Fasteners & drilling
Screw Sizes, Pilot Holes and Drill Bits
Wood screw sizes, pilot and clearance holes, countersinks and drill bit sizes, laid out as charts you can read at the bench, with a countersink calculator for the angle and depth. Each chart covers both hardwood and softwood where the hole size differs.
Screw and bit dimensions come from the standards that define them, checked against makers' published charts. Pilot hole sizes, which published charts do not always agree on, show the median of three or more sources and the span they cover, or name both sources when only two publish a figure. Every chart works on a phone, in inches or millimetres, and offline once you have opened the site.
Calculators
- Pilot hole calculatorThe pilot hole for a wood screw in hardwood or softwood, with the clearance hole and countersink: the median of the published charts, in inches and mm.
- Countersink depth calculatorHow deep to drill a countersink so a flat-head screw sits flush or below the surface: head diameter, 82°, 90° or 100° bit, and a combination bit’s pilot.
Reference
- Wood screw size chartWood screw sizes #0 to #24: the diameter in inches and mm, threads per inch and flat head diameter, from the ANSI B18.6.1 wood screw standard.
- #6 wood screwA #6 wood screw: its diameter in inches and mm, threads per inch, head size, the pilot hole for hardwood and softwood, the clearance hole and countersink.
- #8 wood screwA #8 wood screw: its diameter in inches and mm, threads per inch, head size, the pilot hole for hardwood and softwood, the clearance hole and countersink.
- #10 wood screwA #10 wood screw: its diameter in inches and mm, threads per inch, head size, the pilot hole for hardwood and softwood, the clearance hole and countersink.
- #12 wood screwA #12 wood screw: its diameter in inches and mm, threads per inch, head size, the pilot hole for hardwood and softwood, the clearance hole and countersink.
- #14 wood screwA #14 wood screw: its diameter in inches and mm, threads per inch, head size, the pilot hole for hardwood and softwood, the clearance hole and countersink.
- Pilot hole chartPilot and clearance hole sizes for #4 to #14 wood screws in hardwood and softwood: the median of four or five published charts, with their span.
- Lag screw pilot holesLead holes for 1/4 to 1/2 inch lag screws in soft, medium and dense woods, from the USDA Wood Handbook’s rule, with the drill sizes that fit.
- Countersink guideWhat a countersink is, why wood screws take an 82° bit, how wide and how deep to cut for each screw size, and combination countersink bits.
- Drill bit size chartEvery standard drill bit size from #80 to 1 inch and 0.3 to 25 mm, smallest first, with decimal inches and millimetres for each (ASME B94.11M).
Other sections
- WoodSpecies and wood types: hardness, weight, movement, color and what each is good for.
- FinishingFinishes, glues and fillers: dry and cure times, which to use, and how they compare.
- JoineryJoints and how to size them: dovetails, mortise and tenon, rabbets, dadoes and more.
- Lumber & plywoodBoard feet, actual and nominal sizes, hardwood quarters, plywood sizes and grades.
- Tools & machinesSetup and choice for the table saw, miter saw, router, planer, jointer, lathe and CNC.