Description

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Double Nut Ground Ball Screws provide high axial rigidity and zero-backlash linear motion control. Manufactured using CNC thread grinding technology, these assemblies utilize a preloaded double-nut configuration to eliminate axial play under reversing loads.

Key Features

01/

Zero Backlash: Calibrated shim space eliminates axial clearance under dynamic loads.

02/

ISO C3 / C5 Precision: Ground thread profiles deliver pitch errors within 0.008 mm per 300 mm.

03/

High Axial Rigidity: Dual-nut design resists deflection under heavy force.

04/

Hardened Surface: Induction-hardened alloy steel raceways achieve 58 to 62 HRC.

05/

Smooth Recirculation: Optimized return mechanisms ensure stable ball circulation.

Technical Specifications

Parameter	C3 Class	C5 Class
Shaft Diameter	12 mm – 80 mm	12 mm – 80 mm
Lead Range	4 mm – 50 mm	4 mm – 50 mm
Lead Error (E₃₀₀)	≤ 0.008 mm / 300 mm	≤ 0.018 mm / 300 mm
Preload Force	3% – 10% Ca	2% – 7% Ca
Surface Hardness	58 – 62 HRC	58 – 62 HRC
Roughness (Ra)	≤ 0.2 μm	≤ 0.4 μm

Product Configuration

Double Nut Ground Ball Screw assemblies consist of:

Ground Screw Shaft: Induction-hardened alloy steel with precision ground threads.

Dual Nut Bodies: High-strength steel nuts mounted in tandem.

Precision Spacer Shim: Ground spacer ring positioned between nuts to establish specific preload.

Steel Balls: Grade G10 bearing steel balls matching raceway profiles.

Internal Circulation Units: Deflectors designed for smooth ball transit.

Contact Seals: Wipers fitted at both nut ends to retain lubricant and restrict contamination.

Accuracy & Lead

Accuracy Class	Travel Error (eₚ) / 300 mm	Variation (v300)	Primary Application
ISO C3	± 0.008 mm	0.006 mm	Ultra-precision machining and semiconductor equipment
ISO C5	± 0.018 mm	0.012 mm	Standard automated machinery and precision motion axes

Preload Classes

Code	Type	Force	Operational Characteristic
P1	Light	0.02 Ca	Low friction, minimal thermal expansion
P2	Medium	0.05 Ca	Standard stiffness for position stability
P3	Heavy	0.08 Ca – 0.10 Ca	Maximum rigidity under variable reversing loads

Dimensions & Selection

Model	Diameter (mm)	Lead (mm)	Dynamic Load Ca (kN)	Static Load C0a (kN)	Nut Outer Diameter (mm)
DFU 1605	16	5	13.8	30.5	28
DFU 2005	20	5	15.6	38.2	36
DFU 2505	25	5	17.2	49.0	40
DFU 3210	32	10	43.1	102.5	50
DFU 4010	40	10	48.6	128.0	63
DFU 5010	50	10	54.2	165.0	75

Manufacturing Process

Material Testing:

Ultrasonic inspection and chemical composition analysis of raw steel stock.

Stress Relief:

Rough machining followed by thermal stress relief processing.

Induction Hardening:

Controlled heating to reach 58 to 62 HRC surface hardness.

CNC Thread Grinding:

Multi-pass thread grinding in temperature-regulated environments.

Shim Calibration:

Micro-measurement of nut internal geometry to fit exact spacer thickness.

Laser Verification:

Pitch lead checking along the full thread length via laser interferometry.

Applications of Double Nut Ground Ball Screws

Machining Center Axes: Position feed tables under heavy cutting forces.

Semiconductor Handling: Low-vibration positioning stages in cleanroom systems.

Laser Cutting Equipment: Accurate axis tracking during multi-axis path movement.

Medical Positioning Tables: Controlled displacement for diagnostic scanning platforms.

Quality Indicators

Climate-Controlled Grinding:

Grinding operations take place under constant temperature controls to limit thermal variation.

Individual Inspection Reports:

Every assembly includes a serial-linked laser interferometer pitch accuracy chart.

Material Traceability:

Heat numbers, hardness logs, and inspection metrics link directly to each shaft serial number.

Customization Options

Journal End Machining: Customized shaft ends, keyways, locknut threads, and retaining ring grooves according to provided drawings.

Surface Treatments: Optional black oxide or dense chrome plating for elevated corrosion resistance.

Flange Configurations: Custom bolt patterns and lubrication inlet orientations.

Specialized Wipers: Synthetic or metallic wiper designs for unique operational environments.

CAD Files & Technical Documents

Downloads available for system design:

2D CAD Drawings: File formats include DWG and DXF.

3D Models: STEP and IGES files for spatial layout validation.

Engineering Data Sheet: Shaft critical speed curves, load formulas, and life calculations.

FAQ

Q: What is the primary operational difference between single nut and double nut ground ball screws?

A: Single nut designs reduce backlash using oversized balls within a single thread track. Double nut designs place a ground spacer between two separate nuts, physically pre-tensioning them against opposite thread faces. This structure increases axial stiffness and preserves zero-backlash characteristics under heavy dynamic loads.

Q: How is preload stability maintained over extended operational periods?

A: Preload stability relies on thread hardness and ground surface finish. Thread raceways ground to Ra ≤ 0.2 μm and hardened to 58 to 62 HRC limit initial mechanical wear. The fixed spacer between the nuts maintains constant axial tension.

Q: Can end journal dimensions be adapted to existing machine structures?

A: Yes. Shaft ends are left unhardened during manufacturing, allowing custom machining of bearing journals, keyways, and retaining features according to client engineering drawings.

Q: What technical details are needed to request a formal quotation?

A: Required details include nominal shaft diameter, lead, accuracy class (C3 or C5), total shaft length, working stroke, preload designation, and the technical drawing for end journal machining.

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