Forstner Bits Basics

A Forstner Bit can drill holes other bits only dream about.

Forstner-style bits can go where no other drill bits dare. The reason is simple: A Forstner bit is rim-guided while other bits are center-point guided. That means you can use all or only part of the bit’s diameter to drill overlapped, angled or partial holes. Forstner bits also shine when it comes to drilling clean, precise 90° holes and large-diameter holes. Carbide-tipped Forstner-style bits excel at drilling the precise, flat-bottomed holes required for European-style hinges. Plus, unlike other drill bits, the rim-guided Forster bit can drill into end grain without deflection.

Forstner bits do have their drawback and are not a substitute for your everyday twist- or brad-point bits. For one thing, they are more expensive: A 1/4“ Forstner bits costs between $3 and $23. They’re also designed primarily for use in a drill press, although Forstner bits that are 1“ or smaller can be used in a hand drill if the bit’s center point is firmly engaged. Forstners also require a very slow rpm rate and thus are slow cutting. Finally, they are very difficult to sharpen.

Once you understand when to use a Forstner bit, you too will know why they are a must for your shop. Use these ten tips to learn just that.

1. Obey the Speed Limit

Adjust the speed of your drill press to match as closely as possible, but not exceed, your Forstner bit’s recommended speed. Most Forstners have different speed ratings for hardwoods and softwoods.

2. Keep ‘Em Safe

A clean, sharp rim is critical to a Forstner bit’s performance. Rolling loose in a drawer will damage the bits’ delicate rims. A simple wood block with holes drilled for the bit shanks does the trick.

3. Drill Angled Holes by Hand

You can make angled holes using a Forstner bit in a hand drill. The trick is to start at 90° until the rim and the center point are engaged, and then tip the bit while keeping it spinning. This works best with knife- or wavy-edge bits that are less than 1“ diameter.

4. Hog Out a Mortise

Forstner bits can cut overlapping holes. This is an especially useful technique for hogging out the majority of material in a mortise. It keeps the chisel work and elbow grease to a minimum.

5. Pocket Screws Without a Jig

Drilling angled pocket screw holes is a snap with a Forstner bit and a drill press. Shallow pocket screw holes like this are often used to fasten a table’s top to its apron.

6. Big, Clean, Precise Holes

Forstners can’t be beat for drilling precise, large-diameter holes up to 4“. They are a favorite of clock makers. But be warned. These larger-diameter bits are expensive—more than $150 for a 4“ model. If you’re only drilling the occasional large hole, you’re probably better off with a fly cutter or a hole saw.

7. Drilling on the Edge

Partial holes on a board’s edge are required for figure-eight-style fasteners used to attach a tabletop to an apron. A Forstner is the only drill bit that can drill this style of hole. It’s the perfect choice for this task.

8. No Tear-out Drilling

Forstner bits excel at drilling clean, precise holes for wood plugs. Because the rim scores the wood fibers ahead of the cutters, the Forstner bit virtually eliminates tear-out.

9. Best Bit for a Cup Hinge

Carbide-tipped Forstners are the choice for drilling European-style hinge-mounting holes. They can drill into melamine or MDF all day long and stay sharp.

10. Forstner Bit to the Rescue

Every drill your pilot hole before your counterbore hole? I have. A Forstner bit came to my rescue! Drilling a larger hole over a smaller hole can only be done with a Forstner bit.