Spade bit

What is a spade bit?

A spade bit, sometimes called a paddle bit, is a flat, wide drill bit designed to bore quick holes in wood. It has a sharp center point that guides the bit and two cutting edges along a paddle-shaped head that shave material away. Most spade bits have a 1/4 in. hex shank for a secure grip in a drill chuck and easy quick-change use. They are popular because they make large holes fast, especially in framing lumber and other softwoods, though they can cut hardwood too.

How it works

The center point locates the hole and keeps the bit from wandering. As the drill spins, the cutting edges remove wood, and the flat paddle pushes chips up and out of the hole. Some designs include small spurs on the edges that score the wood fibers for a cleaner entry. Because the bit does not enclose chips like a twist or auger bit, you get speed at the cost of a rougher finish and potential tear-out on the exit side.

Common uses in DIY and home improvement

• Drilling through studs and joists to run electrical cable or plumbing lines
• Boring a 1 in. latch hole in a door edge during lockset installation
• Making pass-through holes for TV cables, speaker wires, or smart-home sensors
• Drilling bolt holes in fence posts, deck posts, and landscaping timbers
• Adding drainage holes to planter boxes or raised beds
• Removing material quickly where precision surface finish is not critical

Typical size ranges run from 1/4 in. to 1-1/2 in., with metric sizes available. For holes larger than about 1-1/2 in., a hole saw or self-feed bit is usually better.

Types and variations

• Standard spade bits: Flat paddle with a center point and two cutting edges. Affordable and widely available.
• Spur-edged or scoring spade bits: Small side spurs scribe the circle before cutting, reducing tear-out on the entry side.
• Threaded-tip or self-feeding spade bits: A small screw at the tip pulls the bit into the wood. These cut aggressively and quickly but can grab; control your speed and grip.
• Impact-rated spade bits: Hardened shanks and heads designed to withstand impact drivers. Look for impact icons on the packaging.
• Stubby spade bits: Short overall length for tight spaces.
• Long or extension spade bits: Extended shanks from 12 in. to 18 in. for reaching through multiple studs or thick beams; some accept extension shafts for added reach.
• Speed-geometry spade bits: Curved cutting edges and optimized profiles to move chips out faster and reduce torque.

Choosing the right spade bit

Consider these factors:
- Size: Match the bit to the hole you need. Common electrician sizes are 3/4 in. and 1 in.; plumbers may use 1-1/8 in. or larger for PEX and PVC.
- Wood type: For clean entry in hardwoods, choose bits with scoring spurs. For rough framing, standard bits work fine.
- Tool pairing: If you plan to use an impact driver, pick impact-rated bits. For large diameters, a drill with a side handle and low gear is safer.
- Length: Use the shortest length that reaches; long bits flex and can wander if not guided.
- Tip style: Threaded tips save effort but can yank the drill; standard tips give more control.

How to use a spade bit for best results

1. Mark and dimple the center with an awl or nail to help the point start.
2. Clamp the workpiece and support the exit side with scrap wood to limit blowout.
3. Set the drill speed appropriately: small bits can run faster; large bits need slower RPM and more torque. As a rough guide, 1/4 to 1/2 in. around 1,200–1,800 RPM; 3/4 to 1 in. around 600–1,000 RPM; 1-1/4 in. and up around 300–600 RPM.
4. Start square to the surface. Begin at low speed so the point seats, then increase speed as the cutting edges engage.
5. Clear chips: every inch or so, ease the bit out to eject chips and reduce heat.
6. For clean exits, stop drilling as soon as the center point pokes through. Flip the work and finish from the opposite side.
7. Let the bit cut. Apply firm, steady pressure but do not force it; excess pressure increases tear-out and heat.

Extra tip: To reduce surface splintering on plywood or veneered panels, score a shallow circle with a utility knife or apply painter’s tape across the hole location.

Common mistakes to avoid

• Using a spade bit on metal, tile, or masonry. These bits are for wood and some plastics only.
• Overspeeding large bits. High RPM creates smoke, burning, and dull edges.
• Not supporting the exit side. Expect severe blowout if you do not back the hole with scrap or drill from both sides.
• Letting the bit wander. Without a starting dimple or steady hand, the center point can skate on hard, smooth surfaces.
• Grabbing with a threaded tip. If you are new to spade bits, avoid aggressive screw tips until you are comfortable controlling feed.
• Drilling too close to the edge of studs. Maintain at least 1-1/4 in. from the edge for code-compliant cable protection, and add nail plates where required.
• Using a dull or damaged bit. This increases heat, tears fibers, and strains the drill.

Care and maintenance

• Cleaning: Pitch and resin buildup cause heat and poor cutting. Wipe bits with mineral spirits and a rag; dry thoroughly.
• Rust prevention: Lightly oil the head and shank before storage.
• Sharpening: Use a small flat file to touch up the cutting lips and the outside of any spurs. Keep both sides even to maintain balance. Do not file the center point shorter than necessary.
• Storage: Keep bits in a holder or case to protect the edges and prevent them from banging around in a toolbox.

Related terms

• Auger bit: Spiral bit with a screw tip for deep, straight holes and better chip evacuation; cleaner exits than a spade bit.
• Forstner bit: Cuts very clean, flat-bottom holes in wood; slower than a spade bit but ideal for precision work.
• Hole saw: Ring-shaped cutter for large diameters in wood and thin materials; leaves a plug.
• Brad-point bit: Twist bit with a sharp point and spurs for clean, accurate small-diameter holes in wood.
• Self-feed bit: Large-diameter cutter with a screw tip for rough framing, typically used with a right-angle drill.

Practical examples

• Running electrical cable through studs: Use a 3/4 in. spade bit in low gear. Drill centered in the stud depth, keep at least 1-1/4 in. from edges, and protect with nail plates where needed.
• Installing a door latch: Bore the 1 in. edge hole with a spade bit. Use a backer block clamped to the door edge to prevent splintering.
• Building a planter: Add multiple 1/2 in. drainage holes across the bottom panel. Back the panel with scrap and drill from both sides for tidy holes.
• Bolting a fence: Drill 3/8 in. to 1/2 in. holes through posts for carriage bolts. Start square, clear chips, and finish from the opposite face for a clean exit.

With the right size and technique, a spade bit is a quick solution for through-holes in wood where speed matters more than a furniture-grade finish.