General Welding equipment

From VW T25(T3)-Tech
Jump to navigationJump to search

MIG Welding

Garage power supply?

Nicola&Tony: I've recently started doing a welding course and have read quite a few threads on the subject on here, 
so I'm now thinking about buying a 150 amp mig welder.

Just one question at the moment; will I be able to power it by plugging it into an ordinary household electrical socket / circuit, or does it need to be on a circuit that's a bit more heavy duty? Tony

andysimpson: May have problems on full power, try it and see.

steveo3002: Should be need for full whack for welding body panels etc.

DiscoDave: Usually it'll work on a 13A socket plugged in to a normal socket. I've got a 150A mig i plug it in to a 16A blue socket that i've put in out side! You'll only have problems using it on its highest power setting, unless your wiring in the house isn't up to much!

dugcati: Can vouch for it being OK short term on 13A plug... I have a 165A welder and it's fine HOWEVER!.... I wouldn't advise using it for too long on higher power on a standard plug and wiring as it WILL put strain on the cabling and start to burn out the pulg/socket!

oldiquana: My biggest welder in't workshop is 185 amp.....running on normal 13 amp sockets......never had any problems long as it's a good quality unit it should be OK on full power as long as you dont go daft. Just to be sure I installed a separate outlet from the main electricity supply to the house then seperate isolator unit then seperate RCB in the workshop via armoured underground cable. The compressor seems to load the supply more than we welder though!. I have to run two welders for everyday 185 is set up for heavy guage gates/railings etc...but for panel and repair work I love my Clarke 100en......more than enough for car repairs, with settings low enough to weld toilet roll... if need be!

Pepperami: I have a clarke 151TE and thats fine (on 13A) but I want a TIG

Nicola&Tony: Thanks ver much for all the info.

Bought meself a welder off ebay today and will pick it up on the way home from Cromer in a couple of weeks time. It's a Cosmo 170 gas/gasless mig with two full gas bottles (small), regulator, auto-darkening helmet, angle grider and discs. All for £140 and listed as being "in excellent working condition" . . . I hope it proves to be as good a deal as it sounds! Tony

Gasless MIG (flux cored)

Rozzo: Anyone know if the gasless mig wire is any good? Seems like a great idea but never actually seen it in action.

lloyd: No expert, but MIG = Metal Inert Gas and leave a slag free weld. Flux core MIG isn't really MIG. It's more an auto feed arc weld. I've used both as well as flux core wire with inert gas. Flux core doesn't require metal to be as clean and can be used in low wind. MIG will not. Sorry I can't help more.

mininut: Personally I wouldn't bother with gasless. Agree with what lloyd said really. MIG should be gas shielded.

BUT if you can only weld outside you'd probably be better with gasles

MIG Modifications

Smoother, more consistent feed
To garner a reliable smooth spool rotation - and hence smoother wire-feed (so important), I finally found this solution works well - to stop the spool juddering, and allow the knurled pressure knob to be set once and left alone (rather than be too tight or too slack when the spool might unwind).
The mod involves simply cutting a rubbing pad of scotchbrite to size, punching a hole in it and mounting it.. basically stops sticking spools. Welder = Clarke 151 TE

Clarke MIG SpoolMod 01.jpg

Better, more reliable earthing
I also decided to put a much higher pressure and heavier duty earth clamp on it (from previous experience of lighweight junk earth clamps letting a good welder down) and because it was easier, left the original.. therefore I usually connect both, so if one drops a good connection, it doesn't affect the current welding process critically. Earth clamp from Screwfix or Axminster Tools... beware, their heaviest one I can barely open with one hand (you really need to be able to easily/quickly mount or adjust it sinmgle-handed).

Clarke MIG EartClampMod 01.jpg

NB. Oh yes, that warning label inside the door! Always take note of that! Cut the new wire dead straight across with side-cutters, then file or sand it to a nice smooth rounded shape, removing any sharp burrs... then feeds beautifully through without carving up the hose-liner.

It's all about equipment maintenance, so its a genuine long term investment that'll still be working well in 10 years time...

TIG Welding

TIG = Tungsten Inert Gas (or GTAW, Gas Tungsten Arc Welding) uses a tungsten electrode (non consumable) to create the arc, uses an inert gas around the arc for shielding, but uses a separate filler rod (like gas welding), making it the most versatile welding technique, as almost any filler rod to match the weld material can be used.

TIG welding equipment is a big step up from MIG, and is the preferred method for high quality welding of either thin or exotic materials (non-ferrous) for structural purposes. It's used a lot in the aviation and spacecraft industries, often manually or semi-automatically. Also many modern duralumin and titanium bicycle and motorcycle frames and parts are TIG welded.

Its considered one of the hardest welding skills to acquire, requiring very steady and accurate control of both the 'gun' and filler rod. Unlike MIG, the power level can usually be varied as the weld takes place, decreasing as the edge of the material is approached. It's also slower than other welding techniques.

Although more expensive than MIG, the equipment isn't that much more bulky, and isn't out of the question for Home workshops, though you don't find TIG sets produced for the 'home' market.

NB. Safety wise, TIG is more dangerous than MIG having even higher UV light emissions and can give bad (sun)burns to exposed skin, as well as high ionisation of air, and production of noxious gases if contaminants are present.

So TIG welding eqpt would usually be restricted to indoors/workshop environments, onlookers face higher hazards than with MIG and much higher than with gas welding.

Stick (arc) welding

See Emergency welding in Techniques

Gas welding

Gas welding has become much less used in the auto-trade, having been eclipsed for many, but not all, jobs by MIG or stick (arc) welding.

It is not generally a Home Mechanics solution because of obvious safety considerations; the bottles require licensing, are getting very expensive to refill, are not particularly portable (see Turbo 2000 micro-welding kit below) and gas welding requires more safety/operational training, and then typically more time developing the welding skills themselves.

One criticism is that distortion can be much greater than electric welding methods, though not true in every case. Generally though a larger area becomes heated than with MIG or TIG.

In the right hands, lovely welds can be produced, particularly in thick or more varied thickness materials.

One advantage is that UV light intensity is much lower, requiring only a No.3 filter shade, electric welding requiring 9~13 shading, as well as the more consistent light emission, making it somewhat easier to see what is happening at the weld pool. However, the advent of auto-darkening helmets for electric welding has made a big difference to the ability to start and pickup the weld area rapidly though.

Gas equipment can also be used for brazing (bronze welding), which is a form of high-temperature soldering. Until recently, almost all bicycle and motorcycle frames were brazed. Less-heat and a sweated joint design gives very high strength, but a higher accuracy of fit is required than welding. With a strong flux, brazing can clean and scour quite dirty metal, yet generally is said to require very thorough preparation.

Today, many garages, general workshops and body shops only retain their gas welding eqpt. for heating up parts, to form them or to remove old/rusted fasteners e.g. exhaust fitting shop. e.g. a quick, powerful and focused heat source.

Because it involves more skill to ensure a good strong weld with adequate penetration, gas welding has become less favoured for structural repair work...

Mini and non-refillable bottles

There are several gas welding setups that are much smaller, lighter and thus more portable than the typical full-size BOC bottles.

Traditionally, 1/2 or 1/3 size bottles were available, though they are now not all supported.

Then there are the true mini kits... but still licensed/rented refillable bottles.

..and now there are welding (brazing/bronze welding) systems based on non-refillable 900gram bottles like the MIG 'hobby bottles'. These are very light and portable, but the bottles are expensive and particualrly the oxygen doesn't last long at all (about 1/3 of the fuel-gas, say 20 minutes depending on nozzle size!)

The fuel-gas is based on propane, but is in fact a modified gas, such as MAP Pro or MAP+ which burns hotter and the oxygen is in a similar sized cylinder (both about £20 each). MAP Pro or MAP+ is also used solo in blowtorches for a slightly hotter fuel/air flame for e.g. plumbing. Those are however hot enough for genuine bronze welding without oxygen and a bespoke torch.

These (micro) welding kits (e.g. Turbo 200 / OxyTurbo set pictured)) are very handy for occasional heating and brazing. True welding cannot be done, due to hydrogen embrittlement (due to the fuel-gas).

Turbo2000 01.jpg

H&S. You would ideally need experience with oxy/acetylene or some training to safely use the above kit.

Electric spot welding

Spot or resistance welding has been the welding process of choice for the mass production of automobile press-formed sheet-steel bodies and chassis for many years now. These days robots weld car panels together very accurately and consistently and fast.

Workshop spot-welders can be bought, but tend to be a bit cumbsersome usually, and heavy... and expensive when new... very handy though to be able to manually electric spot a part panel or seam in-place. They are expensive beacuse they carry large electrical current (for short periods) and thus require very heavy gauge copper electrodes.

Ckarke SpotWelder 01.jpg

The heat is created very locally, at a small diameter (circa 6~7mm) spot where the two sheets contact each other, by passing very high current through the joint, which presents very low resistance. The most intense heat is between the two surfaces, rather than the between the copper electrode and surface, hence the met area is at the join between the steel (having higher resistance there). the time is critical, usually of the order of a second or two, depending on sheet gauge and current capacity of the welder. The adjoining steel (usually) sheets have to have good contact surfaces, so are either bare metal or zinc coated, to prevent subsequent corrosion.

This is the origin of the original usage of 'Weld-thru' zinc sprays, to simulate electro-galvanised steel sheets. Weld-thru high zin solid contents sprays can be sued ad hoc DIY when spot-welding repairs manually.

PS. More & more people are reducing seam welding part and whole panels in place, resorting to modern high-tech adhesives, plus a few rivets or MIG spot welds.

Safety equipment

Leather gloves/gauntlets and an appropraite electric welding helmet are essential for MIG/ARC welding. Typical shades for MIG are 9~13; for gas approx. shade 3 goggles are used

Under a car good body covering is advised, of the non-flammable kind. Nylon/prope overalls are a first line of defence but spatter/ white hot spitz will melt through several layers easily... cotton or natural materials are better. Leather or heavy treated PVC bibs can resist most smaller/medium sized hot particles. Arms & shoulders are particularly vulnerable, so a long sleeved cotton undershirt and an old woollen jumper under overalls is a good idea.