| | | I’ve received many questions about the process, procedures and techniques regarding MIG welding over the recent past. This is written for those brave enough to even consider welding their prized possession – their 914. While welding at first appears to be a “black art”, in reality, it is a practiced talent – and a "talent" which is relatively easy to learn and practice on a regular basis. First, I have to add a disclaimer: Use what I write here at your own risk and responsibility. Unfortunately, people occasionally make mistakes (it’s part of the learning process), but I can't assume risk for their errors, nor can I assume risk for my mis-communications. If you agree, then read on! If not, well, just ignore this post! My personal philosophy in authoring this post is to encourage others to try things that other people do. Welding is one of those “things”. It is not hard “thing” to learn. – it just takes a basic understanding of the proper procedures and a little practice. Step 1: Safety
But “first things first” as they say. The FIRST, and most important “thing”, is to be safe: - Make certain that anything in the area around you that could possibly ignite is removed entirely from that area. “Welding” means heat, sparks and more sparks. Things that could burn, will burn. And yes, that includes your clothing and skin, if you’re not careful! - You must wear a long sleeve shirt, long pants without cuffs (non-flammable, like cotton) and leather welding gloves. - A good eye shield or welding hood must be used.
- Get a fire extinguisher and always have it nearby for immediate use in that event it is necessary.
- NEVER MIG or ARC weld where water will be in contact with you or the surfaces you are welding. This will electrocute you - welding YOU rather then METAL!
- Use proper ventilation, as the fumes are harmful if welding in an un-vented area. I usually leave the garage door open when welding and then take a break away from the area till they expelled.
- Disconnect any and all major electrical components from the car, like the battery, the alternator, etc. before attaching the welder. If you weld with these attached, you might destroy them.
I’ve received many questions about the process, procedures and techniques regarding MIG welding over the recent past. This is written for those brave enough to even consider welding their prized possession – their 914. While welding at first appears to be a “black art”, in reality, it is a practiced talent – and a "talent" which is relatively easy to learn and practice on a regular basis. First, I have to add a disclaimer: Use what I write here at your own risk and responsibility. Unfortunately, people occasionally make mistakes (it’s part of the learning process), but I can't assume risk for their errors, nor can I assume risk for my mis-communications. If you agree, then read on! If not, well, just ignore this post! My personal philosophy in authoring this post is to encourage others to try things that other people do. Welding is one of those “things”. It is not hard “thing” to learn. – it just takes a basic understanding of the proper procedures and a little practice. Step 1: Safety
But “first things first” as they say. The FIRST, and most important “thing”, is to be safe: - Make certain that anything in the area around you that could possibly ignite is removed entirely from that area. “Welding” means heat, sparks and more sparks. Things that could burn, will burn. And yes, that includes your clothing and skin, if you’re not careful! - You must wear a long sleeve shirt, long pants without cuffs (non-flammable, like cotton) and leather welding gloves. - A good eye shield or welding hood must be used.
- Get a fire extinguisher and always have it nearby for immediate use in that event it is necessary.
- NEVER MIG or ARC weld where water will be in contact with you or the surfaces you are welding. This will electrocute you - welding YOU rather then METAL!
- Use proper ventilation, as the fumes are harmful if welding in an un-vented area. I usually leave the garage door open when welding and then take a break away from the area till they expelled.
- Disconnect any and all major electrical components from the car, like the battery, the alternator, etc. before attaching the welder. If you weld with these attached, you might destroy them.
OK. So we have the safety bases covered (i.e. you won’t burn up, your car won’t ignite, your garage will be intact after you start welding – and you'll have a
fire extinguisher handy in case they do :-)
Step 2 – Getting Ready to Practice
When you are ready to start, practice welding on some scrap metal that is close to the thickness of the body part you are going to repair. This is usually 20 or 22 gauge “stock material” which is available at auto body parts stores, auto recyclers and metal scrap yards. It is cheap. Buy a lot of it. Then buy some more. This practice is essential and will show up in your final effort. NEVER - and I mean NEVER - practice on what you intend to repair. Practice materials are cheap – your car is not (nor is paying someone else to fix it!). And, by the way, practicing on cheap stock is kind of fun without the fear of hurting anything. Step 3 – The Welding System
A MIG welder has 2 cables. One of them is the ground. It looks like an alligator toothed clamp – like car “jumper cables”. This lead must be attached either to the metal you intend to weld, or near the piece you are welding for proper grounding. MIG welders work on current flow, so don’t attach the ground at one end of the car and try to weld at the other end. The current would have to pass the entire length of the car – impeding the “arc” (more on this later). The most important point here is not begin welding without this cable attached near the point of welding.
The other lead from the MIG welder is the “business end” that has the electrode and it’s handle with the “welder on” and wire feed button (also, the tip will have a gas outlet if your MIG uses tanks). When you press the button, wire (and gas, with a MIG with tanks) will be fed from a spool in the machine through the feed line and to the handle you hold in your hand and, as importantly - electricity will flow from that electrode. Don’t touch it when the button is on!
Just a short note about the different types of MIG systems – “gas” and “gas-less”. A MIG with a tank attachment will force CO2/Argon into the arc as the weld is being created. This gas help keep the air surrounding the weld uniform – creating a better weld in the process. The second system (“gas-less”) uses a shielded wire electrode. The outer coating of this shielded wire creates its own gas as it burns in much the same way a tank provides a gas source. Either system is fine for light body work!
Step 4 – Preparing the Surface
Electricity is a funny thing – it travels through clean metal best. It doesn’t like rust, oil, grease or other contaminants. Therefore, preparing the surfaces to weld is as important as the weld itself. To prepare the surfaces, cut out all the rust and use a wire brush to clean all the surfaces to be welded so that they are bright and shiny. If parts need to be primed, 3M makes a product called “weld-through primer” which will conduct the electrical current while providing protection to the bare metal. Follow the directions on the label and your finished welds will look professional from the start.
Step 5 – Your First Weld
OK, so get on the proper attire, get your gloves, get your eye protection handy. Ready? Let’s go:
First, the procedure is pretty simple - when you press the switch on the handle, you will strike an “arc” (an electrical contact) between the metal and the electrode protruding from your welding). To start this arc (kinda like lighting a match) hold the electrode about 1/8" from the metal surface to be welded. Once the arc is lit, a lot of stuff happens pretty quickly – the metal gets really hot (molten), new metal is fed from the electrode, and a “puddle” forms on the work pieces. This puddle is molten steel and is actually your weld. In reality, when you weld, you are joining metals within this “puddle” and you’re your welding talent is gauged by your ability to control that puddle. Really, its that simple (or that difficult, depending on your level of optimism at the moment…)
So go ahead - try it. By the way, at precisely the moment you strike the arc, the hooded shield that protects your eyes must be pulled into place – or you won’t see a thing. The bright light will hurt your eyes (not a good thing as you will see “stars” for days or worse, could cause more permanent eye damage.). You might want to practice just pulling the hood into place when you touch the metal without power on until you feel your eyes will be safe from the light. Again, this is imperative for eye protection. Practice doing this until you feel comfortable that it is done correctly. Another option is to hold the electrode in place, pull on the hood, and then start the arc. Either is fine as long as your eyes are covered when you begin to weld. (BTW: You will see everything as you weld even though you can’t see through the shield under natural light. The welding process is REALLY bright. And before raising the shield, make certain that you move the tip away from the grounded metal to stop welding.)
Step 6 – Techniques and Welds Types
My specific technique is to weld in short welds. Generally about 1/8" spots. Start by doing one in the middle of the entire length. Next tack each end. Then eyeball a spot midway between the middle spot weld and the end. Do the other direction likewise. This is called stitching. It maintains the straightness of what you are welding. Do this until you have a line of spots from one end to the other. Don't concentrate too much heat in one spot is the idea. Let the entire work piece cool after stiching. (I drink a coke or whatever and come back and inspect of what I have done during the previous session - typically, I consume a case of the stuff on really big jobs :-).
Spot or Tack Welding: To create a tack, hold the electrode in an area for no more than 2 or 3 seconds. Hold tip in one spot about 1/8" above the metal. Too long will burn a hole in metal. Proceed to next position for the next tack or spot, on and on. Spot and tack welding can be done on a seam or though holes made in the overlaid stock to be attached.
Creating A Seam or Butt Weld: When you are doing long seams, your hand motion will be in small oval movements. These movements are like small circular motions away from you one side on the work piece and toward you on the other. Remember that you are actually moving a molten puddle of metal along a predetermined path. Think of it a “fanning or pulling a drop of water” – it’s pretty much the same principle. Keep repeating this motion into the joining metals about 1/8" to 3/16" from the top of previous circular always working toward your standing position. Never do this type weld without tacking the entire length with spots no more than 6" apart maximum. Here is the best diagram I can draw in e-mail: you handle = + positive lead
_______\__________ <-----direction of welding motion
metal = -- ground lead BTW: A solid weld along the seam is not always necessary. Use what you see on the part that you are going to be repairing on the 914 to be a practical guide on which weld type to use. And remember, heat will distort metal. Too much is worse than too little. It will also weaken the metal. Dwelling too long at one point will burn a hole that will have to be welded later to accomplish good appearing work as you will want your 914 to have.
Summary - a short version of the procedures - Put gloves on.
- Clamp metal to be welded with c-clamps to retain their movement.
- Clamp the ground to the metal.
- Set the amperage switch on the welder to proper amps. Should be instructions that came with your welding system.
- Turn on welding machine.
- Have shield on and comfortable fit.
- Stand or sit where you see the 2 pieces of metal you will join by welding are directly in front of you and be prepared to pull shield over your eyes at the precise moment of contact.
- Now, position the handle with tip about 1/8" from the surface of the metal and along the joining edges of the 2 pieces of metal, pull shield down quickly with one hand while pressing the switch on the handle with the hand that holds it.
- Bright glow on contact begins the welding process. Extremely HOT. Never touch what you are welding with bare hands. It will burn your hand and if like me, cause you to swear.
- Work slowly and never get in a hurry. Speed will come with experience.
- You should keep this 1/8" gap between the metal and the tip constant and move the tip in a direction toward you along the gap and maintain about a 15 or 20 degree angle of the handle in relation to the working surfaces.
You can do it. Practice, practice, practice. And Have FUN with it! Wishing you success.
Mike Cooley This technical article is made possible solely through the support of Pelican Parts. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. |
