# Thread rolling

External thread cold forming: route selection, blank control, rollability, tooling access, heat-treatment sequence and finished-thread acceptance.

Reviewed: 2026-11-01

Tags: processes, shaping, threads, cold-forming

An invented rolling blank limit of **9.000 mm maximum with 0.030 mm minus tolerance** gives **8.970–9.000 mm**. A **9.010 mm blank** is **0.010 mm oversize** and has **0.2223% more cross-sectional area** at equal modeled length than the maximum blank. Check roundness, surface and material condition separately before rolling.

Profiled dies displace material into thread crests, so rolling starts from a smaller prepared diameter than thread cutting. Blank preparation can still require machining. [Landis, Thread Rolling catalog, printed p. 3](https://www.landis-solutions.com/wp-content/uploads/2016/02/LANDIS-Thread-Rolling.pdf)

This guide concerns forming external threads. It does not provide internal forming-tap settings, a finished-thread standard, or a generic recipe for every rollable profile.

## Identify the rolling arrangement

Landis distinguishes cylindrical infeed rolling, where dies move inward and the thread length must fit within their width, from throughfeed rolling, where the part travels axially and the thread can exceed die width. Its segmental arrangement uses cam-relieved dies for a different production sequence. These are equipment arrangements, not interchangeable instructions. [Landis, replacement thread-rolling dies](https://www.landis-solutions.com/products/replacement-thread-rolling-dies/)

Rolling heads also offer a route on machine tools such as lathes and machining centers. LMT Fette describes external threads and other profiles made by rolling heads. Specify the actual head or machine, approach direction, workholding, tool clearance and usable thread length when requesting a process proposal. [LMT Fette, rolling heads and profiles](https://www.lmt-tools.com/en/thread-rolling-and-rollable-profiles)

Resolve these questions before choosing a route:

| Input | Decision it supports |
| --- | --- |
| Thread form, pitch, starts, hand and tolerance class | Correct profile tooling and inspection requirements |
| Full-form length, shoulder, runout and end geometry | Die access, entry and exit clearance |
| Alloy, material condition and section geometry | Rollability and support requirements |
| Quantity and repeatability | Tooling, setup and production economics |
| Later heat treatment or coating | Finished dimensions and qualified property condition |

The table is an RFQ framework. It does not define a permissible thread profile or machine capacity.

## Qualify the material in its actual condition

LMT Fette's general rolling-head guidance gives approximately **7% minimum elongation** and **1,700 N/mm² maximum tensile strength**, then explicitly qualifies its values by machine conditions, microstructure and head type. Those are supplier guide values, not universal acceptance limits. Its examples distinguish rollable grades from brittle, low-elongation materials. Confirm the exact alloy and prior processing with the tooling supplier; a grade name alone does not establish rollability. [LMT Fette, Rollability of Materials](https://www.lmt-tools.com/en/thread-rolling-and-rollable-profiles)

For tubular work, the same supplier discusses internal arbor support and remaining wall thickness. Treat a hollow section as a separate application review rather than transferring a successful solid-bar setup. Do not assume that a machine's nominal diameter range qualifies a thin wall. [LMT Fette, tubular applications](https://www.lmt-tools.com/en/thread-rolling-and-rollable-profiles)

## Control the prepared blank and entry geometry

RWT places the blank diameter near, and below, the thread pitch diameter rather than the finished nominal major diameter. Its published formulas distinguish ISO coarse-thread tolerance classes and explicitly exclude fine threads from those formulas. Use a supplier-approved blank drawing for the actual thread, material and tooling instead of applying one diameter subtraction to every thread. [RWT, blank preparation](https://www.rollwalztechnik.de/en/company/thread-rolling/blank-preparation/)

Chamfers and shoulder reliefs are process features. RWT explains that an absent or unsuitable chamfer can load die ridges unevenly as material flows axially. Its suggested angles and runouts are guidance for the described conditions; establish the required dimensions and clearance with the actual dies. [RWT, chamfer and runout guidance](https://www.rollwalztechnik.de/en/company/thread-rolling/blank-preparation/)

Landis warns that an oversized blank can overfill the dies and damage them. Closing a rolling head further is not the correction for excess blank material. Inspect the incoming blank and investigate preparation drift, rather than using tool adjustment to conceal an out-of-limit diameter. [Landis catalog, printed pp. 52–53](https://www.landis-solutions.com/wp-content/uploads/2016/02/LANDIS-Thread-Rolling.pdf)

### Original blank-control example

Assume a hypothetical supplier has qualified a **9.000 mm maximum** blank with a **0.030 mm minus tolerance**, giving an allowed interval of **8.970–9.000 mm**. These invented values are not a recommendation for any named thread.

- A measured **8.985 mm** blank lies within that diameter interval.
- A measured **9.010 mm** blank exceeds the maximum by **0.010 mm**.
- At the same modeled cylindrical length, its cross-sectional area and volume exceed those of the 9.000 mm maximum by `(9.010² / 9.000² − 1) × 100 = 0.2223%`.

That small excess is a geometric volume comparison, not a prediction of rolling force, finished major diameter or die life. The in-range measurement also proves neither roundness nor surface condition. Resolve the oversized blank through the approved preparation/disposition process before rolling; it cannot be declared acceptable merely because the excess percentage looks small.

## Keep the complete thermal and finishing sequence visible

Thread rolling after heat treatment can introduce beneficial compressive residual stress, but the subsequent process matters. Cioto and Collares' original SAE paper reports that temperatures used in later surface treatments affected fatigue resistance of bolts rolled after heat treatment. Its study concerns the tested fasteners and treatments; it supplies no universal strength improvement or temperature limit for other parts. [Cioto and Collares, SAE 2003-01-3657, November 18, 2003](https://saemobilus.sae.org/papers/reduction-fatigue-resistance-bolts-threads-rolled-heat-treatment-a-result-superficial-treatment-2003-01-3657)

State whether rolling occurs before or after heat treatment and identify subsequent stress relief, coating, curing and other thermal operations. Have the responsible design authority qualify the delivered condition. Do not apply a catalog strength-gain percentage as a joint-design allowable or assume that changing the operation order preserves fatigue performance.

## Process troubleshooting and final acceptance

LMT's F01/K01 EVO operating instructions associate pitch error with alignment and other setup problems, and an unclean profile with incorrect roll installation among other causes. Use the troubleshooting instructions for the actual equipment; a visible defect does not identify one unique cause. [LMT Fette, F01/K01 EVO operating instructions, troubleshooting](https://www.lmt-tools.com/fileadmin/user_upload/Operating_Instruction_-_F01_K01_EVO_-_A4_en.pdf)

For release, specify the controlling thread-standard edition and class, major/pitch/minor dimensions as applicable, profile and runout requirements, gauging method, sampling and delivery condition. Identify any required surface-discontinuity, material or mechanical examination separately. Define whether dimensional acceptance occurs before or after coating and how coating allowance is controlled. A passing size measurement alone does not establish fatigue performance.

Include the approved blank geometry, material condition, tooling identity, process sequence, finishing and inspection requirements in the manufacturing handoff. For a change of material lot, condition, dies, machine or later thermal operation, agree what evidence is needed to preserve the qualification.

## Source versions

Reviewed 2026-11-01. The SAE publisher gives November 18, 2003 for paper 2003-01-3657. No separately verified technical issue date was established for the cited live supplier pages, Landis catalog or LMT operating instructions; hosting-path dates are not treated as editions. Supplier guide values remain bounded to their stated application. The blank-control calculation and handoff recommendations are original.

## Related reference

[Manufacturing processes](../index.md)