---
title: "Fastener and pilot sizes"
url: https://bkgreenstone.com/reference/fastener-and-pilot-sizes/
description: "A pilot hole sized for the shank rather than the root either splits the workpiece or leaves the thread nothing to bite. The pairing differs between softwood and hardwood."
---

# Fastener and pilot sizes

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## Reference sheets

- [Nominal lumber sizes](https://bkgreenstone.com/reference/nominal-lumber-sizes/)
- [Fastener and pilot sizes](https://bkgreenstone.com/reference/fastener-and-pilot-sizes/)
- [Insulation material guide](https://bkgreenstone.com/reference/insulation-material-guide/)

A pilot hole sized for the shank rather than the root either splits the workpiece or leaves the thread nothing to bite. The pairing differs between softwood and hardwood.

*Common wood screw gauges with their usual pilot and clearance holes. Units: inches.*

| Screw gauge | Pilot in softwood | Pilot in hardwood | Clearance hole |
|---|---|---|---|
| No. 4 | 1/16 | 5/64 | 7/64 |
| No. 6 | 5/64 | 3/32 | 9/64 |
| No. 8 | 3/32 | 1/8 | 11/64 |
| No. 10 | 7/64 | 9/64 | 3/16 |
| No. 12 | 1/8 | 5/32 | 7/32 |
| No. 14 | 9/64 | 3/16 | 1/4 |

Scroll the table sideways for the remaining columns.

## Notes on using this sheet

- The pilot hole is drilled in the piece the thread bites into; the clearance hole is drilled through the piece being fixed down, so the screw pulls the joint together.
- Omitting the clearance hole is the reason a joint stays open no matter how hard the screw is driven.
- In dense hardwood, waxing the thread reduces the driving torque more than increasing the pilot size does, and it does not weaken the hold.

[Back to all reference sheets](https://bkgreenstone.com/reference/)