I use oxygen and propane for my brazing. I did not want the expense and extra safety concerns of storing and using acetylene, and in particular did not want to get involved in contracts given the small number of frames I am likely to build as a hobbyist. Recently small contract free acetylene cylinders have become available. Personally I see no advantage in using acetylene for building lugged frames, but it does have advantages for fillet brazing. Propane is relatively cheap and long lasting and widely available for a small cylinder deposit. I use a 11kg cylinder. Smaller ones are OK but I have found the larger cylinder more stable, especially when using a gas fluxer, I don’t know why. Storing the smallest size cylinders of practical use of any flammable gas is common sense.
Cylinders should be secured from falling, preferably with chains which don’t burn! Trolleys are available to store and move the cylinders if you have the space or need to shift station. Oxygen is now easier to obtain contract free. It is more expensive than the propane and you use a lot more of it and you need more compared with acetylene. I would recommend using 20L cylinders which last considerably longer than the smaller 10L size which tends to run out during the second frame. I used to obtain my cylinders from Welding Gases of St Helens who also delivered widely but they have now been incorporated into Gas UK, a much bigger and slicker operation. I have now changed my supplier to Hobbyweld UK who are also a national organisation using agents throughout the country. I now have an agent local to me and use their 20L cylinder (below). This is filled to a higher pressure than the Gas UK cylinder and has a slightly greater capacity and contains nearly 4 times as much gas as a 10L cylinder. Also with the Hobbyweld 20L cylinders the Regulator gauges are included so there is no need to worry about buying and maintaining your own.
Additionally they have a shroud protecting the regulator assembly which would hopefully eliminate the risk of a falling bottle shearing off the regulator assembly and creating a extremely dangerous high velocity missile.
You will need a handset (also called a torch or blowpipe). I use standard lightweight welding handsets which I find adequate, heavier duty handsets are available. They were designed for use with acetylene (see later).
The system also requires check valves and flashback arrestors between the torch and both cylinders. check valves are usually provided in the torch end of the hoses and the hoses are marked to indicate which end to attach them
You are required to insert flashback arrestors usually adjacent to the regulators on the cylinders and a further one adjacent to the gas fluxer if you are using one. Acetylene and Propane arrestors appear to be the same (coloured red), Oxygen has it’s own arrestor (coloured blue). Hoses are available in minimum 5 metre lengths. Propane and acetylene hoses are NOT the same, though I understand a lot of welders use acetylene hoses for propane as they are easier to obtain but will not last as long. Propane hoses are orange as opposed to red. Hose connectors are nearly always 3/8 size to connect to cylinders, flashback arrestors, economisers, gas fluxers and heavy duty torch handsets. The exception is lightweight torch handles which use 1/4, so in this case the run of hose to the handset will have 3/8 at one end and 1/4 at the handset end, these hoses also tend to be narrower. Single stage only regulators seem to be all that is required. Oxygen regulators usually come with two gauges for cylinder pressure and outlet pressure. Standard propane regulators come without gauges but you can obtain them with two gauges which is worth the extra expense, especially if using a gas fluxer which has limits on input pressure making accuracy more important
A Standard propane regulator is difficult to set accurately.
I also use a gas economiser, difficult to obtain for propane, but possible, it has a different nozzle size and most suppliers don’t supply propane nozzles. I am not convinced the use of an economiser saves much gas but as a novice you tend to have to interrupt your work more often and it is very convenient to be able to put down the torch and pick it up without any readjustment but it does mean extra lengths of hose to incorporate it, the same for the gas fluxer.
Sundry equipment will be: sparklighter (cup style for propane as it is heavier than air, but other types work), nozzle cleaners and selection of swaged welding nozzles. I have used everything from size 2 through to size 18 at some time. As a general guide when brazing with brass you need a size larger or more when using propane over acetylene, though with silver soldering this is not always the case. As a general rule a No 3 to No5 tip may be adequate for most lugs and dropouts and No3 for silver soldering. I have found it difficult to maintain a stable flame with a No2 nozzle with my set up. With perseverance , however, it may be possible but unlikely to be worth bothering with. For most fillet brazing again a No3 tip is likely to be adequate but on larger parts such as bottom brackets a 5 or 7 tip may be used. You can use much larger tips on these parts with lugs because it is possible to withdraw the flame to avoid overheating whereas with fillet brazing the proximity of the tip to the work makes tip selection more critical. I know of builders using much larger nozzle sizes than I have been using for lug work and I cannot argue with their validity. Because the propane flame is longer than an acetylene flame when fillet brazing it is helpful to countersink the nozzles which shortens and fattens the flame, though not by much. This is helpful when fillet brazing as it enables you to get the flame nearer the work and deliver more heat. The simplest way to countersink the tips is to rotate a small HSS drill bit into the nozzle by hand. Most drill bits have the same taper so the exact drill size is not critical. You can still use countersunk tips for lug brazing if you only have the one of each size. I have only seen countersunk brazing tips for sale in the USA.
Gas Fluxers: I find a gas fluxer a great boon, mainly for fillet brazing where it enables you to see the braze line clearly. Only the fuel gas passes through the fluxer. I use the same flux as used for oxy-acetylene brazing, indeed there only seems to be one type. They should be filled outdoors. The flux is liquid, toxic and highly flammable, but once loaded (at least 5 litres at a time), lasts a long time. However there is the increased risk of using, storing and monitoring even more flammable substances. You can obtain fluxers from both Sif and Plasmatech who also supply fluxes, I obtained mine from Plasmatech as a reconditioned model which they often sell through Ebay. The difference between some models of fluxer is the ability to switch the fluxer out of the circuit to enable you to change to using paste flux which you would have to do if using silver solder. My type W fluxer has this ability. With lugged frames you have to use flux in the mated joints but I have used the fluxer as well to minimise the amount of external flux to give a better view of the capillary joint. There is no liquid flux for silver yet available so it is only of use for brass brazing. The liquid flux dries to a white residue and this can clog up the hole in the gas economiser and the mesh filter in the flashback arrestor adjacent to the fluxer causing the propane pressure to drop off, so they require occasional cleaning
Gas settings for brazing: My gas fluxer is designed to be used at a max pressure of 9psi (0.62 bar). Whilst to some extent you will have to use trial and error to achieve the desired flame with the chosen nozzle I as a rule use 5-6 psi (0.5 bar) Propane and 5 psi (0.5 bar) Oxygen. Oxygen cylinder instructions refer to opening the valve by one full turn only, though this guidance is omitted on the instructions for Hobbyweld cylinders, whilst propane cylinders can be opened fully. Make sure the regulators are closed when turning on the cylinders (screwed fully out) then turn on by screwing in until desired pressure is reached as shown on the gauges. Shutting down is as for acetylene, turn off at the cylinders first, vent the gas safely at the handset then close the regulators by winding out and shut off he handset. SAFETY NOTE: Please do not forget to leak test all the joints on your gas brazing set up regularly as well as a visual inspection of the whole system. Proprietary leak test sprays are widely available. Every time you use the system would be good.
New Propane Brazing Nozzles from the Welders Warehouse
I have tried these new nozzles specially developed for brazing and they only seem to be available from the Welders Warehouse. I had to purchase a separate handset to use them which appears to be necessary for them to work correctly and is specific for propane.
They are described as multi-jet and seem to be a cross between a heating and single jet nozzle with a larger central port giving a slightly larger central flame surrounded by smaller ones. They are supplied as No’s 1,3,5 and 7 sizes, but they use more gas and are hotter than the similarly numbered swaged nozzles. For fillet brazing I found they were of no use, giving out to wide a heating zone causing the braze line to spread out too quickly. For brazing lugs I have to say I like them. The wider heat distribution seemed to be a benefit rather than handicap and the central larger flame still sufficient to manipulate the solder along the joint edges. I have not tried the No1 size but found the No3 likely to be adequate for most lug brazing and even perhaps a little too hot for silver soldering. I have since spoken to someone who has used similar ones in the past but abandoned them due to repeated blockage of the fine nozzles.
Clarification over the types of welding torches
Recently I have encountered some confusion over the use of Torches. All the equipment I use is for Propane, with the exception of the torch, which is of the same design as used for oxyacetylene welding. As far as I am aware these torches are and have been widely used for oxy-propane with the standard swaged welding tips. The torch referred to in the review above is a propane specific torch and I do not think is suitable for using with swaged welding tips, indeed I tried it and couldn’t maintain a stable flame. Propane specific torches available in the UK seem only to be sold for heating (these have large multi jet nozzles, which may be suitable for lugs) and for cutting applications. They cannot be used with standard swaged welding tips and therefore that leaves the only option of using a standard welding torch and tips or using oxyacetylene instead.
Cobalt Blue Welding glasses from Plasmatech
I have given some information on eyewear for brazing elsewhere, but I have recently tried the Cobalt Blue glasses supposedly developed for brazing using gas flux. I cannot find any other supplier than Plasmatech in the UK though similar blue glasses are sold in the USA. Their principal attraction is they look cool, and also seem to be of considerably better quality than other welding spectacles I have seen, though this is reflected in their price.
The idea is they eliminate the orange glare given off by the heated zone and therefore enable you to see the brazing area much more clearly due to the fact the flame with a gas fluxer is green. You can see below the effect compared with standard shade 3 safety glasses. The Cobalt blue lenses are shade 5 but I could still see more clearly than through the standard shade 3 lenses.
Hopefully you can see how much clearer the flame is through the blue lense. For Fillet brazing I found the blue glasses much better than standard shades. The braze line is much clearer due to the absence of orange glow. For Lug brazing I did not find them particularly helpful, largely because you cannot see the orange glow and therefore can miss the lugs getting overheated, whereas with fillet brazing you do not need to pay much attention to overheating as you are concentrating on the molten brass pool.