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timgunn

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Everything posted by timgunn

  1. 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 you need to ask for help on this, or another, forum, there are likely to be some folk with enough experience and knowledge of Process Control, and Controllers generally, to help you. However, they are unlikely to be intimately familiar with your specific controller. Being able to provide a link to the manual gives them a reasonable chance of being able to provide specific assistance. Some manufacturers put access to their manuals behind a login/signup page. I tend to give up at that point. Manuals are difficult and expensive things to write. A manual translated from Chinese into English by an online translation program is not likely to be very helpful. Pretty much the entire value of a controller lies in it being able to control your process. If the manual is not adequate to allow you to set it up to achieve this, the controller is worthless. Industrial controllers, particularly the ones with higher-end capabilities like ramp/soak, are intended for use by Process Engineers: people who understand both their process and controllers in general. Programming ramp/soak profiles is usually a pain in the neck. The ramp/soak programming is usually set at the same access level as the input type, P,I & D parameters, etc. They are not like the kiln controllers found on the big-name kilns, which are designed to be programmed by an end-user with no real interest in the finer details of process control. These have different access levels for the commissioning technician and the end-user, limiting the amount of damage that can be caused by an incorrect button press. Ideally, you want a controller with the capability to do what you need it to do, with a good manual, written by someone who writes manuals for a living, in your own language (though if Swedish is your mother tongue, your English certainly seems good enough that you could cope happily with a manual in English). Then you want "real" technical support in a time zone you can live with, also in a language you can communicate in. For me, it needs to be telephone support (ageing Luddite and one-finger typist) but YMMV. I seem to vaguely recall a few HT oven builds using the linked controller on different forums. If the manual is ok and available online, it might be a good choice. Alternatives, if you are set on ramp/soak, are the Auber Instruments SYL 2352P, which I have not used myself, but which seems to be highly regarded Stateside. Support is reportedly very good. My personal favourite is the Automation Direct Solo SL4848VR or the Omega CN7823. These are, as far as I can tell, the same controller with different badges and I buy whichever is cheapest at the time. I have used them on all but the first HT oven I built (7 out of 8 so far). Support from both suppliers is superb. Omega are about the biggest name in temperature control worldwide and their technical sales people are extremely knowledgable (and patient, IME): well worth a phone call if you are unsure about thermocouples, etc. If you can live without ramp/soak for the forseeable future, a simpler controller really could be a good plan. If you go for a 48mm x 48mm (1/16 DIN) controller format and leave enough length on the wires to reach a different terminal layout, upgrading to a ramp/soak controller later is simple.
  2. Auber seem to be highly regarded Stateside. They do not have a UK presence, so I have not used them myself. AutomationDirect and Omega are both very good and have knowledgeable support staff at the end of the phone (I'm a Luddite, but they are probably great online too). IME they are also remarkably patient. If you are going to talk to them, make sure you have all your settings noted down and try to appreciate that, whilst they do know their equipment, they do not know the specific process you are trying to control: it is up to you to tell them exactly what the controller needs to do. If you are not sure about your process, a call for help on the forums may be the better first step. You are likely to find someone who has done what you are trying to do and can get you up to the point where you know enough to have a productive conversation with tech support. My favourite controller for homebuilt HT ovens is the AutomationDirect Solo 4848VR or the Omega CN 7823 (same controller, different badges. I buy whichever works out cheapest at the time) with a DC output to drive an SSR and ramp/soak capability. Bear in mind that ramp/soak profile setting is always MUCH less user-friendly on industrial controllers than it is on the likes of Evenheat's and Paragon's HT ovens. For temperature control, you are likely to need a thermocouple. Omega are about the biggest supplier of thermocouples worldwide and it is well worth spending a few minutes with a notebook and a telephone picking their brains.
  3. 2”x4” felt too small for a face. With hindsight, I should have left it. I welded on a couple of offcuts from the tapered end to give about a 4” x 5” face, but welding it ruined the original tine HT. It seems really soft and the plan is to hard-face it as soon as I can source some suitable rods. I made a cutlers stiddy from another short piece of the tine and it seems to be usefully hard with the original HT. I think a tine the size of yours would make a pretty good post anvil if you don’t overheat it when cutting it.
  4. That's a decent size. Lots of folk I know have struggled with cutting forklift tines. I expected to struggle too, but used a 14" carbide-toothed portable cutoff saw (an Evolution Raptor) on my 2" x 4" tine and was absolutely stunned at how quick, clean and cool the cut was.
  5. The best advice I can give on PID controllers: Before you even consider buying one, DOWNLOAD and READ the MANUAL. If you cannot find it to download, do not buy the controller. If you cannot understand (at least most of) the manual, do not buy the controller. Good manuals are expensive things to do well. If you are not already familiar with process controllers, trying to set one up without a good manual will give you migraine. If/when you run into difficulties, it is nice to be able to ask for help on this, or another, forum. You will probably want help from someone who is familiar with controllers in general, but who may not be familiar with the particular model/variant you have. To help, they will need access to the manual. You really need to be able to put a link to said manual in any "Help!" posting.
  6. It looks more like Kaowool board in the photo than IFB. Try shaving a thin slice off it with a sharp knife. You'll either get something that crumbles to dust (IFB), or you'll get something that looks like kaowool fibers (kaowool board). Either way you'll know. And you'll have a blunt knife.
  7. If you can bore for bushings, that is almost certainly the cheapest, easiest way to do things. They are available in several materials and different wall thicknesses for much less than the cost of bronze bearing stock. https://www.grainger.com/category/sleeve-bearings/sleeve-and-clip-bearings/bearings/power-transmission/ecatalog/N-171c#nav=%2Fcategory%2Fsleeve-bearings%2Fsleeve-and-clip-bearings%2Fbearings%2Fpower-transmission%2Fecatalog%2FN-171cZ1z0o05eZ1z0o42g Using sleeve-bearing pillow blocks should be ok, but I'd be more inclined to use Cast Iron housings, rather than pressed steel, and arrange them so that the housing is loaded in compression whilst in use: CI is generally considered strong in compression and weak in tension.
  8. Not nearly enough information. The gas jet size is dependent on a huge range of factors, most of which will be highly specific to your burner. I assume the burner is Naturally Aspirated, not blown. The high-speed gas emerging from the jet is what causes the low pressure at the burner throat and draws the air in. Going smaller on the gas jet will lean off the mixture (make it less reducing/more Oxidizing). Going bigger will richen the mixture (make it more reducing/less Oxidizing). Different tasks are best undertaken with different air:fuel ratios. The maximum flame temperature occurs at the stoichiometric mixture; the air:fuel ratio at which all of the fuel burns with all of the Oxygen in the air, leaving neither unburned Oxygen nor unburned gas. This ratio tends to give rise to quite heavy scaling. We therefore tend to run richer mixtures and consequently lower flame temperatures. We usually size the jet to give the richest mixture consistent with achieving the required temperature. For a given burner design and task, there will be an optimum jet size, but this will be dependent on the ease with which the air can be entrained. The harder it is for the air to get in, the smaller the jet needs to be. Tiny details like radiussing the edges of the air intake cane have a noticeable effect Unless you have an established burner design for which the work has already been done, you will need to do it yourself. You have done some of it, since you have determined that a .035” mig tip is too small and a .045” is too big. Mig tips tend to have holes about .006” larger than the wire diameter for which they are sized, so your required orifice size is likely to be in the range .040” to .052”. In your position, I would equip myself with some .035” mig tips, a pinvice and an assortment of drills for a day of tuning. Mig tips are soft Copper and a pig to drill, but I managed ok going one number drill size at a time drilling by hand with the drill held in the pinvice and the pinvice spun between my fingertips. When I did this with 1” burners, I was starting with a .023” mig tip so the drills were small. Starting at .040” or 1mm, you may be able to use a battery drill and make things easy. Start too small. Open out the hole in small steps until it is too big, testing each time. Drill a fresh tip out to the best size you found and fit it. It’s not difficult to do, just time-consuming. 1 1/4 burners? Plural? Hells teeth that’s huge. Gas consumption is likely to be high enough that a burner based on a commercial/industrial Venturi mixer would pay for itself pretty quickly. I would seriously consider an Amal atmospheric injector. The ones jetted for low-pressure Butane work extremely well when run on high-pressure Propane in gas forges (I use a 0-60 PSI regulator).The Amal units are made by Burlen in the UK and use European pipe threads, a minor pain for those over the pond. I would expect there to be a US manufacturer of something very similar, but I don’t know of one personally.
  9. I'm British, so buying American is not a consideration for me. The DF-series burners are as good as any of the DIY burner designs I've seen and very much better than most. I usually use burners based on a commercial Venturi mixer. Out of curiosity, I bought a DFP to play with and was very impressed. The Blacksmithing boys don't seem to rate them particularly highly, but I don't think they need the adjustability that comes with the screwed choke adjustment. The screwed choke gives exceptionally fine control over the flame temperature and forge atmosphere (they are intimately linked). For Heat-Treating, the precision with which the forge temperature can be set and held is a game-changer. Over here, O1 is easy to obtain and most other blade steels are a pain to source. Having the temperature control that the screwed choke provides (think micrometer-adjustment), means that soak-time ceases to be an issue and O1 becomes a beginner steel. The caveat is that the forge needs to be designed with HT in mind: the burner is not a magic bullet. The DF -Prof series have a sliding choke and I see this as a significant downgrade, despite the higher pricetag. I have not tried one though.
  10. Assuming it's the SYL2352P controller you have, the wiring looks pretty simple: Terminal 4 to thermocouple + Terminal 5 to thermocouple - Terminal 7 to SSR + Terminal 8 to SSR - Terminals 9 and 10 to AC power In the unlikely event you want to use alarms: Terminal 13 to alarm common supply Terminal 1 to alarm indicator/sounder, etc 1 Terminal 14 to alarm indicator/sounder, etc 2 I am assuming you have not downloaded and printed the 11-page manual for the SYL2352P from the link at the bottom of the SYL23X2P page on Auberins site, and given it to your electrician, because it looks very clear to me. If your electrician has seen it and does not understand it, it might be wise to look for another electrician for this project. I know several electricians. Some are superb on domestic wiring but have no idea about industrial and control wiring. Others are superb on plant, machinery and instrumentation, but no good at all with domestic wiring. Surprisingly few are good at both. If I was a gambling man, I'd bet a fiver that you have one of the former.
  11. I'll be interested to see how you get on with this. What seems to be stopping the Venturi burners from reaching temperature? The most common reason for it that I've seen is effectively too big a gas jet for the burner. The second most common is not enough burner for the forge. If you have Dragons Breath and you are not reaching temperature, a (slightly) smaller gas jet is very likely to improve matters.
  12. The correct spelling is "Fluorspar". Also search for "Fluorite" and "Calcium Fluoride". I can find it in "our" sort of quantities as "Calcium Fluoride/ Fluorspar-acid grade" from Mistral Chemicals over here. That big wet patch probably rules it out for you though. Pottery suppliers might carry it, though it looks like it's a major PITA to use in glazes.
  13. The technical term for the fans Owen is describing is "bifurcated" (bif). They are usually "Bifurcated Axial" fans (bifa). It might help you find some details and pricing.
  14. Thermocouple in the forge as Alan says. It works in the forge. A magnet needs to be used out of the forge. Back before IR thermometers became available, there used to be an optical hot-wire pyrometer that used an electrically-heated Platinum wire. The operator held the instrument with the wire between the object to be measured and his eye then adjusted the current in the wire until it became invisible against the background. He then read the temperature of the wire, which would be the same as that of the background object. The thermocouple is used in a similar way. Jonas, what type of burners are you using? Can you get that forge to burn down at 800 degC? If so, can you get the temperature reasonably even throughout the forge at 800 degC? If it'll do what you need it to do, that's wonderful. I'd love to see some more detail so that I, and others, can learn from it.
  15. Thank you Alan. The rich mixture tends to help minimize scaling and I think it probably helps to minimize decarb too: Carbon soot from the incomplete Propane combustion gets deposited on the steel surface. It's difficult to envisage a mechanism that would burn Carbon out of the steel without taking the soot, though it doesn't necessarily mean there isn't one. Over here, O1 is a doddle to get hold of in beginner bladesmith quantities, but most other blade steels are not. Like 52100, O1 does best with a long soak so I wanted to come up with a setup that would let a beginner get decent results with a reasonably low entry cost. The same burner can also be used in a small conventional forge, where it can even (comfortably) achieve welding temperatures. This helps to keep the total startup cost down.
  16. Using a muffle pipe tends to reduce the temperature variation. It is a useful method for getting a more even temperature from an existing forge, given that most "normal" forges are not built with Heat-Treating in mind. However, it is also possible to design/build a forge and burner combination to give precise temperature control with minimal temperature variation, specifically for HT. There are a number of HT-dedicated drum forges around, to a design usually credited to Don Fogg and originally intended for HT of swords. These use a single, relatively small, burner to heat a 55-gallon drum, lined with 1" of Kaowool. Temperature measurement is usually by thermocouple and handheld readout, with manual burner adjustment to get to the desired temperature. Because the temperature is so low, the gas usage is much lower than would be the case with a similar-sized "normal" forge and temperature stability is very close to that achievable with an electric HT oven. Build cost is low. Alternatively, a small pilot burner can be used with the temperature controlled by using a thermocouple and PID controller to switch a solenoid valve on the main burner feed. It's a good modification for the geeky types who enjoy playing with control stuff, or for the frequent user who will recover the additional build time involved by not needing to make the manual adjustments each time the forge is fired up. The Don Fogg design is technically very elegant and is just about optimized: other than the PID control, every "improvement" I have heard suggested would actually be detrimental to its performance (IMO/E). The only major downside to the design is the size and it does not seem readily scalable downwards to make a knives-only forge. A search for "Don Fogg heat treat drum" should bring up a good few hits. I spent some time trying to make something smaller that would work for knives-only. I think I probably did ok-ish. There are 2 or 3 guys who have used my HT forges to make knives to sell while they gather the money to upgrade to an electric HT oven. There's a youtube video one of my test-pilots made at: The target temperature of 816 degC is 1500 degF. The clever bit of this setup is the commercially-made gas mixer (so nothing I can claim any credit for), which allows very fine control of the air:fuel mixture and therefore the temperature. The mixer used in this case is an Amal 354/12BLV http://amalcarb.co.uk/downloadfiles/amal/amal_gas_injectors.pdf These are available from the manufacturer http://amalcarb.co.uk/amal-gas-injectors/butane-injectors.html In a "normal" forge, the flame retention cup is not usually needed, but I do use one in the HT forge. That way I can light the burner then insert it into the forge, eliminating the possibility of filling a big chamber with a gas/air mixture and then igniting it. The forge is a length of 10" thinwall pipe with 1" of ceramic fibre blanket inside and the ends cut from 1" ceramic fibre board and lightly hand-pressed in (to allow the ends to blow out if I am careless enough to fill the chamber with the aforementioned gas/air mixture and ignite it). The Don Fogg design has the burner at the bottom and the workpiece/exhaust port at the top. I just couldn't get the temperature distribution even with this arrangement. Once I tried the burner at the top and the workpiece/exhaust port at the bottom, things got a whole lot better.
  17. Jerrod's suggestion looks good. The way I read it, the input resistance is sufficient to draw no more than 10 mA at 10V (so presumably at least 1000 Ohms). The unit Jerrod linked to seems to give a 1-10V output at up to 30 mA. The important thing is that it is a Voltage output. Something which gave a 0-20 mA current output instead (another common control signal) probably would not work. I can't see anything similar available over here, so left to my own devices, I think I'd probably do it using a 10V power supply and a potentiometer. Connect the supply across the ends of the potentiometer and connect the +10V end to the "high" pin. Connect the wiper to the "low" pin. Adjusting the potentiometer will then adjust the speed. When the wiper is near the +10V end, speed will be low. When it is near the 0V end of the potentiometer, speed will be high.
  18. It should eat the job. The curves look excellent. If I'm reading things correctly, the 116630 has variable-speed capability, taking a 0-10V speed signal, and should be very easy to tune to match the actual duty required. I've never even seen any of the windjammer series in the flesh, though I've used Ametek Rotron Side-channel blowers in the past and found them very good. I used them on Landfill gas systems and the units I used were much bigger than we would typically use for forges/smelting. They were very well-engineered and I'd have no qualms about using Ametek products based on that experience.
  19. The nicest one I've seen in use was a side-channel blower at one of Owen Bush's hammerins. I think Owen's was a Nash/Elmo/Reitschle and had about a 1/3 HP motor. I'd guess it was probably a GBH1100. http://www.gd-elmorietschle.de/uploadedfiles/elmo-rietschle/downloads/content_g/datasheets/g-bh1_g-bh9/standard/2bh1100_ie1_en.pdf There are several other manufacturers, since it's pretty old technology. Side-channels tend to be used where the pressure requirement is higher than can easily be supplied by a conventional centrifugal fan. Centrifugal fans need to be large in diameter or run very fast to give much pressure rise. Side-channel blowers are able to provide usefully high pressures from a very small diameter, whilst still being able to use a conventional induction motor. The impeller is usually mounted directly onto the motor shaft and there are no other moving parts, which means that the motor is what determines the lifespan of the machine. With a "proper" industrial motor, ten years or more of continuous operation is quite common. Also called regenerative blowers, the side-channel units are very quiet. The big advantage of a side-channel is the performance curve, which actually increases the pressure rise as the blower is throttled. This means that the power consumption increases as they are throttled and it is usually better to control the airflow by bleeding off surplus air, rather than simply throttling them. For a conventional centrifugal blower, the 116 CFM/65mmAq description usually means that the blower will flow 116 CFM at zero pressure differential and will generate 65mm Water Column (about 2 1/2") of differential pressure at zero flow. We tend to want some pressure at some flow, so the 116 CFM/65mmAq description is not very helpful. I did a calculation to try to work out whether the CFM value of a forge blower would be particularly helpful in making a selection (I don't think it would). I calculated that 1 CFM of air would provide enough Oxygen to burn 0.42 lb/hr of Carbon to Carbon Dioxide or 0.84 lb/hr of Carbon to Carbon Monoxide. I can email my calculations if anyone wants to check them. In a smelt, I think you want Carbon Monoxide, which will then reduce the ore, Oxidizing to Carbon Dioxide as it does so. If my calculation is correct and you know roughly what your intended charcoal(?) burn rate during your smelt will be in lb/hr, divide it by 0.84 to get a ballpark figure for your CFM requirement. For a smelt burning 200 lb of charcoal over 4 hours, you'd burn 50 lb/hr and need (50 lb/hr)/(.84 CFM/lb/hr) = 60 CFM in round figures.
  20. Could it be that the motor is wired for star (wye) instead of Delta?
  21. A number 60 drill is .040". MIG tips are sized for the wire diameter they are intended to pass and have sufficient clearance to allow this. Using number drills and small metric drills as Go/NoGo gauges, I have tended to find the hole diameter is about .006" larger than the nominal wire size on the MIG tips I have measured. The hole size for the MIG tip is therefore likely to be about .046": about 15% bigger. That equates to about 32% greater area than the #60 hole. In addition, the MIG tip is likely to have a Discharge Coefficient in the region of 0.8, whereas the Discharge Coefficient of the drilled hole is more likely to have been in the region of 0.65. The MIG tips are designed to have a smooth lead-in to admit the MIG wire and this smooth lead-in is coincidentally very good for gas flow. Discharge Coefficient is a dimensionless coefficient that describes how well an orifice flows and the gas flow is a function of both the area of the orifice and its Discharge Coefficient. Assuming a Cd of 0.8, a MIG tip will flow about 23% more gas than a similar-sized square-edged, drilled hole. In your case (and I should point out that I am making some assumptions which may or may not be valid in your case), it seems likely that your MIG tip flows about 62% more gas than the original drilled hole (1.32 x 1.23 = 1.62). The gas flow through a given orifice is dependent on the pressure loss across it, but the relationship is non-linear. Until the flow becomes "choked" (when the gas velocity reaches the speed of sound), the flow varies with the square root of the pressure differential. Because the speed through the orifice depends on the Cd, the Choking pressure will vary between burners, but somewhere in the region of 30 PSI is a ballpark figure. Once the flow is choked, increasing the gas pressure still increases the gas flow because the gas density increases with pressure, it's just that the relationship between pressure and flow changes. There are some graphs showing this on the Hybrid Burners website. http://www.hybridburners.com/BTU-charts.html Over the range of pressures typically seen with Propane forges, the assumption that the gas consumption will vary as the square root of the feed pressure is plenty good enough for our purposes. Therefore, to get the gas flow back down to that seen with your original drilled, #60 hole, you'd need to reduce your pressure considerably. By calculation (1/1.62)^2 = 0.38 so you'd need only 0.38 times the pressure to get the same flow as before. You are unlikely to have a gauge with good enough accuracy and resolution to allow this, so 0.4 is close enough: 4 PSI now vs 10 PSI before, 2 PSI now vs 5 PSI before; you get the picture. You've not told us why you made the burner mods or whether they have had the desired effect. I'm guessing the intention was to get your forge hotter? There are many different factors which affect forge temperature. There's not much information in the OP, but I get the impression that it's "just" the burner that has changed, so we can discount all the variables related to the design of the forge itself and the fuel gas used? If we can do this, there are really only 2 remaining variables. These are: 1/ the amount of gas being fed to the forge, and 2/ the amount of air being fed to the forge. You have changed 1/, the amount of gas being fed to the forge. 2/ the amount of air being fed to the forge, is rather more complicated, but it's a safe bet that you have changed it too. The 2" x 3/4" tee "should" flow slightly more air than the 1 1/4" x 3/4". The change to a MIG tip with its higher Cd "should" mean that you get a higher gas velocity and this will increase the amount of air entrained. However, it seems unlikely that the increase in the amount of air entrained will be as great as the increase in gas flow, given the increase in gas jet diameter. The ratio of air:fuel is very important because it has a big impact on the combustion temperature. There is a value of air:fuel ratio that gives the maximum flame temperature. For all practical purposes, this is the ratio at which the Oxygen in the air exactly matches the Oxygen required to burn the fuel, leaving no unburned fuel and no unburned Oxygen. As we move away from this ratio (termed the Stoichiometric ratio), the flame temperature reduces. It does this on both sides of the stoichiometric ratio. We tend to operate with excess fuel in our forges (a fuel-rich, or simply "rich" mixture) because a fuel-lean ("lean") mixture will have free Oxygen in it and this will cause very rapid scaling of the workpiece in the forge: generally considered a bad thing. A rich mixture will tend to give a reducing forge atmosphere. As the mixture gets progressively richer, the flame temperature tends to reduce. We therefore want a mixture that is rich enough to minimize scaling, but that still gives a hot enough flame to reach the highest forge temperature we need. For those using blown burners, the air adjustment and gas adjustment are independent. This makes it easy to adjust the relative values and get the desired mixture. For those using Naturally Aspirated burners though, the air:fuel ratio obtained is a result of some fairly complex physics. From a hands-on viewpoint, we can keep things relatively simple by only changing one thing at a time and this is how NA burners are normally tuned. Usually, we aim to get the construction settled and then tune the gas jet diameter to get the required mixture. For a given burner and jet diameter, the ratio of air:fuel tends to be fairly constant over quite a wide range of pressures, right up to the choked flow pressure. This means that adjusting the burner feed pressure will vary both the airflow and the fuel flow in more-or-less fixed proportion. This is shown in the graphs at the HybridBurners link. NA burners use the kinetic energy of the fast-moving gas as it leaves the jet to entrain air. The best commercial designs use a true Venturi to maximize the amount of air entrained. A true Venturi is difficult to achieve without machining facilities and most of the homebuild designs use a design that lacks the short "throat" and 1:12 taper of the commercial designs, but is much easier to make. In effect, all this means is that the gas jet needs to be slightly smaller and run at a higher pressure to compensate. The entrained air mixes with the fuel as it moves along the burner tube and burns when it reaches the chamber. The speed of the mixture travelling towards the chamber needs to be higher than the speed at which the flame-front can move through the mixture to stop the flame burning back down the tube. This tends to be the limiting factor in terms of the minimum gas pressure setting. Though not a true Venturi, the Hybrid Burners design is pretty good and I'd expect it to do a better job of entraining air than most homebuilt designs. The MIG tip used in the 3/4" T-Rex is shown on the graph as a "standard 14-35". I understand this denotes a 1/4"-threaded tip for .035" wire, most likely with a hole about .041". I'd therefore expect anything short of a commercial Venturi in 3/4" to need a MIG tip gas jet of .035" (.041" hole) or less (this is assuming Hybrid Burners have done a pretty good job of sizing the T-Rex jet. The general consensus appears to be that the T-rex is very good, so this seems a valid assumption). The upshot of this is that I'd suggest you get hold of a .035" and a .030" mig tip and give them a try: I've seen more forges that will not make temperature because the gas jet is too big than I have forges that won't make temperature because the gas jet is too small. If your burner does not have a choke and can be modified to have one, I'd do that too. The choke does nothing to increase the airflow relative to the gas, so it will not increase the maximum temperature available, but it is very good at reducing the airflow relative to the gas flow when you want a richer mixture and a cooler flame. The best burner chokes have a very fine, progressive (usually screwed) adjustment and can be used to precisely control temperature right down to Austenitizing levels. In a suitable forge, this can make soaking at critical a relatively easy task when dealing with steels like O1 and 52100. When forging, it is certainly helpful for the relatively inexperienced smith to be able to set the choke to give a maximum forge temperature that will not cause damage if a workpiece gets left in the forge for longer than necessary. I'm speaking from personal experience here and "inexperienced" could reasonably be replaced with "inept" in that last sentence.
  22. timgunn

    303 Stainless Steel

    As Jerrod says, it's basically a free-cutting version of 304, which is about the most common (and least-exciting) stainless steel out there. For machinability, it's streets ahead of 304 or 316, making it great for fittings. Back when I used to play with a little Myford ML7 lathe, it was pretty much the only stainless worth putting in the chuck. I'd keep some of it for stuff that needs machining and try to trade the rest.
  23. It's only 60W according to the nameplate, so is only rated for 1/50th the current of a 3 kW kettle or heater (under a quarter of an Amp vs 13 Amps for the kettle or heater). Current carrying capacity is largely a function of cross-sectional-area, so skinny wires are not going to be a problem. There's a lot of exposed electrical gubbins there. Make sure whatever you build is well Earthed (Grounded) and ensure it's run from an RCD-protected circuit (GFCI?). The RCD won't stop you getting a shock, but it will disconnect the power before it kills you. It's no substitute for common sense: if you drop or hurl a piece of hot steel whilst providing a path for 230VAC, the RCD won't put out the fire. Personally, I use RCD plugs (like the 44855 from Screwfix at under seven quid) on anything I cobble together to ensure that it WILL be RCD-protected.
  24. It's a long time since I last used it, but Slo-Zap CA used to be very good for positioning/adjustment time. Not silly money either. I felt that 20 seconds was about what you safely had to get stuff located, perhaps 30 seconds if the planets aligned, Of course, if you got things positioned quickly, it seemed to take a couple of aeons to stick.
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