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Posts posted by timgunn

  1. 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 Unifrax and I think the Insulfrax range is a series of Low BioPersistence products made from Alkaline Earth Silicate fibres. The LBP fibres are soluble (I assume pretty slowly) in body fluids. The presumption seems to be that they are likely to be safer than insoluble Ceramic fibres over the long term. A ceramic fibre inhaled today will still be in the lung in 50 years. An LBP fibre inhaled today will not.

    Different products have different temperature ratings, but the Low BioPersistence fibres generally tend to have significantly lower temperature ratings than the Ceramic fibre products. 

    In the UK and much of Europe, it is becoming increasingly difficult to obtain non-LBP blanket.

    The lower temperature rating of the LBP products means that the material used to provide a hot-face coating should ideally also provide insulative properties. This will help to limit the temperature at the interface of the hard refractory and fibre to less than the rated temperature of the fibre product. If using a 1400 degC-rated Ceramic fibre blanket, insulation is less of a consideration for the coating layer. 

    The big names in refractories are Insulfrax and Morgan Thermal Ceramics. Insulfrax are best known for fibre products. Morgan Thermal Ceramics cover the full range of castables, Insulating Fire Bricks and fibre products. In my (admittedly fairly limited) experience, the Ceramic fibre blankets from other manufacturers seem to perform just as well as the big-name products of similar density and temperature rating. The best materials to use for the hot-face layer tend to be castables. A lot of folk use refractory mortar because it is cheap and readily available, but it does not last nearly as long as a well-chosen castable.

    For burners, I would strongly suggest an Amal atmospheric injector from Burlen Fuel systems. You'll need gas fittings to connect to the injector, but the burner tube can be a straight section of pipe, threaded at one end to screw into the injector: I'd source a long stainless steel nipple from ebay or similar. This does away with any concerns over galv pipework, saves a lot of time and effort on your part and produces a burner that is extremely adjustable. Buy the burner factory-jetted for Butane, not for Propane, as it will give a higher maximum flame temperature on Propane than will the Propane-jetted injector. 

    I'd only use a single burner, mainly to avoid the hassle of trying to balance two burners to the same mixture/temperature, and size it for your chamber. A 3/4" burner is good for about 350 cu in and a 1" burner is good for about 600 cu in, both to welding temperature.

    A rear pass-through port is a good idea if there's any chance you'll want to do long stuff. You can block it off if you are only doing short stuff. I pack in an offcut of blanket personally, but I've seen others use IFB cut to fit.

    With an Amal injector-based burner, the temperature control available with the screwed choke means that you are very unlikely to need a muffle tube for HT, though you MUST do your HT outdoors. Closing down the choke to get HT temperatures causes massive amounts of Carbon Monoxide and death is a very real possibility if you run the forge in an enclosed space. 


    • Like 1
  2. 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 IMHO. They can run motors smaller than their maximum rating, but not bigger.

    If you use a 230V VFD, the output will be 3-phase 230V. The vast majority of 3-phase motors up to 3 HP/2.2 kW are wound for 400V connected in Star (Wye) or 230V connected in Delta and can run fine on a single-phase-input VFD. You'll need to check when ordering though. Over 3 HP/2.2 kW, motors tend to be wound for about 700V in star and 400V in Delta to enable star-delta starting (an old-school way of reducing motor starting current. It has largely been supplanted by VFDs). These cannot run on 230V 3-phase.

    Here in Europe (for the present), we have 50 Hz mains: 50 cycles/sec, 3000 cycles/min. Other parts of the world have 60 Hz mains: 60 cycles/sec, 3600 cycles/min.  It's the reason you'll see the different motor speeds quoted on opposite sides of the pond. 

    A 2-pole motor will run at an RPM equal to or just below the frequency of its power supply (3000 or 3600 RPM). A 4-pole motor will run at, or just below, an RPM equal to half the power supply frequency (1500 or 1800 RPM). 6-pole: one third (1000 or 1200 RPM), 8-pole; one quarter (750 or 900 RPM), and so on.

    We tend to use either 2-pole or 4-pole motors and in Europe, motors generally conform to IEC standards. Across the pond, they tend to use motors to NEMA standards. NEMA motors are pricy over here and offer no inherent benefit. They tend to be used where expensive machine modifications would be necessary to change to an IEC motor. 

    For a serious belt grinder, you'll probably want a 90-frame motor in a long casing (90L). This will most likely be 1.5 kW/2 HP if it's a 4-pole or 2.2 kW/3 HP if it's a 2-pole. The shaft size of 90-frame motors is 24mm.

    Because half the world uses 60 Hz mains and the other half uses 50 Hz, meaning that maximum mains speed is 3600 RPM, motors are designed to run to 3600 RPM. It is not cost-effective for motor manufacturers to design a completely different motor for each speed, so the only difference between the 2-pole, 4-pole and 6-pole motors in a particular frame size is the winding. The winding is attached to the inside of the outer casing and is static. This means that all the moving parts are good to 3600 RPM. 

    We can run a 4-pole motor to 120 Hz  to get 3600 RPM using a VFD, or we can run a 2-pole to 60 Hz to get the same 3600 RPM. 

    At the bottom end of the speed range, most drive/motor combinations are able to run smoothly down to about 10 Hz. Below this, running from the simpler V/Hz drives, things tend to feel "coggy". The V/Hz drives use a fixed (usually linear) relationship between Voltage and Frequency to determine what will be supplied to the motor and this linear relationship tends to break down once it gets that far from the design frequency. There are also drives which have "Sensorless Vector" capability. These measure the time difference between peak current and peak Voltage internally, calculate to determine the phase angle between them, then fine-tune the Voltage in real time to maintain the design angle (the motor Power Factor defines this angle, being its Cosine). These can keep the motor running smoothly well below 10 Hz and usually down to 1 or 2 Hz. 

    A 2-pole motor on a V/Hz drive has about a 6:1 speed range (600-3600 RPM, 10-60 Hz). A 4-pole motor on a V/Hz drive has about a 12:1 speed range (300-3600 RPM, 10-120 Hz). Either motor has a much greater speed range when run from a SV drive with smooth running down to 1 Hz achievable if needed. 

    VFDs switch large currents very fast and produce some heat, which must be dissipated. Most VFDs have ventilation fans and allow airflow over the power components to cool them. They are intended for use in clean conditions (usually sealed electrical enclosures). If there is airborne steel dust (which is both conductive and magnetic) it will flow across the power electronics, where the magnetic fields caused by the switching will capture it and attract the metallic dust right onto the power components. The short-circuit that results is usually quite spectacular and is invariably expensive, killing the VFD completely. 

    If they are going to be in the same room as a grinder, we need to use VFDs that are protected against such dust to IP66 or NEMA4 standards. We can either mount an unsealed drive in a sealed enclosure ourselves, with sealed control switches and speed control knob, or we can buy a drive that is designed to be sealed to IP66 from the factory and which has the sealed control knobs, etc on the front. The latter is by far the better option for the non-electrician. To buy and enclose an unsealed (IP20) drive properly, with sealed controls, to IP66 is about as expensive as  buying an IP66 drive to begin with. 

    In the US, the KBAC series of sealed drives from KB Electronics are the go-to. In Europe, the Invertec IP66 drives tend to be the ones people use for grinders. The current ones are SV drives so you get the low speed capability.

    I'd recommend a 90L-frame motor and an Invertek ODE-3-220105-1F4Y VFD. The drive is expensive, but it's a cry once thing. 

    I'd try for a 2 HP, 4-pole motor for personal preference, but would be pretty happy with a 3HP, 2-pole.

    If you are anywhere near Lancashire, I can sort you a foot-mount 90L 2-pole 3 HP from a compressor, gratis.


    • Like 3
  3. 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.

  4. 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 an domestic oven door to check tempering temperatures. 

    A couple of years ago, I ordered ten of them. When they arrived, I checked them on the calibrator and found they were accurate up to 800 degC but then became progressively inaccurate. I can't remember whether they showed 1370 degC at an input of 1290 degC, or showed 1290 degC at an input of 1370 degC: either way I was not happy with them. They were very consistent and all read the same on any given input signal.

    Side-by-side, there were external differences between the good ones and the bad ones, but these would not be obvious on an ebay listing so I stopped using or recommending them.

    I have since used DM6801 digital thermometers and found them boringly accurate. 10-20 bucks delivered from China. The supplied bead-type probe is PVC insulated and only good to a little over the boiling point of water: not much use to most of us.

    Whatever pyrometer you get, the supplied thermocouple will not be any use in a forge and you'll need to go to a thermocouple specialist.

    The "best" probe I have used for "our" purposes is an Omega KHXL-14U-RSC-24 which is a handled type K Mineral Insulated probe 1/4" diameter and 24" long below the handle. The sheath material is Omegas proprietary "Super Omegaclad XL", which is not really necessary for Heat-Treating, but seems to be the best I've found for surviving being used to occasionally check forge temperatures without going to painfully expensive Type S, Platinum-based, thermocouples. The assembly includes a curly cable and miniature plug.


    Using the part number builder on the page does not allow anything longer than 18", but putting the desired part number into the search box, top-right, will get you a price. For sword-length stuff, a 36", 48" or even 60" might even be worthwhile.

    I am cheap and tend to use similar thermocouples from the company we use at work. However, these "only" have a type 310 Stainless steel sheath, which is rated to 1100 deg (2012 degF) and will last pretty much indefinitely for HT, but doesn't last many cycles to 1300 degC-plus when used for checking welding temperatures are being reached.

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  5. 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 temperature at an hour was 1125 degC, 2057 degF and 1177 degC (2150 degF) took 71 minutes.

    As Brian says, once the desired temperature is reached, the PID controller will cycle the power on and off as needed to maintain temperature, so the average power drawn during the "hold" will be less than the heat-up, which will usually be at full power unless you are "ramping". 

    A fairly typical HT cycle for O1 might be to heat the oven to 800 degC and stabilize it (call it 30 minutes at 3 kW, for 1.5 kWhr), triple normalize; Work in, allow the temperature to recover, soak for 10 min, pull out and cool to black. Repeat. Repeat. (Call it an hour at 33% power, so 1 hr at 1 kW for 1 kWhr) Then Austenitize: work in, allow temperature to recover, soak for 20 min (call it 30 min at 33% power, 30 min at 1 kW for 0.5 kWhr). Quench workpiece(s) and switch off oven. 

    Total power consumed 3 kWhr. 

    You might expect to maybe double that for a Stainless HT, but to put things into perspective, unless you only do single blades each time, 6 kWhr is still unlikely to significantly exceed the cost of HT foil. 

    The numbers I've given are probably high-side figures. I don't have hard data, but I'm pretty sure the same homebuilt 27" oven was actually showing a steady-state output cycle of only 18% during the 1100 degC, 2012 degF hold section of a Stainless Heat Treat: when I delivered it, the new owner gave it a test run while we drank tea. I use a 2-second output cycle and always have an LED that is switched with the elements. I was surprised the "on" part of the cycle seemed so short and pulled up the output cycle display on the controller. It read 18%.

    The heating load of a HT oven is entirely resistive: it does not have the starting surge of a motor load or the horrible Power Factor of some modern electronics. So long as you do not exceed the outlet rating, I would not expect any new and interesting problems with mains power supplies, even in the middle of nowhere. The short-cycling 3 kW output would be harsh on a small generator, were you to run it from one, but I'd not anticipate a problem once the generator gets above maybe 10 kW or so.

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  6. 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 the front, set parameter 00-05 to "1" to enable speed control from it. 

    It looks like it should run on the start and stop buttons on the keypad and should go to whatever speed the knob is set to. Once running, adjust the knob to adjust the speed. It looks like the default acceleration and deceleration times are 10 seconds, so there will be a lag if you turn the knob fast.

    The drive is environmentally protected to IP20: effectively fingerproof. It is not sealed against dust and metallic grinding dust WILL kill it very quickly unless you take steps to seal the drive. Bear this in mind when you first fire it up: do not get over-enthusiastic, start grinding and cause fireworks. The quickest anyone I know personally has killed a drive this way is around 2 minutes from first switching it on.

    You'll then need to decide how you are going to protect the drive and how you are going to control it in whatever protection you come up with (if it's in a box, you won't be able to get at its front panel). You can also decide on the speed range you want.

    Some of the remaining parameters will set the drive up for the speed range and command source you decide to use. Many of the others are there to interface with control processes in industrial automation and will not be needed for a grinder with a human operator.

    I mount IP20 drives in IP66 enclosures and fit a remote control box on a trailing lead with start and stop buttons, a keyed forward/reverse switch (the key is taken out when running a machine that should not be reversed) and a speed control potentiometer. The box has a 3-phase socket on the front so I can plug in different machines. It's usually as cheap to buy an IP66 drive to begin with, and is much less effort. 

  7. 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 so that the flame colour in the photo is not the actual colour.

    Taking a tight shot directly into a forge can be completely useless because the camera will adjust the colour and a real dull red will look in a photo just like a real bright orange in another photo.

  8. 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 applications. "Someone" did some work to identify suitable materials for the tasks and that is what they came up with. Most folk seem to accept the consensus view and pony up for the proven product.

    Using 321 when heat-treating steels that "need" 309 has been known to fail and I'm pretty sure an evening spent searching the knifemaking forums will provide some insight into the sort of things that can go wrong: I'm pretty certain I've seen posts about the foil welding to the workpiece and to failure of the envelope allowing contact of the workpiece with air.

    If you have easy access to other grades of SS foil and can do some testing, I'd certainly love to see your results.

  9. 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 continuously-wound and then cut from a roll. To get connection tails, you'd need to unwind some of the coil and twist it to make the tails. I've just dug one out and measured it at about 0.65mm diameter wire. 

    My advice is to go no thinner than 16AWG, thicker if possible, and to use Kanthal A1 or equivalent. The price will, of course, be considerably higher than that of the thin ones on ebay. 

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  10. 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 and hole are important. These are fixed in your regulator. If your regulator is rated for use with, for example, 50 PSI upstream pressure and 5 PSI downstream pressure and will allow 5 lb/hr of Propane to flow at those pressures, the pressure available to drive the flow is 50-5=45 PSI. The regulator can control the flow to less than 5 lb/hr by moving the plug into the hole, but once the downstream pressure drops below 5PSIG and stays there, the regulator will be fully open and the size of the hole is what matters.

    If you now supply the regulator with 10 PSI gas instead, the pressure available to drive the flow is 10-5=5 PSI. Only 1/9th of the original pressure. Flow through an orifice varies as the square root of the pressure, so the maximum throughput the regulator could provide would be the square root of 1/9th: 1/3rd of the design flow or 1.67 lb/hr.

    The numbers I used were chosen because they are easy numbers. However, the vapor pressure of Propane at 30 degF, just below the freezing point of water, is 51 PSIG. At -20 degF, it is 11 PSI. Both are similar to my easy numbers. The effects of Propane cylinders "freezing" are well known/documented in smithing circles. 

    Be aware that you may find yourself seeing identical symptoms to cylinder freezing as a result of using a, now too-small, regulator fed from a 10PSI supply.


  11. 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.


  12. 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. 

  13. 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.

  14. 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. 


  15. 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.



  16. 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.

  17. 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.


    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.

  18. 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.

  19. 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.

  20. 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. 


  21. 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.

  22. 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.

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