In my last posts, I shared some tips and tricks for working with zippers. Reinforcements are another challenge that many leatherworkers find confusing. When do you use them, what thickness do you use, and how do you install them properly?
When making the zippered wallet in our in-person course, many students noticed how thin and light the piece was despite it being quite sturdy. Reinforcements add both structure and stability to your piece. A well-constructed reinforcement offers more stability than a single layer of leather with the same thickness. Here are some considerations and tips for reinforcements.
Stronger Together
These benefits come not only from the reinforcement but also from the glue holding the pieces together. This is similar to how plywood can be more substantial than a board of the same material and thickness. The glue affixes the multiple layers to a position. Sometimes, you don’t even need the reinforcement. On the valet tray post I wrote about a while back, there is more rigidity because of the gluing. There are no reinforcements on the sides; it is only the glue holding the curve of the sides in place.
When trying to add strength to a component, glue layers together. I often glue two thinner pieces together on a wallet card pocket, which is plenty strong without reinforcement. Add reinforcements to increase stability. I can glue the valet tray in a reinforcement to the bottom to keep it flat.
Thin and Sturdy
As described above, the two thinned, glued layers on a card pocket are stronger than a single layer of the same leather. If the leather is 1.4 mm thick, I can split it to 0.5 mm and glue two layers together to get a 1 mm thick piece. This 1 mm piece is stronger than the 1.4 mm piece, and I shed 0.4mm. This might not seem a lot, but in a wallet with four card slots stacked up, now I’ve taken off 1.6mm from the total thickness. If I split the layers down to 0.4mm each, I can shed 2.4mm, a significant reduction.
Light and Firm
It works the same if I add reinforcements into the mix. A single layer of 1.8 mm leather can be split down to 1 mm. If I add a 0.5 mm reinforcement, the resulting piece at 1.5 mm is stronger than the original single layer. It can also weigh less if I pick the right material. Many reinforcements are lighter than leather of the same thickness. I reduce the overall weight of a piece when using reinforcements without sacrificing strength.
The other benefit of this combination is firmness. Remember, the glue is as important as the reinforcement. When I glue these two pieces together, I can prevent stretching, which is desirable for the body of a bag or the outside of a wallet.
Aside: Give Yourself Room
One of the most common mistakes new students make is sizing the reinforcement and layers. They forget the material thickness and the distance required to travel. When sizing and placing the reinforcement, reduce the size. Also, be sure to cut the top leather larger to account for the extra surface area.
The reinforcement on the upper part of this strap is also a filler, which gives it more contours. Because of its extra thickness, the top red leather is cut wider. The filler is narrower so it doesn’t collide with the stitch holes.
Profile of a strap. The top layer in orange travels more because of the reinforcement. You also have to cut it narrower to avoid colliding with the stitch holes. The holes are set a little further out. The extra room is because the top leather travels slightly diagonally rather than 100% vertically down from the top.
Learn How to Use Reinforcements
Our new course will show you how to choose the right reinforcements and install them in your project. Learn more about reinforcements, zippers, and other advanced techniques in our online course, The Zippered Wallet with Hajime Niwa.
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