Product Knowledge Base FAQs

Linear Motion Block & Rails FAQ

Preload (Radial Clearance Standard) – Linear Motion Blocks

Preload uses oversized balls to make the clearance negative. It increases the rigidity. The block has more resistance.

Products on the THK Online Store are our more frequently purchased and stocked products. Other seals and preload configurations are available but are usually a production item. Please contact the THK Online Store for a quote on those products.

Normal Clearance

The loading direction is fixed, impact and vibrations are minimal and 2 rails are installed in parallel.

Very high precision is not required, and the sliding resistance must be as low as possible.

Light Preload (C1)

An overhang load or moment load is applied.

The LM Guide is used in a single-rail configuration.

Light load and high accuracy are required

Medium Preload (C0)

High rigidity is required and vibrations and impact are applied.

Heavy-cutting machine tools

Preload General Catalog

https://catalog.thkstore.com/General-Catalog-Linear-Motion-Guide/A1-71/

Preload Product Ordering Guide

https://catalog.thkstore.com/Product-Ordering-Guide-Linear-Motion-Guide/80/

Seals – Linear Motion Blocks

Here are our more common seal configurations:

UU With end seal

SS With end seal + side seal + inner seal*

DD With double seals + side seal + inner seal9

ZZ With end seal + side seal + inner seal* + metal scraper

KK With double seals + side seal + inner seal1 + metal scraper

*Some models are not equipped with inner seals

Seals General Catalog

https://catalog.thkstore.com/General-Catalog-Linear-Motion-Guide/A1-508/

Seals Product Ordering Guide

https://catalog.thkstore.com/Product-Ordering-Guide-Linear-Motion-Guide/71/

Other additions to Linear Motion Blocks (QZ, LaCS & LiCS)

Products on the THK Online Store are our more frequently purchased and stocked products. The following specifications options are available but are usually a production item. Please contact the THK Online Store for a quote on those products.

QZ Lubricator

The QZ Lubricator feeds the right amount of lubricant to the LM rail raceway. This allows an oil film to be continuously between the rolling element and the raceway, and drastically extends the lubrication and maintenance intervals.

The structure of the QZ Lubricator consists of three major components: (1) a heavily oil-impregnated fiber net (functions to store lubricant), (2) a high-density fiber net (functions to apply lubricant to the raceway) and (3) an oil-control plate (functions to adjust oil flow). The lubricant contained in the QZ

Lubricator is primarily fed by capillary action, which is also used in devices such as felt-tip pens.

Laminated Contact Scraper LaCS

For locations with an adverse environment, Laminated Contact Scraper LaCS is available.

Minute foreign material adhering to the LM rail is removed in multiple stages and prevented from entering the LM block with a laminated contact structure (3-layer scraper).

Light-Resistance Contact Seal LiCS

LiCS is a light sliding resistance contact seal. It is effective in removing dust on the raceway and retaining a lubricant such as grease. It achieves extremely low drag and smooth, stable motion

QZ General Catalog

https://catalog.thkstore.com/General-Catalog-Linear-Motion-Guide/A1-536/

LaCS General Catalog

https://catalog.thkstore.com/General-Catalog-Linear-Motion-Guide/A1-510/

LiCS General Catalog

https://catalog.thkstore.com/General-Catalog-Linear-Motion-Guide/A1-514/

Product Ordering Guide

https://catalog.thkstore.com/Product-Ordering-Guide-Linear-Motion-Guide/73/

What does (GK) mean in a THK block and rail?

(GK) is the THK symbol for Interchangeable.

Blocks and rails with (GK) symbols are make to work together. Putting (GK) parts together will create the THK standard accuracy and clearance parameters.

Clearance & Accuracy Quick Ship Catalog: https://catalog.thkstore.com/Quick-Ship-Program-Linear-Motion-Guide/5/

Series, Size and Serial Numbers on THK Block and Rails

The non-datum side of the block will have the series and size of your part and possibly a lot number. All of the specifics with regards to preload, seals, and many other non-visible specifications will not appear on the side of the block.

If you are looking for the full part number for a replacement, looking up the serial number is an option. Current serial numbers typically resemble ABC12345 and are located on the top of the linear motion block or the top of the rail. Small assemblies due to the size may have part of the serial number on the rail and part on the block.

Older serial numbers (prior to 2011) typically have a different serial number look and may or may not have traceability to the original part number.

Matched Sets – parts that end with a -II, -III …

If two or more units of the LM Guide are parallelly used in combination on the same plane, specify

the number of the LM rails (symbol for number of axes) used in combination in advance.

Please check the specs in our Product Ordering Guide. Tolerance for the matched sets are tighter than an unmatched set. Pricing for a matched set and a random assembly are usually the same. If replacements are needed, Matched Sets should have all parts replaced together in order to keep the tolerance and height variations consistent.

Axes General Catalog

https://catalog.thkstore.com/General-Catalog-Linear-Motion-Guide/A1-12/

Matched Sets Product Ordering Guide

https://catalog.thkstore.com/Product-Ordering-Guide-Linear-Motion-Guide/89/

Part Number with an E or an S in Linear Motion block and rails

If you are looking for a part number with an E or an S, these are non-standard parts. Please contact us for a quote. We will need to know what is non-standard with the part in order to identify. This could be the 15 digit product code or the drawing of the part.

Some products may not be quotable if they are proprietary to the machine builder.

Need an Assembly Quickly?

For many standard part assemblies, the assembly can be broken down into our Interchangeable parts. Please let us know if you need assistance with part number breakdown.

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Grease Nipple Placement

Whether you are purchasing an assembly from THK or purchasing one of our (GK) interchangeable blocks. You might question which side the grease nipple is or should be on. Placement can be dependent on your application and if it is not the THK standard placement, it will need to be specified prior to purchase or quotation (product code will be different)

THK Standard Placement (Datum facing away from you):

Assemblies with 1 block: grease nipple will be on the left

If more than one block: blocks are added in an alternating pattern with the grease nipples facing the end of the rail from which they are added.

Example: For an assembly with 5 blocks. Block 1 added on the left (grease nipple left), Block 2 added on the right (grease nipple right), Block 3 added on the left (grease nipple left), Block 4 added on the right (grease nipple right), Block 5 added on the left (grease nipple left).

If purchasing one of our (GK) Interchangeable blocks, the grease nipple is included in the box and ready for you to attach to the block. Selection of standard placement or non-standard placement is not necessary.

Datum

The datum is the reference side that helps manage the orientation and positioning of the product. Some instances this is an edged mounting surface. Other instances this is used as a guide with which to correctly position the product.

Other names for Linear Motion

Block - pillow, truck, car, carriage, bearing, carriers, guides

Seals - Wipers

Actuator FAQ

KRs & SKRs - 2 different product names, same product

In order to reduce lead time on KRs and SKRs, Japan created a Semi-Custom product line.

As the Semi-Custom selections are preset and there are no deviations, there is some overlap with our conventional KR and SKR part numbers. Meaning, you could have the same product with 2 different part numbers depending on how they were produced.

Here is an example of 2 of these same products:

SKR4610A-0290-0-10A0 (conventional part number)

SKR4610A-0290-0-1-0-00000 (semi-custom part number)

KR Catalog

https://catalog.thkstore.com/LM-Guide-Actuator-KR/Cover/

SKR Catalog

https://catalog.thkstore.com/Caged-Ball-LM-Guide-Actuator-SKR/Cover/

SKR/KR Semi-Custom Catalog

https://catalog.thkstore.com/Semi-Custom-SKRKR/Cover/

Actuator with an L in the part number

Older KR and SKR actuators have a product code with an L in the middle of the part number.

This is our older part nomenclature, which indicates the length of the actuator. Our current nomenclature uses the stoke on the actuator part.

Here is an example:

KR2602A+150L0-10A0 (old) à KR2602A-0060-0-10A0 (current)

Please let us know if you are looking to updating an older part number.

Part Number with an X in Actuators

If you are looking for an actuator part number with an X , these are non-standard options. Please contact us for a quote. We will need to know what is non-standard with the part in order to identify. This could be the 15 digit product code or the drawing of the part.

Ball screw FAQ

Ball screws

The ball screws that you see on the THK Online Store are our stocked products. These either are without end machining or have the THK Standard end machining (part number ending in A or Y).

Product examples with standard end machining: BNK0601-3G0+130LC3Y, MDK0401-3G2+115LC7A, SDA1010VZ-3TTG0+321LC5Y

Other End Machining

THK can machine the ends of your ball screw for you. Please provide a drawing for any new requests. For replacement items, please provide the 15 digit product code and/or drawing for a quote.

THK Recommended End Machining (no drawing needed)

To ensure speedy estimates and manufacturing of Ball Screws, THK has standardized the shaft end

shapes of the screw shafts. The recommended shapes of shaft ends consist of shapes H, K and J, which allow standard Support Units to be used. These shapes are found at the end of the ball screw name and resemble -J1K, -H2K….

Shaft End Shapes General Catalog

https://catalog.thkstore.com/General-Catalog-Ball-Screw/A15-306/

Dimensions for Standard End Machining General Catalog

https://catalog.thkstore.com/General-Catalog-Ball-Screw/A15-322/

Axial Clearance (Preload) – Precision (Ground) Ball Screws

Within the ball screw part number, you may see a G0, GT, G2, G2 or G3. These indicate the preload of the ball screw. The preload, accuracy and shaft outer diameter determine the max length of the screw.

Example part number: BNK0501-3G0+77LC3Y

Ball Screw & Max Length General Catalog

https://catalog.thkstore.com/General-Catalog-Ball-Screw/A15-18/

Accuracy – Ball Screws

The lead angle accuracy of the ball screw is controlled in accordance with the JIS standard

JIS B 1192 (ISO 3408). Accuracy grades C0 to C5 are defined in the linearity and the directional property, and C7 to C10 in the travel distance error in relation to 300 mm.

Precision or Ground Ball Screws – Accuracy ranges from C0 (most accurate) to C7 (least accurate).

Rolled or Transport Ball Screw – Accuracy ranges from C7 (most accurate) to C10 (least accurate)

Precision Rolled Ball Screws – Accuracy grades look like Cp3, Cp5, Ct5, Cp7

Other names for Ball Screw Types

Precision Ball Screws – Positioning Ball Screws, Ground Ball Screws.

Rolled Ball Screws – Transport Ball Screws

Precision Rolled Ball Screws **

Ball splines FAQ

Apart from the LT-X and the LF-X interchangeable products. Ball Splines are assembly only products.

Other names for Spline Nuts

quill

Other FAQ

Grease Shelf Life

We guarantee the quality of the grease for 1 year after purchase.

We don’t necessarily define an expiration date, as many people have used older grease with no problem. As long as the oil has not separated from the grease, it should be okay to use.

Lubrication General Catalog

https://catalog.thkstore.com/General-Catalog-Accessories-for-Luburication/A24-2/

Application Discussions

Have a quick question you want to ask our engineers? Start a Chat!

Need to discuss your application with one of our THK Engineers? Book a Meeting!

Engineers are available Monday-Friday 8-5 Central Time from our Schaumburg office.

Book a Meeting Link

Chat Link

Distributors

Looking to place an order with a distributor? Please see the link below for our National and Local Authorized Distributors. Pricing and Lead times may differ from the THK Online Store.

Distributors Link

Searching for a part but can’t find it online

The THK Online Store lists products that are stocked in the US and/or Japan or are modified from stocked products. Please contact us for a quote on the part you are looking for. We can set up a link to purchase.

Downloading CAD models

We have CAD models by series on the product model pages as well as the individual product pages. Please make sure you are logged into your account to be able to access this functionality.

Other names for Spline Nuts

quill