Methods for comparing the hardness of minerals and metals, and testing methods using diamonds.

[Reproduction of Private Spring Preparatory School Lecture 1] Comparing Hardness: It's About Scratching! An explanation of metal hardness and a testing machine using diamonds.

last updated Oct 30, 2026

Learn about methods for measuring hardness and the types, roles, and importance of testing machines.

[Reproduction Private Spring Preparatory School Lecture 2] The national standards for power test machines, testing methods, and reference pieces are firmly established in JIS!

last updated Oct 30, 2026

Types of spring hardness testing machines, differentiation and precautions during measurement.

[Reproduction of Private Spring Preparatory School Lecture 3] Explanation of the Brinell hardness testing machine! Hard materials are tested with a red signal, and the testing surface is generally flat.

last updated Oct 30, 2026

The measurement principle and advantages of shore hardness testing machines, and the historical background of the development of the spring industry.

[Reproduction Private Spring Preparatory School Lecture 4] A different measurement method! Explanation of the Shore durometer applying the principle of rebound.

last updated Oct 30, 2026

The evolution from horse-drawn carriages to automobiles and the development and modernization history of Japanese spring manufacturing.

[Reproduction of Private Spring Preparatory School Lecture 5] The rickshaw is also a benefactor for the spring industry! It also discusses the modernization of the spring industry.

last updated Oct 30, 2026

The development of the spring industry in the early Taisho period and technological innovation through the introduction of testing machines.

[Reproduction of Private Spring Preparatory School Lecture 6] Standards and specifications for steel materials and springs have been established! The spring industry made great strides in the early Taisho period.

last updated Oct 30, 2026

The advancement of automobile development and spring technology, as well as innovations in materials and research progress in the late Taisho period.

[Reproduction of Private Spring Preparatory School Lecture 7] The Emergence of Automobile Springs, the Great Earthquake, and the Major Advancement of Automobiles! The late Taisho period was an era when spring research became full-fledged.

last updated Oct 30, 2026

The invention of the Katasa testing machine in the late Taisho period and the characteristics of Rockwell and Vickers.

[Reproduction of Private Spring Preparatory School Lecture 8] Explanation of two new hardness testing machines! Inventions of Rockwell and Vickers.

last updated Oct 30, 2026

The development of the automobile and aircraft industries during the Showa period and the role of the spring industry.

[Reproduction of Private Spring Preparatory School Lecture 9] Explaining the transition of the automotive and aerospace industries! Also discusses war and the spring industry.

last updated Oct 30, 2026

Establishment of Standards and Changes in Steel Materials in the Spring Industry during the Showa Period

[Reissue Private Spring Preparatory School Lecture 10] About the spring industry during the Showa period! Establishment of various standards and specifications, from JES to JIS.

last updated Oct 30, 2026

The evolution of spring technology and heat treatment methods during the Showa period and their historical background.

[Reissue Private Spring Preparatory School Lecture 11] Explanation of single and double quenching methods! Discussion of new materials and technologies as well.

last updated Oct 30, 2026

The relationship and challenges between the development of the Japanese spring industry and the automotive industry.

[Reproduction Private Spring Preparatory School Lecture 12] The hardness of each railway plate spring is measured! Brinell hardness testing machines are installed simultaneously in all factories.

last updated Oct 30, 2026

Experimental study on wire repeated bending tests and fatigue limits, and their industrial applications.

[Reproduction of Private Spring Preparatory School Lecture 13] Explanation of the repeated bending test! It also explains the differences from the repeated bending fatigue test.

last updated Oct 30, 2026

The influence of dynamic stress and fatigue failure in automobile springs and its relationship with road conditions.

[Reproduction of Private Spring Preparatory School Lecture 14] Characteristics of stress on springs! Used under significantly larger static and dynamic stresses.

last updated Oct 30, 2026

Discussion and Analysis on the Progress of Fatigue Destruction and the Geometric Characteristics of Destruction Surfaces

[Reproduction of Private Spring Preparatory School Lecture 15] Explanation of ductile fracture and brittle fracture! Also explains the smooth and rough surfaces of fatigue fracture.

last updated Oct 30, 2026

A detailed explanation of the material fatigue strength testing process and the creation of S-N curves.

[Reprint Private Spring Preparatory School Lecture 16] What is a fatigue test? An explanation of its purposes and how it is conducted.

last updated Oct 30, 2026

Observation of fracture surfaces and understanding of the safety zone in fatigue testing of metallic materials.

[Reproduction of Private Spring Preparatory School Lecture 17] Metals also change when they are fatigued! An explanation of how the results of fatigue tests are organized and utilized in design.

last updated Oct 30, 2026

The Story of Butsushutarou and the Estimation Method of Fatigue Limits Learned from Static Strength and Its Practice

[Reproduction of Private Spring Preparatory School Lecture 18] Study of Fatigue Limit Estimation Method! Estimating fatigue limits from tensile strength and hardness test results.

last updated Oct 30, 2026

The importance of factors affecting fatigue strength, such as notches and surface roughness, and their countermeasures.

[Reproduction of Private Spring Preparatory School Lecture 19] Notches reduce both static strength and fatigue strength! The scary part is the notches that are like bacteria, which are hard to see.

last updated Oct 30, 2026

The impact of surface roughness of steel materials on spring performance and the importance of improving surface quality.

[Reproduction Private Spring Preparatory School Lecture 20] Not only does fatigue strength decrease, but the thickness of the material and wire diameter also decrease: Gama skin, shark skin, and Zenitamus!

last updated Oct 30, 2026

Changes in the fatigue strength of springs due to dimensional effects and the influence of internal defects in the material.

[Reproduction of Private Spring Preparatory School Lecture 21] Yielding and fatigue destruction are related not only to the maximum surface stress but also to the stress at a certain depth from the surface!

last updated Oct 30, 2026

The mechanism of metal rust formation and its effect on fatigue strength.

[Reproduction of Private Spring Preparatory School Lecture 22] Explanation of the relationship between oxides that form on metal surfaces, namely rust, and fatigue strength!

last updated Oct 30, 2026

The importance of corrosion treatment and surface strengthening to enhance the durability of springs.

[Reproduction of Private Spring Preparatory School Lecture 23] Explanation of methods to prevent the decline of fatigue strength and surface treatments aimed at corrosion protection!

last updated Oct 30, 2026

The effects and precautions of shot peening in improving the fatigue strength of spring materials.

[Reproduction of Private Spring Preparatory School Lecture 24] An explanation of the miracle cure for improving fatigue resistance, shot peening, and other important considerations!

last updated Oct 30, 2026

History of spring materials and types of steel: Changes in properties and applications based on carbon content.

[Reproduction of Private Spring Preparatory School Lecture 25] The relationship between the transition of cultures such as stone tools, bronze tools, and iron tools and spring materials!

last updated Oct 30, 2026

Difference between premium liquor and hard steel: Changes in properties brought about by alcohol content and carbon amount.

[Reproduction Private Spring Preparatory School Lecture 26] As the amount of carbon increases, both tensile strength and yield point increase!

last updated Oct 30, 2026

The relationship between yield point, tensile strength, strength, and hardness in steel tensile testing.

[Reprint Private Spring Preparatory School Lecture 27] Explanation of the load and elongation diagram in the tensile test of steel!

last updated Oct 30, 2026

The importance of changes in steel transformation and organizational structure, and hardness adjustment through heat treatment.

[Reproduction Private Spring Preparatory School Lecture 28] We are explaining using a diagram that shows the carbon content and the proportion of organizational components in steel!

last updated Oct 30, 2026

Explanation of the temperature changes due to the steel transformation process and the influence of carbon.

[Reproduction of Private Spring Preparatory School Lecture 29] Pure iron at room temperature undergoes a sudden transformation into gamma iron when the temperature rises to 910 degrees!

last updated Oct 30, 2026

The relationship between ski downhill courses and the cooling rate of steel quenching.

[Reproduction of Private Spring Preparatory School Lecture 30] Explaining what happens when the cooling speed from high temperatures is changed!

last updated Oct 30, 2026