The 17-4PH stainless hex bolt is a precipitation-hardening stainless fastener for machinery, marine, energy, pump, and valve equipment. The material is Type 630 / UNS S17400, also known as 17-4 PH and EN 1.4542. For inch-series finished fasteners, ASTM F593-24 covers Alloy Group 7, Type 630, in age-hardened condition for nominal diameters from 1/4 to 1-1/2 inches. Hex-head geometry is specified separately, commonly to ASME B18.2.1. Because 17-4PH strength changes substantially with heat-treatment condition, the required fastener specification and aging condition should be stated explicitly in the RFQ.
Product Overview and Key Features
17-4PH combines martensitic stainless structure with copper precipitation hardening. It is selected when higher strength than common austenitic stainless fasteners is required.
- Precipitation-hardening stainless: chromium, nickel, copper, and niobium additions enable high strength after aging.
- ASTM F593 Group 7 option: current inch fastener requirements identify Type 630 in age-hardened condition.
- High mechanical performance: F593U full-size products have a specified tensile range of 135-170 ksi and 105 ksi minimum yield strength.
- External hex drive: ASME or ISO geometry can be selected according to the drawing and assembly system.
- Corrosion-resistant base material: natural or passivated surfaces are commonly used without sacrificial zinc coating.
17-4PH Stainless Hex Bolt Specifications
Specification Overview
| Item | Specification / Common Requirement |
|---|---|
| Material | 17-4 PH / Type 630 / UNS S17400 / EN 1.4542 |
| Current inch fastener standard | ASTM F593-24, Alloy Group 7, Type 630 |
| F593 condition | AH — solution annealed and age hardened after forming |
| F593 marking | F593U |
| F593 diameter range | 1/4 in. through 1-1/2 in. |
| F593 tensile strength | 135-170 ksi, full-size product |
| F593 minimum yield strength | 105 ksi |
| F593 hardness | 28-38 HRC |
| Raw bar material reference | ASTM A564/A564M-25 Type 630, when specified |
| Inch dimensional reference | ASME B18.2.1-2012 (R2021) |
| Common surface condition | Natural, cleaned, passivated, or project-specified lubricant |
Selected Inch Hex Bolt Dimensions
The table shows selected ASME B18.2.1 plain hex-bolt dimensions within the ASTM F593 diameter range. s is basic width across flats and k is basic head height. Length and thread length depend on the ordered size and standard.
| Nominal Thread | UNC TPI | s Basic (in.) | k Basic (in.) |
|---|---|---|---|
| 1/4-20 | 20 | 7/16 | 11/64 |
| 3/8-16 | 16 | 9/16 | 1/4 |
| 1/2-13 | 13 | 3/4 | 11/32 |
| 5/8-11 | 11 | 15/16 | 27/64 |
| 3/4-10 | 10 | 1-1/8 | 1/2 |
| 7/8-9 | 9 | 1-5/16 | 37/64 |
| 1-8 | 8 | 1-1/2 | 43/64 |
| 1-1/4-7 | 7 | 1-7/8 | 27/32 |
| 1-1/2-6 | 6 | 2-1/4 | 1 |
UNC is a common inch-series choice, while UNF may be specified where the design requires it. Metric 17-4PH bolts can use ISO 4014 partial-thread or ISO 4017 full-thread geometry, but the withdrawn ASTM F738M should not be presented as a current metric material standard. For metric orders, define material, heat treatment, ISO geometry, thread tolerance, and inspection criteria directly.
Material, Heat Treatment and Surface Finish Options
17-4PH Material and Aging Condition
UNS S17400 contains approximately 15-17.5% chromium, 3-5% nickel, 3-5% copper, and controlled niobium plus tantalum. ASTM A564/A564M-25 permits Type 630 bar in solution-annealed or age-hardened conditions. A564 conditions such as H900, H1025, H1100, and H1150 provide different strength, hardness, ductility, and stress-corrosion behavior.
Do not treat an H900 or H1150 callout as automatically equivalent to ASTM F593U. F593U has its own finished-fastener mechanical-property window. If a project requires an A564 aging condition, define final bolt properties on the drawing or purchase specification.
Surface Finish Options
Natural or passivated stainless steel is common. Project-specific coatings may be used for appearance or friction control when qualified. Zinc plating is generally not the normal corrosion strategy for 17-4PH. Lubrication can help control thread friction and galling.
Typical Applications and Selection Considerations
- Pumps, valves, shafts, couplings, and fluid-handling equipment.
- Marine, offshore, energy, and oilfield equipment requiring high-strength stainless fastening.
- Industrial machinery, tooling, automation, and equipment assemblies.
- Aerospace-support and transportation components where the approved drawing specifies UNS S17400.
Flybear’s hex bolt versus hex cap screw guide helps buyers select the correct dimensional product, while industry fastening solutions provide application context. Do not use the term “high strength” as a substitute for a defined heat treatment, tensile requirement, or approved engineering specification.
Ordering and Quality Documentation
An RFQ should state 17-4PH / UNS S17400, ASTM F593 Group 7 or another controlled material requirement, heat-treatment condition, diameter, thread, length, dimensional standard, partial or full thread, quantity, matching nut, finish, lubricant, and documentation. ASTM F594 Group 7 nuts are the corresponding inch-series stainless nut family when F593 compatibility is required. Flybear’s quality control and inspection page describes material, hardness, tensile, dimensional, and thread inspection support.
Frequently Asked Questions
Is 17-4PH the same as Type 630 or UNS S17400?
Yes. 17-4 PH is the common alloy name, Type 630 is the ASTM stainless designation, and UNS S17400 is the Unified Numbering System designation. EN 1.4542 is a related European material designation, but the applicable product specification should still be stated separately.
Which ASTM standard applies to 17-4PH bolts?
ASTM F593-24 covers inch stainless bolts, hex cap screws, and studs from 1/4 through 1-1/2 inches. Alloy Group 7 covers Type 630 in age-hardened condition with marking F593U. ASTM A564/A564M instead covers age-hardening stainless bar and shapes, not finished-bolt requirements by itself.
Is H900 always the best condition for a high-strength bolt?
No. H900 provides very high strength and hardness, but higher aging temperatures can provide different toughness and stress-corrosion characteristics. The correct condition depends on load, environment, temperature, and the engineering specification.
What nuts can be paired with F593U bolts?
ASTM F594 covers corresponding stainless nuts and includes Alloy Group 7 Type 630 in age-hardened condition. Thread series, nut proof stress, dimensions, finish, and lubrication must match the specified bolt assembly.
What should be included in an RFQ?
Provide alloy designation, finished-fastener standard, heat-treatment condition, diameter, thread, length, dimensional standard, thread length, quantity, mating hardware, finish, lubricant, service environment, and required inspection documents. Include a controlled drawing for special geometry or application-specific mechanical requirements.
Request a Quote for 17-4PH Stainless Hex Bolts
Send Flybear Industrial your 17-4PH stainless hex bolt size, length, thread, heat-treatment condition, dimensional standard, UNS S17400 requirement, quantity, mating hardware, finish, lubricant, and documentation needs. Include drawings for custom or high-load applications. Submit the requirements through the Flybear fastener RFQ page for technical review and quotation.
