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Author Topic: Welding advice  (Read 2378 times)
jonb
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« on: November 15, 2014, 05:54:11 pm »

I am thinking about welding, for small scale items, but have no experience so I would like advice on what would be a good starters kit, how to manuals etcetera.
All replies will be gratefully received.
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Narsil
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« Reply #1 on: November 15, 2014, 06:21:49 pm »

Welding is quite a complex subject and you do need a combination of theoretical knowledge and practical experience to reliably produce good welds. Having said that it is perfectly possible to teach yourself with care, good research and patience.

The first thing is to decide what process you want to use, there are 3 main arc welding processes suitable for home and small workshop use.

- MIG : uses a roll of filler wire and a shielding gas (usually an argon/CO2/Oxygen mix). MIG welders work well on medium gauge materials (say 2mm to 6mm), you can weld thinner stuff with care but it becomes more difficult as the metal gets thinner. MIG is good for all round fabrication in mild steel. Mid range machines will also work OK on stainless and aluminium. although you may need to change some parts to do this. The main advantages of this process are that it's quick, convenient and versatile.  

- TIG : a highly controllable and precise process, a DC machine will produce consistently sound and good looking welds on mild steel, stainless and most copper alloys and can also be used to brae difficult to weld materials like galvanised steel, brass and tool steels. Machines with an AC feature will also weld aluminium and magnesium alloys and its is certainly the best process for these materials.   It is also by far the best process for very thin sheet materials and small parts.

- MMA (stick) : this process uses flux coated rigid electrodes. It's very good for heavy section steel in things like structural and plant repair applications. The equipment and rods are relatively cheap so it's a good choice for occasional jobbing work  it also works well in difficult conditions eg outdoors or on materials which are difficult to clean adequately.


MIG is probably the easiest process to learn and some of the more advanced electronically controlled machines are (almost) foolproof. TIG certainly requires a bit more practice but you can usually see what you are doing wrong and the learning curve is reasonably shallow, although some people find it harder than others. MMA can be tricky to pick up as you can't see what is happening with the weld so easily but once you've got the knack it's not that difficult. All welding processes will require a bit of practice and research before you can reliably produce decent welds.

« Last Edit: November 15, 2014, 06:41:44 pm by Narsil » Logged







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Maets
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« Reply #2 on: November 15, 2014, 06:27:10 pm »

I am thinking about welding, for small scale items, but have no experience so I would like advice on what would be a good starters kit, how to manuals etcetera.
All replies will be gratefully received.

A MIG welder is the easiest and most flexible.  MIG is metal in gas.  There is a flux core version, but use the gas if possible.  For steel a lot of people use Argon/CO2 mix.  I prefer straight CO2.  It is cheaper, gives better penetration and isn't bothered by junk on the metal.

The key to using a MIG is setting the speed and heat to match your work.  With it you can weld heavy things and very light things.  Just a matter of setting the heat properly.  Some machines have auto setting capability.  One of machines does and I use it sometimes.

A acetylene torch is a must have for many metal projects.  You can cut with it, heat for bending, burn off paint etc, or braze.

A little bit to start you off.  One question would be the metal you want to work with and the size and thickness you think you will be welding.



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Narsil
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« Reply #3 on: November 15, 2014, 06:35:14 pm »

In terms of choosing a machine there are a few things to bear in mind.

I would steer clear of the very cheap generic machines, you can get something decent for not a lot more money and will probably end up spending less in wasted time, materials and frustration in the long run.

For a first machine I would probably recommend something like this http://www.r-techwelding.co.uk/welding_equipment/Mig_Welder

It will do both MIG and MMA which should cover most things unless you know that you want to be welding aluminium sheet or really thin steel. THE 180 amp output should cope with anything you are likely to want to do. It's a professional quality machine and isn't that much more expensive than the cheap and nasty ones and in the long run the cost of gas and consumables tends to be the main expense in any case.

You also need to consider the need for shielding gas. There are two sensible options for this either hire bottles from someone like BOC or you can buy and return rent free bottles. Which turns out to be the best value for money depends on how much welding you are likely to do. I would get a rent free one to start with and see how it goes. There is little point in the small disposable bottle as they work out ludicrously expensive.
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jonb
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« Reply #4 on: November 16, 2014, 02:58:02 am »

Thanks folks you have confirmed what I thought, but I wanted to make sure, it is going to have to be TIG because I am looking at making small to very small things. I have only ever seen mig used and would have felt more comfortable with a system I had a least seen used, rather than just on video, but tig it has to be.
So the advice is to spend money on a good machine to start with rather than start with something cheep as a learning device, so do I take it they tend to have a long life time if looked after?
I am making the presumption that initially if I want to start making stuff from the off I should be able to do spot welds that can tack parts together, and then from there I can slowly learn how to make clean joining of edges.
Are there any good manuals you would recommend for Tig welding so I can drop a note to Santa in time?

Once again thanks for the advice, and it is doubly nice to know it is from experts, because looking at work the both of you produce it is that mastery that I would like to eventually achieve.

Thank you
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Maets
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« Reply #5 on: November 16, 2014, 03:22:48 am »

You didn't mention materials you plan to use.  For some things soldering is better than welding.

In terms of TIG I am of no further use. 

I do agree that getting a good machine is cheaper in the long run. 

A torch is always a good thing to have.
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jonb
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« Reply #6 on: November 16, 2014, 03:44:47 am »

Soldering now that I have no experience of at all apart from electric circuits, and I do know it can be used on copper pipes but that is it.
Right what I am initially looking to do is fabricate things from old metal (Steel) cans. I have worked with this as a material for a long time. And now am looking to find better ways to join and fix parts.
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« Reply #7 on: November 16, 2014, 04:25:43 am »

One thing I remember from school is that TIG welding needs very clean metal to work properly.

You'll want to get a small grinder or handheld sander (depending on the size and thickness of parts you want to weld together) to remove scale / paint / oxide.

On steel, scale is the black / grey stuff on top, you'll want to sand or grind it off until the spot you want to weld is silver and shiny.

If you're going to work with aluminum, it's trickier because the oxide is the same color as bare metal, forms quickly, and has a higher melting point than bare aluminum, by several hundred degrees IIRC. This causes problems because if you don't remove the oxide before welding (and periodically during the process) you'll melt the metal just under the oxide layer long before you melt the oxide itself, and this can get messy in a variety of ways.

A few other general welding related things:

You'll want ventilation to remove the smoke, but be careful welding where there is a lot of air movement. Unless you've got the shielding gas flow cranked up, the shielding gas can get blown away and cause intermittent problems. At work we have big frames with plastic sheeting to provide movable shields against drafts.

Some types of metal produce toxic smoke. Don't weld on galvanized/zinc plated things if you can help it (the occasional bolt is probably ok) The vaporized zinc in the smoke bonds chemically to the calcium in your bones, is cumulative, and can do terrible, terrible things to you if you get too much in your system. Some types of stainless contain hexavalent chromium which is also bad for you.

Cast iron can be welded but demands specialized techniques and prohibitively expensive filler rod. (Can't remember if it can even be done with TIG)

Leather gloves are a must, and non-synthetic (read wool or cotton) clothing is a good idea. If you weld for long enough you will catch yourself on fire. (And if you get blisters, leave them alone, they heal much quicker and are far less irritating)

Getting an auto-darkening welding hood instead of a flip-lens one will probably save you a lot of grief when you're first learning to weld, especially if you're doing TIG welding. I think cheaper ones run about $40-50.
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« Reply #8 on: November 16, 2014, 09:16:28 am »

Right what I am initially looking to do is fabricate things from old metal (Steel) cans. I have worked with this as a material for a long time. And now am looking to find better ways to join and fix parts.

Tinplate, you're better off brazing it with flame!

As others have suggested Mig is the most adaptable, sound out your local tech school and see if they do any welding courses, it might be worth a term of "nights" to get your eye in on most types of welding process before you commit any of your cash to the project!
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jonb
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« Reply #9 on: November 16, 2014, 12:02:53 pm »

Yes chaps it is soldering that I should be looking at, what I was presuming to be welds, I now think with your advice were solders, so now all I have to do is find out how to make strong bonds with this method any advice is still more than welcome as you can see my knowledge would not fill the eye of a needle.
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SeVeNeVeS
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« Reply #10 on: November 16, 2014, 12:34:35 pm »

I would say that if you wish to solder tin cans, silver solder (not plumbers soft solder) would possibly be your best option.

Same principal but alot stronger.

Maybe look into "tinning" on google
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Narsil
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« Reply #11 on: November 16, 2014, 12:45:53 pm »

The basic tool for soldering and brazing is a gas torch. For small things a venturi type propane torch should suffice with and oxy-fuel setup you can do heavier work. For some applications gas brazed joints can approach the performance of welded ones (steel bicycle frames are often brazed).

There are lots of different solders available and they are generally classified according to the metals they are intended for and the temperature at which they work. Generally higher temperature fillers will be stronger. You also need  to make sure that you use the correct flux for the job.

The terminology can be somewhat confusing eg 'silver solder' can be variously used for a) any 'silver colored solder' often containing little or no silver b) high silver content fillers used in jewelery c) high strength, high temperature brazing fillers containing relatively small amounts of silver.

Also the terms soldering and brazing are often used interchangeably, depending on the industry and process in question.

The difference between soldering and brazing is down to  temperature. Solders work in a range up to about 500degC and are generally used for sealing joints either to provide a gas/liquid tight seal or electrical or thermal conductivity. Brazing works at higher temperatures,  up  to about 800degC or so and is able to create much stronger joints.

Soldering and brazing require a lot of joint preparation as joints need to be clean, well fitting and well supported. Soldering is poor at filling gaps and cannot be used to build up material in the way that welding can, joints also need to be supported until they are properly cool which may take a few minutes.

With the right filler and flux you can join most metals, including dissimilar ones but plated surfaces and aluminium can be problematic.

It's also important to bear in mind that the filler metal is usually substantially less strong than the base metal and will only adhere to the surface, rather than penetrating the base metal. This means that joints need to be designed with some care to ensure that they have adequate surface area and that the filler can flow properly into the joint. Unlike welding where the aim is usually to keep the heat as concentrated as possible with soldering it is usually necessary to ensure that the whole joint is heated to the correct temperature in one go. Just melting the filler and dripping it onto the joint will not work. You also need to be able to control this temperature within a fairly narrow range as overheating can burn the flux or even boil the solder.

As well as a torch, filler and flux, things like binding wire, firebricks, abrasives, clamps and supports will all be necessary. An infra red thermometer may also be useful in learning how to judge and control temperatures which is probably the most difficult skill to grasp.

« Last Edit: November 16, 2014, 12:54:45 pm by Narsil » Logged
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« Reply #12 on: November 16, 2014, 01:13:19 pm »

If the cans are indeed steel, then MIG welding my be the right choice.  It is possible to weld very thin steel together with a MIG set low.
Are the cans steel? Does a magnet stick?
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« Reply #13 on: November 16, 2014, 02:31:14 pm »

It is possible to weld very thin steel together with a MIG set low.


that is very true, but, its a frickin artform in its own right!
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jonb
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« Reply #14 on: November 16, 2014, 03:10:26 pm »

I think at the moment for what I am looking at doing, soldering is going to be the way forward. I am looking up things on the web now and you probably don't realise how much help you have all been, just giving me the right terminology has progressed me so far forward, I can see already that what I want to do is far more achievable than I had even hoped before starting this thread. Yes I know when I start to get the right equipment there is going to be a lot of swearing from me as I learn how to handle it, but at least I now have a clear idea of where I am going, honestly I cannot thank you all enough.

As you can all see It is going to take me a while to build up to the status of complete-novice, and as such any additional information, from names of tools, types of flux, solders, and their uses, places to go for information etcetera will be more than welcome.

Thank you all this is such a help to me!
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Narsil
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« Reply #15 on: November 18, 2014, 11:20:54 pm »

In terms of tools the single most important thing is a gas torch. From the sound of what you're doing plumbing or electrical soldering stuff probably won't be adequate.

My impression is that you have three main options :

- Disposable cylinder gas torches, these are generally aimed at plumbers but some of the better ones should be adequate for what you want. These systems are easy to find and reasonably convenient but they can be awkward to use compared to modular torches with hoses and separate gas bottles.

- Propane/air torches : these usually concise of a torch body with hose and regulator, various interchangeable nozzles and a bottle of fuel gas. Propane bottles are pretty cheap (especially compared to disposable cylinders) and you can get them easily enough. These systems allow you to change nozzles for different jobs and you don't need an oxygen or compressed air supply. The downside is that in some cases you might struggle to get enough temperature in the work for some of the higher temperature brazing alloys.

-Oxygen/fuel torches : These will give a significantly higher flame temperature  which can be useful for working with bigger pieces and should cope well with all brazing techniques. They also tend to keep the heat a bit more concentrated as the flame is hotter and finer.

Depending on the scale you ant to work at you might want to look at either jewelery suppliers or more general engineering stuff eg :

http://www.cooksongold.com/

http://www.thewelderswarehouse.com/Welding/Gas-Welding-Kits.html

http://www.gasproducts.co.uk/acatalog/Sievert_Neck_Tubes___Burners_1.html

http://bullfinch-gas.co.uk/

With electric arc welding now the norm for many applications gas kit tends to be quite specialised so it's worth doing some research and working out what solution will be best for you.

These pages should give you some idea of teh range of soldering and brazing fillers available :

http://www.weldability-sif.com/pages/results.asp?subcat=GAS%20RODS%20-%20BRAZING

http://www.weldability-sif.com/pages/results.asp?subcat=SILVER%20SOLDER
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jonb
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« Reply #16 on: November 19, 2014, 03:14:16 am »

Thank you those links are just what I want, and need, It is so nice of you to have taken the time to get them and put them together for me and I really appreciate it.

What I am seeking to make would be most equivalent to old tin toys. I have used tin cans just as I did with paper when I was cardboard engineering, but found using glues and epoxy personally aesthetically unappealing (Yes it cant be seen but just knowing it is there deadens the object for me). Until now that has limited me to only joining things mechanically, this has made it impossible to animate some of my work as I would wish.

You have given me everything I need, now it is down to me to make it work.

Thank you so much
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jonb
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« Reply #17 on: November 25, 2014, 12:50:56 pm »

I am still in need of advice.
Because of the small size I will be working at and my own lack of craftsmanship, looking at what I want to do, I think that it is likely I am going to miss bits when soldering my pieces together so I am going to have to go over bits later and put them right and add bits on.

For this intricate work might I be better off using an electric soldering iron?
If so is the little one I have for electric circuits adequate or should I get a different sort?
If so what sort should I look for?

Thank you for your attention, as always any advice will be most gratefully received.

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« Reply #18 on: November 25, 2014, 01:44:13 pm »

My solder skills are limited.  What I use for electric connects to solder isn't even close to being able to do metal to metal joining.  I have used a larger iron, but I usually resort to a propane torch.  It has its own problems, but seems to work best for me.
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jonb
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« Reply #19 on: November 25, 2014, 05:54:08 pm »

So can a good torch be as precise as an iron? I am just thinking if I want to alter a spot after the main work could an iron be useful?
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« Reply #20 on: November 25, 2014, 06:09:44 pm »

A "small" electrician's soldering iron may help as solders that melt a differing temperatures.

I would imagine one of those gas powered irons may be useful in touch up work, not used one mesl' so can't contribute any more an that one
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jonb
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« Reply #21 on: November 25, 2014, 06:15:24 pm »

So does that mean I could tack a missed bit with a softer solder without affecting the parts which are right?
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« Reply #22 on: November 25, 2014, 06:21:04 pm »

Possibly.....quite possibly.
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Narsil
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« Reply #23 on: November 25, 2014, 09:34:35 pm »


Yeah the best way round the problem of soldering adjacent bits at different times is to use different grades of solder. Jewellery solders are commonly grades as hard (highest temp), medium, easy and extra easy.

A smaller torch or iron won't help in itself as the work need to get to the temperature it need to get to, certainly most electrical soldering irons are totally unsuitable for anything other then spot joints on electrical connections where the mass of metal to be heated is very small.

Also bear in mind that if any joint is unevenly filled that tends to indicate an underlying problem so it's almost always better to take it apart and start again. In most circumstances a joint should fully fill in one hit. As opposed to welds which can be poor, adequate, good or excellent solder joints are a much more binary succeed or fail type of deal.

It is also good practice to design your soldered joints so that  they have at least some mechanical support so you might consider designing your assemblies so they work as 'dry' fits and then leave the permanent joints until the last minute using small pinned joins can be effective for this also look at designing in things like slots and tabs. OR at least plan ahead and break the work down into two or three distinct phases. What is very difficult is to keep adding bits one after another, especially when they are close together as you will just melt out your previous joints.

What can be useful is if you design the work so that you solder mechanical fixings onto the separate parts eg screw fittings, pins, sockets or tabs.

Traditionally made steel bicycle frames are worth studying as they often have many different examples of cleverly designed joints which combine mechanical lugs with brazing

http://www.bobbrowncycles.com/stainless_frames.htm
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jonb
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« Reply #24 on: November 26, 2014, 12:58:24 am »

Well I am not sure if I will ever get to that sort of finish, or even if I want to, but yes you are so right. I have been making a few paper models to work out how to approach making something this way and I can see that I am going to have to drastically change my method of thinking already. The planing at the first stage is far more important. Up until now the 3d stuff I have made I have done from the perspective of an oil painter where I can add or remove bits as I go along, but as you are pointing out and I can see from my models that is not going to be so easily done. Thus at the conception I am going to have to have a much clearer vision of the end product than I have needed using other media.

Its funny I was stupidly half thinking just buy a tool and and I can do it, but like with all things, the biggest difficulty is altering what's in ones head so the tool can be used properly. And in saying that don't be to disappointed when I get a torch and post my bits up, because my style is amateurish and cartoon like and not the the sort of thing anyone would associate with a craftsman.
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