Drill Bit Guide: Types, Materials, and Matching Bits to Materials
FriendsWithTools.io earns a commission from qualifying purchases made through links on this page, at no additional cost to you. We do not test these tools ourselves — all claims are sourced from manufacturer specifications, retailer listings, and aggregated user reviews, each linked inline. Prices and ratings were verified on May 2026 and may have changed.
The drill is only as good as the bit you put in it. Each bit geometry is designed for specific materials and hole types. Using the wrong bit produces rough holes, burns material, dulls prematurely, or snaps the bit entirely. Matching the right bit to your material and hole size eliminates most drilling frustrations and extends the life of both your bits and your drill. This guide covers the major bit categories, when to use each one, and how to get the best results from every type.
Twist Bits: The Universal Starting Point
High-speed steel (HSS) twist bits are the standard general-purpose bit. They drill wood, plastic, soft metals, and thin sheet metal. The two-flute spiral design clears chips from the hole as the bit advances, preventing the flutes from packing with debris and overheating. Sizes from 1/16 to 1/2 inch cover most fastener pilot holes and through-holes for common hardware.
Cobalt bits (HSS with 5 to 8 percent cobalt content) handle harder metals that destroy standard HSS bits quickly. Stainless steel, hardened bolts, cast iron, and heat-treated parts all require the additional hardness and heat resistance that cobalt provides. Cobalt bits cost more but last significantly longer in hard materials where standard HSS dulls in just a few holes.
Black oxide coating reduces friction and extends life in wood and soft metal. It also provides mild corrosion resistance for bits stored in damp shops. Titanium nitride (TiN, the gold-colored coating) is harder and lasts longer than black oxide, but the coating cannot be resharpened. Once the TiN wears through at the cutting edge, the bit performs like uncoated HSS. For bits you plan to resharpen on a bench grinder or sharpening jig, uncoated or black oxide is the better investment.
Split-point tips start drilling immediately without walking (skidding across the surface). The self-centering geometry eliminates the need for a center punch mark on metal, which saves time and improves hole placement accuracy. Standard 118-degree tips tend to wander on smooth metal surfaces unless you dimple the starting point with a punch first. For metal work, split-point bits are worth the small premium.
Buy twist bits in an indexed set (a case with labeled slots for each size). Loose bits in a drawer are nearly useless because you can never find the specific size you need. A 29-piece set covering 1/16 to 1/2 inch in 1/64-inch increments costs $20 to $50 for HSS and handles the vast majority of general drilling tasks.
Wood-Specific Bits
Spade bits (paddle bits) cut large, flat-bottomed holes from 3/8 to 1-1/2 inches in wood. They are cheap, fast, and aggressive. The flat paddle geometry removes material quickly for rough holes in framing lumber where wire and pipe need to pass through studs and joists. The hole quality is rough with tear-out around the edges. Spade bits are not suitable for visible surfaces or furniture work where clean holes matter.
Forstner bits cut clean, flat-bottomed holes with smooth walls. They handle overlapping holes, angled drilling, and holes near board edges without deflecting. They are essential for furniture work: hinge cups, dowel holes, counterbores for bolt heads, and decorative recesses. Forstner bits are slower than spade bits and produce the best results in a drill press where the bit is perfectly perpendicular to the work surface. In a handheld drill, they tend to wander unless you start with a guide block.
Brad-point bits are twist bits with a center spur that locates precisely and prevents walking. The outer spurs score the hole perimeter before the cutting lips engage, producing clean holes with minimal tear-out on both the entry and exit sides. Brad-point bits are the standard choice for visible holes in woodworking, dowel joints, and any drilling task where the hole edges need to be crisp and clean.
Auger bits have a threaded lead screw that pulls the bit into the wood without applied pressure, deep spiral flutes that clear chips from deep holes, and cutting spurs for clean entry. Use these for deep holes in timber framing, log building, and any application where the hole depth exceeds two or three times the bit diameter. The self-feeding action means the bit drills at its own pace. Do not force an auger bit; let the screw thread pull it through at a controlled rate.
Masonry, Tile, and Glass Bits
Masonry bits have a carbide tip brazed to a standard steel body. They drill concrete, brick, block, morite, and stone using a hammer drill's percussive action. The carbide tip crushes the masonry material rather than cutting it the way metal and wood bits do. Do not use masonry bits in rotary-only mode on hard concrete. Without the hammer action, the bit overheats from friction and the carbide tip cracks or breaks off.
SDS-plus bits fit rotary hammer drills (not standard 3-jaw chucks) and handle concrete drilling far more efficiently than masonry bits in a standard hammer drill. The SDS shank has slots that lock into the hammer's chuck, transmitting percussive energy directly to the bit without slipping. For more than a few holes in concrete, a rotary hammer with SDS-plus bits saves enormous time and effort compared to a standard hammer drill struggling through the same material.
Glass and tile bits have a spear-shaped carbide tip that scratches and grinds through hard, brittle materials without cracking them. Start without hammer action, at low speed, with constant water cooling to prevent the bit from overheating and the tile from cracking from thermal shock. A piece of masking tape over the drill point helps prevent the bit from skating on smooth glazed surfaces. Once through the hard surface layer, switch to a standard bit appropriate for the substrate behind the tile.
Diamond-core bits are hollow cylinders with diamond-impregnated edges. They cut clean, round holes in porcelain tile, natural stone, glass, and other extremely hard materials. They require continuous water cooling during use and are sized to the exact hole diameter needed. There is no pilot bit and no step drilling. The diamond edge grinds a circular channel through the material, and the resulting plug lifts out. These bits are more expensive than carbide-tipped options but produce significantly cleaner results in the hardest materials.
Hole Saws and Step Bits
Hole saws cut large-diameter holes from 3/4 to 6 inches in wood, plastic, thin metal, and drywall. A center pilot bit locates and starts the cut, and the toothed cylinder cuts the perimeter. The resulting plug pops out (usually with a screwdriver or punch). Bi-metal saws with HSS teeth on a flexible spring-steel body handle both wood and metal and resist the tooth breakage that afflicts cheaper carbon steel saws.
Step bits (unibits) have a conical shape with multiple stepped diameters on a single bit. They drill progressively larger holes in thin material by driving deeper into the cone. Sheet metal, electrical boxes, plastic panels, and thin plywood are ideal applications. One step bit replaces a dozen twist bits for thin-material work. The limitations: step bits only work on material thinner than the step height (usually about 1/8 inch per step), and the hole size jumps in fixed increments.
Self-feed bits are large-diameter wood bits (1 to 4-5/8 inches) with a center screw and aggressive cutting teeth. They pull themselves through lumber quickly for rough holes in framing, which is how electricians and plumbers run wire and pipe through wall studs and floor joists. The self-feeding action demands a powerful drill with a side handle for control, because the bit can grab and twist the drill out of your hands if it catches.
Adjustable hole cutters let you set a specific diameter using a sliding cutter arm on a central arbor. One tool covers a range of sizes, eliminating the need for dozens of fixed-size hole saws. Accuracy depends on careful setup and a drill press for best results. They produce rougher holes than dedicated hole saws but save significant money when you need occasional holes in odd sizes.
Speed, Pressure, and Bit Life
Larger bits need slower speeds. A 1/8-inch twist bit in wood can run at 3,000 RPM or more. A 1-inch Forstner bit in the same wood should run at 500 to 700 RPM. A 3-inch hole saw needs 300 to 500 RPM. Running a large bit too fast generates excessive heat, burns the material, and dulls the cutting edges. Most drills have variable speed triggers that let you control RPM by feel.
Let the bit do the cutting. Excessive downward pressure does not make the bit cut faster; it overloads the cutting edges, generates heat, and can snap small bits. Apply steady, moderate pressure and let the flutes clear chips naturally. If chips stop coming out of the hole, back the bit out to clear the flutes before continuing.
Use cutting fluid when drilling metal. Even a drop of cutting oil on the bit tip reduces friction, clears chips, and dramatically extends bit life in steel and iron. For aluminum, WD-40 or kerosene works as a cutting lubricant. For cast iron, drill dry. Wood should always be drilled dry; lubricants stain the grain and interfere with glue joints.
Sharpen twist bits when they stop cutting cleanly. A bench grinder with a bit-sharpening jig restores the cutting angle in under a minute. A sharp bit cuts faster, cleaner, and with less heat than a dull bit pushed harder. Sharpening extends the life of a good bit set by years.
Frequently Asked Questions
Why Does My Drill Bit Smoke and Burn Wood?
Dull bit, too much speed, or insufficient chip clearance. A dull bit rubs instead of cutting, generating heat through friction. Slow down, back the bit out periodically to clear chips (especially in deep holes), and sharpen or replace the bit. Hardwoods and plywood burn faster than softwoods because they are denser and generate more friction at the same speed.
Can I Drill Metal With a Wood Bit?
Brad-point and spade bits should not be used on metal. The center spurs catch on the metal surface and the geometry is wrong for metal cutting. Standard HSS twist bits work fine on both wood and metal. Forstner bits will cut soft metals like aluminum but dull quickly and are not intended for it.
How Do I Drill a Straight Hole Without a Drill Press?
Use a drill guide, which is a block of wood or commercial jig with a hole drilled at the desired angle, clamped to the workpiece. Or use a portable drill guide attachment that clamps to the drill body and keeps it perpendicular to the surface. Watching from two perpendicular angles simultaneously also helps: align the bit visually from both the side and the front before you start drilling.