Manufacturing reference charts.
The engineering data our shop floor uses every day — tolerance, surface-finish, tap-drill, sheet-metal gauge and material charts, free for your team. Bookmark this page.
General tolerances — ISO 2768
Unless a feature carries a specific callout, it is made to ISO 2768 general tolerances. Most machined parts use the medium (m) class. Tighten only the features that mate or seal — see our tolerances guide.
Linear dimensions (mm)
| Nominal size | Fine f | Medium m | Coarse c | Very coarse v |
|---|---|---|---|---|
| 0.5–3 | ±0.05 | ±0.10 | ±0.20 | — |
| 3–6 | ±0.05 | ±0.10 | ±0.30 | ±0.50 |
| 6–30 | ±0.10 | ±0.20 | ±0.50 | ±1.00 |
| 30–120 | ±0.15 | ±0.30 | ±0.80 | ±1.50 |
| 120–400 | ±0.20 | ±0.50 | ±1.20 | ±2.50 |
| 400–1000 | ±0.30 | ±0.80 | ±2.00 | ±4.00 |
| 1000–2000 | ±0.50 | ±1.20 | ±3.00 | ±6.00 |
Angular tolerances (by shorter side)
| Length | Fine f / Medium m | Coarse c | Very coarse v |
|---|---|---|---|
| ≤ 10 mm | ±1° | ±1°30′ | ±3° |
| 10–50 mm | ±0°30′ | ±1° | ±2° |
| 50–120 mm | ±0°20′ | ±0°30′ | ±1° |
| 120–400 mm | ±0°10′ | ±0°15′ | ±0°30′ |
Achievable by process (critical features)
| Process | Typical | Best |
|---|---|---|
| 5-axis CNC milling | ±0.05 mm | ±0.005 mm |
| CNC turning | ±0.025 mm | ±0.005 mm |
| Grinding | ±0.005 mm | ±0.002 mm |
| Sheet metal | ±0.13 mm | ±0.05 mm |
| Die casting | ±0.1 mm | ±0.05 mm |
Surface roughness chart
Ra is the standard average-roughness parameter. Standard CNC finish is around Ra 1.6–3.2 µm as-machined; finer values need grinding or polishing. Convert values live in our Ra calculator and read the Ra vs Rz guide.
| Ra (µm) | Ra (µin) | Rz (µm, approx) | ISO grade (N) | Typical process |
|---|---|---|---|---|
| 0.05 | 2 | ~0.3 | N2 | Lapping |
| 0.1 | 4 | ~0.5 | N3 | Lapping / superfinish |
| 0.2 | 8 | ~1 | N4 | Fine grinding / polish |
| 0.4 | 16 | ~2 | N5 | Grinding |
| 0.8 | 32 | ~4 | N6 | Fine machining / grinding |
| 1.6 | 63 | ~8 | N7 | Milling / turning (standard) |
| 3.2 | 125 | ~16 | N8 | Milling / turning |
| 6.3 | 250 | ~25 | N9 | Rough machining |
| 12.5 | 500 | ~50 | N10 | Rough / as-cast |
Rz ≈ Ra × 5 is a rough guide; the true ratio depends on the surface profile.
Tap & clearance drill sizes
Tap-drill sizes give roughly 75% thread (the practical standard). Clearance holes let the matching screw pass freely. See thread standards in our threads guide.
Metric coarse threads
| Size | Pitch | Tap drill | Clearance (close / normal) |
|---|---|---|---|
| M2 | 0.40 | 1.6 mm | 2.2 / 2.4 mm |
| M2.5 | 0.45 | 2.05 mm | 2.7 / 2.9 mm |
| M3 | 0.50 | 2.5 mm | 3.2 / 3.4 mm |
| M4 | 0.70 | 3.3 mm | 4.3 / 4.5 mm |
| M5 | 0.80 | 4.2 mm | 5.3 / 5.5 mm |
| M6 | 1.00 | 5.0 mm | 6.4 / 6.6 mm |
| M8 | 1.25 | 6.8 mm | 8.4 / 9.0 mm |
| M10 | 1.50 | 8.5 mm | 10.5 / 11.0 mm |
| M12 | 1.75 | 10.2 mm | 13.0 / 14.0 mm |
Unified (UNC) threads
| Size | TPI | Tap drill | Clearance (close) |
|---|---|---|---|
| #4 | 40 | #43 (2.26) | #32 (2.95) |
| #6 | 32 | #36 (2.71) | #27 (3.66) |
| #8 | 32 | #29 (3.45) | #18 (4.30) |
| #10 | 24 | #25 (3.80) | #9 (4.92) |
| 1/4″ | 20 | #7 (5.11) | 17/64 (6.75) |
| 5/16″ | 18 | F (6.53) | 21/64 (8.33) |
| 3/8″ | 16 | 5/16 (7.94) | 25/64 (9.92) |
| 1/2″ | 13 | 27/64 (10.72) | 33/64 (13.10) |
Sheet-metal gauge chart
Gauge numbers map to different thicknesses for different metals. Use these as a reference and always confirm by stating the thickness in your drawing. Bend-design rules are in our bending guide.
| Gauge | Steel (mm) | Stainless (mm) | Aluminium (mm) |
|---|---|---|---|
| 10 | 3.42 | 3.57 | 2.59 |
| 11 | 3.04 | 3.18 | 2.30 |
| 12 | 2.66 | 2.78 | 2.05 |
| 14 | 1.90 | 1.98 | 1.63 |
| 16 | 1.52 | 1.59 | 1.29 |
| 18 | 1.21 | 1.27 | 1.02 |
| 20 | 0.91 | 0.95 | 0.81 |
| 22 | 0.76 | 0.79 | 0.64 |
| 24 | 0.61 | 0.64 | 0.51 |
Steel/stainless use the Manufacturers' Standard / gauge system; aluminium uses the Brown & Sharpe (AWG) system. Values are nominal.
Material quick-reference
Key properties of the metals and plastics we machine and form. Full detail on each material page — start at our materials overview.
| Material | Density | Tensile | Max temp | Machinability |
|---|---|---|---|---|
| Aluminum | 2.70 g/cm³ | 310 MPa | ~150 °C | Excellent |
| Stainless Steel | ~8.0 g/cm³ | 515–620 MPa | up to ~870 °C (304) | Fair (303 = good) |
| Carbon & Alloy Steel | 7.85 g/cm³ | 565–625 MPa | ~400 °C | Good (1018/1045) |
| Titanium | 4.43 g/cm³ | ~1000 MPa | ~400 °C | Poor (specialist process) |
| Brass & Copper | ~8.5 g/cm³ (brass) | — | — | Excellent (free-machining) |
| Tool Steel | ~7.7 g/cm³ | — | up to ~540 °C (H13) | Fair annealed / poor hardened |
| ABS | 1.04 g/cm³ | ~40 MPa | ~80 °C | Good |
| Nylon (PA) | 1.14 g/cm³ | 70–85 MPa | ~120 °C | Good |
| POM (Delrin / Acetal) | 1.41 g/cm³ | ~70 MPa | ~100 °C | Excellent |
| Polycarbonate (PC) | 1.20 g/cm³ | ~65 MPa | ~120 °C | Good |
| PEEK | 1.30 g/cm³ | ~100 MPa | ~250 °C continuous | Good (sharp tools) |
Typical reference values; exact properties depend on grade, temper and heat treatment. Full certification is provided on every order.
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