If the best of design is followed, joining thick to thin parts should be kept be to a minimum. When we do have to join thick to thin, we should follow some basic guidelines to be successful. The thicker part will always be able to absorb more heat than the thinner part. You should also consider the thermal conductivity of the materials and their effect on the welding process. Materials like aluminum can absorb much more heat than  something like steel, or stainless steel.

When welding something thick to thin, we need to make sure we have our amperage setting correct or we can risk burning the thinner of the two parts. If we set the amperage low to prevent excessive melting when welding, we risk not having enough heat to melt the ticker part. Also, if we set the amperage level too high to heat up the thicker part, we run the risk of burning or melting away the thinner part.

One approach is to use the correct amperage for the thinner material. Using a torch or other heating tool, warm up the thicker part tot the point it easily welds to the thinner part. Using this process is also useful to increase the effective heat you are able to develop with some of the smaller welding machines. If we preheat the base material, we can weld together thicker material than we would normally be able to do so.

Another technique we can use is to set the amperage just high enough to weld the thicker of the two metal parts. As we weld, we just kiss the edge of the thinner part and focus the majority of the heat towards the thicker part. The torch and electrode angle can play a big effect when using this technique. Keeping enough filler metal in the joint also acts like a fire extinguisher on the thinner part.

Still there is another trick we can use when faced with the thin and thick welding problem. We can place a heat sink on the back side of the thinner part. If we place a piece of copper, brass or aluminum on the back side of the thinner part, that can prevent premature melting before the thicker part is ready to melt. A block clamped onto the back of a sheet or plate will do the trick.

A solid rod or bar inserted into a tube or pipe also works well. Having the ability to machine a part to fit sometimes is the best way to make the required heat sink or tooling. Having some scraps of aluminum and copper always comes in handy for these applications. Be creative in your use and application because there is more than one right way to approaching a welding problem.

If the parts are made out of stainless steel, titanium, or nickel alloys, we need to consider using a purge of inert gas on the back side of the thinner component to prevent contamination, sugaring or excessive carbide formation. If we burn through the thinner material and we do not have an inert gas back purge in place we could damage the material beyond the point of repair. We need to take special care as to not overheat these materials and make sure amperage levels are with welding procedure specifications.

Check out the Longevity website (www.longevity-inc.com) or YouTube channel (www.youtube.com/longevitywelding) for more details and information about equipment for different welding and cutting processes. Longevity has the right machine for your exact application, so take a look and choose what is the best fit for your materials, product and needs.