• 2016

CUTTING SHEET METAL

CHALLENGES TO CONSIDER

When a severely damaged vehicle is brought into your shop, it’s highly likely a large amount of sheet metal will have to be replaced. What should be repaired or cut out are questions that have to be answered. If you decide that a particular panel cannot be repaired, it will have to be cut out correctly in order for the replacement panel to be properly fitted and installed. Removing the damaged panel without affecting the adjacent sheet metal is often referred to as sectioning.

Removing a damaged body panel is not as simple as marking a line and cutting the sheet metal. On today’s vehicles, there are several  variables to consider. The use of several high-strength steel (HSS) and high-strength low alloy (HSLA) steels, as well as adhesive bonding, requires that sheet metal cuts be made in specific locations. With unibody construction, an incorrect cut can have a negative impact on the structure and integrity of the vehicle. Cutting sheet metal can also compromise the corrosion protection barrier. Many body panels including the doors, front fenders, hood and liftgate, can be removed and replaced since those components are fastened onto the vehicle.


THE BODY SIDE APERTURE

The rear quarter panel area, known as the outer body side aperture (Figure 1), often requires repair when the vehicle is involved in a collision. Sheet metal cutting, spot weld removal or sectioning, will be required to remove the quarter panel.

This is done when the damaged sheet metal cannot be repaired by conventional means, or if the panel will be repaired on the bench system. When repairing a specific model, always refer to the collision repair manual for that vehicle. It will specify sectioning locations and necessary sealers, foams, adhesives and corrosive protection that must be applied prior to the refinishing process. Vehicle design will determine if the sectioning location is to be in the pillar or the roofline area. With this in mind, the focus of this article will be on sectioning the rear quarter panel and the outer body side aperture on a late model minivan.


REAR QUARTER PANEL PREPARATION

Before you get out the drill and plasma cutting torch to start removing the damaged quarter panel, some of the adjacent pieces must be removed first.Figure1

Remove fascia and tailgate.

Remove the hinge bolts, then remove the strut rods or springs, depending on the vehicle design.

Place the tailgate in an area where it cannot be damaged (unless it requires repair work). Don’t forget to remove the weather-strip along the perimeter of the opening.

Remove the rear wheelhouse splash shield. This is a pretty straight forward procedure. Remove the fasteners that secure it in place and cut an opening around the shock or strut tower.

Remove the fuel door (if it is on the side of the vehicle that has been damaged).


QUARTER PANEL REMOVAL

Today quarter panels are often weld bonded in place. Drilling through these spot welds with a blair cutter or mill bit is the most common method of removal. Using a heat gun will assist in loosening the structural adhesive if required. The best tool to use to remove a quarter panel is an air chisel with a flat bladed bit. This tool allows you to make clean, accurate cuts, which is important when blending the replacement panel into undamaged sheet metal.

First, mark off the area that will be removed with a grease pencil or chalk. On a minivan, this would be a relatively small area above the wheel well, rearward of the door opening and below the quarter panel glass.

Then, follow the contour of the panel, while at the same time trying to make all your cuts in straight lines. Transfer the cut lines to the new panel and cut it, as necessary. Be as precise and accurate as you can be.

Next, dry fi t the replacement panel over the damaged area of the quarter panel (it’s a good idea to use pop rivets or Cleco’s to hold the new panel in place). Scribe the outline of the replacement panel on the existing one.

Finally, remove the replacement panel and carefully use your air chisel to cut out the damaged area. Be sure to cut along the inside edge of your scribed line. Any areas that are bent can be flattened using a dolly and hammer.

Note: When cutting the sheet metal, remember that the new panel will be welded into place using a butt-joint that requires a backing plate; remember to retain a portion of the panel that is removed to use as the backing plate; the piece closest to the cut is easiest to fit as it’s shaped similar to the panel it will reinforce.

If the entire rear outer body side aperture must be removed due to extensive damage (this section would include the doorjamb and tailgate opening), Figure 1 (A), the oval-shaped outlines indicate the areas in which the sheet metal must be cut. Notice that these areas are at the vertical midpoint of the rear quarter panel glass.

After you’ve finished removing the damaged area, or the entire quarter panel, clean the cut edges with an electric drill-powered wire brush. Be sure the edges are clean and free of rust. If any rust does exist, apply a rust arresting compound. This type of chemical will cover the rust to a black oxide and inhibit the rust from spreading.

REMOVING THE FRONT OUTER BODY SIDE APERTURE

Take a look at the front outer body side aperture in Figure 1 (B). Once again, the oval-shaped outlines indicate the areas in which the sheet metal must be cut. Removal of this section might be required if there is extensive collision damage to the front door. Note that the cuts are not made through the rocker panel and the cut in the B-pillar (vertical section of the aperture) is in the upper third of the pillar. As stated previously, sectioning locations are specific to each vehicle. Remember to reference the collision repair manual for the vehicle specific information.

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