SizePlate

Sources

Each chart lists the standards its values follow and the published references its tables were compared against, value by value. Where references disagree, the note says which one the chart follows. References were last checked on October 10, 2026. If a number disagrees with a source you trust, please tell us which one.

Tap Drill & Clearance Holes

Chart SP-TD-01. Follows ASME B1.1 (unified inch threads), ISO 261 and ISO 262 (metric threads), ISO 2306 (tap drills) and ISO 273 (clearance holes).

Inch tap drills (75% thread) were compared against:

Every inch tap drill matches at least two of the three charts. Where one differs, the chart follows the other two: #2-56 (Guhring lists #51), #3-56, #10-24 and #12-28 (Fastenal lists #46, #26 and #15). For 1-12, Little Machine Shop lists 15/16″, which is larger than the class 2B maximum minor diameter in OSG’s table (.9280″); the chart follows Fastenal’s 59/64″.

Inch clearance drills (close and free fit) were compared against Little Machine Shop (above), University of Pennsylvania MEAM.Design, Creating Threaded Holes, and University of Florida Design & Manufacturing Lab, Tap & Drill Chart (PDF).

Metric tap drills match ISO 2306:1972, Drills for use prior to tapping screw threads, Tables 1 and 2 (preview). Dormer Pramet gives the same rule of nominal diameter minus pitch (Which size should I pre-drill?), and Fastenal’s chart (above) agrees except at M8 × 1.25 and M10 × 1.25, where it lists 6.7 and 8.7 mm.

Metric clearance holes match ISO 273:1979, Fasteners — Clearance holes for bolts and screws, fine, medium and coarse series (preview).

Drill Bit Sizes

Chart SP-DB-01. Follows ASME B94.11M, Twist Drills.

Number drills #1–#80 and letter drills A–Z were compared against Fastenal’s decimal equivalents chart and Guhring’s chart (both above), plus Little Machine Shop, Letter Drill Sizes. All 106 match Fastenal. Guhring lists J as .2772″ and M as .2949″, which are its millimetre sizes converted back to inches; the chart follows Fastenal and Little Machine Shop (.2770″ and .2950″).

Fractional and metric drills are exact by name (1 in = 25.4 mm), so they’re calculated rather than copied.

Thread Pitch

Chart SP-TP-01. Follows ASME B1.1 and ISO 261 / ISO 262.

  • Inch major diameters and threads per inch: OSG Vol. 3 and Little Machine Shop (both above).
  • Metric coarse and fine pitches: ISO 2306 Tables 1 and 2 (above) and the ISO 262 selected sizes table in Wikipedia’s ISO metric screw thread.

Bolt & Socket Sizes

Chart SP-BS-01. Follows ASME B18.2.1, B18.2.2 and B18.3; ISO 4017, DIN 933, ISO 4762, ISO 7380 and ISO 10642.

Inch hex bolts and nuts (width across flats):

Inch hex keys (socket cap, button head, flat head):

Metric hex heads: Fuller Fasteners, ISO 4017 and DIN 933 tables, and Bolt Depot, Metric Bolt Head/Wrench Size.

Metric hex keys: the Unbrako and Holo-Krome catalogs above.

A dash means the size isn’t made in that style or two references don’t yet agree on it.

Resistor Color Code

Chart SP-RC-01. Follows IEC 60062 (color code) and IEC 60063 (preferred values).

SMD Resistor Codes

Chart SP-SR-01. Follows IEC 60062.

  • The EIA-96 code table (01 = 100 through 96 = 976) and the multiplier letters A–F, X and Y: Yageo, Chip Resistors Marking (PDF), Table 2. Some decoders also list Z, R, S and H; the chart leaves them out until a manufacturer’s marking table confirms them.
  • Three- and four-digit codes and R notation: the same Yageo specification, Table 1.

Formulas

Percentage of thread for a cutting tap, with major diameter, drill and pitch in the same unit:

% thread = (major − drill) ÷ (1.299 × pitch) × 100

In inch units this is usually written (major − drill) × TPI ÷ 0.01299, the form OSG uses in its Vol. 3 chart. A metric tap drill of major diameter minus pitch leaves about 77% thread.

Revisions

Each chart’s title block shows its revision letter and date. When a value changes, the revision goes up, so a printed sheet shows whether it’s current.