Screws and Inserts
Screws are used to hold the keyboard base plate onto the rest of the keyboard case. Since this connection experiences low stress, strength is of little concern in which size screws or type of insert you use. Instead, all these combinations of mounting methods and screw sizes are provided so that you can use the parts you already have or are easiest for you to buy.
Abbreviations OD: Outer Hole Diameter, H: Height, T: Angle Tapered In from Outer Diameter
| Screw size / Attachment Method |
 |
 |
 Screw Insert |
 Tapped Hole |
|---|---|---|---|---|
| Equipment Needed | Soldering Iron | Soldering Iron | Possibly a Mallet | Tap |
| M3 | OD: 4mm H: 5.1mm |
OD: 5mm H: 4.6mm T: 8° |
OD: 4mm H: 4.8mm |
OD: 2.5mm H: 4.8mm |
| M4 | OD: 5.6mm H: 5.5mm |
OD: 5.6mm H: 5.5mm T: 8° |
OD: 5.6mm H: 6.4mm |
OD: 3.3mm H: 6.4mm |
| #4-40 | OD: 0.159” H: 0.165” |
OD: 0.153” H: 0.165” T: 8° |
OD: 0.156” (5/32)” H: 0.188” |
OD: 0.089” H: 0.188” |
| #6-32 | OD: 0.191” H: 0.18” |
OD: 0.199” H: 0.18” T: 8° |
OD: 0.188” (3/16)” H: 0.25” |
OD: 0.107” H: 0.25” |
The sizes are taken from the recommended parameters in McMaster-Carr’s catalogue. If you’re ordering your parts from elsewhere, make sure the part will fit in the hole’s diameter and height.
These sizes below are taken from the ANSI standards:
| Screw size | OD, Hole in Bottom Plate | OD, Countersunk Hole in Bottom Plate |
|---|---|---|
| M3 | 3.4mm (medium fit) | 6.3mm, 45° taper |
| M4 | 4.5mm (medium fit) | 9.4mm, 45° taper |
| #4-40 | 0.1285” (free fit) | 0.28125”, 41° taper |
| #6-32 | 0.1495” (free fit) | 0.34375”, 41° taper |