithing" book. I've thumbed through other books from time to time, but not well enough to be able to give a review. All this said, though: I think the best way to approach blacksmithing is to try it out first. The very basic introductory safety talk we got on Day 1 of Intro to Blacksmithing took 30 minutes, and then after a 15 minute demo, we were making things. If you can find a class you will learn far more in the first hour than you can possibly glean from a book. Books are great to take you past that first step, to study technique you've just been introduced to, or I suppose they're good for people who just want to learn about what blacksmithing is, without becoming a blacksmith (or trying it themselves). Nothing wrong with that. Leperflesh fucked around with this message at 01:02 on Dec 15, 2010 |
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Dec 15, 2010 00:59
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That phase diagram, and others like it, is a fantastic resource for a practicing blacksmith (or anyone who works with metal). However, it is a daunting and scary thing that I would never show to a rank beginner who just wants to get an introduction to metalwork. Start with banging on mild steel and you need not concern yourself with any of it yet.
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Dec 15, 2010 01:06
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The Scientist posted:Do you guys use IR thermometers to measure the temperature of the steel when its most critical, like when quenching? I can't seem to find any that go up past 1000o F. Also I dunno even know if IR would be most ideal for measuring the average temperature of a billet, like maybe the surface temperature is so different from the internal temperature that an IR Thermometer would tend towards giving an inaccurate or incomplete picture. One of the things that phase diagram shows, which happens to be very convenient to know about, is the "magnetic point". You can see it for steels of about .5% carbon or less, at 1414 degrees F. This means that above 1414 degrees F, a magnet won't stick to the metal. This is somewhere in the mid-reddish orange colors, and (as I was taught) is a useful way to decide when carbon steel is hot enough to quench and achieve hardening. You can see that line at 1333 degrees F, and it runs right the way across the chart. For normal carbon steels, above that line you have austenite in your metal, and when you quench you are locking that structure in place. (There's other interesting phases of things too, but for hardening ordinary carbon steel, austenite is the important bit. Which is why sometimes you'll see a much simpler chart that just shows you where the austenite shows up...) The austinite basically dissolves the carbon in the iron which is what you wanted to happen. Anyway, the cool thing is that you can just stick your carbon steel in the heat and test it with a magnet every minute or so once it starts glowing. When the magnet won't stick you know for sure it's hot enough that you're into an austenite phase and you can quench. Since you're usually quenching because you want to harden a piece that is finished (or nearly so), you don't want to leave it in the forge any longer than you have to because the surface will scale. So when you're quenching you are waiting until you hit that non-magnetic point and then you immediately pull the metal out and quench (and you do that loving quick, because the instant you remove it from the heat it starts to lose temp to the air). Everything I just said is a simplification, because there are complicated alloys and there's more lines on that chart and you might be doing something fancy with balancing cementite and delta iron and whatever, I don't know. I'm really still just a beginner. Also, for carbon steels with higher or lower than .5% carbon, at the magnetic point you do not necessarily have ALL the metal in austenite phase - but you'll have at least some austenite, and therefore you'll achieve some level of hardening. And above 2% carbon, there is no austenite phase, you're looking at cast iron which is not suitable for tools. Point being, a thermometer is nice, but not a required piece of kit, at least for the basic forging, hardening, and tempering of non-exotic carbon steels. Leperflesh fucked around with this message at 06:09 on Dec 15, 2010 |
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Dec 15, 2010 06:06
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The Scientist posted:Wow, that's really good to know. I've never heard of carbon steel "cracking" because it was too hot when you quenched it. But, if there is such a point, its hundreds and hundreds of degrees above the point where you'd want to quench it, and you'll know it's too hot by the bright yellow glowing like the sun coloration it has. Iron with 0% carbon is called "iron". Commonly you can get "mild steel" which is an iron alloy with such a low carbon content (if any) that it cannot be hardened by quenching. Mild steel is incredibly common and pretty much anything that is made of steel and not used mechanically (e.g., not a tool, a mechanical part, or a face against which tools will be used) is made of mild steel. Back in the olden days, people used "wrought iron" for exactly the same things as we use mild steel today; the difference has to do with how it was made, which resulted in different impurities left in the metal which gave it different properties. The invention of the modern blast furnace provided a vastly cheaper and more efficient way to make regular-plain-old-steel, and hence, true wrought iron is vanishingly scarce today. (Most things you see in stores that claim to be made of "wrought iron" are actually made of mild steel.)
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Dec 15, 2010 06:32
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The Scientist posted:Right, what I've read recently is that the very nature of HSS that makes it good for tools is that it holds its hardness at much higher temperatures - which I guess is also a property that changes the quenching characteristics. What makes tool steel good for tools is that it is harder than mild steel. Various exotic alloys can be even harder yet. Hardness means it will resist abrasion, deformation, etc. when struck or scraped or ground against another hard object. Hardness in carbon steel is achieved by heating it until it forms austenite, and then quenching it to 'lock in' that austenite as what is essentially an unstable and unnatural molecular arrangement in the steel. Tempering, then, is a process by which you bring the steel up to a temperature at which it will lose some of its hardness, in a very controlled way. The reason you do this is because, when it comes to hardened carbon steel, hardness and brittleness go hand in hand. Freshly quenched carbon steel is known as being "glass hard"; it is at its hardest, but also brittlest, and thus very prone to breaking or shattering - because it is incapable of even the slightest flexing without breaking. So tempering brings down the hardness a little, in exchange for a little toughness, which is the opposite of brittleness. There is another frequently-used heat treatment, called annealing. To anneal carbon steel, you bring it up to that non-magnetic temperature (just like if you were going to quench it), but then put it in an insulated environment where it will cool down very, very, gradually. Typically sticking it in a box full of sand or pearlite or something works pretty well. This is the exact opposite of quenching in that it allows the steel to gradually cool, all of that austenite to go back to being ordinary pearlite and ferrite, and a new crystalline structure can grow within the current shape of the metal, relieving any stresses that have been created from forging. Typically if a blacksmith is going to work on some carbon steel, he anneals it before doing anything else, to relieve stresses set up from the original creation of the metal or (especially) whatever thing was made of the metal before it was grabbed by the blacksmith for repurposing. quote:Let me see if I remember this right; because it holds its temper at higher temperatures, it also takes a higher quenching temperature in order to reach that phase change point. That's correct, isn't it? Eh... I'm not sure that's quite right, at least for ordinary carbon steels. Any hardened and then tempered carbon steel object is in danger of losing temper beginning at 410 degrees F. Maybe more exotic alloys resist tempering until higher temperatures, in which case that might be true for them? The key thing though is that the temperature at which you quench is much higher than the temperature used to temper. If you bring steel up to that quenching temperature, it has, by definition, lost all of its hardness; it's essentially in a state where atoms can freely migrate through the body of the metal. Tempering (again, for normal carbon steel) is done at temperatures lower than the austenite phase, but hotter than 410 degrees. The exact temperature in a given area of the metal determines the ratio between hardness|brittleness and toughness|ductility. quote:This article is where I first got the notion that you could be able to predict not only the temperature at which it is optimal to bring the metal to just before quenching in order to get that desired phase change, but also that you could predict at what temperatures and/or in what quenching mediums a piece is likely to warp and/or crack. That guy is, at the beginning, discussing a fairly advanced knifemaking technique in which clay is applied to parts of the edges of the metal, after a hardening quench but before tempering. The clay acts as an insulator, allowing the area it covers to cool much more slowly than the area it doesn't cover. In this way, you can leave the very edge of the blade bare; heat to a tempering temperature, and then quench; the blade quenches good and hard, but the spine of the knife cools more slowly, essentially tempering much further into the range of not-brittle-but-quite-tough. Doing this without the clay, you get less of a hard transition between the two, because the whole surface of the blade will cool at about the same rate when you do the secondary quench. You can play with using a point-source of heat (say, a torch) to just heat the blade from the back, allowing the warmth to spread through the metal but then quenching just before it gets to the edge, but it's harder and with some pieces can be impossible. The clay technique can even be used to put a pretty rippling effect into the surface. He goes on to talk about problems with cracking, and he does mention 'high temps' as a source of the problem. I think the actual issue is that when forging metal, you introduce stresses, which you can then relieve with annealing. If you don't anneal, or anneal imperfectly, those stresses remain, and then when you go to quench or temper, the steel can warp as it tries to relieve those stresses. There may also be score-marks from filing or hammering, hard edges, sharp corners, etc. and these are places where hardened steel (made brittle from hardening) differentially cools and the surface cracks because it it shrinking faster than the inside. In other words, cooling the surface of a thick piece too quickly can cause problems; I've never seen this when quenching blades in oil, though. But he's also using words like "shock" that I think are inappropriate (or at least, potentially misleading). I have cracked a thick piece of carbon steel while working it, but always during forging, and always because I kept banging on it after it was too cool to keep working. You can learn bad habits working with mild steel, because it is much more forgiving of being hammered on while black. Carbon steels can 'case harden', that is, the surface can harden just from being hammered and worked, and they are much less tolerant of being worked too cool. A thick piece will cool more on the outside than the inside while forging, too, and the anvil will suck heat out of the piece like the enormous metal heat sink it is. So when working carbon steel, there are rules of thumb about what color to stop hitting the thing and get it back into the fire. quote:Also, are these properties that we're discussing the reason that you use tungsten in a TIG electrode I believe tungsten is used in a TIG electrode because tungsten is a metal that has an extremely high melting temperature. This is also why it's used as the filament in incandescent light bulbs. I don't think it has anything at all to do with carbon steel and/or metal hardening. Tungsten is a metal element sometimes used in steel alloys, but that's a different subject. Then again I am just guessing that that's why it's used in TIG, I don't know much about welding. quote:I guess tungsten is incredibly hard, too. I wonder why we don't use that in drill bits and tools. No, not really. As the article says, pure tungsten is pretty soft and can be cut with a hacksaw, while slightly impure tungsten is extremely brittle. Tungsten Carbide, however, is commonly used to make very very hard and tough and durable drill bits.
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Dec 15, 2010 10:05
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