When buying a hydraulic cylinder, specifying only the bore diameter and stroke is usually not enough. A hydraulic cylinder supplier also needs information about working pressure, piston rod diameter, mounting dimensions, operating speed, hydraulic fluid, temperature, and working environment.

A complete specification helps the manufacturer select the correct cylinder tube, piston rod, seals, ports, and mounting configuration. It also reduces the risk of receiving a cylinder that fits the machine but does not provide the required performance.

For a custom hydraulic cylinder, buyers should consider the following parameters.

1. Hydraulic Cylinder Bore

The cylinder bore determines the piston area and has a direct effect on the available hydraulic force.

For a standard single-rod cylinder, the theoretical extension force can be calculated as:

Force = Pressure x Piston Area

Piston Area = 3.14 x Bore² / 4

For example, a larger bore produces more force at the same hydraulic pressure.

If the required force and working pressure are already known, the buyer can provide those values to the manufacturer instead of specifying the bore. The manufacturer can then calculate a suitable cylinder bore.

2. Stroke Length

Stroke is the distance that the piston rod needs to travel between the fully retracted and fully extended positions.

For example:

Required stroke: 800 mm

Stroke affects more than the movement distance. A long stroke can increase:

• Piston rod buckling risk
• Overall cylinder length
• Installation space
• Rod guidance requirements
• Hydraulic oil volume

For long-stroke hydraulic cylinders, the piston rod diameter should therefore be checked together with the stroke.

3. Piston Rod Diameter

The piston rod diameter affects the mechanical strength and stability of the cylinder.

If the buyer already has a defined rod diameter, it should be included in the specification. Otherwise, the manufacturer can select it according to:

• Cylinder bore
• Stroke
• Load
• Mounting arrangement
• Buckling risk
• Side loading
• Operating conditions

For long-stroke cylinders, rod diameter is particularly important because the rod may be subjected to compression and buckling.

4. Working Pressure

The buyer should specify the normal working pressure and, where applicable, the maximum operating pressure.

For example:

Working pressure: 16 MPa

Maximum operating pressure: 20 MPa

The pressure actually available at the cylinder may be lower than the hydraulic pump's rated pressure because of pressure losses in valves, hoses, filters, and other components.

The cylinder should therefore be designed according to the actual hydraulic circuit rather than the pump rating alone.

5. Required Cylinder Force

If the cylinder is being designed for a specific load, the required force should be provided.

For example:

Required extension force: 100 kN

For a pulling application, the required retraction force should also be specified because a single-rod hydraulic cylinder has a smaller effective area during retraction.

Providing the required force allows the manufacturer to evaluate the appropriate bore and rod diameter.

6. Hydraulic Cylinder Type

The buyer should specify the required cylinder configuration.

Common types include:

• Single-acting hydraulic cylinder
• Double-acting hydraulic cylinder
• Single-rod cylinder
• Double-rod cylinder
• Telescopic hydraulic cylinder
• Tie-rod hydraulic cylinder
• Welded hydraulic cylinder
• Custom industrial hydraulic cylinder

A double-acting single-rod cylinder is widely used when hydraulic pressure is required for both extension and retraction.

7. Mounting Type and Dimensions

Mounting is one of the most important parameters for a custom hydraulic cylinder.

Common mounting configurations include:

• Clevis mounting
• Trunnion mounting
• Flange mounting
• Foot mounting
• Cross-tube mounting
• Spherical eye mounting
• Threaded mounting

The buyer should provide either the required mounting type or a dimensioned installation drawing.

The mounting arrangement affects how the cylinder transfers force to the machine and may also influence side loading and rod stability.

8. Retracted and Extended Length

When installation space is limited, buyers should specify the required overall dimensions.

Important dimensions may include:

• Retracted length
• Extended length
• Mounting center-to-center distance
• Rod extension
• Mounting width
• Clevis dimensions
• Overall cylinder diameter

Two hydraulic cylinders with the same bore and stroke can still have different overall dimensions because of their mounting and construction.

9. Hydraulic Port Size and Location

The hydraulic ports must match the machine's hydraulic connections.

Buyers should specify:

• Port size
• Thread or connection standard
• Port location
• Port orientation

Depending on the market and hydraulic system, different connection standards may be required.

Port position is particularly important when the cylinder is installed in a confined space.

10. Cylinder Tube Material and Bore Finish

The cylinder tube forms the internal running surface for the piston and seals.

For precision hydraulic cylinders, buyers may specify:

• Tube material
• Bore diameter
• ID tolerance
• Roundness
• Straightness
• Surface roughness
• Honing requirements

A precision honed tube provides a controlled internal diameter and surface finish for reliable piston and seal movement.

For a hydraulic cylinder manufacturer, tube accuracy is not simply a material specification. It is directly related to sealing performance, friction, wear, and cylinder service life.

11. Piston Rod Material

The piston rod material should match the mechanical and environmental requirements of the application.

Common materials include:

• CK45
• C45
• 42CrMo
• 4140
• Stainless steel

Material selection depends on load, fatigue requirements, corrosion exposure, heat treatment, surface treatment, and operating conditions.

For general hydraulic cylinder applications, CK45 is commonly used. Higher-strength alloy steels may be considered for more demanding mechanical loads.

12. Piston Rod Surface Treatment

The surface condition of the piston rod is important because it works directly with the rod seal.

Common surface treatments include:

• Hard chrome plating
• Induction hardening
• Chrome plating with additional surface treatment
• Stainless steel solutions
• Application-specific coatings

The buyer should consider:

• Surface hardness
• Surface roughness
• Wear resistance
• Corrosion resistance
• Seal compatibility

A suitable rod material alone does not guarantee good sealing performance. Surface finish and treatment also need to match the application.

13. Seal Type and Material

Seal selection depends on the actual hydraulic and environmental conditions.

The buyer should provide:

• Hydraulic fluid
• Working pressure
• Operating temperature
• Cylinder speed
• Seal material requirements

Common hydraulic cylinder seal materials include polyurethane, NBR, PTFE, and other application-specific materials.

If the buyer does not have a fixed seal specification, providing the fluid, pressure, temperature, and speed allows the manufacturer to select an appropriate sealing system.

14. Hydraulic Fluid

The hydraulic fluid should be specified because it affects seal compatibility and operating performance.

Examples include:

• Mineral hydraulic oil
• Water-glycol fluids
• Biodegradable hydraulic fluids
• Other application-specific hydraulic fluids

The hydraulic fluid should be considered when selecting the seal material, corrosion protection, and operating temperature range.

15. Operating Temperature

The expected temperature range should be included in the cylinder specification.

For example:

Operating temperature: -20°C to +80°C

Temperature affects:

• Seal performance
• Hydraulic oil viscosity
• Lubrication
• Material behavior
• Cylinder service life

A cylinder used outdoors in a cold climate may require a different design from one operating continuously in a controlled indoor environment.

16. Cylinder Speed

Cylinder speed affects seal performance, friction, heat generation, and hydraulic flow requirements.

The buyer should specify:

• Extension speed
• Retraction speed
• Maximum speed
• Operating cycle

Cylinder speed is related to hydraulic flow and effective piston area.

For a given flow rate:

Cylinder Speed = Flow Rate / Effective Piston Area

Therefore, changing the cylinder bore can affect both force and operating speed.

17. Load Direction and Side Load

The manufacturer should know how the cylinder will be loaded.

The application may involve:

• Axial compression
• Axial tension
• Alternating loads
• Impact loads
• Side loads

Hydraulic cylinders are primarily designed for axial loading. Significant side loading can increase wear on the piston rod, rod seal, guide ring, and cylinder tube.

If side loading cannot be avoided, the mounting and guidance system should be considered during the cylinder design.

18. Working Environment

The operating environment can affect cylinder material and surface treatment.

The buyer should indicate whether the cylinder will be used in:

• Construction machinery
• Agricultural machinery
• Mining equipment
• Steel plants
• Industrial machinery
• Marine environments
• Outdoor equipment
• High-humidity environments
• Corrosive environments
• Dusty environments

For corrosive or outdoor applications, additional corrosion protection may be required for the piston rod and other exposed components.

19. Service Life and Duty Cycle

For production equipment, buyers should provide the expected operating cycle where possible.

Useful information includes:

• Cycles per hour
• Cycles per day
• Expected total cycles
• Average stroke
• Load pattern
• Operating speed
• Continuous or intermittent operation

A hydraulic cylinder used occasionally and one operating continuously in an automated production line may require different component specifications.

20. Quality and Inspection Requirements

Buyers may also specify inspection requirements before production.

Typical requirements include:

• Dimensional inspection
• Bore diameter inspection
• Piston rod diameter inspection
• Surface roughness inspection
• Pressure testing
• Leakage testing
• Material certificates
• Chrome thickness inspection
• Weld inspection

The inspection requirements should match the application and purchase specification.

What Should Buyers Include in a Hydraulic Cylinder RFQ?

A practical hydraulic cylinder RFQ should include as many of the following parameters as possible:

Parameter	Example Specification
Cylinder type	Double-acting
Bore	100 mm
Stroke	500 mm
Rod diameter	56 mm
Working pressure	16 MPa
Required force	100 kN
Mounting	Clevis
Retracted length	Drawing required
Extended length	Drawing required
Port size	According to hydraulic system
Port location	According to drawing
Tube material	Specified grade
Bore tolerance	Required tolerance
Bore finish	Honed
Rod material	CK45 / 42CrMo
Rod treatment	Hard chrome plated
Hydraulic fluid	Mineral hydraulic oil
Temperature	-20°C to +80°C
Extension speed	100 mm/s
Retraction speed	150 mm/s
Environment	Outdoor
Seal requirement	Application dependent
Quantity	Required quantity
Inspection	Required inspection standard

Not every parameter needs to be determined by the buyer.

If some specifications are unknown, the buyer can provide the required force, working pressure, stroke, speed, installation dimensions, hydraulic fluid, and operating environment. The manufacturer can then complete the engineering selection.

What Information Should You Send for a Custom Hydraulic Cylinder?

Instead of sending:

Please quote a 100 mm x 500 mm hydraulic cylinder.

A more useful RFQ would provide:

Double-acting hydraulic cylinder
Required extension force: 100 kN
Working pressure: 16 MPa
Stroke: 500 mm
Extension speed: 100 mm/s
Retraction speed: 150 mm/s
Hydraulic fluid: mineral hydraulic oil
Operating temperature: -20°C to +80°C
Application: outdoor industrial equipment
Piston rod: hard chrome plated
Installation drawing: attached
Quantity: 50 pcs

This information gives the hydraulic cylinder manufacturer a much clearer basis for selecting the bore, piston rod, honed tube, seals, mounting configuration, and hydraulic ports.

Common Hydraulic Cylinder Specification Mistakes

Only specifying bore and stroke

Bore and stroke do not define the complete hydraulic cylinder design.

Using pump pressure as cylinder working pressure

The actual pressure at the cylinder can be affected by losses throughout the hydraulic circuit.

Ignoring mounting dimensions

A cylinder with the correct bore and stroke may still not fit the machine.

Not specifying hydraulic fluid

Seal selection depends partly on the hydraulic medium.

Ignoring operating temperature

Temperature can affect seal performance, oil viscosity, and component service life.

Choosing rod diameter without checking stroke

A long-stroke cylinder requires a separate check for piston rod stability and buckling.

Not describing the application

The same bore and stroke may require different designs depending on load, speed, environment, and duty cycle.

FAQ

What are the most important hydraulic cylinder parameters?

The main parameters are bore, stroke, working pressure, required force, piston rod diameter, mounting dimensions, cylinder type, port configuration, hydraulic fluid, operating temperature, and operating speed.

What information should I provide when requesting a hydraulic cylinder quote?

At minimum, provide the required force or load, working pressure, stroke, mounting dimensions, operating speed, hydraulic fluid, and working environment. An installation drawing is especially useful for custom hydraulic cylinders.

Does the buyer need to specify the piston rod diameter?

Not always. If the rod diameter is not fixed, the manufacturer can select it based on bore, stroke, load, mounting arrangement, and buckling requirements.

Should the hydraulic cylinder bore tolerance be specified?

For precision applications, yes. Bore diameter, ID tolerance, roundness, straightness, and surface roughness can affect piston movement and seal performance.

Why should operating temperature be specified?

Because temperature affects hydraulic fluid viscosity, seal behavior, lubrication, and cylinder service life.

Is a technical drawing necessary?

For a standard cylinder, a complete drawing may not always be necessary. For a custom hydraulic cylinder, a dimensioned installation drawing can prevent misunderstandings about mounting, overall length, port position, and connection dimensions.

Conclusion

A hydraulic cylinder specification should contain much more than bore x stroke. The manufacturer needs enough information to understand the cylinder's mechanical load, hydraulic conditions, installation requirements, and operating environment.

The key parameters include bore, stroke, working pressure, required force, piston rod diameter, mounting, ports, tube and rod specifications, seals, hydraulic fluid, speed, temperature, and application conditions.

For custom hydraulic cylinders, a complete RFQ allows the manufacturer to select the appropriate honed cylinder tube, piston rod, sealing system, and mounting configuration from the beginning. This reduces design changes and helps ensure that the finished cylinder matches the actual machine requirements.