Tap/Drill Spec Table
2 types of spec data
Tap drill tables list the pilot hole sizes required before tapping metric threads (standard and fine pitch). The basic formula is pilot hole = nominal diameter − pitch, but fine-tuning is needed based on material hardness and tap type. Too small a pilot hole breaks the tap; too large results in insufficient thread engagement. Accurate selection is critical.
Frequently Asked Questions
What is the difference between coarse thread and fine thread?
Coarse thread (e.g., M10×1.5) is for general fastening with a larger pitch. Fine thread (e.g., M10×1.25) has a smaller pitch, better for fine adjustment, vibration resistance, and thin walls.
How do you calculate tap drill diameter?
Drill size = nominal diameter − pitch. Example: M10×1.5 → drill 8.5mm; fine thread M10×1.25 → drill 8.8mm. Refer to spec tables for exact values; this formula works as a quick field estimate.