Pressure Engagement
Lobed forming surfaces contact the wall of a precisely sized pre-drilled hole.
Taps / Chipless threading tools
Thread Forming Taps
What Are Thread Forming Taps and How Do They Work?
A thread forming tap, also called a roll-form or cold-forming tap, creates a thread by plastic deformation instead of chip-producing cutting. Its lobed profile presses a suitably ductile workpiece into the thread form, so pilot-hole size, lubrication, torque control, and material formability are critical.
Material Displacement
Rotational pressure moves ductile material into the thread crests and roots instead of removing it as chips.
Continuous Grain Flow
Forming redirects the material's grain flow around the thread profile rather than severing it with a cutting edge.
Chipless Operation
The process does not generate cutting chips when the material and setup are suitable for thread forming.
Key Features and Benefits of Thread Forming Taps
Chipless Threading
Material displacement avoids cut-chip packing and can simplify downstream cleaning.
Formed Thread Strength
Retained grain flow and local work hardening can increase thread shear strength in suitable materials and processes.
Strong Tool Core
Fluteless construction provides a larger cross-section than a comparable fluted cutting tap.
Production-Speed Potential
Form taps can run at higher speeds than cutting taps in some ductile materials when lubrication and machine control are adequate.
Smooth Thread Flanks
Plastic forming can produce smooth internal thread surfaces without cutting-edge tearout.
Thread Forming Taps Specifications
| Specification | Range / Details |
|---|---|
| Diameter Range | #0 to 1"+; metric M1 to M30+ available by configuration |
| Body Geometry | Fluteless, multi-lobed form with optional lubrication grooves |
| Thread Forms | UNC, UNF, metric, and custom pitch profiles |
| Shank Type | Straight cylindrical shank with square drive options |
| Pitch Limits | Application-specific GH or metric pitch-diameter limits |
| Pilot Hole Requirement | Form-tap drill size selected for material and target thread percentage |
Materials and Coatings Available for Thread Forming Taps
| Material / Coating | Best For | Key Advantage |
|---|---|---|
| HSS-E (Cobalt) | Aluminum, copper, brass, zinc alloys, and selected ductile steels. | Combines toughness and hot hardness for the pressure and friction of forming. |
| Solid Carbide | Stable, high-volume production in compatible abrasive or non-ferrous materials. | High rigidity supports pitch-diameter consistency where the setup can protect a brittle carbide tool. |
| TiCN / CrN Coating | Aluminum, zinc die-cast alloys, and other compatible ductile materials. | Low-friction surfaces help limit galling and workpiece material adhesion on forming lobes. |
Thread forming requires a ductile workpiece. Match tool substrate, coating, lubrication, and pilot-hole size to material elongation, hardness, thread size, and machine rigidity.
Which Machines Use Thread Forming Taps?
CNC Machining Centers
Run synchronized tapping cycles in aluminum, copper, and other formable materials.
CNC Lathes and Turning Centers
Use turret-mounted tools to form axial or radial internal threads on turned components.
Automated Multi-Spindle Units
Produce repeated chipless threads in high-volume component lines.
Applications and Industries for Thread Forming Taps
Non-Ferrous Threading
Forms internal threads in aluminum, copper, brass, zinc alloys, and other suitably ductile materials.
Blind Hole Threading
Produces threads in blind cavities without cut chips accumulating at the bottom of the hole.
High-Load Fastening
Creates work-hardened formed threads for automotive, aerospace, and machinery joints where the material supports forming.
Clean Manufacturing
Avoids loose cutting chips when threading electronics housings and other assemblies with strict debris controls.
Frequently Asked Questions About Thread Forming Taps
What materials are suitable for a thread forming tap?
Thread forming requires sufficient ductility. Aluminum, brass, copper, zinc alloys, selected low-carbon steels, some stainless steels, and ductile sheet materials may be suitable after verifying elongation and hardness. Brittle cast iron and hardened alloys are generally poor candidates.
Is the pilot hole different for a thread forming tap?
Yes. A forming-tap pilot hole is larger than the cut-tap drill for the same nominal thread because displaced material must flow inward to create the crest. Use the toolmaker's forming-drill chart and adjust for the workpiece material and desired thread percentage.
What is the seam at the crest of a formed thread?
Material flowing from both flanks can leave a small V-shaped seam or cup at the internal thread crest. It is characteristic of the process, but its dimensions should still meet the part's engineering and inspection requirements.
Do thread forming taps require special lubrication?
Forming generates substantial friction and heat. Use a lubricant or coolant with the lubricity and extreme-pressure performance recommended for the workpiece material, coating, and production setup.
Can Bauron manufacture custom thread forming taps?
Bauron can review custom lubrication grooves, lobe geometries, pitch dimensions, chamfers, substrates, and coatings for a specific forming application.
Shared engineering resource
Design and Engineering Support
Bauron provides design and engineering support for forming-lobe geometry, lubrication grooves, pilot-hole strategy, pitch limits, substrates, and coatings. Share material data and process requirements for a technical review.
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