Clevis Fork anatomy
Two precision-drilled prongs (lugs or tines) extend from a base or shank on every Custom CNC Machined Clevis Fork. A rod end, bracket tab, or spherical bearing nests between the prongs. A hardened clevis pin spans all three holes, forming a hinge that supports shear force and angular articulation.
The critical geometric relationships are simple but cruel. Avoid slop by matching prong width to mating bracket thickness with minimal clearance. Pin binding and wear accelerate with even a 0.1 mm misalignment of the pin holes. The prong cross-section must be thick enough to withstand maximum load without increasing weight. CNC machining meets these needs with hole concentricity, prong parallelism, and dimensional consistency that cast or forged alternatives cannot match.
Single-Plane Pivot principle
Instead of multi-axis misalignment, clevis forks pivot in one plane. This constraint is a feature, not a limitation. As their mechanisms cycle, hydraulic cylinder assemblies, agricultural implement linkages, and automobile control rods' load paths arc in one plane. A clevis fork follows that arc accurately without adding degrees of freedom that could create lateral instability.
Engineers can specify a clevis fork with an incorporated spherical bearing bore for load paths that require angular adjustment beyond 2-3 degrees of misalignment. A spherical plain bearing's self-alignment and the fork's shear-load capacity are combined in this hybrid design. Depending on linkage geometry, KEY-CNC may make rigid or bearing-compatible CNC clevis forks.
Shank Configurations and Thread Standards
Clevis forks are specified by how they connect to the rod or cylinder. Three primary shank configurations cover the majority of applications:
Plain Shank
A smooth cylindrical or rectangular base with no threads. Designed for welding, pinning, or press-fitting directly to the rod end. Common in welded hydraulic cylinder assemblies and custom bracket installations.
Threaded Male Shank
External threads (UNF or metric fine) allow the fork to screw into a female rod end, enabling length adjustment during installation. A wrench flat or hex section is machined onto the shank for tightening. This is the most common configuration for DIN 71752 / ISO 8140 compliant hydraulic cylinder clevises.
Threaded Female Shank
Internal threads accept a male rod end. Used when the rod itself is externally threaded and the clevis must thread over it. Often paired with a lock nut to prevent loosening under vibration.
Standard thread sizes range from M4 to M48 in metric and #6-32 to 1-1/2 in imperial. For non-standard geometries - angled prongs, asymmetric fork widths, or integrated mounting flanges - KEY-CNC produces fully custom designs from customer drawings in STEP, IGES, or DWG format.
FAQ
Q: What's the difference between a clevis fork and a rod end?
A: A cross-pin 30 pivots a stiff U-shaped clevis fork 50 with two prongs 52, 54 in one plane. A rod end (heim joint) contains a spherical bearing that allows for multi-axis angular misalignment. Select a clevis fork for one-plane linkage, rod end for self-alignment.
Q: Can you manufacture DIN 71752 or ISO 8140 clevis forks?
A: Yes. We produce our clevis forks according to DIN 71752 (fork head) and ISO 8140 (threaded clevis). Thread sizes are M4 to M48. Customer drawings may specify non-standard dimensions.
Q: What is the maximum load capacity of your clevis forks?
A: Load capacity is dependent of the pin diameter, material grade and prong geometry. A 30 mm 4140 steel pin in a C45 clevis fork has a working load of 78 kN at 4:1 safety factor. Please provide the application load requirements for our engineers to validate the design.
Q: Do you have clevis pins and hardware to match?
A: Yes. We also sell complete assemblies of clevis pins, cotter pins, R-clips and lock nuts. Pins can be induction hardened at 55-60 HRC for maximum wear resistance.
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