Tap and Clearance Drill Chart

Pick the right drill for any standard inch thread. A tap drill produces the hole for cutting internal threads with a tap; a clearance drill is sized larger so a bolt shank passes through freely without cutting new threads at all.

This chart covers the most common UNC (coarse) and UNF (fine) thread sizes from #4-40 up to 3/4-10. For the full thread pitch listing across every standard size, see the imperial thread size chart.

Every tap drill size in this chart targets roughly 75 percent thread engagement, the standard balance between thread strength and tapping ease. Full 100 percent engagement is rarely used in practice; it dramatically increases the torque needed to cut the thread and the risk of breaking the tap, for very little added holding strength over 75 percent.

For bolt diameters and their closest metric equivalents, see the bolt size chart. For the wrench or socket size that fits a given bolt head, see the wrench and socket size chart. For letter and number drill sizes referenced in the table above, see the letter drill chart and the number drill chart.