Common Drill Bits Reference
Why this matters
Wrong bit + wrong speed = ruined material + ruined bit. Field techs drill into wood, drywall, concrete, metal, tile, glass - each needs a different bit. The tech with the right bit assortment + technique drills cleanly + fast. This is the field card.
Bit types by material
Wood + framing: standard twist bit, spade bit, auger bit, hole saw, Forstner bit.
Metal (sheet metal + steel): HSS twist bit, step bit, cobalt bit, carbide-tip (hardened steel).
Masonry / concrete: carbide-tip masonry bit, rotary hammer SDS bit.
Tile (ceramic + porcelain): spear-point carbide, diamond-tip, diamond hole saw.
Glass + mirror: spear-point carbide (slow speed + water), diamond.
Composite + laminate: brad-point bit, carbide-tip.
Drywall: drywall bit (auger style), keyhole saw.
Twist drill bits (most common)
HSS (High-Speed Steel):
- General purpose; wood, metal, plastic
- 1/16" - 1/2" diameter common
- Most home/light commercial
Cobalt (HSS-Co5, HSS-Co8):
- Higher heat tolerance
- Stainless steel + hardened metals
- 3 - 4x life of standard HSS in metal
Carbide-tipped:
- Hardened steel + difficult metals
- Slower speed, higher torque
- Expensive
Black oxide coating:
- Standard finish on HSS
- Mild corrosion resistance + reduced friction
TiN (titanium nitride) coating:
- Gold color
- Harder edge; 3 - 5x life of black oxide
- Premium HSS
Drill bit point + flute
118° point: standard; general purpose.
135° split point: self-centering; less walking; better for metal.
Brad-point (wood): center spur prevents walking; cleaner exit hole.
Spade bit: flat paddle; fast, rough exit (chips out the back side). 1/4" - 1-1/2" sizes. Wood only.
Auger bit: screw-tip pulls itself in; deep holes in wood. Slow + powerful.
Hole saw
Bi-metal hole saw: 3/4" - 6" diameter; wood + plastic + thin metal. Center pilot bit + mandrel. Lenox, Milwaukee, Starrett.
Carbide-tipped hole saw: cast iron + heavy metal.
Diamond hole saw: tile + porcelain + glass; wet-cut.
Use: doorknob holes, can-light openings, pipe penetrations, electrical box cutouts.
Step bit (Unibit)
Stepped cone bit: drills multiple hole sizes from single bit. 1/8" - 1-3/8" common.
Sheet metal + thin material: 22 ga - 18 ga preferred. Avoid for thick metal.
Use: electrical box knockouts, sheet metal panel openings, HVAC duct entry.
Brands: Irwin, Klein, Bosch.
Masonry + concrete bits
Carbide-tip masonry:
- Bullet-shaped carbide tip
- For corded drill in hammer-drill mode OR cordless impact
- 1/8" - 1/2" common
- 5 - 8" lengths
- 5 - 10 holes per bit life
SDS-Plus rotary hammer bit:
- For SDS-Plus rotary hammer (Bosch, Hilti, Milwaukee)
- 1/8" - 1-1/4" common
- 10 - 50 holes per bit life (much harder use)
- Higher cost but engineered for the tool
SDS-Max (larger):
- Heavy-duty masonry / structural drilling
- 1-1/8" - 2"+ diameters
- Commercial / structural use
Diamond core bit: hole saws for concrete; wet-cut at slow speed. 1" - 6"+ diameters.
Tile + glass bits
Spear-point carbide:
- Triangular point
- Cuts ceramic + glass at low speed
- Cool with water
- 6 - 10 holes per bit
Diamond-tip tile bit:
- Hollow OR solid diamond
- Cuts porcelain + harder tile
- Slow speed + water
- 20 - 50 holes per bit
Diamond hole saw:
- Pilot hole then hole saw
- For pipe penetrations through tile
- Wet-cut critical (heat kills diamond bond)
Speed guidelines (RPM)
General rule: smaller bit = faster RPM; larger = slower.
Wood:
- 1/16" - 1/4": 2,000 - 3,000 RPM
- 1/2": 1,500 - 2,500 RPM
- Spade 1": 1,000 - 1,500 RPM
Metal:
- 1/16" - 1/4" HSS: 1,500 - 2,500 RPM
- 1/2" HSS: 600 - 1,000 RPM
- 1/4" cobalt in stainless: 500 - 1,000 RPM
Masonry / concrete:
- 1/4" carbide: hammer mode 1,500 - 3,000 RPM
- SDS Plus: per tool (rotary hammer with proper torque)
Tile (porcelain):
- 1/4" diamond: 300 - 600 RPM with water
Glass:
- 100 - 300 RPM with water flow
Lubrication + cooling
Metal: cutting oil OR WD-40 reduces friction + extends bit life. Mandatory for stainless steel.
Stainless: dedicated cutting fluid (Tap Magic, Trefolex) required.
Tile + glass: water spray OR sponge during cutting.
Wood: no lubrication needed.
Concrete (dry): dust extraction; no lubrication needed.
Cordless drill vs corded vs impact
Cordless drill (1/2" chuck): most versatile; 18V - 20V; 50+ ft-lb torque.
Hammer drill function: percussive impact while spinning; for masonry up to ~1/2" diameter.
Impact driver: 1/4" hex shank; for driving screws, fast removal, light drilling with hex-shank bits.
Corded SDS rotary hammer: heavy masonry; concrete > 1/2" diameter.
Right-angle drill: tight spaces (between studs, joist penetrations).
Common drill bit mistakes
Wrong bit for material (HSS in concrete = ruined bit; masonry bit in steel = won't cut). Wrong speed (too fast melts steel; too slow doesn't cut). Skipping pilot hole on large bit (walks; breaks bit). Skipping lubrication on stainless (dulls bit instantly). Skipping water on tile/glass (chips; cracks). Forcing dull bit (extra force breaks bit; injures user). Using wood bit in metal (no edge geometry; ruined). Carbide masonry in regular drill not hammer mode (very slow, may not work).
Stocking truck
Essential basic kit:
- HSS twist bits 1/16" - 1/2" (set)
- Cobalt twist bits 1/8" - 3/8" (set)
- Spade bits 3/8" - 1-1/2"
- Hole saws 1", 1-1/4", 2", 2-1/2", 3", 4" (common penetration sizes)
- Step bit (Unibit) for sheet metal
- Masonry bits 1/4", 3/8", 1/2" (concrete fasteners)
- Tile bit 1/4" diamond
- Center punch (start metal holes accurately)
Add for trade specialty:
- Long auger bits (running cable through framing)
- SDS-Plus bits (if rotary hammer carried)
- Forstner bits (cabinet hardware, doorknob recess)
- Glass bit (mirror install, glass panel)
Bit storage + organization
Bit index (organized case): keeps bits sorted; replaces dull.
Magnetic strip in truck: visible at-a-glance; grabs bit fast.
Replace dull: a dull bit makes the work twice as long + breaks more often. bit costs less than 30 minutes lost.
References
- Manufacturer technical data (Bosch, Milwaukee, DeWalt, Irwin, Lenox)
- ANSI B94 (HSS twist drill standards)
- Manuall internal: Common Fastener Types, PPE Selection