| Product Definition | What is a hemispheric bolt? | A titanium fastener with a rounded, dome-shaped head. The hemispherical head provides a smooth external profile and reduces sharp edges compared with a conventional hexagonal head. | The supplier should provide controlled head geometry, dimensional drawings, and inspection records for the finished head profile. |
| Product Definition | Common alternative descriptions | Depending on the drawing and head configuration, similar products may be described as dome-head, round-head, button-head, or spherical-head titanium bolts. These terms are not automatically interchangeable. | A reliable supplier confirms the exact head style, bearing surface, drive feature, thread form, and dimensional standard before quoting. |
| Material | Commercially Pure Titanium Grade 2 | Commercially pure titanium with excellent corrosion resistance and good formability. ASTM B348 Grade 2 bar has a minimum tensile strength of approximately 345 MPa and a minimum yield strength of approximately 275 MPa, subject to the applicable product specification. | Suitable when corrosion resistance, low density, and formability are more important than maximum strength. |
| Material | Titanium Alloy Grade 5 | Ti-6Al-4V, an alpha-beta titanium alloy commonly used for high-strength fasteners. ASTM B348 Grade 5 bar is commonly specified with minimum tensile strength near 895 MPa and minimum yield strength near 828 MPa, depending on the required condition and specification. | A strong general-purpose choice for aerospace, marine, motorsport, and high-performance engineering applications. |
| Material | Titanium Alloy Grade 23 | Ti-6Al-4V ELI, a lower-interstitial version of Grade 5. It offers improved fracture toughness and ductility for demanding aerospace and biomedical applications, subject to the governing material standard. | The supplier should demonstrate traceability to heat number, chemistry, mechanical testing, and the specified ELI material condition. |
| Physical Properties | Density and weight reduction | Titanium has a density of approximately 4.5 g/cm³, compared with approximately 7.8 g/cm³ for carbon steel. A titanium bolt can therefore provide substantial mass reduction while retaining high specific strength. | Useful for weight-sensitive assemblies, but the design must still verify preload, fatigue, thread strength, and joint stiffness. |
| Corrosion Performance | Resistance to seawater and chemicals | Titanium forms a stable passive oxide film and generally provides excellent resistance in seawater, chlorides, and many oxidizing environments. Performance depends on temperature, concentration, crevices, contamination, and galvanic contact. | The supplier should identify material compatibility and recommend isolation washers, coatings, or lubricants where dissimilar-metal contact may occur. |
| Typical Sizes | Metric and inch threads | Custom and catalog titanium hemispheric bolts are commonly requested in metric sizes such as M4–M12 and inch sizes such as #8–1/2 in, although actual availability varies by manufacturer, tooling, head design, and production quantity. | The quotation should state nominal diameter, pitch or threads per inch, thread tolerance, length, head diameter, head height, and under-head radius. |
| Thread Options | Thread form and engagement | Metric coarse, metric fine, Unified National Coarse, and Unified National Fine threads may be available. Titanium’s lower modulus and tendency toward galling make correct thread fit, surface condition, and installation lubrication important. | Select suppliers that can control thread accuracy and provide an installation recommendation supported by testing or application experience. |
| Manufacturing | Cold heading, machining, or hot forming | Small titanium bolts may be produced by machining, heading, or a combination of forming and machining. Complex hemispheric heads and low-volume parts are often produced from bar or wire using CNC machining or specialized forming processes. | Ask for process capability, tooling capability, burr control, surface-finish limits, and sample approval procedures. |
| Surface Finish | Machined, polished, passivated, or coated surface | Titanium fasteners may be supplied in an as-machined, polished, anodized, or specially treated condition. Coating selection must consider thread fit, corrosion environment, electrical requirements, and torque-preload behavior. | Surface treatment should be defined on the drawing or purchase order rather than assumed from the material grade. |
| Installation | Galling prevention | Titanium threads can gall, particularly during repeated assembly or when titanium is mated with titanium. Appropriate anti-seize compounds, compatible coatings, controlled tightening speed, and clean threads can reduce the risk. | A technically capable supplier should provide torque guidance only when supported by the exact fastener, lubricant, joint, and test conditions. |
| Applications | Aerospace and aviation structures | Used where low mass, high specific strength, fatigue performance, and corrosion resistance are important, including aircraft interiors, fairings, brackets, and selected structural or engine-adjacent assemblies. | Require full material traceability, approved-process controls, inspection documentation, and compliance with the customer’s aerospace specification. |
| Applications | Marine and offshore equipment | Commonly considered for saltwater-exposed fittings, deck hardware, underwater equipment, pumps, valves, and lightweight marine structures. | The supplier should address galvanic compatibility with aluminum, steel, and carbon-fiber-reinforced components. |
| Applications | Chemical processing and energy equipment | Used in selected heat exchangers, process equipment, piping supports, and corrosive-service assemblies when the specific chemical and temperature conditions are suitable. | Material compatibility must be confirmed against the actual medium, concentration, temperature, pressure, and crevice conditions. |
| Applications | Medical and biomedical equipment | Grade 5 ELI and other approved titanium materials are used in certain orthopedic, dental, surgical, and medical-device applications because of biocompatibility and corrosion resistance. | Medical applications require applicable regulatory controls, cleanliness, material certification, packaging, and sterilization compatibility. |
| Quality Documentation | Certificates and traceability | A complete documentation package may include a material test report, heat-number traceability, dimensional inspection report, hardness or mechanical test results where required, certificate of conformity, and coating or surface-treatment records. | Documentation quality is a more reliable supplier-selection factor than price alone for safety-critical or regulated applications. |
| Best Supplier Criteria | Technical capability | Prioritize suppliers that can manufacture the required head profile, maintain thread accuracy, control galling-related surface defects, perform dimensional inspection, and support prototype-to-production changes. | Request drawings, samples, inspection plans, process certifications, and evidence of experience with titanium fasteners before placing a production order. |
| Purchasing Checklist | Information required in an RFQ | Specify titanium grade and condition, governing material standard, thread designation, nominal diameter, length, head dimensions, drive type, surface finish, quantity, inspection level, packaging, certificates, application environment, and delivery requirements. | A complete RFQ enables comparable quotations and prevents substitutions between different titanium grades, thread systems, or head geometries. |
