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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		 Img Screw Insert Img Tapered Screw Insert Img Screw-to-Expand
Screw Insert		 Img 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