The SFU1605 model code identifies a ball screw with a nominal shaft diameter of 16 mm and a nominal lead of 5 mm. It does not specify a fixed pitch or lead accuracy.
DLY commonly supplies the SFU1605 as a C7 rolled ball screw. When higher positioning accuracy is required, a C5 ground version can be selected. The required accuracy grade should therefore be stated separately when requesting a quotation.
What Does SFU1605 Mean?
- SFU: standard flanged single ball nut series
- 16: nominal screw shaft diameter of 16 mm
- 05: nominal lead of 5 mm per revolution
In theory, rotating an SFU1605 screw through one complete revolution moves the ball nut 5 mm. Ten revolutions produce 50 mm of nominal linear travel, while 100 revolutions produce 500 mm.
The actual travel may differ slightly from the nominal value. The permitted difference is controlled by the ball screw's specified accuracy grade.
Pitch or Lead: Which Term Is Correct?
Pitch is the axial distance between adjacent thread grooves. Lead is the linear distance traveled by the nut during one complete revolution of the screw.
For a typical single-start SFU1605 ball screw, the pitch and lead are numerically the same: 5 mm. However, the parameter used to describe positioning travel and accuracy is normally called lead or lead accuracy.
Key point: "05" indicates a nominal 5 mm lead. It does not indicate how accurately the screw produces that travel.
What Is the Lead Accuracy of an SFU1605?
There is no single lead-accuracy value for every SFU1605. The answer depends on whether the screw is supplied as C7 rolled, C5 ground or another specified accuracy grade.
| Accuracy Grade | DLY Supply Type | Lead Accuracy Information | Typical Selection |
|---|---|---|---|
| C7 | Rolled ball screw | Confirm according to the ordered specification and inspection standard | General automation, transfer equipment and machines using controller compensation |
| C5 | Ground ball screw option | ±0.018 mm per 300 mm | CNC feed axes and higher-accuracy positioning systems |
| C3 | Higher-precision ground option subject to confirmation | ±0.008 mm per 300 mm | Precision equipment with stricter positioning requirements |
Values such as "±0.05 mm per 300 mm" should not be presented as the universal accuracy of an SFU1605. If that value appears in a quotation or catalog, it applies only to the stated product specification and inspection method.
How to Understand ±0.018 mm per 300 mm
For a C5 ball screw specified at ±0.018 mm per 300 mm, the actual travel over a nominal 300 mm reference length is permitted to deviate from the specified travel within the applicable tolerance definition.
This should not be interpreted as saying that every 5 mm revolution independently has an error of ±0.018 mm. Lead accuracy is evaluated over a defined travel range using the applicable accuracy standard and inspection method.
The complete inspection may consider several characteristics, such as:
- Representative travel deviation over the useful stroke
- Variation within a specified travel length
- Short-range travel variation
- Useful stroke and reference travel
Lead Accuracy Is Not the Same as Backlash
Lead accuracy and backlash affect positioning in different ways.
| Item | Meaning | Main Effect |
|---|---|---|
| Lead accuracy | Difference between commanded and actual travel over a distance | Absolute positioning accuracy |
| Axial clearance | Relative axial movement between the screw and nut | Lost motion during direction reversal |
| Preload | Internal load used to reduce clearance and increase rigidity | Reversal response, rigidity, torque and heat |
| Repeatability | Ability to return repeatedly to the same position | Consistency of repeated positioning |
A ball screw can have good repeatability but still show a systematic travel deviation over a long stroke. Conversely, a high lead-accuracy screw can still lose motion during reversal if axial clearance, coupling play or bearing movement is present.
Does a C7 SFU1605 Work for CNC Machines?
A C7 rolled SFU1605 may be suitable for CNC routers, engraving machines, woodworking equipment and other systems where the positioning requirement is compatible with its specified accuracy.
Some control systems can compensate for repeatable lead error using measured correction data. Compensation cannot fully correct mechanical backlash, weak support-bearing rigidity, misalignment, thermal growth or structural deformation.
A C5 ground SFU1605 is more appropriate when the machine requires tighter absolute positioning, more controlled travel accuracy or verified precision over the working stroke.
What Affects the Actual Positioning Accuracy?
The accuracy grade of the ball screw is only one part of the complete positioning system. Actual machine accuracy is also affected by:
- Axial clearance or preload of the ball nut
- Rigidity and preload of the fixed-side support bearings
- Coupling torsional stiffness and connection play
- Ball screw installation alignment
- Machine-frame and mounting rigidity
- Screw temperature and thermal expansion
- Encoder resolution and motor-control accuracy
- Load direction and changing external force
- Wear, lubrication and contamination
For this reason, selecting a C5 ball screw does not automatically guarantee that the completed machine will position within ±0.018 mm over every 300 mm under all operating conditions.
How to Select the Required SFU1605 Accuracy
Choose C7 When:
- The machine has a general positioning requirement
- Cost and delivery time are important
- The system can use position compensation
- A rolled ball screw is acceptable
Choose C5 When:
- The axis requires higher absolute positioning accuracy
- The useful stroke must have controlled travel deviation
- The machine is designed around a ground ball screw
- An accuracy inspection report is required
View the DLY SFU ball screw series for available diameters, leads and accuracy options.
Information to Confirm Before Ordering
Do not request only "SFU1605" if lead accuracy is important. Include:
- Required accuracy grade: C5 or C7
- Overall screw length and useful stroke
- Rolled or ground manufacturing requirement
- Axial clearance or preload requirement
- End-machining drawing
- Support-unit arrangement
- Required positioning accuracy and repeatability
- Whether an inspection report is required
Conclusion
An SFU1605 ball screw has a nominal diameter of 16 mm and a nominal lead of 5 mm. Its model number does not define its lead accuracy.
DLY commonly supplies the SFU1605 in C7 rolled accuracy, while C5 ground versions are available for higher positioning requirements. For DLY C5 ball screws, the confirmed lead-accuracy value is ±0.018 mm per 300 mm. Always specify the required accuracy grade and useful stroke when ordering.
Need an SFU1605 ball screw?
Send DLY the required length, accuracy grade, end-machining drawing, preload or clearance requirement and order quantity for specification confirmation.
