Jump to content


  • Content Count

  • Joined

  • Last visited

  • Days Won


Everything posted by timgunn

  1. Dudley is actually in the "Black Country", west of Birmingham (England) and about 80 miles as the crow flies from Sheffield. This thread reminds me of the saying that to an American, 200 years is a long time and to an Englishman, 200 miles is a long way.
  2. I'm not sure whether it applies to your controller, but I've come across some that are initially set for 1 decimal place, limiting the maximum to 999.9 degrees. Changing to zero decimal places gives access to the full temperature range. Worth a try?
  3. It'll almost certainly be Auber Instruments. Auber tend to be highly rated in America. They don't have a presence in Europe so I have not used them myself. I use Omega or Automation Direct for the ramp/soak controllers on my HT ovens. Both seem to be US companies with a presence in the UK. Both have knowledgeable and patient technical support staff. I gather Auber also have knowledgeable and patient support staff. The best advice I can give to anyone on controllers, VFDs and other electronic gizmos is as follows: Shop around. Read the specs carefully and list the "possibles". F
  4. My recommendation would be to build a completely separate control box: Preferably a metal enclosure (to help with cooling the SSR) fitted with cable and plug to plug it into a mains socket, power to the PID controller taken from inside the box and the PID controller output switching an SSR, which switches the power to a power socket on the front of the box. I fit a miniature thermocouple socket to the front of the box so that the thermocouple just plugs in. The one in the photo is larger and much fancier than necessary, having been assembled for a 28"-long HT oven I built.
  5. Looks pretty reasonable so far. It looks like you are using the terminals on the PID controller to carry the full element power with 2 wires in each? If so, I would suggest a minor wiring change to keep the big currents off the PID terminals: incoming power directly to the SSR and a second small wire in the SSR terminal to take power down to the PID controller. It's probably easiest to use a big terminal block to join the power wires on the other leg, with a small wire from that terminal to the other PID power terminal. The PID controller terminals are unlikely to be rated for hig
  6. I don't know how much you've played with the burners yet, but it's worth choosing a fixed value for the gas pressure, letting the forge get to temperature, then making adjustments to the choke to see how that affects the temperature. Adjusting the choke should adjust the air:fuel ratio and with it the flame temperature. Adjusting the pressure should adjust the amount of flame you have. You'll adjust both in normal use, but it's worth spending half an hour or so early on just getting a feel for what does what. Maximum flame temperature is reached at an air:fuel ratio that is close to
  7. "The reason for the 5 HP is because running a 3 phase motor on a VFD you only get 2/3 the rated HP just like running a static phase converter." That's news to me. What is your source for this information? I'm pretty sure it's wrong generally, though there may be specific circumstances under which it is the case. The only one I can think of offhand is when the supply Voltage is less than the motor rated Voltage, but I'm sure there are others. I've been using VFDs for over 30 years and I've never been told by a motor- or drive-supplier that I need to derate a motor by 1/3rd in or
  8. “Venturi” is the term used to describe the shape of the classical Naturally-Aspirated mixer. It tends to get used (incorrectly) for any Naturally Aspirated burner: one which does not use an air blower to provide the air. Get the back-pressure down by reducing the restriction on the openings and see if it improves. If you still can’t get it hot enough, have Dragons Breath and the gas jets are changeable, fitting the next size down jets will probably get the temperature significantly higher.
  9. Looks like it's a high-speed drill press from a quick google: possibly 1500-10000 RPM, though the one in the link below looks to be 3-phase and is in Europe. If the pulleys and motor pole count are the same, it'll be around 1800-12000 RPM on 60 Hz mains. A bargain if that's what you need, but not really a general-purpose tool. http://unimachines.at/tischbohrmaschine-super-valmer-model-6-1970-14105.html
  10. Note that it makes it more rigid, rather than hard: When you press a thumb into blanket, it doesn't take much force to press it down by, say, 1/8" and it springs back. With rigidizer, it'll take noticeably more force and it won't spring back. The rigidizer seems to get fairly rigid as soon as it is fully dry, then get more rigid once it has been fired to high temperature. If your plan is to rigidize, then coat with a castable refractory, I'd not worry too much about it. The general consensus seems to be that the refractory bonds better to wetted blanket and the usual practice
  11. 1/4 DIN is definitely better for my middle-aged eyes, but 1/16 DIN is cheaper. My first homebuilt HT oven used a relay-output controller and contactor. It was noisy and when I did some testing with a borrowed high-end controller, several thermocouples and a datalogger, it was clear that shorter cycle times gave better stability. It was also clear that radiative (over)heating was a potential issue, particularly at tempering temperatures, and that ramp/soak capability would be worth having. The controllers I have been using for my more recent homebuilt ovens have been either Omega CN7
  12. The kiln is almost certain to be able to achieve Austenitizing temperature for Carbon steels at its design Voltage. There's a good chance it'll be able to handle most of the less-exotic stainless steels too. I don't know which of the controllers from Banggood you are looking at. They list several and I don't think they are all suitable for a HT setup. Some, particularly the Rex C100, seem to have factory-configured input ranges which cannot be changed by the end user. A 400 degC maximum on a typeK thermocouple seems to be the most common input and this is not much use to us. There
  13. Some conversion factors might prove helpful. 64 kg/m3 is 4 lb/cu ft 97 kg/m3 is 6 lb/cu ft 128 kg/m3 is 8 lb/cu ft 160 kg/m3 is 10 lb/cu ft The 128 kg/m3, 8 lb/cu ft, density is usually recommended. 160 might be marginally better, but it's not usually easy to come by. 2 layers of 25mm, 1", are usually best in a round forge, as single layer of 50mm, 2", is more difficult to wrap smoothly. In general, the material recommended for forges is high-temperature Ceramic Fibre Blanket. Usually rated to around 2600 degF or 1400 degC. Insulfrax products are made by Unif
  14. A VFD takes mains power in, rectifies it to DC internally, then synthesizes something that looks to a 3-phase motor sufficiently like a 3-phase sinusoidal waveform for the motor to behave as if it is powered by one. The clever bit is that the VFD can vary the apparent Voltage and Frequency and make the motor run at variable speed. VFDs are available for single-phase 230V input or for 400V 3-phase input. If you get a 230V single-phase one, it can run on UK domestic mains. The biggest you'll be able to run from a 13A socket will be a 3 HP/2.2 kW. It's not really worth getting any other size
  15. Given that a failing hammer can also take parts of the operator off, I'd feel happier with: yes, mild would have worked in that application just fine as long as the fatigue limit didn't get exceeded.
  16. What with? With 2 cuts and probably some tidying up with a grinder, it should be less than a days work to make a better post anvil than many smiths are ever likely to own. That seems like an excellent use of your time to me.
  17. I've had pretty good results with a few of the cheap Chinese pyrometers. I have access to a thermocouple calibrator and always check the accuracy of the pyrometers across the intended working range before using them in anger. Until a couple of years ago, I used to recommend the TM902C, available for around 5 bucks delivered. I'd had maybe 20, ordered in ones and twos over maybe 4 or 5 years. They were boringly accurate from 0 degC to 1370 degC (32 degF to 2500 degF) and came with a glassfiber-insulated bead probe that was good to 400 degC (750 degF) and was flexible enough to be closed in
  18. A Kiln/HT oven will certainly allow you to do things that no forge can realistically manage. Power input is typically around 3 kW. I have built HT ovens up to 27" long that will reach 1300 degC (in about an hour and 45 minutes) and will run from a standard UK domestic outlet: 13A at 230V nominal rating, so 3 kW. Bigger ones might use more power, smaller ones might use less. Lower temperatures are reached much faster. When I first tested the 27" oven from cold (maybe 10 degC, 50 degF), 800 degC, 1472 degF was reached in 22 ½ minutes, 1100 degC, 2012 degF took 54 ½ minutes, the temper
  19. The first question is probably "what does the motor rating plate tell you about the motor?" and the second is "what do you want it to do and how do you want to tell it to do it?" The motor rating plate should give you a bunch of values that need to go into group 2 of the programming. The values you are likely to have are 02-01, 02-03, 02-04, 02-05, 02-06. If the motor plate gives you any others in an obvious way, put them in. Otherwise leave the settings as the defaults. The default command source seems to be the keypad. If you have a speed control potentiometer (twiddly knob) on th
  20. It looks like the burner is choked down to me: The air holes are covered so there is not much air flow for the gas to burn with. Try changing absolutely nothing except the choke sleeve position: move it towards the forge and uncover more holes to get more air in. See what happens and let us know. If you can, take photos in the dark. The most useful shot is often one across the mouth of the forge to show how much Dragons Breath there is, and what colour it is: In daylight, the DB flame does not show particularly well and digital cameras tend to do strange things to the white balance s
  21. timgunn

    Heat Treat Foil

    Are 17-4 and 18-8 foils actually that much more readily available at .001"-.002" thicknesses and in knifemaker-type quantities? 321 is not all that far off being an 18-8 stainless: it's effectively 18-10 with up to 0.8% added Titanium, which apparently improves high-temperature stability. I think 321 was developed to counter cracking in aircraft engine exhausts. Neither 304 nor 316 are particularly recommended for high temperatures. 309 is higher in both Chromium and Nickel for use at higher temperatures. They get used because they are known to work reliably in their specific a
  22. The Auber stuff should be OK. I'd forget the element you linked to entirely. It is waaay too thin to last. I built my first 5 ovens using 16AWG (1.29mm diameter) elements wound from Kanthal A1. These were ok-ish: fine for occassional hobby use, but a couple of the guys who use them to put food on the table had element failures. I then went up to 1.6mm diameter Kanthal A1 and they seem to be lasting better. I got some of the Far-Eastern elements off ebay, just because they were so cheap that I had to check them out. They really are very thin indeed. They also appear to be contin
  23. Give it a try and see if there is a problem. As you will have a regulator in the system already, a local shutoff valve and a needle valve to control the flow to the forge would probably get the job done.
  24. It will "probably" be fine, but with caveats. Inside the regulator, a plug moves in and out of a hole, controlling the amount of gas getting through. The plug is attached to a diaphragm and this works against a spring. The gas, downstream of the plug and hole, presses on the diaphragm and spring. As the pressure rises, the plug moves into the hole. As the pressure falls, the plug moves out of the hole. The steady state is where the pressure on the diaphragm balances against the pressure of the spring. Adjusting the spring preload adjusts the regulator pressure. The size of the plug a
  25. First question: what do you want to HT? If you are absolutely sure you are going to need Ramp/Soak, go for a Ramp/Soak controller. If you are unsure at this stage, go for a basic controller. You'll have a pretty steep learning curve ahead of you (unless you are already familiar with PID controllers. This seems unlikely because you are asking the question). NEVER buy a controller until you have downloaded the manual from a non-password-protected site, read it thoroughly and understood at least most of it. The reasoning is this: you have a steep learning curve ahead of you. If y
  • Create New...