Drill bits are essential for DIY projects. You can use it for many materials such as wood, concrete metals, and many more. When you use it for wiring, the hole should be smooth and match the diameter of the wire. Because wire diameter varies with the current and voltage. Normally, we use 1-conductor (1-20 gauge), 2-conductor (10-20 gauge), and 3-conductor (10-20 gauge) cables for many purposes in both DIYs and industrial. When you drill for these wires, you should know the diameter of the wire before selecting a drill bit.
The larger diameter holes are always better, but they can acquire more space than you think. So, let’s see what kinds of drill bits are suitable for wires.
What are the Standard Wire Sizes and Insulation Thicknessess?
These standard wires are insulated with Poly (Vinyl Chloride) in order to prevent the current leaking. According to the voltage and current, the layer’s thickness varies. As a result of this, the wire diameter will be increased due to this layer.
| Conductor Size AWG | Wire Gauges Diameter (mm) | Insulation Thickness (mm) |
| 26 to 16 (0.13 to 1.31) | 1.3 – 0.4 | 0.76 |
| 14 to 9 (2.08 to 6.63) | 1.57 – 2.9 | 1.14 |
| 8 to 2 (8.37 to 33.6) | 3.25 – 6.55 | 1.52 |
| 1 to 0000 (42.4 to 10.7) | 7.34 11.68 | 2.03 |
Wires are available in different diameters and gauges. These gauges are maintained according to IEC organization standards. Normally, single wire size diameters are available from 0.08mm to 11.6mm. According to the diameter, its voltage and ampers are varied.
Drill Bit Sizes For Single Conductor Wires
When you choose a drill bit for a wire, it should be more or equal to the diameter of the wire (including insulation and conductor). So let’s see what are the suitable drill bit sizes for each wire size.
| Wire gauge | Wire Diameter (mm) | Total Insulation Thickness (mm) | Hole Diameter (mm) | Drill Bit Size in Inches | Drill Bit size in mm |
| 1 | 7.34 | 4.06 | 11.4 | 15/32 | 11.9 |
| 2 | 6.55 | 3.04 | 9.59 | 25/64 | 9.92 |
| 3 | 5.82 | 3.04 | 8.86 | 23/64 | 9.12 |
| 4 | 5.18 | 3.04 | 8.22 | 21/64 | 8.33 |
| 5 | 4.62 | 3.04 | 7.66 | 5/16 | 7.93 |
| 6 | 4.11 | 3.04 | 7.15 | 19/64 | 7.54 |
| 7 | 3.66 | 3.04 | 6.7 | 9/32 | 7.14 |
| 8 | 3.25 | 3.04 | 6.29 | 1/4 | 6.35 |
| 9 | 2.90 | 2.28 | 5.18 | 7/32 | 5.55 |
| 10 | 2.59 | 2.28 | 4.87 | 13/64 | 5.15 |
| 11 | 2.31 | 2.28 | 4.59 | 3/16 | 4.76 |
| 12 | 2.06 | 2.28 | 4.34 | 11/64 | 4.36 |
| 13 | 1.83 | 2.28 | 4.11 | 11/64 | 4.36 |
| 14 | 1.57 | 2.28 | 3.85 | 5/32 | 3.96 |
| 15 | 1.45 | 2.28 | 3.73 | 5/32 | 3.96 |
| 16 | 1.30 | 1.52 | 2.82 | 1/8 | 3.17 |
| 17 | 1.14 | 1.52 | 2.66 | 7/64 | 2.77 |
| 18 | 1.02 | 1.52 | 2.54 | 7/64 | 2.77 |
| 19 | 0.91 | 1.52 | 2.43 | 7/64 | 2.77 |
| 20 | 0.81 | 1.52 | 2.33 | 3/32 | 2.38 |
Drill Bit Size for Double Conductor Wires
2 conductor wires, double wires, and 2 core cable wires are the same wires that have 2 wires in a single cable.
Both cables are coated with electrical insulations. When you drill a hole for 2 conductor wires you can select drill bit sizes from below table.
I have prepared a guide to find drill bit sizes in inches and mm. It helps to find any drill bit related to the mm or inches easily.
| Wire Gauge | Wire Diameter in mm | Drill Bit Size in inches |
| 10/2 | 10.5 | 31/64 |
| 12/2 | 9.5 | 7/16 |
| 14/2 | 7.5 | 5/16 |
| 16/2 | 6.5 | 5/16 |
| 18/2 | 4.5 | 1/4 |
| 20/2 | 3.5 | 1/4 |
Drill Bit Size for 3 Conductor Wires
3 conductor wires and 3 core cables are the same in name and have 3 conductive cables inside the single wire. 3 conductor wires have different size gauges. Mostly used gauges are 10, 12, 14, 16, 18, and 20. You can use below drill bits when you drill a hole for 3 conductor wires.
| Wire Gauge | Wire Diameter in mm | Drill Bit Size in inches |
| 10/3 | 16.76 | 3/4 |
| 12/3 | 15.49 | 3/4 |
| 14/3 | 13.33 | 5/8 |
| 16/3 | 8.38 | 3/8 |
| 18/3 | 6.10 | 3/8 |
| 20/3 | 5.4 | 1/4 |
When you drill for screws, this guide will help you to find the drill bit sizes for screws.
Drill bit size is very important for wirings. Drill holes should always be equal to or larger than the wire size. Normally, wires have conductive cable and insulation thickness. Those are standard sizes. Hence you should know both thicknesses in order to determine the hole diameter.
