Get the minimum and safe drill depth for a blind tapped hole. Enter the thread depth you need, the bottom clearance and the tap chamfer length — drill too shallow and the tap bottoms out and breaks.
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Request a Proposal →Tapping a blind hole requires extra depth beyond the threaded portion for the tap chamfer, chip accumulation, and clearance. This calculator determines the minimum drill depth to safely tap a blind hole to the required thread depth.
Drill at least 3-5 pitches deeper than the required thread depth. For M10x1.5 requiring 15 mm of thread: drill to 15 + 1.5x3 = 19.5 mm minimum. For production, use 5x pitch margin: 15 + 1.5x5 = 22.5 mm. This prevents tap breakage from bottoming on chips or the hole bottom.
Spiral-flute taps (also called helical-flute) pull chips upward out of the hole -- essential for blind holes. Spiral-point taps push chips forward and are for through-holes only. Using a spiral-point tap in a blind hole packs chips at the bottom and breaks the tap.
Use a spiral-flute tap with correct lubrication, drill deep enough for chip clearance, use a floating tap holder (not rigid tapping unless your machine has rigid tapping with torque monitoring), and consider thread milling for holes over M12 or high-value parts.
Enter the required thread depth and thread pitch. The calculator shows the minimum and recommended drill depths. For production tapping, use the safe depth. For shallow blind holes where depth is limited, use the minimum and consider a bottoming tap with shorter chamfer.
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CUTTING BLIND HOLES? Blind-hole taps are the family most often substituted without telling you. Before buying in volume, read how MOQ and grading work by tool family.
Blind-hole tapping is where cheap taps fail first — a bottoming tap with the wrong chamfer lead either bottoms out short or snaps. Send the thread, the hole depth and the material.