TOOLS / MACHINING

Drill tip & blind-hole depth calculator

Find the drill tip length and the total travel needed so a blind hole reaches full diameter at the required depth.

Drill tip length3.00 mm
Total drill travel23.00 mm

The drill must travel 23.00 mm so that 20 mm of the hole is at full diameter. The tip alone accounts for 3.00 mm.

For pressure parts, thin walls or blind holes near a cavity, check the remaining wall after the full tip travel, not just after the full-diameter depth.

Formula

Tip length = (drill diameter / 2) / tan(point angle / 2). Total drill travel = required full-diameter depth + tip length. At 118 degrees, tip length is about 0.300 x diameter; at 135 degrees, about 0.207 x diameter.

Standard / source

Standard drill-point geometry, as summarised in the MetalCalz tool-expansion research (2026-10-27): tip = (D/2) / tan(angle/2), 118 degrees = about 0.300 x D. No code table is reproduced here.

Worked example

Drill diameter 10 mm, point angle 118 degrees, full-diameter depth 20 mm: tip = 5 / tan(59 degrees) = 5 / 1.6643 = 3.00 mm. Total travel = 20 + 3.00 = 23.00 mm. These are the calculator defaults, so the page loads showing 3.00 mm tip and 23.00 mm total travel.

Safety note

Planning estimate for drilling. For pressure parts or thin walls, check the wall remaining after the full tip travel, not just after the full-diameter depth, and have a qualified person verify blind holes that must not break through.