Tap Drill Size for M12x1.5

Thread Specifications for M12x1.5

Here are the complete specifications for the M12x1.5 thread:

• Major Diameter: 12.0mm (0.4724″)
• Pitch: 1.5mm
• Tap Drill Size: 10.5mm (0.4134″ / 10.5mm)
• Thread Engagement: ~75% (standard)

How Is the Tap Drill Size Calculated?

The tap drill size for metric threads is calculated using this simple formula:

Tap Drill Diameter = Major Diameter – Pitch

For M12x1.5:

Tap Drill = 12.0mm – 1.5mm = 10.5mm

The recommended tap drill is 10.5mm, which gives approximately 75% thread engagement — the industry standard for most applications.

Why 75% Thread Engagement?

Thread engagement percentage determines how deep the threads are cut. While more might seem better, there is a practical limit:

• 50% engagement provides about 90% of full thread strength — ideal for softer materials or when tap breakage is a concern.
• 75% engagement is the industry standard — excellent strength with reasonable tapping effort. This is what the 10.5mm drill provides for M12x1.5.
• Beyond 83% adds almost no additional strength but significantly increases tapping torque and tap breakage risk.

Pro tip: In aluminum, brass, or other soft materials, 50-60% thread engagement is often preferred to reduce tap breakage. Save 75%+ for steel and harder materials.

Related Thread Sizes

• Tap Drill for M12x1.0 — 11.0mm (0.4331″)
• Tap Drill for M12x1.25 — 10.8mm (0.4252″)
• Tap Drill for M14x1.0 — 13.0mm (0.5118″)
• Tap Drill for M14x1.25 — 12.8mm (0.5039″)