Automotive Welding Projects: Step-by-Step – Part 6

This chapter details a few projects that are commonly used when working on automotive projects such as restoration, modification for racing, or hot rod construction. The practice welding exercises in Chapter 3 were designed to help you practice the skills needed to undertake these projects, and strong, solid welds are needed any time you’re working on a car’s frame. The bodywork projects involve working with sheetmetal and require the skills and information described in the previous chapter.

 


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Remember that these projects are critical to the finished product when you’re adapting or building your own car. Do not undertake one of these on a car that anyone will drive until you’re sure of the quality of your work and the strength of your design.

 

Chassis and Frame Projects

The following projects deal with ladder frame and unibody chassis repair and improvement. For all these projects, you should first take the chassis in question to a professional frame and body shop to ensure that it is straight and level. You can measure it yourself, but if adjustments are needed, a professional frame shop is uniquely equipped to make those pulls and get your frame in shape for your project.

 

The chassis is the foundation of an automobile, and it pays to make it straight, true, and as strong as possible. You can reinforce an old frame easily, and keep it straight and level while you work.

The chassis is the foundation of an automobile, and it pays to make it straight, true, and as strong as possible. You can reinforce an old frame easily, and keep it straight and level while you work.

 

On the Square and On the Level

Whenever you work on a ladder frame, and especially when you’re welding, you need to be careful not to warp the structure. Many old frames were never completely flat or square from the factory, and most have been hit at some point in their careers. So it’s a fair bet that your chassis isn’t square or level when you start. But the time to fix those things is now, before your car is assembled. You might choose to invest a small amount of money in a trip to a body and frame shop. But before you do that, you can check it yourself by measuring it on diagonals for squareness and by setting it on a level floor for a basic flatness check.

Once you’re confident that you’re starting with a square and level chassis, you want to keep it that way while you work. Here’s a quick and easy method to ensure that your chassis stays true. When you put your frame up on sawhorses or jackstands, make sure that it’s level. A carpenter’s spirit level is good enough for most purposes. Then suspend a plumb bob from each corner of the chassis so that the point hangs about 1/16 inch above the floor. You may have to weld a bolt or tab onto each corner to do this. Then, as you weld on the chassis, keep an eye on those plumb bobs. If one or more of the bobs start to rise or fall, the heat and stress from your welding is warping the chassis. Stop what you’re doing immediately or you risk permanent damage. Wait for 24 hours and the chassis should return to level. At the worst, if the chassis does not normalize it’s an easy pull to get it back to level.

 

Boxing and Bracing a Vintage Frame

One of the most common automotive projects involves creating a hot rod or custom car out of a vintage domestic street car. These cars use a traditional ladder frame that for most of automotive history was made from C-shaped channel stock. These frames are made from mild steel and at their most basic are just two pieces of channel iron with some crossmembers bolted, riveted, or welded into place. Depending on your make and model, the chassis may be made of hat steel— which is to say, steel that has been shaped into a channel with small lips at the sides. If you look at this material from the end, it looks something like a hat with a brim.

The pieces of channel iron in a traditional frame were shaped to accommodate the spring mounts for the suspension and they were connected with just a few basic crossmembers. One of the first things done to virtually every hot rod is to enclose the channel with more steel to make it a box, and then to add some support to the crossmembers to strengthen the frame structure. If you buy a new hot rod frame, it already has this done.

 

A vintage car like this one, being built up into a period-correct gasser drag racer, will take some serious chassis work before it can handle the forces of a modern racing engine.

A vintage car like this one, being built up into a period-correct gasser drag racer, will take some serious chassis work before it can handle the forces of a modern racing engine.

 

This example project looks at Rob Zeller’s 1937 Chevrolet as it is being prepared for drag racing. It’s the same Chevy used for the roll cage project in Chapter 7. In 1937, Chevrolet made their frames out of stamped hat steel with a thin plate spot-welded onto the bottom. That’s better than the C-channel that Ford was using at the same time, but not by much. And it’s certainly not sufficient to absorb the forces that the drag racing engine will deliver. Amateurs will be pleased to note that Rob completed this frame reinforcement using only a bandsaw, MIG welder, body grinder, and an oxy-acetylene torch.

It’s also worth noting again that the roll cage project is an integral part of the chassis reinforcement in this car. The roll cage creates a dome over the ladder frame and helps it resist twisting forces. The cage is attached to six points on the chassis: three points on each side, front to back. If you imagine trying to twist the chassis from any corner, you’d be working against a very strong arch of steel. Even a basic roll bar helps eliminate twist, but a cage is much better.

But there’s more to be done, especially if you plan to put a big engine in an older car. The frame must be reinforced in several key areas. Because old frames are stamped, they tend to have nice curving shapes. Use your plasma cutter to carve out matching pieces of plate from 1/8- to 3/16- or even 1/4- inch mild steel. Because these frames are virtually always made from mild steel, your MIG welder is the best choice for this work.

1: Clean the entire frame and make sure it’s free of rust and dirt. You can have it sandblasted or blasted with walnut shell, glass, or plastic media, or you can have the chassis dipped in a caustic solution that dissolves rust, paint, grease, and undercoating. It’s important that the chassis be clean and that you are able to see any rusty spots. Then have it checked to be sure it’s square and level.

2: For a race car, you must reinforce the front crossmember. In the case of this Chevrolet, the crossmember was originally hotriveted to the chassis members. Welding up the mating surfaces also helps keep everything in place. The pieces of the crossmember were originally spot-welded together, so grinding and welding the seams helps hold it together under increased stress. On an older car, you can never get all the rust out from between two plates that have been sandwiched together unless you separate the plates, clean them, and then weld them back together.

3: If you want to keep all the original crossmembers, you can reinforce them. Cover any open channel iron with 3/16 plate to make it a box. If you do not care about maintaining the original components, consider using modern mild steel box tube for mid-chassis and rear crossmembers.  This material will be stronger than the reinforced original material, especially if the material had been rusted. On this project, the rearmost crossmember was replaced with basic 2-inch square box steel, with 3/16-inch wall thickness. Plate gussets are also useful for multiplying the stiffening effect of your new crossmembers.

 

Make sure everything is as clean as you can make it before you start. As you can see here, rust gets started working at the same time you do. This will all be cleaned again before it gets painted.

Make sure everything is as clean as you can make it before you start. As you can see here, rust gets started working at the same time you do. This will all be cleaned again before it gets painted.

 

You can still see the original hot rivets that held the main engine crossmember into this frame. It’s been reinforced with extra plates and welds all around.

You can still see the original hot rivets that held the main engine crossmember into this frame. It’s been reinforced with extra plates and welds all around.

 

The rear crossmember was replaced with 2 inch box steel, reinforced with lightened gussets to the frame. The frame rails had already been reinforced, so this is a very strong setup.

The rear crossmember was replaced with 2 inch box steel, reinforced with lightened gussets to the frame. The frame rails had already been reinforced, so this is a very strong setup.

 

This structure serves as an additional crossmember support, as well as the required driveshaft support and mounting point for exhaust supports.

This structure serves as an additional crossmember support, as well as the required driveshaft support and mounting point for exhaust supports.

 

Detail shot of the center crossmember, showing the mounting points for the trailing arms that will locate the rear axle.

Detail shot of the center crossmember, showing the mounting points for the trailing arms that will locate the rear axle.

 

These darts in the frame reinforcement are easy to make, they look great, and they’re vintage-correct for this type of gasser.

These darts in the frame reinforcement are easy to make, they look great, and they’re vintage-correct for this type of gasser.

 

This lightened engine mount connects to the frame reinforcement and shows another of the dart-shaped panels in the frame.

This lightened engine mount connects to the frame reinforcement and shows another of the dart-shaped panels in the frame.

 

This is the rearmost of the plates used to reinforce the bottom of the hat channel frame on the old Chevrolet.

This is the rearmost of the plates used to reinforce the bottom of the hat channel frame on the old Chevrolet.

 

Rob carefully welded this plate with small stitches to recreate the spot welded look of the original parts.

Rob carefully welded this plate with small stitches to recreate the spot welded look of the original parts.

This is a basic drawing of a homebuilt Camaro subframe connector. You need two of these, and they require cutting your floor.

This is a basic drawing of a homebuilt Camaro subframe connector. You need two of these, and they require cutting your floor.

 

This is the front mount of a commercial bolt-in subframe connector. You can see how it inserts into the front subframe member and drops down to clear the floor.

This is the front mount of a commercial bolt-in subframe connector. You can see how it inserts into the front subframe member and drops down to clear the floor.

 

The rear attachment of this bolt-in subframe connector bolts to the forward perch of the rear leaf spring.

The rear attachment of this bolt-in subframe connector bolts to the forward perch of the rear leaf spring.

 

Another view of the rear attachment point of the bolt-in subframe connector.

Another view of the rear attachment point of the bolt-in subframe connector.

 

4: The center crossmember is made of larger material and was designed to function as the required driveshaft retainer as well as a structural support on the car. This part was executed in 2-inch by 3-inch .188 wall mild steel. Also attached to this piece are the supports and retainers for the 4-inch exhaust system for the car. Every bit adds to the support for the chassis. Again, gusseting at the connection between the chassis members and the new crossmember adds strength.

5: To reinforce the chassis members themselves, use the plasma torch to cut 3/16-inch plates that match the curve of the chassis and weld them to the inside face of the chassis member. Work by jumping around to weld on different places on the chassis—don’t start at one end and work straight through. When it’s complete, this reinforcement helps reduce bowing under the weight of the big block engine and under the stresses created when the car transfers weight to the rear under acceleration. These reinforcing plates were cut and installed in a dart style to create a stylish and period-looking effect. You could cut them with straight ends, but it takes just a little extra effort to make your project unique and fun.

6: In addition to the inside face, the bottom face of the Chevy’s longitudinal frame members was originally just a thin piece of sheetmetal. Cut and weld more 3/16-inch plates here to complete the reinforcement. This helps resist the individual chassis members’ tendency to flex and also helps resist bowing. As you work, use a lot of C-clamps to hold the parts together. Rob used up to 10 C-clamps at a time to hold the parts in precise alignment while he welded.

It’s a big job to reinforce a frame, but the results are outstanding and the original frames on older cars simply do not stand up to the forces exerted by modern engines, suspensions, and tires. It pays to take your time and get your frame in order.

 
MuscleCarB

 

Making Subframe Connectors for a Partial Unibody

 In this project, you’ll make subframe connectors for a partial unibody car. Many popular GM muscle cars made since the 1960s, specifically the Nova, Camaro, and Firebird, have used unibody shells for the passenger compartment and then bolted front subframes (also called clips) to that unibody section. The unibody tub on a Chevrolet Camaro is bolted onto the front subframe with rubber pads in between the two metal parts. The rear subframes are integrated with the chassis. Obviously, this is not an optimal design for chassis stiffness! Therefore, subframe connectors and braces are used to turn the factory’s design into something like a full-frame car. Connecting the front and rear subframes together approximates a traditional ladder frame and makes a more rigid chassis. A rigid chassis improves structural integrity and handling for all cars, and improves power delivery in high-torque and horsepower applications.

You can buy a set of subframe connectors for about $100 to $200. These can generally be bolted or welded into place. If you choose to make your own subframe connectors, you can use 2-inch by 3-inch .120 wall box steel if you don’t mind cutting your floorpan, or slightly bent 1.5-inch .120 wall round tube if you’d rather leave your floor intact. To make a subframe connector, you need to locate the proper mounting points and create a pair of braces to tie the two sections together under the car. This project was completed on a 1970s Chevrolet Camaro built for drag racing.

On a GM car, the body is mounted on the front subframe using large rubber bushings. Buy some replacement aluminum or polyurethane body bushings and replace these before you begin work on a subframe brace. You also need to strip the seats and carpet out of the car if you plan to cut the floor.

1: The best way to do this job is in a shop with a work pit or on a four-post lift with ramps. This is because there’s enough flex in the body and front subframe that the relevant parts will move if you just jack up the car from the usual jack points. Make sure that your car doors open and close normally before you lock things into position with your brace! Whatever you do, always make sure any car is well supported with proper stands before you get under it. Having a car fall on you could be fatal.

2: Once you’re under the car, look for the front subframe. They are usually made of rectangular stamped steel sections. In the case of GM models, they are roughly 2.5-inch by 3.5-inch stamped steel. You can make your braces out of round tube or square tube; it really doesn’t matter much. Under the driver and passenger footwells, you can see the raw ends of the subframe where they are bolted to the passenger tub. Note the location of the bolts that mount the subframe to the passenger section you don’t want to block those in case you ever have to replace the body. For the Camaro or Firebird, the ends of the front subframe are angled and that angle and an open space in the underside of the subframe provides access to the bolt and bushing, which mounts the subframe to the body. Check to see if the ends of the subframe have been crushed in any way they often get dented.

3: In the Camaro and Firebird body, next find the forward mount of the rear frame rail on either side. These are stamped steel and are located just inboard of the bolt-on front mount for the leaf springs. To get at this area, you need to remove the rear seat and cut through the sheetmetal. You’re looking for four or five spot welds where the stamped frame rail is welded to the tub. These frame rails also terminate at an angle, so you need to cut your brace to match that angle before installation. Also, you can now see that you must cut a strip out of the Camaro’s floorpan to fit straight subframe connectors.

4: Once you can test-fit your brace, carefully measure the distance from the rear of the front subframe to the front of the rear frame rail on each side. Also note anything else in the belly of the car that might interfere with your braces. Convertibles are known to present additional challenges because they have more underbody structure. When you have the overall length you need, you can work on getting the rear angle just right. Different cars are known to be slightly different in overall length, but for 1970s-era Camaros and Firebirds, it’s about 31.5 inches. You can cut the front off cleanly at 90 degrees for this project, as you’ll be making a fitting for the front subframe.

 

This is a clean and freshly powdercoated front subframe end. The large hole on top is where the body bushing goes.

This is a clean and freshly powdercoated front subframe end. The large hole on top is where the body bushing goes.

 

This front subframe end looks more like what you’re likely to find in a car. Insert the front end of your brace into this square opening.

This front subframe end looks more like what you’re likely to find in a car. Insert the front end of your brace into this square opening.

 

Here’s what it looks like when you’ve welded your brace to the rear of the front subframe. Note the extra reinforcing gusset on this installation.

Here’s what it looks like when you’ve welded your brace to the rear of the front subframe. Note the extra reinforcing gusset on this installation.

 

Another view of the front subframe connecter installation. You can see that space is left to access the body bushing, in case it needs replacement.

Another view of the front subframe connecter installation. You can see that space is left to access the body bushing, in case it needs replacement.

 

Viewed from the underside, this is the rear connection of the subframe connector to the stamped frame rail that is part of the unibody tub of the Camaro. Note that it’s located just inboard of the front leaf spring mount.

Viewed from the underside, this is the rear connection of the subframe connector to the stamped frame rail that is part of the unibody tub of the Camaro. Note that it’s located just inboard of the front leaf spring mount.

 

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This is the rear end of the connector viewed from above. You’re looking down under the rear seat of the car. This subframe connector is tied into the car’s roll bar for extra strength.

This is the rear end of the connector viewed from above. You’re looking down under the rear seat of the car. This subframe connector is tied into the car’s roll bar for extra strength.

 

The subframe connector viewed from underneath the car where it cuts through the floor. Note that where the crossmember was cut, it has been rewelded to the subframe connector.

The subframe connector viewed from underneath the car where it cuts through the floor. Note that where the crossmember was cut, it has been rewelded to the subframe connector.

 

5: For the front mount, create two U-shaped sleeves of steel to slip on and bolt or weld to the inner sides of the front subframe piece. These will be 1/8 inch thick, about 4 inches long, 3 inches wide, and 2 inches tall. Measure your particular subframe to get the width dimension correct. Weld a sleeve to the front of each subframe brace. You can add outside gussets for additional strength.

6: Position the front of a subframe brace in its subframe arm, and hold the brace up against the floorpan of the car in line with the front and rear frames and you can mark where you need to cut. It’s right under the front seats. Before you cut the floor, make sure that all brake lines, fuel lines, and wires are clear of your work area. When you cut, you will be able to move the brace up until it meets the rear frame rail and lines up correctly with the front subframe.

7: Drill and bolt or weld the front of your brace to the sleeve at the open end of the front subframe. The reason for using a sleeve around the outside of the front is to retain access to the body bolt and mounting bushing. If you don’t want to retain that easy access, you can weld additional plates on the bottom for added strength.

8: Repeat steps 1 through 9 for the other side of the car. As an alternative to this project, if you don’t want to weld the subframe brace to your car and you don’t want to cut your floor, you can bend 1.5-inch tube slightly to make braces that drop down enough to clear the floorpan, or you can buy a set of bolt-in braces appropriate to your year, make, and model. Installation is easy and requires only basic hand tools and jack stands to suspend the car while you work.

If you make your own braces, you can weld the brace to the rear frame rail or create a flange to integrate the spring perch bolts with the brace for a solid mount. But if you’re cutting your floorpan, chances are you’re also willing to weld the brace to your rear frame rail.

 

Rebuilding a Front Subframe

This is an ambitious project undertaken on a dedicated drag racing car. The car being modified is a 1966 Plymouth Fury III, which uses a full ladder frame. However, the old front end of the frame had been modified, updated, and worked on so much that wholesale replacement was the right answer to accommodate the owner’s future plans.

As discussed before, straightness and level are the keys when it comes to frame work. We’ll use a jig made right on a steel welding table to get this frame material lined up correctly and the proper tabs welded on for steering, suspension, and engine mounts. When we’re done, the front frame is stronger, straighter, and easier to use than the original unit. You can modify this procedure to fit your make and model of car.

1: Carefully measure the existing frame for wheelbase, engine mounts, suspension pickup points, crossmembers, and any other relevant dimensions. Take plenty of pictures of all frame members from all angles because you never know when you might need to precisely locate a mounting bracket or threaded hole! Also pay careful attention to bends in the existing frame. Most frames rise at the front and rear of the car, and you’ll want to be able to replicate the bend angles.

2: Plan your new frame, paying attention to crossmembers, mounting locations, and structural improvements. If you plan to change the steering, suspension (including sway bars), or any other configuration, be sure that your new plan won’t interfere with other systems. Cut and tack-weld a spreader bar between the remaining frame members to keep them in line while you work.

3: Carefully support the frame while you cut the front portion loose. Be sure to give yourself enough material for a solid connection when you install the new parts. We cut down through the body of the frame box section, but left an extension in the bottom side of the frame. This provides us with a place to set and weld the new pieces, helping us maintain the squareness and level of the new structure and helps improve the strength of the new structure as well.

 

The original frame on this 1966 Plymouth Fury is pretty beat up, so we’ll replace it with something customizable.

The original frame on this 1966 Plymouth Fury is pretty beat up, so we’ll replace it with something customizable.

 

Before we cut the frame rails off, we removed the engine crossmember and put in spreader bars to hold everything in the correct relationship while we work.

Before we cut the frame rails off, we removed the engine crossmember and put in spreader bars to hold everything in the correct relationship while we work.

 

We cut the frame rails off, leaving plenty of supporting material to support the new structure when we weld it on.

We cut the frame rails off, leaving plenty of supporting material to support the new structure when we weld it on.

 

Detail shot of the raw frame end after taking off the front section. Note the spreader bar and the lip for reinstallation.

Detail shot of the raw frame end after taking off the front section. Note the spreader bar and the lip for reinstallation.

 

This is the new frame material, marked to take a wedge out to match the bend angle in the original.

This is the new frame material, marked to take a wedge out to match the bend angle in the original.

 

Russ uses the cutoff wheel to take the section out of the new frame rail to make the required bend.

Russ uses the cutoff wheel to take the section out of the new frame rail to make the required bend.

 

The frame rail with the wedge taken out. Russ left the top wall of the rail intact and simply bent the beam over for tack welding.

The frame rail with the wedge taken out. Russ left the top wall of the rail intact and simply bent the beam over for tack welding.

 

Tacking support beams into place to ensure that the frame stays square. We’ve already tacked each frame rail to the welding table after careful measurement.

Tacking support beams into place to ensure that the frame stays square. We’ve already tacked each frame rail to the welding table after careful measurement.

 

Preparing to tack on a suspension mount point. These were precisely measured and created out of thin plate.

Preparing to tack on a suspension mount point. These were precisely measured and created out of thin plate.

 

Both frame rails are tacked to the welding table and the suspension pickup points are tacked into place. From this supported framework, we’ll create the crossmember and add other necessary fittings.

Both frame rails are tacked to the welding table and the suspension pickup points are tacked into place. From this supported framework, we’ll create the crossmember and add other necessary fittings.

 

Since we’ve got the frame tacked to the table upside-down, some parts will end up floating in the air in this orientation. So we’ve created some supports to hold the sway bar mount where it needs to be in relation to the frame.

Since we’ve got the frame tacked to the table upside-down, some parts will end up floating in the air in this orientation. So we’ve created some supports to hold the sway bar mount where it needs to be in relation to the frame.

 

Here’s the new frame section being fitted to the car. We have spirit levels on it to make sure it lines up with the rest of the structure, which we’ve already squared and leveled. We’ll also measure from fixed points on the chassis to make sure everything is where it should be before we weld.

Here’s the new frame section being fitted to the car. We have spirit levels on it to make sure it lines up with the rest of the structure, which we’ve already squared and leveled. We’ll also measure from fixed points on the chassis to make sure everything is where it should be before we weld.

 

Russ has created plates to reinforce the joint with the existing chassis structure. The whole assembly is trued up to the chassis and is ready to be welded into place. We’ll stitch weld the connections and use plumb bobs to make sure the structure doesn’t warp during welding.

Russ has created plates to reinforce the joint with the existing chassis structure. The whole assembly is trued up to the chassis and is ready to be welded into place. We’ll stitch weld the connections and use plumb bobs to make sure the structure doesn’t warp during welding.

 

4: With the old piece cut free, we’ll start the new structure by obtaining some 2-inch x 4-inch .125 wall box steel. This is the same basic dimension as the old frame rail, but instead of being a pair of stamped pieces spot-welded together, this is a manufactured piece, welded along its entire edge. The first thing that we’ll do is cut the frame pieces to length. We’ll measure a little extra to account for the cuts we’ll make to replicate the bends in the original frame.

5: The old frame rail rose up from underneath the car’s body and then bent to become level again. Measure and mark the new frame rails for the bend that brings the frame level with the ground. This bend is expressed as a wedge that must be removed from the new rails. Using a cutoff wheel, we cut the wedge out of each rail, leaving the top side of the rail intact. Then we gently bend each rail to eliminate the gap, creating the bend. After tacking the bend shut and rechecking against the existing parts and the frame remaining on the car, we’ll weld the bend into the new frame rails.

6: This step is absolutely critical to perform exactly right. Use a welding table to lay out the new frame parts exactly as they will be located on the car. Tack each piece directly to the table in its proper orientation. This step takes multiple tries even for professionals. Measure across the diagonals for squareness and also check your table and the parts to ensure they are level. Check each measurement several times to be absolutely sure.

7:  Now we can lay out ancillary parts such as crossmembers and suspension pickup points. Because the parts need to be located in a particular relation to the frame, we’ll weld some more pieces to the table to support suspension parts in their proper location. We measure and mount another piece of straight steel perpendicular to the frame rails to line up the suspension mount points. We also weld a support to the table to hold the sway bar at precisely the correct point in space relative to the frame. In short, we’re making a complete jig to match the desired structure of the new frame.

8: When the ancillary parts are all tacked into place, we weld up the new frame and then cut it free of the welding table with confidence that it’s built square and true with respect to the measurements we made at the start of the project. Then we’ll tack the new frame into place on the car and remeasure just to be sure everything is lined up correctly. Finally, we commit heavyduty welds to the joint to fix the new frame in place.

9: With the structure welded into place and all the tabs, holes, and support members in place, we’re ready to reassemble the front end of this car.

A project like this is also a great chance to add some more support to a car by adding braces to the roll structure, building an arch to protect the radiator, and gusseting the suspension pickup points. If you look at a structure like this and compare it to the original frame, the new work is much more sturdy, and that will help this car on the race track.

 

Bodywork Repair Projects

These projects address the most common bodywork tasks that require welding or hot-work. Bodywork is the part of your car that people see first, and most people never look beyond the bodywork, so it pays to take your time and do this work carefully. If you have any doubts, take this kind of work to a professional. However, the satisfaction of performing your own body welding and rust repairs is substantial when others admire the car and ask who did the work. It’s easy to find sacrificial body panels to use for practice while you build up your skills!

 

Filling Small Body Holes

Holes in the bodywork of a car are one of the most common problems auto metalworkers face. Whether it’s repairing bullet holes in a vintage body that you rescued from the woods or removing the telltale holes left by side marker lights or the radio antenna you removed, everyone has some holes to fill.

The first consideration when filling holes is the size of the hole. Large (greater than 1/2 inch) holes should be filled by cutting a plate out of comparable metal and welding it into place as described in Chapter 5. Smaller holes can be filled with welding material. You can use MIG, TIG, or oxy-acetylene welding effectively for this task. Wire-feed and stick welding are not recommended for this type of job.

 

This hole was welded up with just some filler rod and then ground smooth. The paint preparation process will make it disappear entirely.

This hole was welded up with just some filler rod and then ground smooth. The paint preparation process will make it disappear entirely.

 

1: First ensure that there’s enough surrounding metal to weld on. If you’re filling a rust hole, chances are that the surrounding metal has also been rusted thin. If you try to weld on that, you’ll shortly have a larger hole. In that case, cut out the rusted portion and use a patch panel. After all, the rust is probably still eating your car from the back side, right?

2: Get some heat shielding putty from your welding supply shop. This is simple stuff that is designed to be used wet. It surrounds your work area and soaks up residual heat. This is handy if you don’t want to repaint a whole panel just to weld up a small hole. Spread the putty thickly around the hole with about 1/4 inch of metal showing.

3: Use a circular motion to deposit filler rod at the edge of the hole until it closes up. This is another use of the rosette weld technique. If possible, use the hammer welding technique to smooth your work as you go. When the weld has closed the hole, you can grind, file, or sand it smooth. For very small holes, a simple dab of filler rod is often enough.

 

Shrinking Small Fender Dents

One set of techniques that is indispensable in automotive sheetmetalworking is shrinking a dent. When you have door dings and other small dents in sheetmetal, you don’t want to simply fill them or grind them down. With a gas torch and some gentle work, you can actually repair these dents as if they never existed.

When it is heated to bright red, mild steel is actually malleable like moist clay. It can be shaped with a variety of presses, hammers, and anvils. Auto bodyworkers have a specific set of hammers and handheld anvils (called dollies) for fixing dents. If you don’t have a set of auto body tools, they’re not expensive and when it comes to sheetmetal, nothing else really works as well.

1: To shrink a dent, you work it from the convex side—that is, the raised side. First, pound out the dent as smooth as you can with a hammer and dolly. Notice that no matter how careful you are, the hammer leaves small dents in the material. These are actually places where the hammering action on the cold steel has stretched the sheetmetal. If you look at the back side of the sheetmetal, those dents appear as little pimples on the surface.

 

We used a chipping hammer to put some big dimples in a sample fender to practice our hot shrinking technique. We’ll get rid of these in a matter of minutes.

We used a chipping hammer to put some big dimples in a sample fender to practice our hot shrinking technique. We’ll get rid of these in a matter of minutes.

 

The same piece of fender a few minutes later. It’s not perfect yet, but a little work with a file and sander will make it so.

The same piece of fender a few minutes later. It’s not perfect yet, but a little work with a file and sander will make it so.

 

The perfect shrinking flame—just a little blue tip for precise heat placement in your dent. Have your hammer ready to go, because that heat won’t last.

The perfect shrinking flame—just a little blue tip for precise heat placement in your dent. Have your hammer ready to go, because that heat won’t last.

 

Strike while the iron is hot! You need to gently tap down the dent.

Strike while the iron is hot! You need to gently tap down the dent.

 

Keep the heat from your oxy-acetylene torch focused on the dent, but don’t let it create a puddle. You just want a bright glowing red spot.

Keep the heat from your oxy-acetylene torch focused on the dent, but don’t let it create a puddle. You just want a bright glowing red spot.

 

2: To shrink those dents flat again, use a fine welding tip and get a small, precise welding flame going on your oxy-acetylene torch. Heat up the pimple of metal just until it glows red, but keep the heat focused right on the raised bit so the surrounding metal stays cool. Then gently tap down the high point with a light hammer from your bodywork kit while backing up the dented place with a smooth dolly. The hot metal is melted just enough to become malleable, and as it is pressed down and outward, it thickens where it hits the surrounding cool metal.

3: Take a wet rag and cool the hot spot as quickly as possible. The result is that the high point of the dent is gone and the metal is now much smoother, but you didn’t create a thin spot by grinding it down! You might need to repeat this process a few times, and as always, practice improves your results. All auto body work takes time and practice to master, but that’s the fundamental trick for eliminating door dings. Obviously, using this technique means having to repaint when you’re done. The heat from the torch burns your paint right off for about an inch around the dent.

 

Repairing Rust

One of the common problems that plagues restorers and customizers alike is rust. Rust attacks almost every car at some point, and it needs to be repaired in every restoration, race car build, and often just to keep a car on the road safely.

If you happen to have a popular model of car, you’re in luck. Companies are now making panels stamped to match the bottoms of body panels, fenders, and doors. These panels are made specifically for rust repair purposes and they cover the areas where rust strikes. Cars as diverse as the Ford Model A, 1957 Chevrolet Bel Air, Porsche 356 and MGB all have panels readily available. Check your parts supplier to see if rust panels are available for your car.

If rust panels are not available for your car, you must create new parts by shaping basic sheetmetal to match the old fender or door skin. Rust usually strikes below the belt— that is, at the bottom of a body, fender, or door panel. This area is usually flat or at least simply curved with a lip or roll under at the base.

 
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We’ll look at a common problem a fender with a rusty corner. We’ll use the plasma cutter to cut a corner out of our sample fender and replace it with a piece of flat 20- gauge mild steel.

1: Determine the extent of the rusty area. After cleaning off paint, body filler, and any other covering on the steel, probe the area around the actual rust hole with a scratch awl or other sharp steel implement. Dark spots on the metal can indicate very thin areas that are prone to rust-through in the near future. Poke around with the awl and see if it pokes through in any location.

2: Cut the rusty piece out in a square, if possible. This makes your fabrication task a little easier. Make sure you’re cutting into good metal—you need as much thickness as possible to weld in your patch.

3: Cut a template out of your sheet cardboard to match the shape, plus any lip or shape that you’ll have to put into the metal. Also include about 1/4 inch around the mating sides of the patch for a recessed lip behind the surrounding metal.

4: Transfer your template shape to a piece of sheetmetal of the same gauge as the receiving panel and use your plasma cutter, band saw, hacksaw, hole saw, or bench shear to cut the shape. Any accurate cutting tool works. If you use a hole saw to cut a circle, fill the pilot hole when you’re done putting in the patch.

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Here’s a familiar sight. There are small holes to be filled with weld, dents to be hammered out, and rust along the bottom of the fender. The best way to deal with this kind of rust is to cut away the rotten metal and replace it with a patch panel. Sometimes you can buy the panels premade, but more often you need to make your own.

Here’s a familiar sight. There are small holes to be filled with weld, dents to be hammered out, and rust along the bottom of the fender. The best way to deal with this kind of rust is to cut away the rotten metal and replace it with a patch panel. Sometimes you can buy the panels premade, but more often you need to make your own.

 

We’re working with our sample fender again. Here we’re checking the curvature of the fender to see if we will need to do some shot bag or anvil work on our patch piece before we match it up.

We’re working with our sample fender again. Here we’re checking the curvature of the fender to see if we will need to do some shot bag or anvil work on our patch piece before we match it up.

 

Corners are among the most challenging pieces to patch because they require a double lip and are often on a compound surface curve as well.

Corners are among the most challenging pieces to patch because they require a double lip and are often on a compound surface curve as well.

 

Here’s the fender with the bad spot cut out. We’re making a template to create our replacement piece.

Here’s the fender with the bad spot cut out. We’re making a template to create our replacement piece.

 

The template, with space marked for the two lips and with space behind the fender for two recessed attachment lips. We’ll create those four lips using the bead roller and the brake.

The template, with space marked for the two lips and with space behind the fender for two recessed attachment lips. We’ll create those four lips using the bead roller and the brake.

 

We cut out our patch on the notching tool because of its great precision and clean cuts. With thick steel, getting a good cut with hand shears could be a challenge.

We cut out our patch on the notching tool because of its great precision and clean cuts. With thick steel, getting a good cut with hand shears could be a challenge.

 

Putting a recessed lip on the patch with the bead roller will let us weld it to the fender with good backing and still keep the surfaces flush.

Putting a recessed lip on the patch with the bead roller will let us weld it to the fender with good backing and still keep the surfaces flush.

 

Finally, we finish our patch by bending the lips crisply in the box and pan brake. Now we’ll see if it fits as well as our template.

Finally, we finish our patch by bending the lips crisply in the box and pan brake. Now we’ll see if it fits as well as our template.

 

Here’s the piece, ready for fitting. You can see the recessed lip for welding. That will really help make this a strong repair.

Here’s the piece, ready for fitting. You can see the recessed lip for welding. That will really help make this a strong repair.

 

Test-fit the piece and hold it in place with clamps. We could have matched that bottom lip a little better, but overall the fit is excellent because we used a template.

Test-fit the piece and hold it in place with clamps. We could have matched that bottom lip a little better, but overall the fit is excellent because we used a template.

 

Cleaning the paint, scale, and any dirt from the welding area is always a good idea. This little disc sander is just right for the job.

Cleaning the paint, scale, and any dirt from the welding area is always a good idea. This little disc sander is just right for the job.

 

As always, tack your work into place before you commit any welding beads. Remember, this is sheetmetal, so use low power and let the work cool between stitches.

As always, tack your work into place before you commit any welding beads. Remember, this is sheetmetal, so use low power and let the work cool between stitches.

 

Stitch-weld in short strokes of less than an inch to prevent the metal from warping, but weld the entire perimeter of the patch.

Stitch-weld in short strokes of less than an inch to prevent the metal from warping, but weld the entire perimeter of the patch.

 

Here you can see the stitches Russ made, and you can see the excellent penetration of the weld into the recessed tabs we made. This is a solid weld that will hold up under bodyworking.

Here you can see the stitches Russ made, and you can see the excellent penetration of the weld into the recessed tabs we made. This is a solid weld that will hold up under bodyworking.

 

The front of the weld isn’t very smooth, but we’ll work it with the disc sander to bring that down to level with the rest of the metal.

The front of the weld isn’t very smooth, but we’ll work it with the disc sander to bring that down to level with the rest of the metal.

 

5: Use your bead roller to make a step a little greater than the thickness of the sheetmetal on the extra material around the mating edges of the patch. This is so you can insert the patch and have the front surfaces match up nicely. If your patch has a lip, as ours does, use your brake to make any necessary bends.

6: Clean the paint, rust, and body filler from your patch so you get a nice clean weld, free of ash, slag, or other impurities.

7: Insert the patch from the back side and use your welder’s magnet or clamps to hold the patch in place. You might need to work with the metal a bit to follow any gentle curves—it’s rare that an automotive panel is ever truly flat!

8: Make a few tack welds to hold the patch in place. If the curve of the patch is not exactly right, you can tack one end and then flex the patch into place and make more tacks along its length to get the curve just right. Once the piece is tacked, move the magnet or clamps before you weld all the way around. Keep the welding heat as much as possible on the patch piece rather than the surrounding metal, because it’s likely to be thicker.

9: Stitch-weld the rest of your patch perimeter. Be careful about getting too much heat in the piece and warping it. You may want to use a moist rag to cool your welds. You may also want to do some hammer welding to keep the weld bead as flat as possible.

10: When you’re done welding, grind the surface welds down with your body grinder. For the final touch, use your files and a sanding block to bring the weld down to the level of the surrounding metal. Afterwards, you can work further with hammer and dolly, or just fill any low spots with lead or body filler, then file and sand it smooth and level with the surrounding metal. If you choose lead for authenticity, however, be sure to wear a respirator when sanding!

When you’re done welding, grind the surface welds down with your body grinder. For the final touch, use your files and a sanding block to bring the weld down to the level of the surrounding metal. Afterwards, you can work further with hammer and dolly, or just fill any low spots with lead or body filler, then file and sand it smooth and level with the surrounding metal. If you choose lead for authenticity, however, be sure to wear a respirator when sanding!

This was one of the more challenging pieces in that there is a lip to work with, but comparatively easy in that the panel is nearly flat. Some rusty spots happen on compound curves and creating a patch panel requires extensive English wheel or shot bag planishing work to match up.

 

Making a Patch Panel

Many automotive suspension and chassis components are made from thicker pieces of stamped sheetmetal, welded together into strong structures. Still, over time and especially if placed under greater stress than the manufacturer intended, these parts can crack and break.

This project reinforces a lower suspension control arm from a 1967 Austin-Healy Sprite, modified for vintage racing. The original part was designed for the stresses made by a 60-horsepower engine, a tiny front anti-roll bar and a hard, narrow tire. The part is now over 40 years old and subject to about 100 horsepower and hard cornering with a fat, sticky racing tire and a stiff anti-roll bar. No wonder it cracked!

When you’re faced with a situation like this, you can repair a part over and over until it fails catastrophically, or you can really get on top of the situation and make the part as stout as it needs to be. Some builders would throw away the original part and make a new one from tube steel, and they wouldn’t be wrong to do so. But since this is a vintage car, we wanted to make an old school repair and improvement to keep this car appropriately authentic for competition.

Our solution was to make a patch panel to cover the stressed area of the control arm. This reinforces the arm and repairs any cracks already present in the part. We decided to perforate the patch to allow access to existing mounting holes and to lighten the part, as this control arm counts as unsprung weight.

1: Take the control arm (or any part) off the car and clean it thoroughly. This arm had been powder coated, so getting it clean took a long time with the wire wheel.

2: Make a cardboard template for the patch piece. In this case, the patch needed a slight curve, and needed to wrap around the kingpin pinion receiver at the outer end. That receiver is the focal point of the stress on this part, so it was important to support that point.

 

After grinding down the welds, things are looking pretty good. There’s still some hammer and dolly work and maybe even a bit of body putty in our future, but the rust is gone and replaced with shiny new metal.

After grinding down the welds, things are looking pretty good. There’s still some hammer and dolly work and maybe even a bit of body putty in our future, but the rust is gone and replaced with shiny new metal.

 

With the A-arm cleaned up, you can see the crack and a previous repair down at the bottom of the picture. We’ll put a strap along this side of the arm for reinforcement.

With the A-arm cleaned up, you can see the crack and a previous repair down at the bottom of the picture. We’ll put a strap along this side of the arm for reinforcement.

 

This template will be more challenging to cut out because it curves to match the stamping of the A-arm.

This template will be more challenging to cut out because it curves to match the stamping of the A-arm.

 

We cut the curve for this piece with a set of heavyduty aircraft shears. The piece was small enough that the plasma cutter would have been overkill.

We cut the curve for this piece with a set of heavyduty aircraft shears. The piece was small enough that the plasma cutter would have been overkill.

 

Tack welds with the TIG welder let us be sure that we had the strap positioned correctly

Tack welds with the TIG welder let us be sure that we had the strap positioned correctly

 

With this reinforcement, this piece is not likely to crack again. However, we should have left the locating bolt in place at the outer end, because the heat from the welding warped the arm just enough to make reassembly a challenge. Live and learn!

With this reinforcement, this piece is not likely to crack again. However, we should have left the locating bolt in place at the outer end, because the heat from the welding warped the arm just enough to make reassembly a challenge. Live and learn!

 

3: We used the heavy duty aircraft shears to cut the repair piece out of 16-gauge mild steel, then a step bit to cut the 3/4-inch holes to lighten the repair piece. We refined the shape and cleaned up the cut on the belt sander.

4: After some test-fitting and adjustment, the piece was ready to weld. We used the TIG welder to tack the piece to the control arm in several locations. Using clamps to keep the repair form-fitted to the part, we stitch-welded the perimeter. As always, we alternated the stitching areas to allow the welds to cool and normalize so as not to warp the repair piece or the original stamping.

5: We finished up with some rosette welds inside the holes in the repair piece. This helps the reinforcement by creating additional points of attachment to the original stamping. We paid extra attention to the cracked area around the kingpin pinion receiver, making sure we welded up the original crack as we put on the reinforcement.

6: The TIG welder offered us great control and penetration for this project. Almost no grinding was required. We’ll do the same repair on the other side of the car after racing season is over.

Written by Russell Nyberg & Jeffery Zurschmeide and Posted with Permission of CarTechBooks

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