Tap Drill Size for M22x2.5

Thread Specifications for M22x2.5

Here are the complete specifications for the M22x2.5 thread:

• Major Diameter: 22.0mm (0.8661″)
• Pitch: 2.5mm
• Tap Drill Size: 19.5mm (0.7677″ / 19.5mm)
• 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 M22x2.5:

Tap Drill = 22.0mm – 2.5mm = 19.5mm

The recommended tap drill is 19.5mm, 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 19.5mm drill provides for M22x2.5.
• 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 M18x2.5 — 15.5mm (0.6102″)
• Tap Drill for M20x2.5 — 17.5mm (0.689″)
• Tap Drill for M24x3.0 — 21.0mm (0.8268″)
• Tap Drill for M27x3.0 — 24.0mm (0.9449″)