Here you can see all the parts you need to build the keyboard.
The plastic parts are easiest to print with PLA. A keyboard case weighs about 200g including support material. A wrist rest weighs about 100g. All parts together weigh a little under 600g. This includes 120g for support material. I have had good experiences with PolyTerra PLA. It's not expensive, has a nice matte finish, and prints easily. I printed the parts you see here with that material.
You'll need at least 40 neodymium magnets measuring 10 x 2mm. These will fit: Magenesis Neodymium 10x2 mm 52 pieces Mini Magnets Extremely Strong approx. 2 kilo adhesive strength, 10 x 2 mm : Amazon.com: business, industry & science
Rubber feet not only prevent the keyboard from slipping, but also serve as a buffer between the keyboard and the wrist rest. The optimal shape for the buffer rubber is a ball section with a base diameter of about 9-10mm. This shape is also good for the feet, as it is more slip-resistant than other shapes. Therefore, I recommend these feet for both purposes: SAIYU Rubber Feet Pads 100 Pieces Adhesive Bumper Pad Silicone Bumper Foot Protector Pad (100 Pieces, 9mm x 3mm, Black, Hemispherical Shape) : Amazon.com: hardware store
You need 30 x M2 x 5mm screws. Single screws are hard to get, but in this set they are included: 800 pieces M2 black carbon steel with countersunk head and flat cross head, self-tapping screws, machine screws, fasteners, repair tools : Amazon.com: Hardware Store
Raspberry Pi Pico
You need two Raspberry Pi Pico microcontrollers. Some suppliers also offer pin headers. You don't need these pin headers. I bought mine here: Raspberry Pi Pico, 4,20 € - Welectron
The magnets and the TRRS sockets are fixed with glue. A great alternative to epoxy is viscous superglue. This one works great: Pattex PSPP3 superglue Perfect Pen 3 g, black, 1 x 3g : Amazon.de: Baumarkt
You need at least 4.50 meters of copper wire with a diameter of 0.5 mm. It does not have to be in different colors, as shown in the picture above, but make sure that the cable does not consist of many small strands, but has a solid copper core: [10m copper switch wire blue Ø0,5mm / 0,2mm² 1-core copper switch wire 10 Meter | eBay](https://www.ebay.de/itm/153177374956?_trkparms=ispr%3D1&hash=item23aa1540ec:g:sJ0AAOSw-Wdf9LAF&amdata=enc%3AAQAGAAACsPYe5NmHp%252B2JMhMi7yxGiTJkPrKr5t53CooMSQt2orsStEKTPzZMfQmny3knR97t0GBgpkPTIAS2RSdQUcvijI0i3HkvQNxjeJp3D6vGMlqYEQKzSBX3sQi8Tg7U%252B0uw3jSf06q9IumgtKDLmfYb6DoAarKfh57PnljgCUSWEvMdRZnKJpdoBiXHZdsTUJBYsurxsjnmABkiQHCYp%252B%252BBoorLoavVjLPxwC9ddB7%252FnJOguoPw0igqOIl%252BspvUuko2mqJw%252BL3fABn9cjIGAUJyVHbubmVYBvd%252B25SCSdW3D%252BVOyNgxr59OKJ8BoiwkK4AI236NupHmfEGe1MMjqRGztBur6ru36dlvMHM3LG2PoSu%252BIubNI4BYjVXiv51U22qbn6vw16eZOUfMh6GR1Pw%252Bcbt%252Bx6X6GkHxYV8oiZLU4ZU29YKLr3ox6M9MMT0U%252BjxU%252BoKdOafe5FXnxhdRfRNHfEfwtBm9YdqSCNgzvCZu1Q9Yn6NaEy95z8mZ5T58BJIBHq00cznOn2eoxVfKAc5bn%252FVLchJsA%252FucIaAcxclinb5%252BDqIzS1hgpDoGNty3jp2AmJlaOJKeOexawBGILhBL2DuYc1renvxmDDT8ezFca00Sypb5AsZ10XCzdDfJRyrYrAOHsPzv353rg9DLqW%252Ba0drWKY35UfjXDKtyL%252Bb6LdyyYKL2ztL8qozFQF3McNxZIneap0s2LlVFCL7YVnd0aGzMqg%252FkKFrZtq
You need two TRRS jacks. Stores who offer accessories for do-it-yourself keyboards often have them as well: 2x TRRS jacks 3.5mm | Parts | Keyboard Parts | Keycapsss
The TRRS cable is used to connect the two halves of the keyboard. One is enough. It should have a length of at least 30 cm, so that you can place the keyboard halves far apart if necessary: TRRS Cable 4-pole 3.5mm jack 30cm 12inch | Accessories | Keycapsss
One of the Raspberry Pi Picos is connected to the computer with a Micro-USB cable. For example, with this one: Amazon Basics 7T9MV4 Connecting Cable, USB 2.0, USB-A male to Micro-USB-B male , 1.8 m, Black: Amazon.com: Computers & Accessories
You need a total of 40 mechanical keys. The selection is huge and everyone probably has their own idea of the perfect key. I've tried a lot. I like the sound of self-oiled Glorious Panda switches, for example. The Gazzew Boba U4 are very quiet but with a great pressure point. I also tried the Kailh Low Profile Choc Switches (V1). They also fit into the PicoSplit keyboard . But keep in mind that low-profile keys don't stick out that far, and at least that's inconvenient for the thumb keys. You may have to put something under the corresponding keycaps in order to fix this.
Here are a few links to German retailers who offer keys and keycaps:
You need just as many keycaps as there are keys, i.e. 40 pieces. The keycaps must mechanically fit the keys and they must all be 1U keys (the smallest size). Most manufacturers copy the Cherry MX system and there is a huge variety in this universe.
Keycaps come in different shapes:
The PicoSplit keyboard works best with symmetrical DSA or XDA keycaps. All other shapes are either not symmetrical or too tall.
Kailh Low Profile Choc Keys (V1) also fit, but there are significantly fewer keycaps for this system and you need to raise the thump keycaps a little bit. Therefore I can not recommend these switches.
The keycaps used in this building instructions can be found on Aliexpress: [milk honey keycaps - Buy milk honey keycaps with free shipping on AliExpress version] (https://de.aliexpress.com/af/milk-honey-keycaps.html?d=y&origin=n&SearchText=milk+honey+keycaps&catId=0&initiative_id=AS_20211003054555)
Hot swap sockets
You need 40 hot swap sockets to match your keys. These sockets are actually intended for mounting on circuit boards, but they also make manual wiring easier in the PicoSplit keyboard. On one hand, they stabilize the buttons' pins, which are prone to kinking, and on the other hand, they offer a larger soldering surface, which simplifies the soldering of the cables. Only with hot swap sockets, you are able to swap the buttons as you like. You can get hot swap sockets here: [Kailh Hotswap PCB Sockets 10 pcs | Parts | Keyboard Parts | Keycapsss] (https://keycapsss.com/keyboard-parts/parts/49/kailh-hotswap-pcb-sockets-10-pcs?number=KC10019_MX)
Make sure to choose sockets that fit your keys (MX or Choc system).