What Lens Shade to Use When Spot Welding Steel?

This may be the most commonly used and most often referred to form of welding. It may also be the most incorrectly used welding term as well. Spot welding is a welding technique used to join two pieces of metal together that are one on top of the other. It uses a combination of electrical resistance, heat and pressure. It is different than arc welding in that no actual arc is produced to join the metals. Rather the two pieces to be joined are pinched with a set of pointed tongs. One of the tongs is set to a high voltage and the other at ground potential. The resistance to the flow of electricity heats the metal and causes them to weld together. It is an extremely localized procedure. Heat is created only at the point where the two tongs are held together, so the entire piece does not get hot. The joins also will cool down again rather quickly.

The Right Lens Shades for Spot Welding Steel

Chicago Electric 240-Volt Spot WelderBecause of the mechanical nature of the welding points, it is very easy to automate and is widely used throughout manufacturing. The robots you see welding together automobiles are almost always spot welders. Because it is so common, many people not trained in welding will refer to any small joining of metal parts as “ Spot welding “ even though what they are actually referring to is tack welding, arc welding or some other technique. Spot welding is almost never used by hobbyists or in construction as it requires specialized machinery and is not very portable.

Because of its localized nature, and repeatable accuracy, spot welding has been miniaturized and is used in the manufacture of microelectronics, very small mechanical assemblies and even in medical devices. When you are operating a spot welding machine, there is not a very bright arc like what is present when arc welding. So the eye protection recommended is usually no greater than a Shade 5 lens. In comparison, you would not want to view arc welding with anything less than a Shade 10. This is 5 times darker!

Shop Welding Lenses

The most important eye protection for spot welding is a good quality pair of safety glasses and possibly a face shield to protect against flying chips or sparks from the operation. Like all other welding lens choices, the starting shade is a recommendation. It is what you are most comfortable with, and what allows you to best see the work you are doing. In certain machine setups, the arc may be totally enclosed by guards and shielding. So a shaded lens might actually be a bad choice because it could cause you to not be able to see clearly. It is also recommended that you wear clothing that protects against flying sparks and other particulates. So as in all things else, common sense and reasonable caution should be the rule of the day, and the way to keep you vision safe.

2 Responses to What Lens Shade to Use When Spot Welding Steel?
  1. Bill Brown
    January 12, 2015 | 10:29 pm

    Yes that is correct, however I did not want to get into a primer of the relationship between voltage and current. The main point is that there is ground on one side (negative) and voltage on the other side (positive) and the flow between creates heat that causes the weld. I felt that would be clear to most people.

  2. Dave Burton
    January 7, 2015 | 7:14 am

    This article says, “One of the tongs is set to a high voltage and the other at ground potential.”

    That is incorrect. Spot welders use a very low voltage, not a high voltage. Because of the relatively low resistance of the joint being welded, A very high current (and high power output) can be achieved with only a few volts.

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