Tapping Threads

Roll Forming Taps vs. Cutting Thread Taps on a CNC Mill

Choosing the correct tap depends on the workpiece material, hole type, required thread, and chip-control needs.

Cutting Taps

Cutting taps remove material to create threads and therefore produce chips. They can be used in many materials, but the tap geometry and chip direction should suit the application. Spiral-point taps push chips ahead and are commonly used for through-holes, while spiral-flute taps pull chips out of blind holes.

Roll-Forming Taps

Roll-forming taps create threads by displacing material instead of cutting it. Because they do not produce chips, they can be useful for blind holes and applications where chip control is difficult. They require a ductile material and a larger, more closely controlled tap-drill diameter than cutting taps.

Setup Considerations

• Tap-drill size: Use the drill diameter specified for the selected tap type and desired thread engagement.
• Material: Confirm that the workpiece is suitable for cutting or forming.
• Lubrication: Apply an appropriate tapping fluid or coolant to reduce friction and tool wear.
• Synchronization: Match spindle speed and feed to the thread pitch during rigid tapping.
• Hole depth: Leave sufficient clearance for the tap lead, chips, and any incomplete threads at the bottom of a blind hole.

Before machining production parts, verify the tap manufacturer’s recommendations and test the finished thread with the correct go/no-go gauge.