Haynes Forums - Buying a Welder

UNFINISHED

Recently there have been a lot of questions based around what type of welders are recommended and if certain models should be purchased.. So I felt that one thread should be able to clear up a lot of questions around the subject.

This post is mainly for a source of information for new members.
If you have any questions or want to add anything then feel free to post on this thread.

As you'll all know there are many different methods for joining metal together. The main 3 I’ll be discussing (mainly MIG/MAG) in this article are:

MIG/MAG - Metal Inert Gas/Metal Active Gas
TIG - Tungsten Inert Gas
Arc/Stick

Arc/Stick

Arc/Stick welders are the cheapest and simplest welders you can get your hands on.

MIG

The majority of users on this forum, have used, or are using a MIG welder for their builds. It is the easiest type of welding to learn.

Should I go gas or gasless?

You can use a MIG/MAG welder with 2 different types of wire, either flux coated wire (meaning you won't need a shielding gas) or plain wire (requiring a shielding gas to stop the weld from oxidising).

Gasless MIG welding is supposed to be much harder than gas MIG welding, as you can't see what the weld pool is doing, its similar to arc welding. Flux coated MIG wire also costs more than normal MIG wire, and when the weld has cooled you get a hard slag on top of the weld which needs to be chipped off (if you are good at welding it virtually falls off), also you can't go over a previous part of the weld without stopping and chipping off the slag as it causes impurities in the weld, making them very weak.

What shielding gas should I use?

You can use several different types of shielding gas with MIG welding, Pure Argon, Argon/CO2 mix, Pure CO2 (as used in pubs).

I personally use CO2 as my shielding gas as it is cheap (approx £8 for a pub sized CO2 bottle, with no rent). I have used approximately 1 and a half bottles to tack and fully weld my chassis, along with a lot of practise and welding together a shelving unit for the garage.

What gauge of wire should I use?

You can get 2 different thickness of plain MIG wire, 0.6mm or 0.8mm. 0.6mm wire is used for thinner materials as the thinner the wire, the less amps, therefore the less heat put into the work piece. 0.8mm is used for steel thickness's greater than 1.5mm. Also 0.6mm MIG wire actually costs more than 0.8mm wire, so don’t think you are saving money by going for 0.6mm.
Should I buy new or used?

If you are looking to buy a used MIG welder then try and see it working before you buy it. I bought my welder without seeing it working, it only cost me £80, but it needed a new gas valve (£25) and a new swan neck (£13), as well as all of the consumables.

How do I know which regulator to buy?

You will also need to buy a regulator to lower the pressure of the gas bottle to a suitable one to use when welding. Depending on your gas choice, you will need a different regulator. Argon regulators CAN’T be used with CO2.

Should I use refillable or disposable bottles?

Try to get hold of a refillable gas bottle, it will work at much cheaper than using disposable gas bottles and will make welding a much more enjoyable experience as disposable bottles are never very good and cause countless issues with gas flow problems.

What consumables will I need for my welder?

There are several different types of consumables that you'll need for a MIG welder. These are:

Electrode tips (Approx £5 for 5)
Gas Shrouds (Approx £6 for 2)
MIG Wire (Approx £15 for 5kg)

Electrode tips come in different sizes depending on the type of wire you will be using, either 0.6mm, 0.8mm or 0.9mm (flux cored), keep this in mind when buying consumables.

What welding mask should I use?

You can either get a dark mask or an autodarkening mask. I much prefer (and I guess this is the same for the majority of other welders) autodarkening masks. This is because react to the light created by the welding process to auto darken the mask. They start off with a dark shade of green, but light enough so that you can see what you are doing. This allows you to easily start off the weld as you know it will be in the right place everytime. You can pick up autodarkening masks for £40 upwards. I myself have a Parweld £40 autodarkening mask and I honestly can't fault it.

A normal dark mask has the advantages of not needing replacement batteries (mine is rechargeable by the solar panel on the top), normal masks also can't fail (however autodarkening masks block out the UV light, meaning you will not suffer from Arc eye, in the case of a failure for whatever reason).

If using a disposable gas bottle how do I set the gas flow rate?

You purchase gas flow measurement device to accurately measure the gas flow rate when using either disposable or refillable (if your regulator doesn't have a gas flow gauge), which you put over the end of the gas shroud and pull the trigger when the welder is off, and it shows you the gas flow rate:

http://www.mig-welding.co.uk/shop/gas-flow-tester.htm

MIG Welding Issues:

Wire feed issues can be caused by a few things:

The wire feed mechanism may not be tight enough, or could be too tight.
The wire feed roller may be on the wrong way round.
Debris could be caught in the liner, meaning the liner needs to be replaced (not as hard as it sounds and cheap to fix)
The wrong size electrode tip could be used.

Useful hints:

Stay well clear of SIP welders, these are renowned for having rubbish wire feed mechanisms, causing countless problems and frustration. Even if it seems like a bargain you will regret it in the future if a problem does occur.
Also never use rusty MIG wire. The rust coating comes off in the liner and causes wire feed issues. If it is only light surface rust then just reel off the rusty wire until you are back to shiny wire.

The normal gas flow rate for a welder is 10l/min. Set the regulator to 10l/min, and then with the welder turned OFF, pull the trigger and watch the needle of the regulator, you want 10l/min of gas to flow when the trigger is pulled. So if the needle drops below 10l/min then increase the gas flow rate. With insufficient gas flow, the welds will be porous and very week. With too much gas flow you will just be needlessly wasting gas, and therefore money.

It is highly recommended to get a regulator which shows both gas flow rate and how much gas is left in the bottle.

As a beginner you can happily weld everything on the chassis together with a 150A welder. However, with experience and the correct preparation you can weld together the thicker elements with a smaller welder.