Fractional drill bit sizes

How to use this table

Scan the Size column for the fraction on your bit or plan. Decimal inch helps when a drawing shows 0.250 instead of 1/4". The mm column is a shop equivalent (inch×25.4), not a claim of lab tolerance. Click Find on a row to open the size finder with that label preselected — that path is where kit matching lives. Mapped fractional staples (1/16"–1/2" common steps) resolve to an explicit kit entry; shopping still happens on the tool page, not as a product grid here.

Fractional steps are coarser than number or letter series. If 1/4" is slightly large for a pilot and 3/16" is small, check the full chart number/letter blocks or a tap-drill reference before forcing a fit. For screw pilots and clearance holes, pair this table with a screw→drill workflow when available — diameter alone does not choose thread engagement.

Typical shop flow: read the fraction on the plan or the worn stamp on a loose bit, find the row, note decimal and mm if you need to cross-check a metric bit box, then Find → size finder for kit context. Do not treat every row as a buy button. This split page stays a quiet reference so the flagship chart and the finder can own navigation and commerce. Printable or job-site use is fine; critical aerospace or bearing fits still need a gauge.

If your case skips a common step (many 21-piece sets jump unevenly), the missing fraction is still listed here for identification. Map coverage for kits focuses on staples that consumer titanium sets actually print on the lid — that is why hub chips promote mapped fractionals only. Unmapped long-tail fractions still look up; the kit card may show the default set with an honest default note instead of a fake “includes this size” claim.

Sources

Fractional progressions follow common published inch drill indexes. Millimeter values are nominal conversions for workshop comparison. Confirm critical fits on the bit or with a gauge. See the site disclaimer for limits of use.