Buzzkill

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  1. Disposable helium tanks and refrigerant tanks work pretty well and don't have the explosion risk.
  2. Sure. you probably just wouldn't want the blower on full blast at startup, which is what would tend to happen with a simple on/off PID setup. It might be ok though. Certainly once you get the temperature up past the point of the FA ignition then both the air and the gas could be cut simultaneously. I'd probably want to leave the blower running and have a NC solenoid controlling the air flow for safety reasons, but then my paddle idea might not work. A 3 way valve could solve that problem though. Dan brings up some good points if the blower continues to push air into the forge without any fuel. It would be desirable when you shut down for the day, but maybe not while trying to maintain a specific temperature and forge atmosphere simultaneously. A NARB setup would certainly be simpler/safer from that point of view. Any time the gas is flowing through the jet orifice you have air induction too so there's only one thing to control. However, if it was set up to be all on or all off you'd potentially get backfiring every time the gas shut off. That type of system would probably be better off set up with an "always on" idle circuit with the main gas supply controlled by the PID using a NC solenoid for the gas line. I've only used a PID setup for a DIY heat treat oven, but the cycle times can be very short as you approach the desired temperature, so I don't think I'd want a NARB cycling completely off and on repeatedly with those durations.
  3. I don't remember who posted it, but a few years ago one of our members posted a way to get tight spirals just using the jaws of the post vise. I think he was making small candle holders at the time, but the same principle applies.
  4. Of course you will need a way to start the blower with that circuit open. You can put in a momentary switch to bypass it on start up or manually hold the switch that your flow indicator will operate when you start the blower, but it should be fairly easy to do.
  5. I think it's simpler than that billy. All you need is an arm in the air flow with a paddle on it that will move with even light air flow. That goes to a switch or relay. If the air is flowing it moves the paddle and closes the circuit. If there is no air flow the paddle will drop and open the circuit. It just has to be sensitive (light) enough at the low end. You don't care exactly how much air is flowing, just that it is flowing - a flow indicator rather than a flow meter.
  6. Only off by a factor of 7. Now, 4 smiths working 12.5 hours per day on the same anvil ........
  7. Also, that is not the T that Frosty recommends for a 3/4" burner. Since it has larger openings for air induction it may require the jet to be deeper. That also may result in the ratio of air to fuel not being consistent throughout the operating range of the burner. To answer your question though, jet placement is critical for proper tuning of these burners. If you can post a picture or two of the flame in the forge shortly after lighting it then one or more of the gurus can probably suggest alterations for fine tuning. Unless you are planning on trying to return the burner then try what you have. We all may be pleasantly surprised with the flame - or maybe some minor tweaks can get you what you want.
  8. Whether it's alloy content that changes, crystal structure, or something else, many of us have personally experienced significantly different behaviors/results within inches of the same bar of stock. When that happens it doesn't really matter if someone claims it doesn't happen, can't happen, or won't happen. It just is. I have personally had rebar stock that behaved like mild steel on one section of the bar and didn't harden when quenched and then a foot away or so on the same bar of stock it did harden and break. I've also had A36 where I've drilled several holes without incident and then the next one didn't get more than about 1/8" in before the bit started screeching. Skipping that hole temporarily and moving over to the next resulted in another hole that drilled as expected. This was on stock that I had not heated at all before drilling, so it was not affected by forging or anything of that nature. Whenever that happens to me I find that heating the piece up to a dull red and letting it cool to ambient temperature tends to allow for normal drilling. So again, regardless of what anyone claims is true or not true, it's pretty darned hard to convince some of us who have personally experienced differences in the same piece of stock within a few inches that it's all homogeneous tightly regulated product.
  9. Springs tend to be not quite as hard as we prefer the cutting edges on a knife-like object to be. Leaf springs also tend to have an uncanny ability to regain the curvature they had when in the spring pack. For a bone chopper you may want a little softer edge than for a slicer, but still probably harder than the spring temper. This may be a good place for an edge quench if you have a straight blade with a thick spine. Otherwise I'd recommend going through the entire annealing, normalizing, quenching, etc. process and doing a differential temper at the end.
  10. You do realize his anvil isn't a concrete anvil so much as I-beam which has the channels filled with rebar and concrete. As I understand it the concrete merely provides some additional inertia value and sound dampening. Even if the concrete does fail it will not result in a catastrophic failure for his hammer.
  11. That's a definite improvement to my eye. The flow of the curves is more appealing for sure. I'm looking forward to seeing the finished product, but I don't think I'd want to see it coming at me. That thing looks like it will be wicked!
  12. I doubt you have the same issue as a friend of mine and I had when we were teenagers, but we had similar symptoms. We checked out all the usual things, tried creative swear words to encourage it to work correctly, and nearly gave up when we finally figured it out. A hot wire going to the distributor had the insulation rubbed through. When out of gear with no load on the engine the wire didn't touch anything (barely), but when there was a load on the engine it moved things just enough so the wire shorted out.
  13. You are much further along than I like to be when putting the bend in a kukri blade. I keep it simple. I heat up the area I want to bend and then I hold what will be the tang end and slam it edgewise where I want the bend to be over the horn of the anvil a few times. Once I have the bend then I can move to the profile and getting nice straight lines on the spine. Since you already have the profile close to where you want it except for the bend and you have bevels started I'm not sure how well that technique would work for you. You could try heating the area you want to bend, support the two ends on some pieces of wood and smack it where you want the bend with a wooden mallet to keep the deformation to a minimum. As for the grinding part I'm not sure I can give you a definitive answer. In general if you have a perfectly symmetrical blade, regardless of whether it was forged to that point or ground, and you do proper normalization cycles there shouldn't be much warping, but so many things come into play. If you get one side just a bit hotter than the other, if both sides aren't exposed to the quenchant equally, if you move the blade side to side a little while it is still cooling in the quenchant, etc., you can still get warps. For large blades you can even get a warp just pulling it out of the forge for the quench if the spine isn't perpendicular to the ground. Gravity can be a harsh mistress. If it were me I'd do my best to get everything centered and symmetrical, prepare something to keep it flat and straight after the quench, do the normalization cycles, quench and immediately get it into the "straight jacket." And of course temper immediately afterwards.
  14. Typically the more complex stainless alloys require specific temperatures and ramp times to get all the contributing elements in the alloy fully into solution in the proper order. This requires that the steel is kept at an elevated temperature for a long time. Most people use electric heat treat ovens for this task so the temperatures and ramp times can be tightly controlled. Most non-professional heat treat ovens don't have a good way to keep oxygen out during the process, so the work-around is the stainless foil. Otherwise, because the steel is at elevated temperatures for so long - several hours in some cases - there would be significant decarburization of the steel during that time. Obviously you got a hard blade with your method. What I don't know is whether you got the most out of the steel that it has to offer by cutting some corners. It would be interesting to see how much difference there is between your method and the manufacturer prescribed sequence though.
  15. There are a few threads scattered throughout the forum on this topic. For the most part we see PIDs used on electric ovens and kilns rather than used on gas forges. In principle it can still work, but you most likely will not be able to keep a gas forge within a few degrees as well as you can with an electric oven. Personally I'm not sure it's worth the hassle. If you need accurate ramp and soak times for certain alloys then electric is the way to go for the heat treating. For forging you can get by with a thermocouple and readout if judging by color isn't close enough. Once you have it set where you want it you just wait for the steel color to match the forge interior color and go to work. Having said all that, here's one of the threads on the topic and Wayne Coe gives his pyrometer setup.