Rodless screw actuator
THK KR rodless screw actuator
LM Guide actuator with U-shaped outer rail and ball screw, sizes 15 to 65; series maximum 1,490 mm stroke and 1,480 mm/s, repeatability 0.003 mm in precision grade.
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What are you specifying?
Select everything you need. A motor, drive and gearbox can be specified together as one axis.
Key specifications
| Stroke (max) | 1,490 mm |
|---|---|
| Linear speed (max) | 1,480 mm/s |
| Screw lead | 1 to 25 |
| Screw type | ball screw |
| Repeatability | 0.003 mm |
| Sizes | KR15, 20, 26, 30H, 33, 45H, 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 · Source 2
Specify Motion is not affiliated with THK CO., LTD.. THK and KR are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
THK KR replacement and alternative options
Use these supply-network options as a starting point for an engineering check. We can also help source the original THK part. Published series figures do not establish an exact-model or drop-in replacement: confirm ratings, fit, interfaces and approvals for your application.
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 | KR | B3S Screw-Drive Rodless |
|---|---|---|
| Force | — | 12,010 N |
| Stroke | 1,490 mm | 4,547 mm meets or exceeds |
| Speed | 1,480 mm/s | 1,524 mm/s meets or exceeds |
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 | KR | BCS Rodless Screw (BCS/MCS) |
|---|---|---|
| Force | — | 11,700 N |
| Stroke | 1,490 mm | 3,048 mm meets or exceeds |
| Speed | 1,480 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 | KR | MXE Screw-Drive Rodless (MXE-S / MXE-P) |
|---|---|---|
| Force | — | 19,127 N |
| Stroke | 1,490 mm | 3,411 mm meets or exceeds |
| Speed | 1,480 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.
Typical applications
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 KR
Send these with your enquiry and an engineer can confirm the right KR 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 KR: frequently asked questions
Can you help replace THK KR or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including supply-network options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the THK KR?
LM Guide actuator with U-shaped outer rail and ball screw, sizes 15 to 65; series maximum 1,490 mm stroke and 1,480 mm/s, repeatability 0.003 mm in precision grade. Published series figures include stroke 1,490 mm, linear speed 1,480 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 KR?
The THK KR 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 KR?
The published series maximum stroke is 1,490 mm. Individual models and sizes in the KR 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 KR?
We can assess suitable replacement options. On published figures, Tolomatic B3S Screw-Drive Rodless and Tolomatic BCS Rodless Screw (BCS/MCS) are options to assess 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
Engineer support
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Tell us how you use the THK KR: the load, speed, duty and environment. Our engineers will confirm whether it is still the right part, find it for you, or propose an alternative that fits better.
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How it works
From enquiry to delivery
Send a part number or describe the application. Our engineers take it from there: the right product, a clear quotation, and delivery and support arranged.
- 01Tell us what you needSend a part number, or configure the application, quantities and timing.
- 02An engineer reviews itWe check the specification and find the original part, a checked equivalent or a complete axis.
- 03Receive your quotationProducts, pricing, lead time and compatibility notes in one reply.
- 04Order and deliveryWhen you are happy, the order is placed and delivery and after-sales support are arranged.