Forstner Bits

A Forstner bit cuts a clean, flat-bottomed hole guided by its rim rather than a center point doing most of the work — which is what lets it do things a twist or brad point bit simply can't: drill a hole that overlaps the edge of a board, bore a hole that partially overlaps a hole already drilled next to it, or stop at a precise depth with a flat bottom rather than a conical one.

Why the flat bottom matters

Hinge mortises (particularly European-style concealed hinges), stopped holes for dowels or hardware that need a consistent depth, and shelf-pin holes all benefit from a flat-bottomed hole rather than the pointed bottom a twist bit leaves. It's the standard bit for cup-hinge boring specifically because the hinge cup needs a flat register surface to seat against.

Overlapping and edge holes

Because a Forstner bit's cutting geometry is guided by its outer rim rather than depending on a full circle of material to bite into, it can drill a hole that's partially off the edge of a board, or a hole that overlaps a previous one — useful for slotting, elongated mortises, or edge treatments a twist bit can't attempt cleanly.

Speed and technique

Forstner bits cut best at lower RPM than twist bits — spinning one too fast tends to burn the wood at the rim rather than cutting cleanly, especially in hardwoods. Clearing chips periodically (backing the bit out partway through deep holes) also matters more here than with a twist bit, since a Forstner bit's flat-bottomed cutting action doesn't self-clear chips as readily.

Sizing

Forstner sets commonly run from around 1/4" up to 2" or more, and — same advice as brad point bits — buy toward what you actually need (typical hardware and hinge-boring sizes) rather than the biggest set on the shelf. Individual large-diameter Forstner bits get expensive fast, so filling in a set piece by piece as projects demand it is a reasonable approach.