According to the raceway manufacturing process, ball screws are mainly divided into ground ball screws and rolled ball screws.
The main difference is how the helical raceway on the screw shaft is formed. This difference influences the achievable lead accuracy, production efficiency, available length, cost and typical application range.
This article compares ground ball screws vs rolled ball screws by manufacturing process, accuracy, surface quality, strength and service life, length and customization, cost and suitable applications.
| Comparison Item | Ground Ball Screw | Rolled Ball Screw |
|---|---|---|
| Raceway formation | Material removed by precision grinding | Raceway formed by plastic deformation between rolling dies |
| Typical DLY accuracy | C5 | C7 |
| Surface consistency | Precisely finished raceway surface | Stable industrial surface after rolling and finishing |
| Production efficiency | Lower because of multiple grinding and inspection stages | Higher and suitable for volume production |
| Available length | Influenced by grinding-machine capacity and accuracy requirements | More practical for long standard shafts, subject to manufacturing and transport limits |
| Cost | Generally higher | Generally more economical |
| Typical use | Precision positioning and machine-tool axes | General automation and cost-sensitive industrial motion |
Comparison of Manufacturing Processes
How Are Ground Ball Screws Made?
Ground ball screws use a precision grinding process to form and finish the screw-shaft raceway. After the shaft blank is prepared and rough-machined, it undergoes the specified heat-treatment process. The hardened raceway is then finished using a thread-grinding machine.
Grinding removes a controlled amount of material during multiple passes. This allows the raceway profile, lead and surface condition to be corrected more precisely than with a standard rolling process.
The manufacturing sequence may include:
- Material preparation and shaft straightening
- Rough machining of the shaft
- Heat treatment and stress control
- Precision thread grinding
- Straightness and lead inspection
- Nut matching, assembly and running inspection
- End machining according to the installation drawing
Because thread grinding and inspection require more processing time, ground ball screws generally have a longer manufacturing cycle than rolled ball screws. The actual lead time depends on diameter, lead, length, accuracy grade, nut structure, quantity and end-machining requirements rather than one fixed number of days.
How Are Rolled Ball Screws Made?
Rolled ball screws form the helical raceway through cold rolling. A prepared shaft blank passes between rolling dies, and controlled pressure plastically deforms the material into the required raceway profile without cutting away the same amount of material as thread grinding.
The rolling process provides high manufacturing efficiency and is suitable for standardized production. After raceway formation, the shaft undergoes the required heat treatment, straightening, surface finishing and inspection processes.
The final performance of a rolled ball screw depends not only on the rolling stage but also on:
- Rolling-die condition and raceway consistency
- Raw-material quality
- Heat-treatment control
- Shaft straightening
- Raceway cleaning and surface finishing
- Ball and nut matching
- Axial-clearance and running-torque inspection
Rolled ball screws are widely used for volume production and long industrial shafts where C7 accuracy provides sufficient motion performance.
Comparison of ground and rolled ball screw manufacturing methods
Accuracy and Applicable Scenarios
Accuracy Grade
Ground ball screws are selected when tighter lead control is required. Depending on the manufacturer's production capability and product specification, ground screws may be produced in accuracy grades such as C5 and higher precision levels.
DLY commonly supplies C5 ground ball screws for precision positioning applications.
Rolled ball screws are commonly supplied in C7 accuracy for general industrial equipment. Lower-precision rolled grades may also be available in the wider market, while achieving a higher grade through rolling requires more demanding process and inspection control.
DLY commonly supplies C7 cold-rolled ball screws for automation equipment, packaging machinery, CNC routers and other cost-sensitive industrial applications.
Important: Accuracy-grade values must be interpreted according to the applicable standard, measurement length and manufacturer specification. A grade such as C5 or C7 should not be converted into one universal deviation value without confirming these conditions.
Ball screw accuracy also should not be confused with complete axis accuracy. Couplings, support bearings, end-machining runout, installation alignment, preload, temperature and control compensation all influence the final movement of the machine.
Applicable Scenarios
Ground ball screws are suitable for equipment in which lead accuracy and positioning control are critical, including:
- Precision CNC machine tools
- Grinding and inspection equipment
- Semiconductor manufacturing equipment
- Precision positioning stages
- Measuring and optical systems
- High-accuracy automation axes
Rolled ball screws are more suitable for industrial applications that require efficient linear transmission and repeatable motion without the tighter lead accuracy of a ground screw, including:
- Packaging equipment
- CNC routers
- Woodworking machinery
- Material-handling systems
- General automation equipment
- Industrial linear modules
High load alone does not automatically require a ground ball screw. Load capacity is primarily determined by the screw diameter, ball diameter, nut structure, number of loaded circuits, material, heat treatment and actual operating conditions. Both rolled and ground ball screws can be designed for different load requirements.
Surface Quality and Friction Performance
A ground ball screw has a raceway finished by precision grinding. This generally provides tighter control of raceway geometry and surface consistency, supporting stable motion in applications with demanding accuracy and running requirements.
A rolled ball screw receives its raceway profile directly from the rolling dies. Die condition, forming pressure, heat treatment and subsequent surface finishing all influence the final raceway condition.
Rolled shafts normally require appropriate cleaning and finishing after forming and heat treatment. This helps remove surface residue and supports consistent contact between the balls, screw raceway and nut raceway.
However, manufacturing method alone does not determine the total friction or noise of the assembly. Important additional factors include:
- Raceway-profile accuracy
- Ball diameter and grade
- Nut matching
- Axial clearance or preload
- Lubricant type and quantity
- Circulation-component condition
- Shaft straightness and installation alignment
A correctly manufactured and lubricated C7 rolled ball screw can provide smooth motion for many industrial applications. A ground screw is preferred when tighter lead control and more demanding motion consistency are required.
Strength and Life
Cold rolling plastically deforms the shaft material and creates a continuous material flow around the raceway. This can provide favorable surface and residual-stress characteristics when the rolling and heat-treatment processes are properly controlled.
It is not accurate, however, to state that every rolled ball screw has a fixed percentage increase in tensile strength or service life compared with every ground ball screw. Fatigue life cannot be determined from the raceway-forming method alone.
The service life of both rolled and ground ball screws depends on:
- Actual equivalent axial load
- Basic dynamic load rating
- Shock and vibration
- Lubrication condition
- Contamination protection
- Mounting alignment
- Operating speed and duty cycle
- Preload or axial clearance
- Material and heat-treatment consistency
A ground ball screw is not inherently weaker or shorter-lived than a rolled ball screw. Likewise, a rolled ball screw is not automatically more durable. The correct comparison must use the load ratings, expected operating conditions and life calculation for the specific models being considered.
Length and Customization Capability
The available length of a ground ball screw is influenced by the capacity of the thread-grinding equipment, heat-treatment control, straightness requirements and the accuracy that must be maintained over the usable travel.
Ground ball screws can be customized in diameter, lead, nut form, preload, shaft length and end machining, but longer shafts become more difficult and costly to grind and inspect to a tight accuracy grade.
Rolled ball screws are more practical for producing long standard shafts because the raceway-forming process is efficient and does not require grinding the full thread length in multiple precision passes.
DLY can supply selected rolled ball screw shafts with lengths up to approximately 6 meters, subject to diameter, lead, straightness, manufacturing feasibility, transport and packaging requirements. Long-shaft capability should be confirmed for the specific model rather than treated as a universal specification.
Both manufacturing types can support customized end machining. Typical options include:
- Fixed-end and supported-end bearing seats
- External or internal threads
- Locknut and retaining-ring grooves
- Coupling sections
- Keyways and wrench flats
- Special lengths based on customer drawings
Cost and Production Efficiency
Ground ball screws generally have a higher unit cost because precision grinding, repeated measurement, correction and matching require more production time and specialized equipment.
The final ground ball screw price depends on:
- Accuracy grade
- Screw diameter and lead
- Total and threaded length
- Nut structure and preload
- End-machining complexity
- Inspection and documentation requirements
- Order quantity
Rolled ball screws have higher production efficiency and are more suitable for standardized batch production. They usually provide a lower unit cost when C7 accuracy meets the application requirements.
Cost should be evaluated at the machine-system level. Selecting a ground screw for an application that does not require C5 accuracy may add unnecessary expense. Selecting a rolled screw for an axis that depends on tighter lead control may require additional compensation or may fail to achieve the required positioning result.
Selection Suggestions
Ground ball screws are generally suitable when the machine requires tighter lead accuracy, controlled positioning over the travel and more demanding motion consistency.
Rolled ball screws are generally suitable when the machine requires reliable linear transmission, economical volume supply and standard industrial accuracy.
| Application Requirement | Suggested Direction | Reason |
|---|---|---|
| Tight lead accuracy over the working stroke | Ground ball screw | Grinding provides tighter control of lead and raceway geometry |
| General automation positioning | Rolled ball screw | C7 accuracy is sufficient for many industrial axes |
| High-volume standard production | Rolled ball screw | Efficient raceway forming supports batch production |
| Precision machine-tool or inspection axis | Ground ball screw | Tighter lead control better supports precision positioning |
| Long, cost-sensitive industrial axis | Rolled ball screw | Long standard shafts are generally more economical to produce |
| High axial load | Calculate both options | Load capability depends on size and nut design, not only the manufacturing method |
Before making the final choice, engineers should consider accuracy, load, speed, stroke, shaft length, critical speed, buckling, nut structure, axial clearance, service life, cost and delivery requirements together.
Summary
Ground and rolled ball screws use different methods to create the screw-shaft raceway, and each method has a suitable application range.
- Ground ball screw: provides tighter lead control and a precision-ground raceway, making it suitable for machine tools, inspection systems and other high-accuracy positioning equipment.
- Rolled ball screw: provides higher production efficiency and a more economical cost, making it suitable for general automation, packaging machinery, CNC routers and long industrial axes.
The manufacturing method should not be used as the only indicator of load capacity, strength, noise or service life. These characteristics depend on the complete ball screw design, material, heat treatment, nut matching, lubrication and operating conditions.
DLY supplies C7 rolled ball screws and C5 ground ball screws with standard or customized nuts, shaft lengths and end machining. Send the required diameter, lead, length, accuracy, load, speed and drawing for technical confirmation.
