How to choose the right sfu1605 ball screw for my machine?

An SFU1605 ball screw has a 16 mm nominal screw diameter and a 5 mm lead. It is a common choice for compact CNC machines, engraving equipment, 3D printers, automation systems and other axes that require efficient rotary-to-linear motion.

However, the model code alone is not enough to confirm that an SFU1605 will work in a particular machine. The nut configuration, axial load, stroke, speed, accuracy grade, shaft-end machining and support arrangement must also be checked.

Reading the SFU1605 Model Code

SFU1605 can be divided into three parts:

• SFU: A standard flanged single-nut ball screw structure.
• 16: The nominal diameter of the screw shaft is 16 mm.
• 05: The lead is 5 mm, so the nut travels 5 mm for each complete screw revolution.

The flange is part of the ball nut and provides a mounting surface for connecting the nut to the moving table or nut housing.

A complete model may also include a suffix indicating the number of loaded ball circuits or another structural detail. Different SFU1605 nut versions can therefore have different nut lengths, load ratings and flange dimensions even though they use the same 16 mm diameter and 5 mm lead.

First Confirm Whether 16 mm × 5 mm Is Suitable

Before selecting the accuracy grade or machining details, confirm that the basic diameter and lead fit the machine.

The 5 mm Lead

With a 5 mm lead, the theoretical linear travel is:

The 5 mm lead provides a practical balance between linear travel per revolution and drive torque. If the machine requires substantially faster travel at the same motor speed, a 10 mm lead model such as SFU1610 may be more appropriate. If finer mechanical movement per motor revolution is the priority, a smaller lead may be considered.

Changing the lead also changes the model. An SFU1605 cannot be ordered with a 10 mm lead and still be called SFU1605.

The 16 mm Diameter

A 16 mm screw is commonly used in compact and medium-size axes, but suitability depends on more than the moving weight. A long screw may be limited by critical speed, shaft deflection or buckling before the ball nut reaches its rated load.

For a longer stroke, higher axial load or higher rotational speed, SFU2005 or SFU2505 may provide a more suitable shaft diameter. Both still have a 5 mm lead, so they do not create faster linear motion than SFU1605 at the same rotational speed.

Calculate the Actual Axial Load

Ball screws are designed primarily to transmit axial force. The load calculation should include more than the mass of the moving table.

For a horizontal axis, consider:

• Acceleration and deceleration force
• Cutting or process force acting along the screw axis
• Friction in the guide system
• Seal and lubrication resistance
• Impact or other external loads

For a vertical axis, also include:

• The gravitational force of the moving mass
• Acceleration in both upward and downward directions
• Loads that may occur during emergency stopping
• Any counterweight, brake or balancing mechanism

The ball screw should not carry the table weight as a radial load. Linear guides or another guide mechanism should support the moving mass and overturning moments.

After calculating the operating loads, compare them with the basic dynamic load rating, basic static load rating and permissible axial load of the exact SFU1605 nut configuration. Do not use the rating of a different circuit version simply because the diameter and lead are the same.

Choose the Required Accuracy Grade

The required accuracy depends on how the machine controls position and how much travel error the application can accept.

DLY commonly supplies SFU ball screws in cold-rolled C7 accuracy. C7 is suitable for many CNC auxiliary axes, engraving machines, 3D printers, positioning tables and general automation equipment.

For applications requiring higher lead accuracy, a C5 precision-ground ball screw can be considered. The decision should be based on the permissible travel deviation and positioning requirements rather than a general assumption that every machine needs the highest available grade.

Accuracy grade and repeatability are related but not identical. Repeatability can also be affected by axial clearance, preload, bearing arrangement, guide accuracy, coupling installation, machine rigidity and control feedback.

Confirm the Required Stroke and Total Length

Required travel is not the same as the overall screw length. The total length must include:

• Usable machine stroke
• Ball nut body length
• Safety allowance at both ends of the stroke
• Fixed-side shaft-end machining
• Supported-side shaft-end machining
• Coupling and locknut installation space
• Any required protective cover or mounting clearance

The ball nut must not run beyond the finished thread section. Allow sufficient safety distance so that normal operation, homing errors or overtravel do not cause the nut to leave the raceway.

For long or high-speed axes, the effective unsupported length must also be checked. Increasing the overall length without checking critical speed can result in screw whirling, vibration and unstable positioning.

Check Speed and Critical Speed

The required screw rotational speed can be estimated from:

For example, an axis speed of 3,000 mm/min requires approximately 600 rpm with an SFU1605.

The calculated screw speed must remain below the permissible rotational speed for the selected screw length and support arrangement. A fixed–fixed support arrangement generally provides better high-speed stability than fixed–supported or fixed–free arrangements, but it also requires more careful installation and thermal-expansion control.

If the required speed is too high for a long 16 mm screw, possible solutions include:

• Selecting a larger screw diameter
• Using a larger lead to reduce screw rpm
• Changing the support-bearing arrangement
• Reducing the unsupported length
• Using a rotating-nut structure for an appropriate long-travel application

Match the Nut Dimensions to the Machine

An existing machine may require a specific SFU1605 nut version. Before ordering, compare the drawing with the installation space and check:

• Nut body diameter
• Overall nut length
• Flange outside diameter
• Flange thickness and shape
• Mounting-hole quantity and bolt-circle diameter
• Lubrication port position
• Space for seals and ball-return components

The circuit-number suffix should not be ignored. Two nuts described only as "SFU1605" may not have identical outside dimensions or load capacity.

For replacement projects, send the complete model number and a dimensioned drawing or clear photos of the existing nut. This is more reliable than confirming only "1605."

Specify the Shaft-End Machining

A ball screw cannot be installed correctly until both shaft ends match the bearings, support units, locknut and motor coupling.

DLY can provide length customization and shaft-end machining, including steps, threads, keyways, flats and other features according to the confirmed drawing.

Common support-unit arrangements include BK/BF, FK/FF and EK/EF. When ordering, confirm:

• Fixed-side support-unit model
• Supported-side support-unit model
• Bearing-seat diameters and lengths
• Locknut thread
• Coupling diameter and engagement length
• Motor-side keyway or flat, if required
• Overall length and finished-thread length

DLY also supplies matching ball screw support units for common mounting arrangements.

Consider the Operating Environment

Dust, chips, moisture and insufficient lubrication can shorten ball screw life. Standard nut seals provide limited protection but should not be treated as a complete enclosure for a contaminated machine environment.

For CNC machining, woodworking or other applications with airborne particles, use bellows, telescopic covers or another suitable protective structure. Select a lubricant compatible with the machine speed, load, temperature and maintenance schedule.

If the machine operates in an unusual temperature, vacuum, cleanroom or corrosive environment, confirm the material, lubricant and sealing requirements separately instead of assuming a standard SFU1605 is suitable.

When SFU1605 Is Not the Right Choice

Consider another model when:

• The 16 mm shaft is insufficient for the required length, load or speed.
• The machine requires more than 5 mm of travel per revolution.
• A double-nut structure is required for greater rigidity or preload adjustment.
• The existing nut flange or overall dimensions do not match SFU1605.
• The required axial load exceeds the rating of the available SFU1605 nut configuration.
• A special circulation structure or compact internal-circulation nut is required.

You can compare the SFU1605 with other models on the DLY SFU ball screw page.

Information Needed Before Ordering

To confirm the correct SFU1605 configuration, provide:

• Machine type and axis direction
• Moving mass and external axial force
• Required stroke
• Required linear speed and acceleration
• Accuracy requirement
• Overall screw length
• Nut model or nut dimension drawing
• Support-unit models
• Shaft-end machining drawing
• Operating environment and lubrication requirements

Conclusion

SFU1605 is a standard flanged single-nut ball screw with a 16 mm nominal shaft diameter and a 5 mm lead. It is suitable for many compact motion systems, but the final selection must be based on the exact nut configuration, axial load, stroke, speed, accuracy, mounting dimensions and shaft-end requirements.

For general automation and CNC applications, a cold-rolled C7 SFU1605 is often a practical starting point. Where higher lead accuracy is required, a C5 ground version can be evaluated according to the machine's positioning requirements.

DLY supplies 1605 ball screws with length customization and shaft-end machining based on the confirmed application and drawing.

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