Linear guides and ball screws are often specified together, but they solve different mechanical problems — a linear guide carries the load and constrains motion to a straight axis, while a ball screw converts rotary input into linear thrust with controlled lead [S5].
Current OEM datasheets from Chinese suppliers dated 2026-05 through 2026-06 confirm both components are sold as integrated catalog items, with stroke envelopes from 50 mm up to 1,200 mm on a single actuator and ball-screw leads of 16–20 mm in C7 tolerance classes [S1][S3].
Functional Split: Guide Carries Load, Screw Generates Thrust
A linear guide is a recirculating-ball or crossed-roller carriage running on a hardened rail; its job is to constrain motion, absorb moment loads, and let the payload travel with minimal friction over the full stroke [S5]. Reference load figures for a compact BSGS5-1-160 rail are 44 kgf and 73 kgf on a 160 mm rail length, which is a useful low-end baseline for office-automation-class sizing [S2].
A ball screw is a separate transmission element: a threaded shaft with a recirculating-ball nut, driven by a servo or stepper, that converts torque into linear force. The QF8 ball-screw linear actuator datasheet lists 420 mm max stroke, 30 kg max payload, 80 mm body width, and ±0.006 mm repeatability for a precision-assembly-class module [S4]. The functional rule is: the screw provides the thrust and positioning accuracy, the guide provides the straightness and the moment capacity [S5].
Stroke, Speed and Repeatability Numbers from 2026 Datasheets
Stroke windows differ by an order of magnitude depending on whether the spec is for a bare rail or a packaged actuator. The FUYU FSL80 ball-screw linear unit lists stroke from 50 mm to 1,200 mm with servo-motor or linear-motor drive options, an aluminum body, and a vertical/horizontal mounting claim [S1]. The QF8 sits at the compact end with 420 mm max stroke, while the BSGS5-1-160 is a bare 160 mm rail — closer to a sub-assembly than a full actuator [S2][S4].
Repeatability is where the two diverge most. Ball-screw-driven actuators quote ±0.006 mm (QF8) [S4], while linear guides are typically specified by static load rating, dynamic load rating, and travel accuracy per length, not as a single repeatability number. Lead is a screw-only variable: the Made-in-China directory lists SFS1620 ground ball screws at 16 mm lead, 40 mm nominal diameter, with C7 tolerance and CF53 material, and SFJ/SFNU nut variants up to 2,000 mm length in stainless steel [S3].
Comparison: Guide-Only vs Screw-Only vs Integrated Module
Four criteria frame the engineering choice between a bare linear guide, a bare ball screw, and an integrated ball-screw linear module. [S1]
1. Function. A linear guide constrains straight-line motion and carries moment loads; a ball screw converts rotary torque to linear thrust; an integrated module combines a screw-driven actuator with a built-in guide rail [S1][S4][S5].
2. Typical stroke. Compact rails run 50–1,200 mm (FSL80), QF8 modules top out at 420 mm, and individual screw shafts reach 2,000 mm in stainless SFJ/SFNU form [S1][S3][S4].
3. Positioning. Ball-screw modules carry an explicit ±0.006 mm repeatability on the QF8; rails are specified by load (44 / 73 kgf on BSGS5-1-160), not by a single repeatability figure [S2][S4].
4. Source. Both components are widely catalog items in 2026, with ISO 9001-certified factories in Lishui (Zhejiang), Nanjing, Shanghai, and Hefei (Anhui) listing ball screws, linear guide rails, blocks, and crossed-roller guides as main products [S3][S6][S7][S8].
Who Should Specify Which — and When Both Are Mandatory
If the load path is purely radial or moment-loaded with no thrust requirement (a sliding tray, a gantry cross-beam, a pick-and-place Y-axis where the screw lives elsewhere), a linear guide alone is correct, and a crossed-roller guide may be the better pick when the moment load is dominant and the stroke is short. [S2]
If the application is a leadscrew-driven Z-axis on a CNC or a press-fit station, a ball screw alone is often enough, but in practice it is almost always paired with a linear guide because the screw does not resist moment loads on its own. Anhui Ximai lists both ball screws and crossed-roller guides as main products, which matches this co-specification pattern at the catalog level [S8]. For compact, pre-engineered axes, the integrated ball-screw linear module (FSL80, QF8) removes the alignment burden between screw and rail [S1][S4].
Sourcing Signals From the June 2026 Made-in-China and Supplier Pool
Cross-referencing 2026-05-14 to 2026-06-02 catalog pages, the active Chinese supplier pool for both components sits in four clusters: Zhejiang (Lishui) for ISO 9001:2015-certified ball-screw and linear-guide factories [S3], Shanghai for trading companies bundling ball screws, guide blocks, and guide rails [S7], Anhui (Hefei) for combined ball-screw and crossed-roller-guide makers [S8], and Jiangsu (Nanjing) for high-SKU distributors claiming 1,000+ linear-motion part numbers with custom support [S6].
Material signals worth tracking on ball screws: CF53 chrome steel is the standard ground-screw body material on the SFS1620 line, and stainless SFJ/SFNU nuts reach 2,000 mm length [S3]. For rails, the BSGS5-1-160 spec lists steel carriage and steel rail with 44 kgf / 73 kgf load points, which gives a quick sanity check against the load rating a designer will need [S2]. Repeatability and lead-time claims should be verified against a fresh RFQ — a 15-year factory claim on Made-in-China is a vendor statement, not a third-party test [S3][S7].
Failure Modes and Common Spec Traps
Three traps come up repeatedly. First, a ball screw without a parallel guide will deflect under moment load and lose the ±0.006 mm class repeatability shown on the actuator datasheet — the screw provides thrust, not stiffness against overturning [S4][S5]. Second, lead selection changes dynamics: a 16 mm lead (SFS1620) is faster but lower resolution per servo revolution than a 5 mm lead screw; matching lead to drive resolution and load is mandatory, not optional [S3]. Third, lubrication and seal selection on a 1,200 mm-stroke FSL80 in a vertical mount is a different maintenance regime than a horizontal 160 mm rail in a clean room, and the FUYU datasheet flags vertical/horizontal mounting as separate use cases [S1].
A useful sanity rule from the FUYU engineering note: in a linear-motion system, the linear bearing sits inside the linear guide, the screw provides the drive, and the two are co-specified — a precision linear motion system is rarely built from a single component [S5].
Selection Criteria: Six Gates That Lock the Model Code
For buyers working through a 2026 RFQ, the Linear Guide Selection Criteria: Six Gates That Lock the Model Code in 2026 framework applies: stroke envelope, load (static + dynamic), repeatability, drive interface, environment, and supplier certification. The QF8 passes those gates at 420 mm / 30 kg / ±0.006 mm with a servo/stepper mount [S4], the FSL80 passes at 1,200 mm / heavier load with servo or linear-motor drive [S1], and the BSGS5-1-160 is a sub-component that satisfies only the load and stroke gates inside a larger assembly [S2].
Trackable signals include C7 tolerance data on Chinese ground ball screws, an SFJ stainless-steel ball screw nut SKU at 2,000 mm, and ISO 9001:2015 certification at a Lishui manufacturer and ISO 9001 certification at a Hefei supplier [S3][S6][S8].