Shrinking Metal with a Mallet & a Stump

Big Joe's guide to sheet metal continues

So now that we have a stump for metalworking, we should probably start to do stuff with it. In this story, we’ll put it to use showing you the very basics of how to effectively shrink material with only a single wooden mallet and wooden stump.

Shrinking Metal with a Mallet & a Stump

For this demonstration I’ve cut a disk approximately 8 to 9 inches in diameter out of 13-gauge aluminum.

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Shrinking Metal with a Mallet & a Stump

Whenever I talk about shaping aluminum the question of annealing always comes up. No annealing was used in this demonstration. We’ll talk about annealing in the future when the time is right.

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Shrinking Metal with a Mallet & a Stump

To start the shrinking process you need to put the edge of the disk toward the lip of the dish.

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Shrinking Metal with a Mallet & a Stump

We will be using the pointed end of this shaping mallet.

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Shrinking Metal with a Mallet & a Stump

I concentrate mallet blows all the way around the perimeter of the disk all while rotating the disk to keep the blows just off the lip of the dish.

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Shrinking Metal with a Mallet & a Stump

Once you’ve worked the outer edge of the disk you will see the edge start to pucker or tuck, which creates a wavy edge. That is what we want it to do.

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Shrinking Metal with a Mallet & a Stump

Now we take the blunt end of the mallet and hammer those tucks flat on a flat portion of the stump surface.

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Shrinking Metal with a Mallet & a Stump

Once those tucks are flattened we have effectively shrunk the edge of the disk to allow us to create a radiused dish from the flat disk.

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Shrinking Metal with a Mallet & a Stump

Next we will do the same thing, but the pattern of hammer blows will be within the first round.

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Shrinking Metal with a Mallet & a Stump

You will again position the disk so that the hammer blows are located near the lip of the dish to force the disk to continue to tuck.

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Shrinking Metal with a Mallet & a Stump

As you work farther inward, the tucks may become fewer but can be more pronounced as seen here.

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Shrinking Metal with a Mallet & a Stump

I do the same thing again to hammer those tucks flat on the stump.

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Shrinking Metal with a Mallet & a Stump

This process will continue...

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Shrinking Metal with a Mallet & a Stump

...until you reach the center of the disc.

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Shrinking Metal with a Mallet & a Stump

Once we’ve reached the center we will see quite a drastic change in the disk, as it is starting to get some depth and radius.

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Shrinking Metal with a Mallet & a Stump

I made this stump many months ago, and it has traveled and shaped a lot of material. I made this one about 6 inches thick to keep down the weight and make it easy to transport. I lost a good chunk of the stump because it has dried out and taken a lot of abuse, but that didn’t render it useless.

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Shrinking Metal with a Mallet & a Stump

I continued to use the dish and the flat portion of the stump to make a uniform radius to the once flat disk. You can actually see how the disk has started to match the radius of the dish in the stump.

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Shrinking Metal with a Mallet & a Stump

With continued work with only this one wooden mallet and this stump you can see that you can get a lot of shape from a sheet of metal.

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Shrinking Metal with a Mallet & a Stump

I was able to reach a radius tighter than that of the dish on the stump. I also achieved a pretty smooth surface.

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Next time we’ll take a look at using a planishing hammer to bring mallet work to a silky smooth finish. If you have questions or suggestions for future issues, please email me at [email protected] Cheers!