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Dan Hertzson

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  1. I've never needed a needle valve to regulate the flow in my builds. A good regulator can very precisely adjust the pressure within 1/2 psi. For a given fixed geometry gas train piping system the pressure of the gas at the source directly dictates the flowrate (unless some kind of compressor is added, reference the extended Bernoulli's equation). A good needle valve changes the piping system dynamics by adding a local restriction to the flow and allowing you to reduce the flowrate without adjusting the main system pressure at the regulator (if you initially set the regulator to run very rich at full air flowrate you can use the needle valve for more modulation, both up and down, but you need to plan that in advance). The same thing can be accomplished by adjusting the regulator, but you can also increase the flowrate using the regulator. It is my opinion that one point of control for the gas is better than two, but each to his own. A needle valve would certainly make it easier if your propane tank and regulator were located outside your shop. It will allow gas flow adjustment while viewing the results in the forge. I believe that the use of needle valves in DIY burners dates back to the time when folks on shoestring budgets did not wish to purchase quality propane regulators. Needle valves used to be cheaper and more common. The popular RISD glass furnace/ceramic kiln burners from the late 60's (I think) are a good example of this. The valves on torches are extremely useful because they are localized to where you are working, and the typical regulators are less precise. These days I use a commercial burner/mixer system for forced air/natural gas on my personal forge. It has a sophisticated zero pressure regulator which allows you to set the desired gas/air proportion (within a general range), then adjust the volume flowrate of the gas air mixture with a single control (similar to the upgraded shower controls where you set the temperature on one dial and the flowrate on another). It works very well, but I probably wouldn't use it if I hadn't gotten it for free while dumpster diving after a local university completely relocated their glass studio and threw away all the original piping. I would leave it at 1/4" and only change it if you have trouble with either mixing or controlling flowrate down to the minimum desired (watch out for preignition at low flow...)
  2. Depending on the length of tubing t may be worth upping the size of your propane supply to 1/4". You need to be prepared for friction loss at a certain point. It is kind of a mixed bag. On one side you have a restriction that could limit your overall propane (and thus heat) supply, on the other a smaller orifice at the mixing point will speed the entry of propane into the mixing tube, aiding in mixing. The compromise I've made in the past is to run a larger tube to the mixing chamber, then cap same inside the chamber with a drilled orifice. See this site for a typical example: https://www.joppaglass.com/burner/rt_alf.html . For a forge a multiport outlet isn't required (though they are nice, and a good choice for a long thin forge), and you can vary which arm of the TEE the air and gas enter on depending on your blower characteristics and fuel source pressure. I reiterate that I prefer variable pressure regulators over needle valves, but if you are set on the latter, be sure your's is rated for gas service.
  3. A recommendation for wrought iron axes: you might consider wrap and weld rather than punch and drift. That is the more common historical method of making these. Wrought has issues with splitting along the "grain" depending on how hot or careful you work, especially with the back of the eye close to the "edge" of the billet. You might want to forge weld a high carbon poll first before you try to make the split. If you do go wrap and weld, make sure you are careful with the tight bends at the back of the eye as well, very prone to cracking if you work the wrought the same as standard mild steel. Keep it very hot and it will behave nicely.
  4. I've run blown forges, glass furnaces and glory holes for many years. In all cases the blower was below the gas inlet and I've never had a problem in the blower either. The key, as others have stated is the sequence for lighting and turning off your forge. That being said there are a few other things I agree with: No small orifice is required for your burner construction. However I would substitute a proper propane regulator with gauge and a 1/4 turn gas rated ball valve for the proposed needle valve. In my experience needle valves are not reliable long term and it is nice to have a quick shut off in case of any issues (like power going off to your blower for whatever reason). That being said, a 1/8" -1/4" pipe connection to the burner mixer is a bit more common for propane. Your's looks like at least 3/8"? You need bubble tight joints on your fittings. This is easier to accomplish with the correct gas rated pipe thread compound. The allowable length of pipe between the blower and burner outlet is more a function of the blower capacity than any worries about burn-back. The only times I've seen people having trouble with preignition is when they let the mixer assembly get too hot. This is more often a problem when you are trying to run your forge at a lower temperature after it has been very hot, or light it when a chimney effect has come into play. In my experience this is less of a problem with multi-outlet burners (like your ribbon burner) That looks like a rather large forge for a first forge. What is your planned interior volume? Beware of gas hogs and try to plan for doors early...
  5. Really like this one. Were you looking at any source images when you came up with the design? Feels very authentic. Is it a "thru tang" with a rivet button? How did you achieve the patina on the blade?
  6. Those are very nice Gerhard. Starting to make me worry that my skills are not adequate for KITH submission. Did you rivet, like Lin, or forge/arc weld the loop closed?
  7. In a forced air forge you can avoid this problem by running your air source for a few minutes after you shut off the gas.
  8. No riveting on scales, right? Would a Lin Rhea style X-Rhea be acceptable? I was thinking about trying a version of one of the simpler ones...
  9. The best option for quieting down a gas forge is to use a multi-port burner outlet (popularly called a ribbon burner). While these are easier to design for forced air/gas forges they certainly can be used with naturally aspirated burners as well. Careful consideration to matching forge volume and configuration, burner size and multiport outlet are required. I believe that Dudley Giberson at Joppa Glassworks has a packaged design that is worth looking at. Note that they are still not quiet, but certainly quieter than a typical burner flare (or even worse a post mix burner system like the old Eclipse burners).
  10. Note: Cross posted with Doug. I agree completely with his comments. The other issue with the length of your forge is that, particularly as a beginner to forging, you will be heating far more of your stock than you can effectively hammer in one heating session. A long forge like that one is really only useful if you have a power hammer or press and are working architectural scale (or are using it for relatively low temperatures for heat treatment of swords (though I think a vertical heat treatment tank, ala Don Fogg, is a better choice there). The issue with heat treating too much steel for bladesmithing is more chance of decarb as well as wasted propane (not to mention a more complicated burner setup). I visited Albert Paley's studio recently, and his gas forge is no larger than the one you plan on building. IMHO an 8" forge length is pretty optimal for most bladesmithing (particularly if you have a dedicated heat treatment chamber). The real problem with gas forges is that no one design works for all smithing operations. That is where solid fuel forges shine. If you keep the current configuration I would recommend the following (all my opinion, so take or leave as you will): Replace the vinyl propane hose with hard piped copper with flare fittings or at least propane rated hose. Bubble test any joints up to the mixing tube. To run (3) 3/4" forced air/propane burners you will need a large propane source. A standard 20 gal barbeque tank will slurry up with that much draw. You will also need an adjustable propane regulator (0-30 psi minimum). Tank should be kept outside your building, if possible, with 1/4 turn shutoff valve at building entry. I recommend using a minimum 2" pipe size from the blower right up to the main mixer tube header (you can pipe your 3/4" individual burners for t-fittings off that header). This will allow you to use a blower with a reasonable airflow to static pressure ratio. Blowers of this type will be quieter and more efficient. I'm not going to do the calculations, but I expect that a blower that supplies around 160 CFM at 0.5" WG will be adequate. You will want some method of modulating the airflow from your blower. If you are scrounging, the new high efficiency furnaces often have combustion inducers with ECM motors that can be controlled with a 0-10 VDC signal. For a conventional blowers you will need a manual damper at the outlet or waste gate, to allow control of the airflow. Note that dimmer switches will not work well for the typical cheap squirrel cage blower motors and likely not on your leaf blower either for extended use. Make sure your pipe reducer/burner flares are well covered by the inner insulation layer/refractory. Otherwise they will burn up in use. It is extremely costly and difficult to coat the ceramic wool directly with ITC. At bare minimum you need to seal the surface first with a solution of fumed or colloidal silica and water. This will harden the refractory blanket and seal it. Otherwise the fibers become friable after heating and will get into the shop and eventually your lungs. Don't make my mistake and damage your lungs! Personally I like to have an inner coating of at least 1/2" thickness of castable refractory (Kastolite 30, or similar). If you ever plan on forge welding with flux, you need to think again about the floor of your forge. Hot flux will eat the blanket like water on cotton candy.
  11. The aesthetics and finish of your hammer are quite lovely. A couple of points from my experience forging and using this type of hammer: Often the hammer head, or the punched hole, are offset to keep the face at less than a true right angle to the main axis of the handle. The theory is that this helps with the primary task that this hammer type is optimized for: setting bevels. I see that you deliberately chose to go 90 degrees. What was your logic for that? The first dog's head hammer I made had a face just as flat as yours. It is now relegated to final planishing work as the flat face didn't move metal in any significant way without leaving edge divots. After you use yours some you may consider regrinding the face, if you have a similar problem. The better ones I've used have more of a dished face.
  12. IF you are making your own micarta you could use a fabric with a cross pattern already woven into it...
  13. This may be helpful for you to better understand file terminology: http://www.crescenttool.com/MagentoShare/media/documents/nicholson-guide-to-filing-2014.pdf
  14. Or just forge weld a collar around it if you are going traditional
  15. Looking great, as usual. Any trouble getting through the hardened tang to drill the pin holes and bolster holes?
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