Grade 4.6 UIC 864-1 Plain Finish Screw Spikes

Railway screw spikes are core fasteners in the track fastening system. They are driven or screwed into the sleeper through the rail base or through a tie plate, holding the rail in gauge and resisting the vertical, lateral and longitudinal forces generated by train traffic. Grade 4.6 screw spikes to UIC 864-1 with a plain finish are a widely used, economical specification for standard track conditions.

Role of the Screw Spike in the Track Structure

The screw spike transfers loads from the rail into the sleeper and anchors the fastening system against movement. Depending on the track design it may be used directly through the rail base, through a tie plate, or into a plastic dowel cast into a concrete sleeper. Because the threaded shank engages the sleeper material over a long length, screw spikes provide high pull-out resistance and can be removed and re-driven during maintenance.

What Grade 4.6 Means

The property class designation follows ISO 898-1, which is used for the mechanical properties of steel fasteners. The two digits indicate the tensile strength and the yield ratio:

The first digit (4) refers to one hundredth of the nominal tensile strength: 4 x 100 = 400 MPa minimum tensile strength.

The two digits together (4.6) indicate the yield ratio: 6 x 10 = 60 percent of the tensile strength, giving a minimum yield strength of 240 MPa.

Grade 4.6 is a low-to-medium strength class, well suited to lines where the loads are moderate and where the plain carbon steel specification keeps cost and welding or fabrication issues simple. The mechanical values below are the general requirements of the property class.

Property	Grade 4.6 requirement
Tensile strength	400 MPa minimum
Yield strength	240 MPa minimum
Elongation after fracture	22% minimum
Cold bending	90 degrees without cracking

Materials Commonly Used

Screw spikes in this class are normally produced from plain carbon steel. Grades such as 45 steel and similar medium-carbon steels are common because they provide the strength, toughness and wear resistance needed for driving and service without requiring expensive alloying. The steel is machined or forged, then threaded, and the finished part is straightened to meet the straightness requirements of the standard.

Plain Finish Explained

A plain finish means the spike is supplied without plating, galvanizing or painting. In practice plain finish screw spikes are usually lightly oiled to protect the surface against rust during storage and transport. The plain finish is suitable for standard installation environments and for projects where a protective coating will be applied on site, or where the track is located in a dry, low-corrosion environment. Where the line runs through coastal, humid or chemically aggressive areas, coated versions such as zinc plated, hot-dip galvanized or Dacromet finished spikes are normally preferred.

Application and Standards

Screw spikes of this type are used across high-speed, heavy-haul and conventional railways as well as urban transit and industrial lines. UIC 864-1 is the international railway standard that defines the technical delivery conditions for screw spikes and similar fastening elements; the standard covers dimensions, material, heat treatment, mechanical properties and testing. In addition to UIC 864-1, project specifications may reference national standards such as GB, AREMA, DIN, BS or NF for equivalent products.

Inspection and Quality Verification

For procurement, the key documents are the material certificate, the tensile and yield test results, dimensional inspection records (diameter, thread profile, length, straightness), and hardness or heat-treatment records where applicable. Samples should be checked against the drawing for thread fit and head geometry before batch acceptance.

FAQ

What does "grade 4.6" mean for a screw spike?

Grade 4.6 is an ISO 898-1 property class. It means the fastener has a minimum tensile strength of 400 MPa and a minimum yield strength of 240 MPa. It is a standard carbon steel class used where moderate strength is sufficient.

What is UIC 864-1?

UIC 864-1 is the International Union of Railways leaflet covering the technical specification and delivery conditions for screw spikes used in rail fastening systems. It defines dimensions, materials, mechanical properties and testing procedures.

What does "plain finish" mean?

A plain finish screw spike is supplied without plating or coating, usually with a light oil film to prevent rust during transit. It is suited to dry, standard environments; coated finishes are recommended for humid or corrosive sites.

Which sleeper types can these spikes be used with?

They can be used with wooden sleepers, composite sleepers, and concrete sleepers where a plastic dowel or insert is cast into the sleeper to accept the thread.

What sizes are typical for this type of spike?

Dimensions are defined by the project drawing. Common configurations for railway screw spikes are shank diameters in the 22 to 26 mm range with thread lengths and overall lengths from roughly 105 mm up to about 200 mm, depending on the sleeper and plate design.

How do plain finish spikes differ from zinc plated or galvanized spikes?

The plain finish offers no sacrificial corrosion protection; zinc plating or hot-dip galvanizing add a protective layer and are chosen when the track is exposed to moisture, de-icing salts or coastal conditions.