John in Oly, WA Posted March 9, 2017 Share Posted March 9, 2017 Probably old news to everyone but me, but I was browsing the local Goodwill store looking for a pressure cooker to use as a vacuum chamber and came across this for $6.99. Measured out, it's 20 feet of 1/4" round stock. Equivalent amount at the box stores would cost over $20. I know, who buys metal at the big box stores, but anyway another possible source of material to forge - Goodwill and thrift stores. Also state government surplus sales stores can be a source of material. Just bought an outer axle shaft for $5 - about 1 1/4" x 14" of ??? 4140? or some medium carbon steel, and a crow bar for $3. Washington State's surplus store is selling an awful lot of elk and deer antlers right now - knife handles maybe? Unfortunately, they've been in an auction format and going for some pretty high prices. Quote Link to comment Share on other sites More sharing options...
TwistedCustoms Posted March 9, 2017 Share Posted March 9, 2017 I've harvested metal from those kinds of widgets and it can be a hassle. 20' of 1/4" round at my local steel plant is around $3.00 USD. That all depends on how close you live to a steel plant and if the plant sells small quantities. I do agree that scrounging beats hardware store prices on 3 and 4 foot pieces though! The axle shaft is probably 4140 ish, I've water hardened a bunch of them and never had a problem using them for striking tools when tempered to straw. You can never have too much antler on hand! Quote Link to comment Share on other sites More sharing options...
Mark Ling Posted March 9, 2017 Share Posted March 9, 2017 if I had to guess about the axle I would say 1045, but it may just as likely be 4140, just depends on who made it. Littleblacksmith Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 9, 2017 Share Posted March 9, 2017 From a friend who used to work in an axle factory: the industry standard was 1045H below 1 3/8" stock and 1541H for axles above that size, for trucks. We did use 4140 for some of the very large axles used in off road equipment like big front end loaders. Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted March 9, 2017 Author Share Posted March 9, 2017 On closer inspection, it has 4340 stamped in the shaft. From a bit of searching, it looks workable for making tools from. I'll have to see what the local metal supplier charges for 1/4" round to see if what I bought was worth it or not. Thinking of making a couple of hammer racks to mount on my anvil stand with the 1/4" widget metal. Quote Link to comment Share on other sites More sharing options...
Kevin Olson Posted March 9, 2017 Share Posted March 9, 2017 Hey john. Careful forging with that metal from that do dad in the first pic. It could have a coating that really stinks when heated. I once tried to forge with a plant hanger i found and the coating was so nasty to burn off i threw it out. Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted March 9, 2017 Author Share Posted March 9, 2017 Thanks for the heads up Kevin. It does look like it's coated with something. I'll look into scraping/stripping it off and see how much work is involved in removing it. Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 9, 2017 Share Posted March 9, 2017 About using a pressure cooker for a vaccum chamber. BAD idea, they make much better IIDs. (Improvised IMplosive Devices) I suppose safety depends on how much vaccum you draw but . . . Be very VERY careful! Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
chimmike Posted March 9, 2017 Share Posted March 9, 2017 Agreed. A pressure vessel does not necessarily equate to a vacuum chamber. Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted March 9, 2017 Author Share Posted March 9, 2017 Thanks Frosty. I haven't found one yet, but my thinking, obvious of course, was if it could handle the pressure outward, it could handle the pressure inward. Not so? So far, I've tried stainless stockpots - crumpled them. Was pondering an old propane tank with the top cut off. Was thinking I might have to go with a very large piece of steel pipe, 1/4" wall thickness, maybe 8 - 10" dia. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 9, 2017 Share Posted March 9, 2017 how much pressure differential are your trying to get and for what? Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted March 9, 2017 Author Share Posted March 9, 2017 Well, I'm just using one of those inexpensive vacuum pumps (1 Stage 4 CFM 1/3HP Rotary Vane Deep Vacuum Pump HVAC AC Air tool Kit R134 R410a) to stabilize wood, remove bubbles from silicone rubber molds and investment casts. On this vacuum gauge, my last test was to approx. 29.1 inHg. Not sure I really need that much, but was just testing the latest chamber. Quote Link to comment Share on other sites More sharing options...
SLAG Posted March 9, 2017 Share Posted March 9, 2017 Effort to breach a pressure cooker is very different for pressure to escape the appliance. In is not the same in & out. (unless it is specifically designed so). It is the same for money holding safes. Hard to get in but much simpler to get out. The pubic did not know that. But Harry Houdini, the magician and escape artist, certainly did. (he was a locksmith among many other talents & expertisies). In many cases escape was so easy that he read the newspaper in order to expend time to let the suspense rise. Regards to all site denizens. SLAG. Quote Link to comment Share on other sites More sharing options...
doc Posted March 9, 2017 Share Posted March 9, 2017 I would assume ( you know what that means ) That if you can draw a full vacuum in a glass bell jar then you should be able to do it in a pressure cooker. Pressure cookers generally run a 15 lb psi on their highest end at sea level. I don't know if you are at sea level or not ,but if you are the HIGHEST pressure you'll be able to exert on the outside of the container is 14.7 psi. The pressure of the atmosphere.If your elevation is above sea level then even less. PS There is a fellow on YT that stabilizes his wood for handles in a mason jar! Quote Link to comment Share on other sites More sharing options...
Frosty Posted March 10, 2017 Share Posted March 10, 2017 Entirely different device, materials and force. Cast aluminum is strong in tension and fair in bridging strength. It's bridging strength is poor in compression. Lastly pressure cookers rarely carry more than a couple lbs. pressure. Glass has tremendous strength in compression, much stronger than steel. It has decent bridging strength. Now consider the shape of a bell jar, a cylinder with a dome end. Both structures are enormously strong in compression. Mason jars are intended to support a vacuum. I've never heard of a bell or Mason jar nearly as large as your typical pressure cooker. If you just have to give a pressure cooker a try as an IID. put it in a properly coffered chamber with scatter shielding. Implosions can be really nasty things. Most blast damage caused by FAE and nuclear explosions is the implosion once the plasma ball cools to a point the internal pressure doesn't exceed atmospheric. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
doc Posted March 10, 2017 Share Posted March 10, 2017 All I can say is look at this........... Quote Link to comment Share on other sites More sharing options...
AnBello Posted March 10, 2017 Share Posted March 10, 2017 For non-blacksmith related applications, I am also in need of a vaccuum chamber. For safety reasons, I would like for it to be designed for full vaccuum (1 atm total pressure), with a big safety margin (2x, at least). In most of my calculations, the most important parameter ends up being its size. Shape is also really important, but for simple homemade stuff there aren't many choices. The bigger you want to make it, the stronger it has to be (and therefore more expensive/harder to make). So keep it as small as possible (just like a gas forge, why make it big if you don't need it?).Also, a big vaccum chamber catastrophic failure is a lot more dangerous than a small one. Steel was my first idea (didn't want glass shards flying everywhere), but corrossion-weakening over time and the possibility of cracking near the welds actually means it's a lot harder to "do it right" than it seems at first. It must be done with good care, by an experienced welder (which I am not). My second option was plexiglass (I think that is the name? the acrylic used for roof tiles and windows), which was a very good option in technical terms and is even transparent, but it is actually quite expensive in the required thickness. I have not decided yet, but I will maybe end up doing doing it out of steel (with a small window) and have it welded by an experienced person, or a steel reinforced plexiglass one. Just thinking out loud, but maybe a bolted steel version could work? It would just need to have the joints and bolt holes sealed somehow... I am certainly open for ideas, experiences and criticism, and sorry for derailing the topic further. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 10, 2017 Share Posted March 10, 2017 look into the aging difficulties with plexiglass and possible issues with exposure to common shop chemicals or even the stuff you are treating the workpiece with. Quote Link to comment Share on other sites More sharing options...
AnBello Posted March 10, 2017 Share Posted March 10, 2017 5 minutes ago, ThomasPowers said: look into the aging difficulties with plexiglass and possible issues with exposure to common shop chemicals or even the stuff you are treating the workpiece with. I knew it was a good idea to post it here. Thank you for the info/experience! Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 10, 2017 Share Posted March 10, 2017 One of my more interesting classes in college was a MatSci class that should have been names "Things Break" By the end of the class you were terrified wondering if the engineers for basic items had worried enough about stress corrosion cracking, hydrogen embrittlement, creep, cold temp embrittlement, fatigue. Class 1 the professor handed out chalk to the class and has us twist break it "This is the kind of spiral fracture you get skiing" and then the math to show how the spiral formed... Every failure mode was presented through a real world case history Including "this large chunk of heavy steel went through a concrete block wall right by my ear..." (tooling mark starting a crack under over pressuring a pressure vessel but with fluid and then propagating when cycled at a lower pressure with a compressed gas until boom! He didn't mention if it affected the grade of the Grad student involved... Quote Link to comment Share on other sites More sharing options...
AnBello Posted March 10, 2017 Share Posted March 10, 2017 That sounds like a really interesting class! The only MatSci I had was in their electrical properties. Although I had a metals technology class in my 5th (last) university year, which I aced without any effort thanks to the knowledge from IFI! Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted March 10, 2017 Author Share Posted March 10, 2017 Thanks for all the info everyone. Time for some more data gathering and head scratching on the vacuum chamber. Geez Thomas, it sounds like from your MatSci class, everything falls apart (Well, I guess everything does. Except the pyramids; they seem to be hanging in there, but look what they're made of). Just have to make sure that things fall apart in the safest way. On the 4340 drive shaft part, I'm pondering putting it in my heat treat oven to anneal it so I can cut it into smaller pieces to work - it sounds like a long process. Or just put it in the forge and hot cut it. But I don't have a hot cut - would have to chisel it apart. Want to make a hardie hot cut out of the forked end. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted March 10, 2017 Share Posted March 10, 2017 Pyramids show quite a bit of wear and corrosion and outright damage! I had a Geology Prof that made a big thing on how the local environment affected rocks exposed to it and so some that were slow weathering in some locations might be fast weathering in others. His suggestion on how to get a good overview of various rocks over time was to check out the graveyards as a number of various rocks were very nicely dated and then left exposed to the elements in the local microclimate. The field trip he led showed us *exactly* when the local ares got piped natural gas as the sulfur smog damage to the Headstones had a hard cutoff as of that date. Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted March 10, 2017 Author Share Posted March 10, 2017 Interesting about the headstones and natural gas introduction. The pyramids, IIRC, had a smooth outer layer of that was stripped off as well. Helps though that they're in a desert environment. Quote Link to comment Share on other sites More sharing options...
JHCC Posted March 11, 2017 Share Posted March 11, 2017 In the Northeast, at least, there's an interesting progression from the seventeenth and early eighteenth century tombstones that are still crisp and clear and the later ones that are almost totally illegible. The difference? The earlier ones were slate, which is much less reactive to weathering and acid rain, while the later marble is fancier and more expensive, but doesn't wear as well. Quote Link to comment Share on other sites More sharing options...
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