Tapping Speeds and Feeds Guide

Tapping SFM — Why It's So Much Lower Than Drilling

Drilling SFM for mild steel with a cobalt bit runs 100–120 SFM. Tapping SFM for the same material runs 20–40 SFM — one quarter the speed. The reason is geometry. A drill bit has two cutting edges and large chip clearance flutes. A tap has multiple cutting edges packed into a small diameter with minimal chip clearance — the thread form itself limits how fast chips can evacuate. Running a tap too fast packs the flutes with chips, the torque spikes, and the tap snaps.

The second reason is that taps are self-feeding — the pitch of the thread determines the feed rate automatically. On a CNC machine, the feed must be synchronized exactly to the RPM (feed = RPM × pitch). On a manual drill press or hand tapping, the tap pulls itself in at the correct rate — your job is just to control the speed and back off regularly to clear chips.

Tapping SFM Quick Reference Table

Start at the lower end of the SFM range for your material and tap type, then increase only if chips evacuate cleanly and torque stays manageable. For blind holes, reduce speed 10–20% compared to through holes — chips must travel back up the flutes rather than exit the bottom. Hand tapping always runs slower than machine tapping because chip clearing depends on your back-off rhythm.

Spiral flute taps can run at the upper end of the range in through holes because chips exit freely. Gun taps are fastest in through holes on CNC but are wrong for blind holes. Roll taps run at similar SFM to cutting taps but require fluid and a larger tap drill — never use them on cast iron or tool steel.

RPM Reference by Thread Size and Material

Use these tables for quick RPM lookup. Values calculated at midpoint SFM for HSS spiral flute taps.

Mild Steel (25 SFM HSS spiral flute)

Stainless Steel (12 SFM HSS spiral flute)

Aluminum (65 SFM HSS spiral flute)

Tap Geometry — Matching the Tap to the Job

Using the wrong tap geometry for the hole type is the second most common cause of broken taps after running too fast.

Cutting Fluid for Tapping — Requirements by Material

For stainless steel tapping, cutting fluid isn't optional — it's what stands between a successful thread and a broken tap embedded in the part. Use a dedicated tapping fluid or heavy sulfurized cutting oil. Apply it to the tap before entry and re-apply after every few turns on hand tapping. On CNC, use flood coolant directed at the tap entry point.

For aluminum, WD-40 works well for occasional shop tapping. For production work, use a dedicated aluminum cutting fluid — it provides better lubrication and chip evacuation. Roll tapping aluminum without fluid is the fastest way to seize and snap a tap. The tap expands slightly from heat, locks in the hole, and snaps on the next turn.

Tap Drill Sizes — Quick Reference

The tap drill creates the correct minor diameter for the thread. Using the wrong drill size is the third most common tapping mistake — too small and the tap binds, too large and thread engagement is insufficient.

Metric tap drills:

Roll tap drill sizes are larger — always check manufacturer specs for forming taps.

For exact RPM on your thread and material, use the Tapping Speed and Feed Calculator. Related tools: Tap Drill Size Calculator, Why Is My Tap Breaking?, Thread Pitch Calculator, and Drill Speed Calculator.