Fastening material
Cylinder
Fastening material for pneumatic cylinders covers flex couplings (FK) and flex couplings with mounting plate (FKB) for connecting the cylinder rod to the driven element. Flex couplings compensate for minor misalignment between the rod and the mating part, protecting seals and guides from transverse loading. Available in zinc-plated steel and stainless steel (1.4305, 1.4301) with thread sizes from M 4 to M 36x2, covering cylinder bores from 8/10 mm up to 160/200 mm.
| Type | Thread | Cylinder bore | Material |
|---|---|---|---|
| FK 8/10 / FK 8/10 ES | M 4 | 8-10 mm | Zinc-plated / 1.4305 |
| FK 12/16 / FK 12/16 ES | M 6 | 12-16 mm | Zinc-plated / 1.4305 |
| FK 20 / FK 20 ES | M 8 | 20 mm | Zinc-plated / 1.4305 |
| FK 25/32 / FK 25/32 ES | M 10x1.25 | 25-32 mm | Zinc-plated / 1.4305 |
| FK 40 / FK 40 ES | M 12x1.25 | 40 mm | Zinc-plated / 1.4305 |
| FK 50/63 / FK 50/63 ES | M 16x1.5 | 50-63 mm | Zinc-plated / 1.4305 |
| FK 80/100 / FK 80/100 ES | M 20x1.5 | 80-100 mm | Zinc-plated / 1.4305 |
| FK 125 / FK 125 ES | M 27x2 | 125 mm | Zinc-plated / 1.4305 |
| FK 160/200 / FK 160/200 ES | M 36x2 | 160-200 mm | Zinc-plated / 1.4305 |
The flex coupling is selected to match the thread on the cylinder rod. Standard zinc-plated versions suit dry and oil-present production environments. For food, pharmaceutical, or outdoor applications, the stainless steel variants (ES, grade 1.4305 or 1.4301) are recommended. Flex couplings with mounting plate (FKB) provide an additional bearing face and simplify installation on guides or slides.
Typical applications: Connecting cylinder rods to linear guides, valve actuation, clamping and gripping fixtures, and anywhere that axial misalignment between the drive and the load would reduce the service life of cylinder seals.