How to Machine a Pilot Hole

Drilling a pilot hole will significantly reduce the risk of splits.

Drilling a pilot hole is an important time-saving step when it comes to product assembly. Pre-drilling into wood helps prevents splitting and lessens the resistance when driving a screw into place while drilling pilot holes into metal allows you to properly align the hole and eliminate the risk of slipping and damaging the material you are working with. While it may seem like you are wasting time by drilling a hole before driving a screw, you will save time and money in the long run by minimizing damage to the material being drilled and by doing less damage to the screw heads.

Things You'll Need

• Drill or drill press
• Drill bit
• Countersink bit
• Screws
• Wood
• Center punch
• Painter's tape

Instructions

1. Determine the size of the bit and screws needed for your job. Make sure you have the correct type of drill bit for the material you are using. Use the charts in the reference section if you are unsure if the drill bit you have will work with your screws.

2. Mark the hole location with a center punch. This is particularly important if you are working with metal. Marking the metal by denting it slightly will minimize the possibility of the bit slipping and marring the finish surface of the metal. If you are working with wood you can use a pencil to mark where the hole should be.

3. Continue drilling until you either drill through the material or you have gone deep enough to accommodate your screws. Wrap painter's tape around the bit or draw a line using a permanent marker to determine when you have gone far enough.

4. Switch the bit in your drill to a countersink bit. Using your pilot hole as a guide, drill into the wood. The countersink bit will allow you to drive screws deep into the wood so they will rest below the surface. If you are working with metal you may want to switch to a bigger bit to make the hole larger and widen the pilot hole.

5. Removed any burrs on the backside of the metal by flipping the piece over and drilling through to the other side.

Tips & Warnings

• If you find you are frequently drilling pilot holes that require you to countersink the screw, you should consider investing in a combination bit that will drill both the pilot and countersink hole simultaneously.

• If you are drilling holes in sheet metal, the drill could distort the shape of the metal so you may want to place a piece of wood behind it so the hole will maintain its shape.

References

• Woodworking Tips: Drilling Deep Pilot Holes
• This Old House: Norm Abram's Best Tricks of the Trade --- Drilling a Pilot Hole

Resources

• Engineered Parts Sourcing: Recommended Pilot Hole Sizes