Pilot hole, predrilled hole, and advanced borehole are the same terms for the same hole which is drilled on the material before starting the complete drilling process or driving the screws. Pilot holes are essential for a safe, accurate, efficient, low-force, and faster drilling process. When you drill a pilot hole, you have to use a special drill bit according to the workpiece material.
For the wood pilot hole, you can use a countersink drill bit, and for the metal, you can use a center drill bit and spotting hole drill bit successfully. The minimum depth for a wood pilot hole should be 1/4,” and for the metal, it can be 2 – 3 times of the used drill bit.
When you drill a pilot hole, you should pay attention to many sectors for safety, accuracy, and efficiency. So let’s keep reading on until the end with the proper guide for the drill pilot hole.
How Deep Should a Pilot Hole Be?
Pilot Hole depth is very important factor. According to the material, the pilot hole depth is varied. Normally, a deeper pilot hole is good for woodworking, and a shallow pilot hole is good for metalworking.
1. Pilot Hole Depth for Metal
The average depth of the pilot hole for metal is 2-3 times the used drill bits diameter for the drilling pilot holes. For the screws, you must use recommended pilot hole depth according to the nominal diameter of the metal.
In most cases, screw pilot holes are not prepared in metals. If there is a special design or case screws, pilot holes can be created in the metal.
2. Pilot Hole Depth for Wood
For the drilling pilot hole, you can use the least depth for the pilot hole, and if you use the pilot hole for the screw driving, you should maintain the below depth for the optimum result.
| Screw Size | Screw Length | Hole Depth |
| #2 | 1/2″ | 1/4″ |
| #3 | 5/8″ | 1/4″ |
| #4 | 3/4″ | 3/8″ |
| #5 | 3/4″ | 3/8″ |
| #6 | 1 1/2″ | 3/8″ |
| #7 | 1 1/2″ | 3/8″ |
| #8 | 2″ | 1/2″ |
| #9 | 2 1/4″ | 3/4″ |
| #10 | 2 1/4″ | 3/4″ |
| #12 | 2 1/2″ | 3/4″ |
| #14 | 2 3/4″ | 1″ |
What Will Happen When a Pilot Hole is More Depth and More Diameter?
When the pilot hole is deeper than its recommended depth it will not tight well with inner materials. The screw will be loosened and it can’t hold more force. You can pull it out easily.
Pilot Hole Size For Wood and Steel
Pilot hole size for wood as below.
| Screw Size | Drill Bit Size for Soft Wood | Drill Bit Size For Hard Wood |
| #0 | 1/64 | 1/32 |
| #1 | 1/32 | 1/32 |
| #2 | 1/32 | 3/64 |
| #3 | 3/64 | 1/16 |
| #4 | 3/64 | 1/16 |
| #5 | 1/16 | 5/64 |
| #6 | 1/16 | 5/64 |
| #7 | 1/16 | 3/32 |
| #8 | 5/64 | 3/32 |
| #9 | 5/64 | 7/64 |
| #10 | 3/32 | 7/64 |
| #11 | 3/32 | 1/8 |
| #12 | 7/64 | 1/8 |
| #14 | 7/64 | 9/64 |
| #16 | 9/64 | 5/32 |
| #18 | 9/64 | 3/16 |
| #20 | 11/64 | 13/64 |
| #24 | 3/16 | 7/32 |
Soft Woods
Pine, Cedar, Redwood, Spruce, Douglas fir
Hard Wood
Oak, Maple, Hickory, Walnut, Cherry
The pilot hole size for steel is as below.
How to Drill a Pilot Hole in Wood and Metal?
Drilling the Pilot hole will need a few steps. You can follow these steps to make the pilot hole in the wood and metals.
Step 01 – Select the drill bit.
- Wood pilot hole drill bit
Select the drill bit according to the diameter of the screw. You can check it with your screw size and select the appropriate drill bit sizes in inches using the above table. When you drill pilot hole in the wood, you can use a countersink drill bit successfully.
And also, for the metals, you can follow the same step.
- Metal pilot hole drill bit
When you need to drill a hole on the metal, you should have a pilot hole every time. Because the drill bit can wobble or slipper easily, and that affects the accuracy directly. Therefore you can use a center drill bit, spotting hole drill bit, as a pilot hole drill bits successfully.
Step 02 – Locate the point
The drilling location should be marked with a clear sign. You can use ink to mark the place. You can punch the exact point using the puncher.
Step 03 – Apply the cutting oils.
If you drill a pilot hole in the metals, you should apply the lubricants in order to reduce the drill bit by overheating and improving the cutting speed.
Step 04 – Start drilling.
You can start drilling slowly at the beginning and then increase the drilling speed slowly. Do not start high-speed drilling. The drill bit will move here and there due to the high-speed drilling, and it will not tap the exact place correctly.
Step 05 – Clean the hole
After you drill the pilot hole, you should clean the hole. If you use to drive screws through the pilot hole, it will need to apply more force. But if you drill that hole again, you do not need to clean it additionally.
Why You Should Use A Pilot Hole for Metal and Wood?
The pilot hole is really important in many ways, such as safety, accuracy, low force, and speed drilling and driving screws are them. These are common for both metal and wood
➤ Safety
Safety is the most important thing when we are working. Whatever task we do, we must prioritize safety. When you are drilling on a hard and polished surface such as tile or metal, your drill bit can be moved here and there due to the soft surface.
So you will not be able to point the drill bit in the exact place. This really affects the accuracy. When we drill a soft surface with a larger diameter drill bit, we will not point to the exact place due to slipperiness.
➤ Accuracy
When we drill on a slippery surface, we will not be able to point the drill bit correctly. This has mostly happened in the hard drilling process. But if there is any punch or small drilled hole, this will make it easier.
Sometimes you will need to angle drilling in such materials. Can you do it? You can’t. The drill bit will slip, and it moves away, So you need a predrilled hole for the angle drilling also.
➤ Low Force
When we drill a pilot hole, it will remove all the materials inside the hole. Therefore inside material volume is reduced and it helps to drive the screw or drill bit easily inside the material.
➤ Drilling Speed
When we start drilling, we have to start slowly from the beginning until we tap (punch) the point. But if there is a predrilled hole, we can start speed drilling as soon as possible we start drilling on it. Speed drilling will finish the work quickly.
When we dive in-depth into this topic, we can apply all these facts when we drill materials such as wood, metal, concrete, stone, bricks, etc.
➤ Drive Screws
Most screws do not need a pre-drilled hole. These can be drilled into the wood directly. But when you work on the edge, the wood can be damaged when you drill without the predrilled hole.
When we drive the screws, the material will be compressed and moved away from the hole. When this has happened at the edge, it will be cracked. By drilling a pilot hole you can reduce the inside material volume and it will reduce the compressor of the material.
How to Drill Pilot Hole without Drill Bit?
You can drill a pilot hole without a drill bit easily. You just need to use any type of nail without its head, or any small steel bar with one end in a chisel shape can use as a pilot drill bit for the wood. For the metals, you can use a puncher for that.
All these methods will create a small hole as the drill bit can hold tightly without moving here and there for the drilling purpose.
But for the screw drilling, you should have an equal diameter nail or steel bar for the screw-driving pilot hole preparation. If the hole is not enough for the shank diameter, the wood will be cracked easily. This can happen easily when you work on edges.
Conclusion
Pilot holes are really important for screw driving as well as drilling holes. Whatever material you use, you should use prepare the pilot hole for a safe, accurate, efficient and speedy drilling process. For that, you should follow these steps.
