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I Forge Iron


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About timgunn1962

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    Lancashire, England

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  1. What are you doing in a forge that needs hotter than Propane can get? I know that a Naturally Aspirated Propane forge can get hot enough to melt Wrought/Pure Iron, because I've done it, albeit unintentionally. Oxygen injection can increase the flame temperature by reducing the proportion of Nitrogen that gets dragged along for the ride. Burning a cubic foot of acetylene in air releases exactly the same amount of heat as burning a cubic foot of acetylene in Oxygen. It's just that burning it with Oxygen, those BTUs are just heating the products of combustion, whereas burning in air, t
  2. How much Lime are you adding? I was under the impression that Calcium Hydroxide melted at about 600 degC (Wikipedia tells me 580 degC, 1076 degF). Having experimented unsuccessfully with Waterglass (Sodium Silicate) as a rigidizer for blanket and as a binder for Zircopax, I have experienced the instant conversion from rigidizer to lubricant at around the melting point of the Waterglass ("about" 1100 degC, 2000 degF). The blanket just moves away from where the flame hits it and the Zircopax/Waterglass becomes a dribbly mess. It may well be that you are seeing the same effect from the
  3. Old thread on what appears to be the same grinder.
  4. 2 bar, 30 PSI is usually fine. The square law for pressure vs flow through a jet in compressible fluids (gases) holds until the flow "chokes": the speed through the jet reaches the local speed of sound. This happens somewhere "around" 30 PSI for Propane. Going from 2 bar to 4 bar (30 PSI to 60 PSI) will therefore get you less than the 41% increase in gas flow that you'd expect to get if the flow didn't choke. There's no cost difference between a 0-2 bar and a 0-4 bar reg, and there's no noticeable difference in adjustability with the welding regs, so I tend to buy 4-bar for the "free" little e
  5. I'm pretty sure that's a 0.5 bar to 4 bar regulator; about 8 to 60 PSI. There are lots of them on ebay in the UK and they are complete dog-toffee IMO/E. I had a couple of them, tried one, threw both away. The 8 PSI minimum tends to make lighting the forge unnecessarily exciting and there's obviously no control at the lower end of what would normally be the working range. The best regulators I have found tend to be plugged (no gauge) 0-4 bar Propane regulators from welding suppliers. These usually have a scale showing the (approximate) pressure setting on the side of the body, where t
  6. As Latticino says, this is (often?) caused by the speed of the flame-front moving through the mixture faster than the mixture is moving in the opposite direction. It usually starts when the forge gets fairly hot because the flame speed increases as the temperature rises. The flame will run back along the burner tube until it runs out of mixture (Propane will not burn unless it is mixed with air (or another Oxidising agent). The flame goes out. The gas keeps flowing, draws in air and mixes with it. The mixture reaches the hot forge and ignites. The process repeats. Every time the flam
  7. To get from your hose to the BSP inlet (presumably 3/8" BSP), it is best to buy suitable fittings. Over here, NPT is the PITA and NPT-BSP adaptor fittings are available at decent pneumatic/hydraulic suppliers. In a pinch, I have been known to run a tap down the existing threads (BSP tap and NPT thread in my case) and fit a "local" fitting with plenty of anaerobic pipe seal, though not, as yet, with gas pipework. I think that the pipe nipple will probably screw in relatively easily, at least in the 3/4" size (1/2" and 3/4" have the same thread pitch in both NP and BSP). I always use a
  8. Twaddell units are a hydrometer density scale: the higher the number, the greater the density. Both are solutions of Sodium Silicate in water, as far as I can tell. Either will do the job: you'll (almost certainly) dilute it with water. I think I used the 140 Twaddell and it was seriously thick and viscous as it came. It's probably "about" twice as concentrated as the 75 Twaddell. Be careful with Sodium Silicate. It seems to melt somewhere around 1100 degC, 2000 degF. Used as a rigidizer for blanket, it is ok up to its melting point, but then it becomes a lubricant for the fibres allowin
  9. There are many variables and it's a really good idea to sit down and work out exactly what you need to do and what you have to do it with BEFORE you start building. Some of the stuff I can infer from the information provided: You have a 220V supply available. What current (amps) can it provide? I am in the UK, where the domestic outlets are 230V nominal and are rated for 13A, limiting me to 3 Kw in round figures (If I need to, I can go to 16A or 32A, but it means the user needs to have non-standard, industrial, sockets to feed the oven). I'm assuming the 1500-2000 degrees is Fahren
  10. Are they Devil Forge burners? I would replace the worm-drive hose clips with 2-eared "O" clips. I am slightly (?) anal about it and use 2 of them at 90-degrees to each other. You squeeze up the ears on the O-clips with end-nips. The worm drive ones tend to drag the hose to a sort of D-shape and are more prone to leakage at the corners of the D in my experience (and yes I did use the recommended size). If you are using parallel-threaded fittings, use a good anaerobic pipe seal. As said above, you may need quite a lot more pressure to overcome burn-back up the burner tube. Moreso
  11. If you are only heat-treating, you will not need a 3/4" burner. A 1/2" NA burner with fine adjustment of the airflow can easily heat a much bigger volume than that. I have built a few small HT forges using a burner based on a 1/2" Amal atmospheric injector. Intended as a cheap way to get good temperature control for a knifemaker on a budget. I used a 20" piece of 10" pipe, lined with 1" of blanket and with disks of 1" board for the ends, giving around 900 cu in. Everything got a wash of china clay in a solution of Sodium Silicate and water because it was cheap, immobilized the surface fi
  12. What is the smallest burner tube diameter and how many burners/ports? There is little point in jumping through hoops to get a blast gate in a 3” line if you are going to be reducing to a 1 1/2” burner with only a quarter of the area further down the line.
  13. One factor in attainable thickness that I've noticed is the size of the grog/aggregate used. It's not really practical to cast a 1/4" thick wall if the lumps are over 1/2". Sieving it can overcome this, but may make it more crack-prone due to lack of reinforcement. These castables are/were formulated by competent folk who do/did it for a living. Generally speaking, I find it is best to read the manufacturers spec sheets and use a product suited to the task in hand, unless you are fortunate enough to have access to one of the technical guys who genuinely knows how far outside the publishe
  14. I can't think where I've seen it, but I have a feeling that Devil Forge may use a MegaPascal-marked gauge, though I would imagine this may vary by destination. The cylinder fittings vary by country and, IME, regulators usually come with gauges marked in the customary units for the country/region they fit. .1 MPa is 1 bar or 15 PSI.
  15. The highest I have measured in a Propane forge was 1556 degC (2833 degF) and still rising. I didn't want to risk the $400+ typeS thermocouple, so didn't wait to see what it would top out at. I measured a forge at a hammerin a few years ago. It was being used for pattern-welding blade steels and was right around 1300 degC (2372 degF). As I understand things, it had been adjusted to give a temperature suitable for "anyone" to weld in and I regard 1300 degC as a good target temperature for a (bladesmiths) welding forge. The more experienced pattern welders tend to use a lower temperature (probabl
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