Modern Tech & Old School Hammerforming

How 3D Printing Improves One of The Oldest Metalworking  Process

By Ron Covell   –   Photography by Adam Cecil

What Is Hammerforming?
Hammerforming is one of the oldest metalworking processes around. It involves making a form from some durable material in the shape of the desired part, clamping a sheet of metal to it, and hammering the metal until it takes on the shape of the form.

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01 This shows the rough layout for the end cap of the turbo heat shield
A great way to start any project is with a chipboard pattern. This shows the rough layout for the end cap of the turbo heat shield, which will provide about a 1/4-inch air gap all around.

Often these forms were made from wood, since it is fairly easy to work and the harder grades of wood provide enough durability to be used indefinitely. A properly constructed hammerform allows even a beginning metalworker to make a part that looks die stamped.

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02 made with Fusion 360 CAD software which can be downloaded free from Autodesk com
This is a computer rendering of the completed shield, made with Fusion 360 CAD software, which can be downloaded free from Autodesk.com.

Technology always evolves, and a few computer-savvy metalworkers have realized that the new, affordable desktop 3D printers can be used to make excellent hammerforms, with no sawdust involved!

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03 Here’s a rendering of the hammerform and clamping blocks
Here’s a rendering of the hammerform and clamping blocks. It helps visualize the parts before printing to see if any revisions are required.

In this article, we will follow the work being done by Adam Cecil, a classic truck enthusiast who has had great results using this process. We’ll take a detailed look at the stainless turbocharger heat shields he made and a pair of tanks for the coolant overflow and the windshield washer fluid. All of these are for his ’68 Chevy truck with a twin-turbo LS engine.

04 This is a 3D rendering of what the printed model will look like
This is a 3D rendering of what the printed model will look like. It’s always best to print and test a model before making the part from metal.

The first step is to create a computer model of the part to be made. These days there are many choices for CAD (computer-aided design) software, but Cecil uses Fusion 360 from Autodesk, which is available as a free download.

05 The 3D printed model is test fitted on the turbocharger
The 3D printed model is test-fitted on the turbocharger. Cecil went through a few revisions until he was happy with the fit. This prototype took four hours to print.

After the CAD model is created, the next step is to design the hammerform and clamping blocks, which will be a snug fit inside and outside the model. Alignment pins are generally used to keep the parts properly aligned and, when possible, these are made to coincide with features on the finished part so no extra holes will have to be filled. For the turbo cover, Cecil used the studs for the turbine outlet/wastegate cover for the alignment pins; for the fluid tanks, he used the centers for the cap and the plumbing fitting.

06 The hammerform is being printed here one thin layer at a time
The hammerform is being printed here one thin layer at a time. You can see the coil of filament that feeds the heated print head.

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Once the parts have been designed in CAD, another software package is required to generate the G-code that the printer runs on. Cecil used another free software package for this called PrusaSlicer.

07 Note that the borders of all features are printed solid but the infill areas are left 40 percent open
Here’s a close-up of the partially printed hammerform. Note that the borders of all features are printed solid, but the infill areas are left 40 percent open. This speeds the printing considerably and saves material.

There are many printers on the market, at widely ranging price points. Cecil chose a Prusa Mini+ printer. Its build volume is a 7-inch cube. He reports they provide excellent customer support. This printer is just over $400 in kit form, but several other companies make simplified versions that start around $200. You get more features at the higher price points but the entry-level machines are VERY affordable these days.

08 A mock up was made for the first part to be hammerformed and checked on the buck
A mock-up was made for the first part to be hammerformed and checked on the buck. After verifying the dimensions, a piece of 18-gauge stainless sheet was cut to match.

There are many different filaments used for 3D printing. Cecil chose PLA, one of the most common, and a 2.2-pound spool costing $30 was sufficient to print the hammerform and clamping blocks for the turbo heat shield.

09 From top to bottom the clamping block the stainless blank and the hammerform itself
From top to bottom: the clamping block, the stainless blank, and the hammerform itself. This assembly is held in a vise to hold it at a convenient height while hammering.

It took about 24 hours to print the parts needed for the heat shield, but the printer can run unattended, day and night.

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10 Here’s the part after the initial hammering As you can see the printed hammerform provides all the strength required for this application
Here’s the part after the initial hammering. As you can see, the printed hammerform provides all the strength required for this application, even with stainless steel.

Once the forms are printed, it’s a simple job to cut the metal blanks, clamp them in place, and hammer the edges. Then the parts can be fitted together and welded. Once the welds are smoothed you are left with a clean, accurate construction that rivals the look of a die-stamped part!
Look through the accompanying photos to see the details of this process. It could open up a whole new world of possibilities for many classic truck builders!

11 The stainless band for the perimeter of the heat shield is bent to the approximate shape
The stainless band for the perimeter of the heat shield is bent to the approximate shape and is shown along with the printed clamping blocks.
12 a standard body hammer is used to form the stainless sheet against the printed hammerform
With all the parts assembled and clamped, a standard body hammer is used to form the stainless sheet against the printed hammerform.
13 Here it is laid over the perimeter piece and the overlapped area is scribed for trimming
The formed endcap was made slightly oversize. Here it is laid over the perimeter piece and the overlapped area is scribed for trimming. This will make a tight butt joint—ideal for welding.
14 The parts are tack welded together off the hammerform
The parts are tack-welded together off the hammerform.
15 Compare the finished part with the printed mockup
Compare the finished part with the printed mockup; they are virtually identical in size and shape.
16 Here’s how the turbo heat shield looks mounted to the turbo
Here’s how the turbo heat shield looks mounted to the turbo. It keeps the heat away from sensitive components and presents a very attractive appearance underhood.
17 The hammerforming process can be used for all sorts of parts
The hammerforming process can be used for all sorts of parts. This is the printed form for a windshield washer fluid reservoir.
18 This is the hammerform and aluminum blank for the endcap of the tank
This is the hammerform and aluminum blank for the endcap of the tank. Note the recesses provided for steel nuts, allowing the plastic parts to be bolted tightly against the metal.
19 The perimeter of the tank was formed in a clever homemade radius brake which mounts in a vise
The perimeter of the tank was formed in a clever homemade radius brake, which mounts in a vise.
20 Here’s the finished custom reservoir tank alongside the printed mock up
Here’s the finished custom reservoir tank alongside the printed mock-up. A similar tank was made for the other side of the truck to capture coolant overflow.
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