Pilot Hole Sizes for Screws
Standard/Specialty Industrial machine screws and industrial fasteners, including Lo-Driv Screws and Tri-Round screws, are available in various diameters and materials. The chart below lists the Lo-Driv and Tri-Round recommended pilot hole sizes for both inch and metric screws.
Lo-Driv & Tri-Round Recommended Pilot Holes Sizes – Inch Screws
| Material Thickness Inch Nominal Screw Size Diameter – TPI | Inch Approx.US Gauge Material | .020 - .055 (26 - 17) Dia. | .016 - .122 (16 - 11) Dia. | .125 - .245 (11 - 3) Dia. | .250 - .312 (3 - 5/16") Dia. | .313 - .500 (5/16" - 1/2") Dia. |
|---|---|---|---|---|---|---|
| 4 – 40 | Steel* /Aluminum** | .098 / .098 | .102 / .100 | .104 / .102 | ||
| 6 – 32 | Steel / Aluminum | .120 / .120 | .120 / .120 | .125 / .125 | .128 / .125 | |
| 8 – 32 | Steel / Aluminum | .147 / .147 | .150 / .150 | .154 / .152 | ||
| 10 – 24 | Steel / Aluminum | .166 / .166 | .172 / .166 | .177 / .170 | ||
| 10 – 32 | Steel / Aluminum | .173 / .173 | .177 / .173 | .180 / .177 | ||
| 12 – 24 | Steel / Aluminum | .193 / .191 | .199 / .196 | .203 / .199 | ||
| 1/4 – 20 | Steel / Aluminum | .219 / .219 | .224 / .221 | .228 / .224 | .234 / .228 | |
| 5/16 – 18 | Steel / Aluminum | .281 / .278 | .288 / .284 | .290 / .286 | ||
| 3/8 – 16 | Steel / Aluminum | .342 / .339 | .348 / .343 | .350 / .343 |
Lo-Driv & Tri-Round Recommended Pilot Holes Sizes – Metric Screws
| Material Thickness Nominal Screw Size Dia. Pitch | Millimeters Material | .05 - 1.2 Dia. | 1.3 - 2.4 Dia. | 2.5 - 4.0 dia. | 4.1 - 5.9 dia. | 6.0 - 8.1 dia. |
|---|---|---|---|---|---|---|
| M3 x 0.5 | Steel | 2.72 | 2.74 | 2.77 | ||
| M4 x .07 | Steel | 3.58 | 3.60 | 3.63 | 3.68 | |
| M5 x 0.8 | Steel | 4.55 | 4.57 | 4.60 | 4.65 | |
| M6 x 1.0 | Steel | 5.41 | 5.46 | 5.51 | 5.54 | |
| M7 x 1.0 | Steel | 6.45 | 6.51 | 6.58 | ||
| M8 x 1.25 | Steel | 7.31 | 7.39 | 7.47 | ||
| M10 x 1.50 | Steel | 9.10 | 9.17 | 9.27 |
