Materials and design advantages of rolled threads
This blog article is a continuation of part 3/9, the basics of thread rolling. In this article, you will learn more about the materials steel, non-ferrous metals and the design advantages of rolled threads.
Steel
Steel is the most common material used for rolled threads today. Steel is an alloy and therefore a combination of several metals. Iron makes up the largest proportion. Different strength classes are created depending on the quality of the material used. For screws, the strength class can be read on the head, whereas for threaded spindles there are attempts to standardize the material specification, but these have not yet become established. Each manufacturer still has its own designation. Both non-alloyed and alloyed steels (quality and stainless steels) are used. Alloyed steels often have considerably poorer elongation properties than non-alloyed steels. For this reason, screws in VA quality (stainless steel) prove to be problematic in many areas of application.
Non-ferrous metals
Non-ferrous metals are all metals other than iron, i.e. non-ferrous metals. In addition to steel screws, there are also screws made of aluminum, brass and even titanium. However, aluminum and brass have the disadvantage that they are far inferior to ordinary steel in terms of either elongation or strength. For this reason, screws made from these materials are only used in non-load-bearing screw connections. Although titanium can compete with steel in terms of elongation and strength, it is so expensive that it is only used as a material for screws or nuts in special cases (implants in medicine, aerospace, aircraft technology). Only far less than 1% of all rolled threads are therefore made from non-ferrous metals.
Design advantages of rolled threads
As a non-cutting forming process, the material fibers are not interrupted during thread rolling, but merely diverted. By bundling the longitudinal fibers of the base material, the thread is anchored in the core cross-section. The material is compacted and smoothed at the most stressed points. This increases its resistance to wear, significantly increases the strength and ensures very good roughness (also known as roughness, which is the unevenness of the surface height and is standardized in ISO 25178) on the thread flanks and in the radius of the thread root. The notch impact strength also increases significantly.
However, special designs are available with a preload: a spring braces the two
nut parts against each other and thus eliminates the play.
From the designer's point of view, rolled threads are mainly characterized by three advantages:
- They have a higher strength than threads produced using machining processes.
- They have a significantly more favorable price-performance ratio than comparable threads produced by machining.
- A special design enables a screw drive with zero play (Fig. 13).
Find out more about the advantages of rolled lead screws from Eichenberger here
Technical principles of thread rolling
Service provider in development
With state-of-the-art production methods, many years of expertise and our tool inventory of over 1000 rolling tools, we produce rolled threads that meet even the most unusual requirements:
- Gradients up to 6 × diameter
- Spindle lengths up to 6 m
- Spindle diameter from 2 to 160 mm
- All standard profiles (M, Tr, UNC, UNF, UNEF, Whitworth)
- Multi-start threads, also as right/left-hand threads
- Steep thread profiles
- Ball screw profiles
- Special profiles
- Screw profiles (special quality and price advantages!)
- Serrations and knurling
- Conical thread
- Threads on prefabricated and/or bulky parts, e.g. also on forged parts
The 9 blogs contain excerpts from the - Library of Technology -, Volume 286, Thread rolls, included.
This book was compiled with the technical support of Kurt Husistein and published by Verlag Moderne Industrie, ISBN 978-3-937889-30-6.
Literature and sources
Kübler, Karl-Heinz, Mages Walter J. Handbook of high-strength screws, 1st ed. Essen: W. Girardet Buchverlag, 1986.
http://www.hp-gramatke.de: Hans-Peters Mathematical-Technical-AlgorithmicA linguistic smorgasbord.Verein Deutscher Eisenhüttenleute (ed.): Werkstoffkunde Stahl, vol. 1 Berlin: Springer, 1984. Apel, Heinz: Gewindewalzen: Kaltverformen von Präzisionsgewinden und Spindeln, Munich: Hanser 1952.
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Illustrations: No. 1, 23-25 RWT Rollwalztechnik GmbH, Engen; No. 2 Photo Deutsches Museum, Munich; No. 3 Musée du tour automatique et d'histoire de Moutier, Moutier (Switzerland); No. 16 Fette GmbH, Schwarzenbek; No. 18 Meinrad Plaz, Staufen (Switzerland); No. 26 Habegger SA, Court (Switzerland); No. 34-36 FBT Fahrzeug- und Maschinenbau AG, Thörigen (Switzerland); No. 37, 38 Schleuniger AG, Thun (Switzerland); No. 39, 40 Max Planck Institute for Physics (Heisenberg Institute), Munich; No. 41 Saurer AG, Arbon (Switzerland); No. 42 Line Tech AG, Glattbrugg (Switzerland); all others Eichenberger Gewinde AG, Burg (Switzerland). Typesetting: abavo GmbH, D-86807 Buchloe. Printing and binding: Sellier Druck GmbH, D-85354 Freising. Printed in Germany 889030.
