Tapping Basics: Feed and Thread Pitch

In rigid tapping, feed must be synchronized with the thread pitch. Any mismatch can damage the tap or the thread.

1. Feed from pitch and rpm

For metric threads, the basic relationship is:

feed (mm/min) = rpm × pitch (mm)
    

Example: M8×1.25 at 600 rpm → 600 × 1.25 = 750 mm/min. You can calculate this with the CNC Tapping Feed Calculator.

2. Choosing spindle speed

Tapping speeds are usually lower than drilling speeds for the same diameter, to reduce torque and risk of breakage. Consult tap manufacturer data for recommended cutting speeds per material.

3. Practical tips for tapping

• Use rigid tapping cycles when available to keep feed synchronized
• Minimize runout and check chuck quality for small taps
• Use proper lubrication and chip evacuation, especially in blind holes
• For through holes, consider spiral-point taps; for blind holes, spiral-flute taps

Always test tapping parameters carefully, especially in hard or abrasive materials, to avoid tool breakage and scrap.