This article describes the characteristics of tools and dies and the causes of their failures. It discusses the failure mechanisms in tool and die materials that are important to nearly all manufacturing processes, but is primarily devoted to failures of tool steels used in cold-working and hot-working applications. It reviews problems introduced during mechanical design, materials selection, machining, heat treating, finish grinding, and tool and die operation. The brittle fracture of rehardened high-speed steels is also considered. Finally, failures due to seams or laps, unconsolidated interiors, and carbide segregation and poor carbide morphology are reviewed with illustrations.

This article discusses failure mechanisms in tool and die materials that are very important to nearly all manufacturing processes. It is primarily devoted to failures of tool steels used in cold working and hot working applications. The processes involved in the analysis of tool and die failures are also covered. In addition, the article focuses on a number of factors that are responsible for tool and die failures, including mechanical design, grade selection, steel quality, machining processes, heat treatment operation, and tool and die setup.

Several surgical tool failures were analyzed to understand why they occur and how to prevent them. The study included drills, catheters, and needles subjected to the rigors of biomedical applications such as corrosive environments, high stresses, sterilization, and improper cleaning procedures. Given the extreme conditions to which surgical tools can be exposed, and the potential for misuse, failures are inevitable and systematic methods for analyzing them are necessary to keep them in check.

This article describes the six fundamental factors that decide a tool's performance. These are mechanical design, grade of tool steel, machining procedure, heat treatment, grinding, and handling. A deficiency in any one of the factors can lead to a tool and die failure. The article presents a seven-step procedure to be followed when looking for the reason for a failure. A review of the results of the seven-point investigation may lead directly to the source of failure or narrow the field of investigation to permit the use of special tests.

A failed H-11 tool steel pylon attachment stud was found during a routine walk-around inspection. The stud exhibited gross localized corrosion pitting at several different areas on its surface. Light general rust was also evident. Severe pitting occurred near the fracture location. The fracture face contained evidence of intergranular SCC as well as ductile dimples. The protective coating was found to be an inorganic water-base aluminide coating having a coating thickness of 7.5 to 13 micron (0.3 to 0.5 mil). The coating was of a nonuniform mottled nature. It was concluded that the failure of the pylon attachment stud was caused by general corrosion followed by SCC. The stud was not adequately protected against corrosion by the coating. It was recommended that the coating be applied to a thickness of 38 to 75 micron (1.5 to 3 mil) to provide long-time corrosion resistance. The coating must be either burnished or cured at 540 deg C (1000 deg F) to provide cathodic protection to the steel. Other coatings, such as cadmium or aluminum, were also recommended if a thinner coating is needed.

This article provides background information needed by design engineers to create part designs optimized for plastics and plastic manufacturing processes. It describes the four essential elements of plastic part development, namely, material, process, tooling, and design, and provides general design rules for the plastic forming processes covered. It also discusses the steps involved in design validation and verification.

A copper alloy C51000 (phosphor bronze, 5%A) failed prematurely during life testing of several such springs. The wire used for the springs was 0.46 mm (0.018 in.) in diam and was in the spring-temper condition. The springs were revealed to be subjected to cyclic loading, in the horizontal and vertical planes during the testing. The fracture was revealed to have occurred in bend 2. An indentation, presumably caused by the bending tool during forming, at the inner surface of the bend where fracture occurred was revealed by microscopic examination. Spiral marks produced on springs during rotary straightening were observed. A crack that had originated at the surface at the inside bend and had propagated toward the outside of the bend was revealed by microscopy of a longitudinal section taken through bend 2. The small bend radius was interpreted to contribute to spring fatigue as a result of result in straining at the bend zone. The spring was concluded to have failed in fatigue. It was recommended that the springs should be made of wire free from straightener marks and the bending tool should be redesigned so as not to indent the wire.

The conical helical spring sealed, within each switch enclosure, fractured to lead to the failure of several electrical toggle switches. The spring was fabricated from 0.43 mm diam AISI type 302 stainless steel wires. Appreciable amount of scale was observed on the fracture surface and tool marks were revealed on the inner surface of the broken spring. A typical fatigue fracture that originated at a tool mark on the wire surface was revealed by inspection of a fracture surface of the broken springs. Regions which displayed beach marks around the fracture origin and parallel striations within the beach-mark regions were revealed by scanning electron microscopy. As a corrective measure, the spring-winding operation was altered to eliminate the tool marks.

Two A6 tool steel (free machining grade) shafts, parts of a clamping device used for bending 5.7 cm OD tubing on an 8.6 cm radius, failed simultaneously under a maximum clamping force of 54,430 kg. The shaft was imposed with cyclic tensile stresses due to the clamping force and unidirectional bending stresses resulting from the nature of operation. Nonmetallic oxide-sulfide segregation was indicated by microscopic examination of the edge of the fracture surface. Both smooth and granular areas were revealed on visual examination of the fracture. The shaft was subjected to a low overstress as the smooth-textured fatigue zone was relatively large compared with the crystalline textured coarse final-fracture zone. The fatigue crack was nucleated by the nonmetallic inclusion that intersected the surface and initiated in the 0.25 mm radius fillet at a change in section due to stress concentration. To minimize this stress concentration, a larger radius fillet shaft at the critical change in section was suggested as corrective measure.