Can You Legally Weld a Car Frame?


The frame of a vehicle is like its skeleton, hidden from sight and providing the strength a vehicle needs to fulfill its purpose – getting you from point A to point B safely. If a situation arises where you need to weld the frame – also known as the chassis – of a vehicle, you may be wondering about the legality of welding it yourself.

Can You Legally Weld a Car Frame?

There is no federal law prohibiting welding the frame of a vehicle but there are some guidelines that need to be followed for passenger-carrying vehicles. The strength and safety of a chassis weld depend largely on the skill and experience of the welder as well as the equipment and materials they use.

If you are going to weld your car frame yourself, make sure you have the right tools to do the job and practice on something else for a while first.

Federal, State and Local Laws

While some countries have made welding the frame of a vehicle illegal or regulate it extensively, the United States remains relatively liberal in this regard. The primary concern of U.S. law regarding this procedure is that it be done following the recommendations of the manufacturer.

States and localities may have their guidelines and rules regarding frame welding. It is important to contact the transportation authorities in the area where you live to determine the specific laws by which you are bound.

Welding a frame is generally only an issue if the vehicles in question are listed as destroyed, rusted, or stolen but some other situations are unacceptable as well.

What Is A Cut And Shut?

An automobile that is composed of two or more donor vehicles welded together to make one operating vehicle is known as a cut and shut. The donor autos are often those that have had one end destroyed in an accident of some sort.

To create this Frankenstein’s monster of vehicles, a welder will cut away the damaged half to salvage what is left. Then the two intact halves are then joined together.

Even with the world’s best welder, this kind of hodge-podge automobile is extremely dangerous.

After the vertical cut needed to separate the donor cars, the frame is not strong enough to hold up to a high-speed collision. Cut and shuts tend to fall apart in even the most minor of accidents and are often the cause of injury to passengers.

A cut and shut can be identified by checking the multiple vehicle identification number (VIN) points around the car. In addition to the one on the lower-left corner of the dash, there are several other locations to look for including:

  • Doorpost on the drivers’ side: With the door open, look in the area around the seat belt return and where the door latches.
  • Front of the engine block: Pop the hood and look at the front of the engine.
  • Rear-wheel well: On the underside, directly above the tire.
  • Spare tire well: You may have to pull out the spare tire to locate it.
  • Front of the frame: This one is often found near the windshield washer fluid reservoir.
  • Driver-side Doorjamb: Open the door and look on the body under where the door would be shut at, opposite from where the door latches.

If any of the VINs do not match, it is likely that you are dealing with a cut and shut. Be wary if you cannot find more than one or two VIN tags on the same half of a vehicle as well.

What Is the FMCSA?

FMCSA stands for the Federal Motor Carrier Safety Administration. They are the ones who answer the question, can you legally weld a car frame?

FMCSA is the federal government body in the U.S. that sets vehicular safety rules. Section 393.201 outlines the rules for car frame welding. It reads dictates that:

  • All vehicle frames must be in “good condition,” i.e., no cracks or sags
  • All required brackets securing the vehicle to the frame must be present and appropriately tightened.
  • Frame rail flanges, unless otherwise noted by the manufacturer, cannot be cracked, bent, notched, or have holes drilled in.
  • Welding may only be done to the frame of the vehicle. You cannot weld additional parts or accessories onto the frame of the vehicle.

These rules are the federal regulations for welding frames and a vehicle can be seized if they are violated. Moreover, businesses that provide passenger-carrying services can be fined as well.

Frame Welding Challenges

There is much more to welding a cracked frame than there may seem. It seems straightforward and simple, but some common problems may make it unsafe to weld a frame.

A lack of skill and control is one of the most common of these issues. It takes a tremendous amount of skill to properly weld a chassis. Poorly done welds may lead to the frame failing and cause a dangerous situation.

A lack of skill also leads to poor penetration of the weld. Many novices – and even some more experienced – welders perform surface welds that fail to join the two pieces on a deeper level. This kind of weld offers little to no support if the frame is put under any sort of pressure.

Equipment Needed for Frame Welding

If you are reading this article, chances are that you are considering welding your chassis. As long as it is your personal vehicle and not a commercial truck, you should not have to worry about driving on public highways legally if you do.

If you are a novice welder, you may want to reconsider or get a little more experience before tackling frame welding. If your set on doing the job yourself, however, you are going to need some equipment to make sure you are in a good spot to do the job right. To that end, you will need:

  • Pneumatic Saw – This allows for precise cuts to allow for better lining up of the pieces to create a finer weld.
  • Welding Clamps – Used to keep the metal pieces in place while you weld, clamps that lock are the best option.
  • Sheet Metal Gauge – Especially useful with MIG welders, being able to gauge the thickness of your sheet metal allows you to get a more accurate weld.
  • Angle Grinder – Important for keeping weld sites flush and clean by grinding away any excess filler.
  • Aviation Snips – Cutting patches out of sheet metal is a snap with these snips. A good pair can cut up to 23 gauge stainless steel.
  • Dolly and Hammer Set – Essential to shaping sheet metal for projects with bodywork.

The Best Weld for a Frame

The world of welding cannot reach a consensus on what is the absolute best type of welding for auto work in general. Instead, the welding community is divided between MIG (Metal Inert Gas) welding and TIG (Tungsten Inert Gas) welding. While both are forms of arc welding, there are subtle differences between the two.

TIG welding uses rods to bond two metals. It tends to work better for thinner pieces of metal and thus, would not work well for welding a chassis.

MIG welding is generally considered to be better for bigger welds, easier to use and correct and able to weld thicker pieces of metal. It feeds wire filler through the welder to create a weld that bonds the two pieces of metal together.

The ability to weld thicker metals together alone is a good reason to choose MIG over TIG for frame work. Being able to fix minor errors is also a huge benefit over the TIG for the MIG welder.

John Nelson

You can find John stringing a hammock from the back of his SUV to a tree camping in the outdoors most weekends during warmer weather. John loves the outdoors and the freedom four-wheel-drive vehicles offer.

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