Short answer: yes — Songju LG series linear guideways are dimensionally interchangeable with HIWIN HG/HGW, THK SHS/HSR, and NSK LH series at equal rail widths from 15 to 45 mm. Rail cross-section, carriage mounting bolt patterns, and connecting dimensions follow the international standards those brands established, so a Songju rail set can replace a worn HIWIN, THK, or NSK system without re-machining the mounting surface. Below is the size-by-size cross-reference, what interchangeability does and does not cover, and the exact information we need to quote a drop-in replacement.
What "Interchangeable" Means for a Linear Guideway
Interchangeability in linear guideways is a mounting-dimension statement, not a marketing one. For a replacement rail to bolt onto an existing machine bed, and a replacement carriage to bolt onto an existing table, the following dimensions must match at the same nominal size:
- Rail: cross-section height and width, mounting hole diameter, hole pitch, and the distance from the rail reference edge to the first hole.
- Carriage: overall height (top surface to rail mounting plane), foot bolt pattern, and the lateral dimension from the carriage center to the rail reference edge.
Songju LG series is a four-row ball guideway built to the same architecture as the HIWIN HG, THK SHS/HSR, and NSK LH families, with induction-hardened raceways at 58–62 HRC (the industry-standard rail hardness), running parallelism of ≤ 0.003 mm per 1000 mm depending on grade, maximum acceleration of 40 m/s², maximum velocity of 150 m/min, an operating range of −20 °C to +80 °C, and single-piece rails up to 3000 mm. Seal and grease-nipple positions follow the same conventions, though minor differences exist between brands — we confirm these against the interchange drawing for your specific model.
Size-by-Size Cross-Reference: Songju LG vs HIWIN / THK / NSK
| Rail width | Songju LG series | HIWIN | THK | NSK |
|---|---|---|---|---|
| 15 mm | LG 15 | HG 15 (HGH15 / HGW15) | SHS 15 / HSR 15 | LH 15 |
| 20 mm | LG 20 | HG 20 (HGH20 / HGW20) | SHS 20 / HSR 20 | LH 20 |
| 25 mm | LG 25 | HG 25 (HGH25 / HGW25) | SHS 25 / HSR 25 | LH 25 |
| 30 mm | LG 30 | HG 30 (HGH30 / HGW30) | SHS 30 / HSR 30 | LH 30 |
| 35 mm | LG 35 | HG 35 (HGH35 / HGW35) | SHS 35 / HSR 35 | LH 35 |
| 45 mm | LG 45 | HG 45 (HGH45 / HGW45) | SHS 45 / HSR 45 | LH 45 |
The LG series covers 15–45 mm rail widths in the standard-duty ball type shown above; wider 55 mm and 65 mm rails are available through our broader guideway line on request. A few naming notes when reading competitor datasheets: HIWIN uses HGH for flange-type carriages and HGW for square-type carriages on the HGR rail; THK's current four-row ball model is SHS, with HSR still widely referenced on legacy drawings; NSK's equivalent family is LH. Songju guideways are also manufactured to IKO-compatible mounting standards for miniature and medium sizes — send us your IKO model for confirmation.
Carriage Forms: Flange vs. Square
Every nominal size is available in the two standard carriage forms: a flange type (bolted from the top, HIWIN "HGH" convention) that sits low against the mounting table, and a square type (bolted laterally through the sides, HIWIN "HGW" convention) that allows thinner table edges. Both forms are offered in the standard and extended lengths of each series. If your existing machine mixes forms — common on Z-axes where a wide flange carriage resists moment loads — send us both codes and we match each position individually.
Accuracy Grades and Preload: Map Tolerances, Not Letters
A common sourcing mistake is assuming that accuracy letters align across brands — they do not. Songju grades are H (high), P (standard), and SP (super precision), while HIWIN, THK, and NSK each publish their own letter systems with different boundaries, so the same letter can mean different tolerances. The reliable method is to compare numbers: for the LG series, height/width tolerance is ±10 µm (SP), ±20 µm (P), or ±40 µm (H), with running parallelism of 3–5 µm, 5–8 µm, and 12–15 µm per 1000 mm respectively. Every shipment includes an inspection report so incoming goods can be verified against your original brand's datasheet.
Preload works the same way. The LG series offers light and medium preload, selected by application: light preload minimizes friction and heat for high-speed transfer axes, while medium preload maximizes rigidity for machining axes that see cutting reaction forces. Tell us the axis duty and we recommend the class — no need to decode another brand's Z0–Z3 nomenclature first.
How to Order a Drop-In Replacement
- Read the old part number. The brand and model code is stamped on the carriage end face — for example HGW25CC, SHS25C, or LH25 — and the rail length is marked on the rail end.
- Send it to us. Email [email protected] or message +86-186-9779-6262 with the model, rail length, quantity, and any preload or accuracy requirements.
- Confirm and receive. Our engineers reply with the LG equivalent, pricing, and lead time — standard models ship within 2–4 weeks with pre-shipment inspection video and 24-hour technical support.
Frequently Asked Questions
Are Songju LG guideways a true drop-in replacement for HIWIN HG rails?
At equal nominal rail widths (15-45 mm), the LG series matches HIWIN HG series rail cross-section and mounting dimensions, so replacement does not require re-machining the mounting surface. Because preload and accuracy class affect fit and feel, we confirm the exact equivalent against your current part number before you order.
Can I keep my existing HIWIN carriages and mount them on a Songju rail?
No. Rails and carriages are precision-matched pairs lapped by the same manufacturer; mixing a Songju rail with another brand's carriage is not supported even when mounting dimensions look identical, because raceway geometry and ball pitch must match. Order rails and carriages as matched sets.
How does Songju accuracy compare to HIWIN, THK, or NSK grade letters?
Grade letters are not standardized across brands, so compare tolerance values instead. Songju LG series achieves running parallelism of 3-15 um per 1000 mm depending on grade (SP +/-10 um, P +/-20 um, H +/-40 um height/width tolerance), and every shipment includes an inspection report so you can verify against your original brand's datasheet.
What information do you need to quote an interchange?
Send the brand and model code printed on the carriage end face (for example HGW25CC, SHS25C, or LH25), rail length and quantity, preferred preload and accuracy class, and your application. Our engineers confirm the LG equivalent and reply with pricing and lead time - standard models ship within 2-4 weeks.