Thread Rolling

Cold-formed threads.
Stronger than cut.
Production standard.

Thread rolling cold-forms threads by pressing the workpiece between rotating dies. Grain structure flows around the thread form instead of being cut — producing threads with 30–50% higher strength, better surface finish, and improved fatigue life than cut threads.

Thread Rolling Quote Thread standards

30–50% stronger Ra 0.4 µm Fast production No chips

01 · What it is

How Thread Rolling works.

Thread rolling forms threads by pressing the workpiece between two hardened rolling dies with mating thread profiles. The material flows plastically into the thread form — no material is removed, in contrast to cut threads that remove material to create the thread. The grain structure of the original metal bends around the thread profile, creating a continuous grain pattern that is stronger than the cut-thread equivalent.

Three primary rolling approaches: flat die rolling (workpiece moves between two flat dies), two-roll rolling (workpiece spins between two cylindrical rolling dies — common for production), and three-roll rolling (three cylindrical dies in a Y pattern — used for large-diameter rolls). Each approach has specific volume and geometry advantages.

Rolled threads are standard for production fasteners, aerospace bolts, automotive hardware, and any application where thread fatigue life or strength matters. The tradeoff: requires specific blank diameter, limited geometry flexibility (can't roll blind end-of-bolt threads), and tool cost for custom thread profiles.

02 · Specifications

Capability specs.

30–50%

Strength improvement

Over cut threads. Due to grain flow around thread profile

10–20×

Fatigue life

Improvement over cut threads for cyclic loading

Ra 0.4 µm

Surface finish

Smoother than cut threads. Less stress concentration, better seal performance

Production

Fast cycle time

Single-die pass per thread. Much faster than thread milling or tapping

No chips

Cold forming

No material removal — blank diameter specifically chosen to produce correct thread

1–100 mm

Diameter range

Practical rolling range. Smaller and larger via specialty equipment

Any thread form

Custom profiles

UNC, UNF, metric, ACME, specialty — custom die costs $2000-8000

Fastener grade

Material requirements

Ductile enough to cold-form — most common fastener materials work well

03 · Applications

Where Thread Rolling excels.

Aerospace fasteners

Aerospace bolts per AN, NAS, MS specifications — rolled threads standard

Production fasteners

Commercial bolts, screws, threaded rod — high-volume production

Automotive hardware

Engine bolts, wheel studs — fatigue life critical, rolled threads standard

Precision threaded rod

Precision lead screws, threaded actuator rods

Medical fasteners

Medical device fasteners, surgical hardware — rolled for strength and smoothness

Industrial bolts

Structural bolts, anchor bolts, heavy-duty threaded hardware

Set screws

Hex socket set screws in production quantities

Bolts for aerospace

Aircraft bolts per AN/MS specifications — rolling required for flight qualification

Stud bolts

Threaded stud bolts for pressure vessels, structural connections

04 · When not to use it

Not suitable for:

Every process has its limits. Being honest about where Thread Rolling isn\'t the right answer saves time and money.

Internal threads — rolling works on external threads only (use tapping for internal)
Blind-end threads — rolling requires thread to exit the workpiece end
Brittle materials — cannot cold-form without cracking
Hardened materials above 35 HRC — too hard to cold-form
Very small quantities — tooling cost not justified for 1-10 pieces
Non-round blank cross-sections — rolling requires round starting material

FAQ

Thread Rolling questions.

Rolled threads are 30–50% stronger than cut threads of same specification. Why: cut threads sever the grain structure of the material, leaving each thread as a separate "island" of metal. Rolled threads bend the grain structure around the thread profile, creating continuous grain flow. Under load, stress follows the grain continuity — rolled threads distribute load better. For fatigue loading, rolled threads are 10–20× better.

Small quantities (1–100 pieces): cut threads cheaper — rolling dies expensive for small batches. Medium (100–1000 pieces): rolling breaks even. High volume (1000+ pieces): rolled threads significantly cheaper per part. For production fasteners at 10,000+ units, rolled threads are 3–5× cheaper per part than cut threads plus far better performance.

Yes — custom rolling dies can be manufactured for non-standard thread forms. Typical custom die cost: $2,000–8,000 per thread profile. Amortizes over production volume. Common customs: specialty aerospace threads, automotive-specific forms, oil and gas downhole threads. Lead time for custom dies: 4–8 weeks. Plan early in product development for optimal roll-out.

No — rolling cannot form internal threads. Internal threads require: tapping (standard for most applications), thread milling (for tight tolerance or blind holes), or wire EDM (for hardened materials). For parts needing both internal and external threads, combine processes: roll external, tap internal. Very common on stud bolts and similar hardware.

Critical: blank diameter must be precisely sized for rolling. For standard M10 × 1.5 thread: blank diameter typically 9.15–9.20 mm (below major diameter, above pitch diameter). Oversized blank won't fit dies; undersized blank produces incomplete thread. CNC blank turning for roll-threading requires tight diameter tolerance. We handle this precisely in production workflow.

Small quantities (under 100 pieces), hard materials (>35 HRC), internal threads, unusual geometries (taper pipe threads), prototyping where thread geometry may change. Cut threads have lower setup cost and more flexibility. For production quantity fasteners in standard geometries and materials, rolled threads always win.