Rodless screw actuator
THK SKR rodless screw actuator
Caged-ball LM Guide actuator integrating an LM guide and ball screw in a compact outer rail, sizes 20 to 65; series maximum 1,490 mm stroke and 3,000 mm/s, repeatability to +/-0.003 mm (precision grade).
Key specifications
| Stroke (max) | 1,490 mm |
|---|---|
| Linear speed (max) | 3,000 mm/s |
| Screw lead | 1 to 50 |
| Screw type | ball screw |
| Repeatability | 0.003 mm |
| Sizes | SKR20, 26, 33, 46, 55, 65 |
Summarised in our own words from THK CO., LTD.'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Notes on this data
Speeds limited by screw critical speed or 6,000 min-1 motor; 3,000 mm/s is SKR65 with 50 mm lead. Normal grade repeatability +/-0.01 mm.
Specify Motion is not affiliated with THK CO., LTD.. THK and SKR are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a THK part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Economical rodless screw actuator derived from the BC2 band cylinder, with solid-bearing rods and a stainless band seal for light to moderate loads.
| Published maximum | SKR | BCS Rodless Screw (BCS/MCS) |
|---|---|---|
| Force | — | 11,700 N |
| Stroke | 1,490 mm | 3,048 mm meets or exceeds |
| Speed | 3,000 mm/s | — |
Screw-driven rodless actuator in six sizes, with a solid-bearing (S) or profiled-rail (P) carrier for moderate to heavy guided loads.
| Published maximum | SKR | MXE Screw-Drive Rodless (MXE-S / MXE-P) |
|---|---|---|
| Force | — | 19,127 N |
| Stroke | 1,490 mm | 3,411 mm meets or exceeds |
| Speed | 3,000 mm/s | — |
Screw-driven rodless actuator with recirculating ball-bearing guidance integral to the extrusion, so it carries loads up to 35.6 kN (with carrier options) without external guides.
| Published maximum | SKR | B3S Screw-Drive Rodless |
|---|---|---|
| Force | — | 12,010 N |
| Stroke | 1,490 mm | 4,547 mm meets or exceeds |
| Speed | 3,000 mm/s | 1,524 mm/s |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a rodless screw actuator is
A rodless screw actuator moves a carriage along the actuator body using a ball or lead screw inside a profile. The load mounts directly on the carriage, which runs on guides, either internal bearings or profile rails, so the actuator carries and guides the load as well as moving it. A sealing band typically closes the slot along the body. The motor mounts at one end, inline or folded, and stroke is set by the body length.
When engineers choose a rodless screw actuator
Choose a rodless screw actuator when the load needs carrying along a guided path with good positioning accuracy and stiffness, such as in pick-and-place, gantries and positioning axes. Screw drive gives high thrust and precision. The trade-offs are speed and length: long screws hit critical speed limits, so long strokes run slower. For long, fast strokes with lighter loads, a belt-driven rodless actuator is usually better.
How to specify the THK SKR
Send these with your enquiry and an engineer can confirm the right SKR variant or an equivalent:
- Payload mass and position offset (kg, mm)
- Moment loads on the carriage (Nm)
- Stroke (mm), speed (mm/s) and acceleration (m/s²)
- Thrust force needed (N)
- Repeatability (mm)
- Orientation: horizontal, vertical or wall-mounted
- Environment and sealing (IP code)
Common mistakes to avoid
- Ignoring moment loads from offset payloads
- Choosing a long stroke at high speed and exceeding screw critical speed
- Not adding a brake for vertical axes
- Assuming the sealing band keeps out fine dust or liquids
THK SKR: frequently asked questions
What is the THK SKR?
Caged-ball LM Guide actuator integrating an LM guide and ball screw in a compact outer rail, sizes 20 to 65; series maximum 1,490 mm stroke and 3,000 mm/s, repeatability to +/-0.003 mm (precision grade). Published series figures include stroke 1,490 mm, linear speed 3,000 mm/s, repeatability 0.003 mm. It is made by THK CO., LTD.; Specify Motion can help source it or propose an equivalent.
Who makes the THK SKR?
The THK SKR is made by THK (THK CO., LTD.) and is listed here for engineers comparing options. Specify Motion is not affiliated with THK CO., LTD.; brand names are used only to identify the product.
What is the stroke of the THK SKR?
The published series maximum stroke is 1,490 mm. Individual models and sizes in the SKR range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the THK SKR?
Yes. On published figures, Tolomatic BCS Rodless Screw (BCS/MCS) and Tolomatic MXE Screw-Drive Rodless (MXE-S / MXE-P) are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
Is a belt or screw rodless actuator better?
A screw rodless actuator gives more thrust, stiffness and positioning accuracy, which suits pressing, vertical axes and precise positioning. A belt actuator is faster and handles longer strokes, which suits transfer and pick-and-place over distance. Many machines use both: belts for long horizontal moves and screws for shorter, precise or vertical axes.
What limits the speed of a screw-driven actuator?
Speed is limited by the screw's critical speed, the rotation at which it starts to whip. Critical speed falls sharply as unsupported length increases, so long strokes have lower maximum speeds. Screw supports, larger diameters or a coarser lead raise usable speed. Manufacturers publish speed against stroke curves that should be checked.
Further reading: Rodless belt vs screw actuators · How to size a linear actuator · Linear actuators
Other rodless screw actuator series
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