Workshop Pocket Card — Drill Depths & Tolerances
Printable workshop card with ideal drill-point factors, selected blind-hole allowances, and inch-to-metric tolerance half-widths from shared reference data.
Updated September 6, 2026
Keep two easily confused dimensions beside the machine: a drill’s point allowance is added below its full-diameter depth, and a symmetric ± tolerance is half of its total zone width. These calculated lookup values use the same data as the detailed references and calculators. They are geometry and unit conversions, not tool-selection advice, fit classes, or machine commands.
Workshop Pocket Card — Drill Depths & Tolerances — updated September 6, 2026
Point allowance: h = D / [2 tan(θ/2)]
| Included angle | Multiply D by | h at Ø10 mm |
|---|---|---|
| 90° | 0.500000 | 5.0000 |
| 118° | 0.300430 | 3.0043 |
| 120° | 0.288675 | 2.8868 |
| 135° | 0.207107 | 2.0711 |
| 140° | 0.181985 | 1.8199 |
Tip depth = full-diameter depth + h. Verify the actual tool profile.
Selected drill diameters — point allowance (mm)
| Ø mm | 118° | 120° | 135° | 140° |
|---|---|---|---|---|
| 3 | 0.9013 | 0.8660 | 0.6213 | 0.5460 |
| 5 | 1.5022 | 1.4434 | 1.0355 | 0.9099 |
| 6 | 1.8026 | 1.7321 | 1.2426 | 1.0919 |
| 8 | 2.4034 | 2.3094 | 1.6569 | 1.4559 |
| 10 | 3.0043 | 2.8868 | 2.0711 | 1.8199 |
| 12 | 3.6052 | 3.4641 | 2.4853 | 2.1838 |
Ideal cone only; no extra breakthrough or tapping allowance.
Symmetric tolerance conversions
| ± in | ± mm | ± µm | Full zone mm |
|---|---|---|---|
| 0.0001 | 0.00254 | 2.54 | 0.00508 |
| 0.0002 | 0.00508 | 5.08 | 0.01016 |
| 0.0005 | 0.01270 | 12.70 | 0.02540 |
| 0.0010 | 0.02540 | 25.40 | 0.05080 |
| 0.0020 | 0.05080 | 50.80 | 0.10160 |
| 0.0050 | 0.12700 | 127.00 | 0.25400 |
1 inch = 25.4 mm exactly. Full zone = 2 × half-width; drawing requirements govern.
Sources
- NIST SI Units — Length: exact international inch definition — https://www.nist.gov/pml/owm/si-units-length
- Ideal conical-point triangle h = D/[2 tan(θ/2)]; point angle convention: Harvey Performance Company, Spot Drilling — https://www.harveyperformance.com/in-the-loupe/choosing-spot-drill/
Try the Calculators
Workshop Pocket Card — Drill Depths & Tolerances — reuven.tools/cheat-sheets/workshop-depth-tolerance-card — verified against: NIST SI Units — Length: exact international inch definition — https://www.nist.gov/pml/owm/si-units-length; Ideal conical-point triangle h = D/[2 tan(θ/2)]; point angle convention: Harvey Performance Company, Spot Drilling — https://www.harveyperformance.com/in-the-loupe/choosing-spot-drill/