Complete Forstner Bit Size Chart
Photo via Unsplash
Your comprehensive reference for forstner bit sizes in both imperial and metric. Includes recommended drill press speeds, common uses, and tips for clean flat-bottom holes every time.
Photo via Unsplash
Your comprehensive reference for forstner bit sizes in both imperial and metric. Includes recommended drill press speeds, common uses, and tips for clean flat-bottom holes every time.
| Size | Decimal (in) | Millimeters | Best Use |
|---|
Quick reference for the most common forstner bit applications in woodworking.
| Application | Size Needed | Notes |
|---|---|---|
| European hinge cups (35mm) | 35mm (1-3/8") | Most common cabinet hinge; use drill press with depth stop |
| Compact hinge cups (26mm) | 26mm (1-1/32") | For smaller overlay hinges and thin face frames |
| 1/4" dowel holes | 1/4" | Furniture dowel joints; use depth stop for consistency |
| 5/16" dowel holes | 5/16" | Medium-duty dowel joints and shelf pins |
| 3/8" dowel holes | 3/8" | Heavy-duty dowel joints; common in table and chair construction |
| 1/2" dowel holes | 1/2" | Large dowel joints for heavy structural connections |
| Counterbore for 1/4" bolts | 5/8" or 3/4" | Recesses bolt head or washer below surface |
| Counterbore for 3/8" bolts | 7/8" or 1" | Allows bolt head to sit flush or below surface |
| Counterbore for 1/2" bolts | 1-1/8" or 1-1/4" | For heavy-duty furniture and workbench construction |
| Pocket hole plugs | 3/8" | Standard pocket hole plug size for Kreg-style joints |
| Shelf pin holes | 1/4" or 5mm | Adjustable shelf supports in bookcases and cabinets |
| Cable management holes | 1-1/2" to 2" | Desk and entertainment center wire routing |
| Lamp cord holes | 3/4" or 1" | Floor lamp bases, table lamp stands |
| Wooden toy wheels | 1" to 2" | Cut partial depth for decorative wheels and discs |
Recommended forstner bit sets for different budgets and needs. Quality bits make a noticeable difference in cut quality and longevity.
IRWIN Marples 14-Piece Forstner Bit Set
Freud PB-100 16-Piece Precision Shear Forstner Set
Famag Bormax 2.0 Metric Forstner Set
STEELEX 16-Piece Forstner Bit Set
Recommended maximum RPM for forstner bits. Reduce speed by 25-30% for hardwoods like oak, maple, and cherry. These speeds apply to drill press use.
| Bit Size Range | Max RPM (Softwood) | Max RPM (Hardwood) | Notes |
|---|---|---|---|
| 1/4" - 1/2" (6-12mm) | 2,400 | 1,800 | Can use handheld drill at these sizes |
| 5/8" - 1" (15-25mm) | 1,500 | 1,100 | Drill press preferred; clamp workpiece firmly |
| 1-1/4" - 1-1/2" (30-38mm) | 1,000 | 700 | Drill press recommended; clear chips frequently |
| 1-3/4" - 2" (40-50mm) | 700 | 500 | Drill press required; use slow, steady feed rate |
| 2-1/4" - 3" (55-76mm) | 500 | 350 | Drill press essential; retract often to clear chips |
Forstner bits are used to drill clean, flat-bottomed holes in wood. They excel at overlapping holes, angled holes, and partial holes near edges. Common uses include European hinge cups (35mm), dowel joints, counterbore holes for bolt heads, pocket holes, and decorative woodworking. Unlike spade bits, Forstner bits leave smooth walls with minimal tear-out, making them the preferred choice for visible joinery and precision work.
Yes, you can use Forstner bits in a hand drill, but a drill press is strongly recommended for sizes over 1 inch. Hand drills make it harder to maintain a consistent angle and apply even pressure. For handheld use, start at low speed, clamp the workpiece securely, and let the bit do the work without forcing it. Smaller sizes (under 1 inch) are more manageable. Consider a drill guide attachment if you frequently use Forstner bits without a drill press.
Forstner bit speed depends on the diameter. For 1/4" to 1/2" bits, use up to 2,400 RPM. For 5/8" to 1" bits, use up to 1,500 RPM. For 1-1/4" to 1-1/2" bits, use up to 1,000 RPM. For 1-3/4" to 2" bits, use up to 700 RPM. For 2-1/4" to 3" bits, use up to 500 RPM. Reduce speed by 25-30% when drilling hardwoods. Too much speed causes burning, while too little causes rough, torn cuts. When in doubt, start slow and increase gradually.
Forstner bits produce cleaner, flat-bottomed holes with smooth walls, while spade bits are faster but leave rougher holes with a pointed bottom. Forstner bits can drill overlapping holes, angled holes, and partial holes at edges -- capabilities spade bits lack. Spade bits are better for rough work like running wires through framing, while Forstner bits are preferred for fine woodworking, joinery, cabinetry, and any hole that will be visible. Forstner bits cost more and cut more slowly, but the quality difference is significant.
Imperial Forstner bits typically range from 1/4 inch to 3 inches, with common increments of 1/16 inch. The most popular sizes are 1/4", 3/8", 1/2", 5/8", 3/4", 7/8", 1", 1-1/4", 1-3/8", 1-1/2", and 2". Metric Forstner bits range from 6mm to 50mm, with 35mm being especially common for European cabinet hinges. Sets typically include 8 to 16 pieces covering the most popular sizes. Individual bits are available for specialty sizes.
To prevent tear-out with Forstner bits: (1) Place a sacrificial backer board underneath your workpiece to support the exit side, (2) Reduce drill speed -- especially for larger bits and hardwoods, (3) Clear chips frequently by retracting the bit periodically (peck drilling), (4) Use a drill press for consistent pressure and a perpendicular angle, (5) Score the hole outline first with a knife or compass for critical visible work, and (6) Apply masking tape over the drilling area to reduce surface splintering. Keeping your bits sharp is also critical -- dull Forstner bits cause far more tear-out than sharp ones.