Created Appendix D: Hardware (markdown)

Appendix-D:-Hardware.md

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+# Buying hardware from us
+
+Getting all of the hardware on your own can be tricky because the parts you select may not fit perfectly. [That's why we sell kits with everything you need to build a Ploopy Mini Trackball](https://www.ploopy.co/product/trackball-full-kit-preorder/4) **TODO fix this link**. Here's why that's great for you:
+
+- Everything is guaranteed to fit together perfectly
+- Everything is guaranteed to work as intended
+- You'll end up saving money - probably quite a bit of money - by not spending on extra parts
+
+Your call. You'll sort it out.
+
+# Getting your own hardware
+
+This guide was a bit light on detail in the other sections, and that's because the hardware has to conform to many specifications. They'll all be listed here.
+
+First, a complete list of all the hardware you'll need:
+
+- 8x M3x8mm flat-countersunk machine socket head screws
+- 3x MR63ZZ roller bearings
+- 2x 3mm x 18mm metal dowels
+- 2x 3mm x 12mm metal dowels
+- 1x silicone ring
+- 4x friction pads
+- 1x snooker ball
+
+We'll be going over all of them in detail. There will be mentions of *critical specifications*; if you're going to be sourcing your own parts, **you must get parts that conform to the critical specifications**. If you go off-menu, the parts will not fit the way that we intended when we designed the trackball. That might mean that your trackball **doesn't work**.
+
+Let's get cracking.
+
+## M3x8mm flat-countersunk machine socket head screws
+
+Here are the critical specifications:
+
+- M3
+- 8mm length
+- 5.6mm head diameter
+- 1.7mm head height
+- 90 degree countersink angle
+
+## MR63ZZ roller bearings
+
+Here are the critical specifications:
+
+- MR63ZZ bearing
+- 3mm inner diameter
+- 6mm outer diameter
+- 2.5mm thickness
+
+## 3mm x 18mm metal dowels
+
+Here are the critical specifications:
+
+- 3mm diameter
+- 18mm length
+
+## 3mm x 12mm metal dowels
+
+Here are the critical specifications:
+
+- 3mm diameter
+- 12mm length
+
+## Silicone ring
+
+We use decorative rings for this. Here are the critical specifications:
+
+- Size 10 (19.8mm diameter)
+- Width between 8.0mm and 8.7mm
+
+## Friction pads
+
+Here are the critical specifications:
+
+- Circular shape
+- Up to 3/4" diameter
+- Up to 1/8" thickness
+- Non-slip
+
+## Snooker ball
+
+We use 1.5-inch diameter (38.10mm) miniature snooker balls. Any ball between 47.60mm and 38.30mm will work.