What Is Preload in a Linear Guide?

Oct 1

Linear guide preload is an intentional internal load applied between the carriage, rolling elements, and rail before the guide carries the machine's external working load. Preload reduces or eliminates internal clearance and increases rigidity, but greater preload also increases rolling resistance and internal bearing load and can reduce calculated service life if it is higher than the application requires.

In practical terms, preload determines how tightly the:

balls or rollers,
carriage raceways,
rail raceways

are engaged with one another.

A guide with clearance allows a small amount of internal movement before all rolling contacts fully react to a change in load direction. A preloaded guide intentionally creates interference within the rolling contacts so the system responds more rigidly.

According to THK's linear guide selection guidance, preload is an internal load applied in advance to the rolling elements specifically to increase carriage rigidity. THK also treats radial clearance/preload as a distinct part of the guide-selection process.

Schaeffler's Technical Pocket Guide makes the same fundamental engineering point: increasing preload increases static rigidity, but higher preload creates additional internal loading and can reduce basic rating life.

The objective is therefore not:

maximum preload.

It is:

the appropriate preload for the machine's required rigidity, accuracy, loading, speed, life, and operating environment.

Key Takeaways

Preload is an intentional internal load in the linear guide.
Preload reduces or eliminates internal clearance.
Increasing preload generally increases rigidity.
A preloaded carriage deflects less when external load changes.
Preload can improve behavior under reversing loads, moment loads, vibration, and shock.
Higher preload generally increases running resistance.
Excessive preload creates unnecessary internal bearing load.
Preload must be considered when calculating service life.
Preload is not the same thing as accuracy class.
Preload is not the same thing as external payload.
More preload is not automatically better.
Manufacturer preload symbols and classes are not universal.
Replacement blocks should preserve the required preload specification.
Mounting error can unintentionally add load that behaves like unwanted preload.
Preload should be selected after understanding the actual machine requirements.

What Does Preload Actually Do?

Preload intentionally changes the internal contact condition of the guide.

Imagine the balls inside a ball-type profile rail guide.

Without preload, the guide may have:

positive clearance,
approximately zero clearance,

depending on the manufacturer and specified clearance class.

With preload, the rolling elements are intentionally loaded against the raceways before an external machine load is applied.

This creates what is often described as:

negative clearance.

THK explicitly describes preload as the selection of a negative radial clearance and notes that radial clearance strongly affects running accuracy, load-carrying behavior, and rigidity. THK — Selecting a Radial Clearance

Positive Clearance vs. Zero Clearance vs. Preload

The concept can be visualized like this:

Internal ConditionGeneral DescriptionTypical EffectPositive clearanceSmall internal freedom existsLowest resistance, lower rigidityNear-zero clearanceInternal play minimizedBalanced general-purpose behaviorLight preloadSmall intentional interferenceIncreased rigidityMedium preloadGreater intentional interferenceHigher rigidity and resistanceHeavy preloadStrong internal loadingVery high rigidity but greater internal load

The exact classes and terminology vary by manufacturer.

Do not use this conceptual table as an ordering-code cross-reference.

How Is Preload Created?

In a ball-type profile rail guide, preload can be established by controlling the relationship between:

ball diameter,
raceway geometry.

THK explains in its current product knowledge documentation that preload can be created using oversized balls so that the internal clearance becomes negative.

THK — Preload and Radial Clearance

Schaeffler similarly explains that preload in monorail guidance systems can be induced through specific sorting of oversized rolling elements, establishing the desired spring behavior at the rolling contact. Schaeffler — Technical Pocket Guide

The result is controlled elastic deformation at the rolling contacts before the machine's external load is applied.

Why Does Preload Increase Rigidity?

Rigidity describes resistance to displacement under load.

A simple expression is:

K = F ÷ δ

where:

K = rigidity or stiffness,
F = applied force,
δ = resulting deflection.

A more rigid guide produces less displacement under the same external load.

Preload increases rigidity because the rolling elements are already engaged against the raceways.

There is less transition through internal clearance when:

load direction changes,
a moment is applied,
vibration occurs.

THK notes that specifying negative radial clearance reduces displacement and increases rigidity. THK — Prediction of Rigidity

What Does This Feel Like in a Machine?

Consider a carriage subjected alternately to:

upward force,
downward force.

A guide with internal clearance can experience a small amount of movement as the internal contact condition shifts from one side of the raceway to the other.

A preloaded guide keeps opposing rolling contacts engaged.

The result can be a more immediate and predictable response.

This is especially valuable in machinery that repeatedly changes:

force direction,
travel direction,
cutting force.

Preload and Deflection

THK provides an especially useful explanation of preload behavior.

According to its current rigidity-selection guidance, a preloaded LM Guide can exhibit substantially less displacement under external loading than a comparable guide without preload within the relevant operating region. THK — Prediction of Rigidity

The exact deflection should always be taken from the manufacturer's rigidity data for the specific guide.

The engineering principle is:

preload increases resistance to displacement.

Why Not Use Maximum Preload Everywhere?

Because preload is not free.

The rolling elements are carrying an internal load before the machine payload is even applied.

Higher preload can therefore increase:

rolling resistance,
frictional force,
heat generation potential,
drive-force requirements,
internal bearing stress.

It can also affect fatigue life.

Schaeffler explicitly warns that high preload adds load to the rolling-element set and reduces basic rating life, which is why very high preload classes should be critically evaluated rather than selected automatically. Schaeffler — Technical Pocket Guide

Preload vs. Clearance

Preload and clearance describe related internal conditions.

Positive Clearance

The rolling elements have a small amount of internal freedom.

Zero or Near-Zero Clearance

Play is minimized without substantial intentional internal loading.

Negative Clearance

The rolling elements experience intentional interference.

That negative-clearance condition is preload.

This is why manufacturer catalogs may describe the specification under headings such as:

radial clearance,
clearance class,
preload,
preload class.

Is Zero Clearance the Same as Preload?

Not necessarily.

A guide can be manufactured with very little free clearance without carrying the same intentional internal load as a genuinely preloaded guide.

Manufacturer terminology matters.

Do not translate terms such as:

zero clearance,
light preload,
medium preload

across brands without checking their definitions.

THK Preload and Radial Clearance

THK's current guidance illustrates the concept with three broad operating conditions:

Normal Clearance
C1 — Light Preload
C0 — Medium Preload

THK associates these with different machine requirements rather than treating one class as universally superior. THK — Preload Radial Clearance

Normal Clearance

THK identifies normal-clearance applications with conditions such as:

fixed loading direction,
minimal impact and vibration,
two parallel rails,
low desired sliding resistance,
no requirement for extremely high precision.

Representative applications include:

packaging machinery,
welding equipment,
material feeders,
general industrial XY axes.

C1 Light Preload

THK identifies light preload as useful where conditions include:

overhung loading,
moment loading,
single-rail guidance,
light loading with higher accuracy requirements.

Representative applications include:

industrial robots,
measuring instruments,
precision XY tables,
vertical industrial axes.

C0 Medium Preload

THK associates medium preload with:

high rigidity requirements,
vibration,
impact,
heavy machine-tool applications.

Examples include:

machining centers,
lathes,
milling machines,
boring machines.

These are THK-specific classifications and application guidelines. They should not be assumed to describe another manufacturer's preload codes.

Preload Codes Are Manufacturer Specific

This is extremely important in replacement work.

A code such as:

can have a particular meaning within one manufacturer's guide family.

Another manufacturer may use:

or another system.

The letters and numbers are not universal engineering standards.

Always verify the manufacturer-specific catalog.

Never Cross-Reference Preload Codes by Appearance

Suppose one carriage is marked:

and another manufacturer's block also contains:

K1.

That does not establish equivalent preload.

Compare the actual manufacturer's definition.

The same rule applies to:

accuracy,
seals,
carriage style,
preload.

Complete part numbers must be decoded using the correct manufacturer's nomenclature.

Preload vs. Accuracy Class

These specifications are frequently confused.

They solve different problems.

Preload

Primarily changes:

internal clearance,
rigidity,
deflection,
rolling resistance.

Accuracy Class

Primarily controls:

running parallelism,
height tolerance,
width tolerance,
block-to-block dimensional matching.

A Precision-grade guide does not automatically have heavy preload.

A heavily preloaded guide does not automatically have Precision-grade manufacturing accuracy.

Why Preload Can Still Affect Running Behavior

Although preload and accuracy are separate specifications, preload can influence how consistently the carriage responds to changing loads.

Removing internal clearance can reduce small displacements associated with load reversal.

That can be valuable in precision machinery.

But it does not replace the need for an appropriate accuracy class.

Preload vs. Load Rating

Preload also should not be confused with:

C,
C₀.

C

Basic dynamic load rating used in fatigue-life calculations.

C₀

Basic static load rating used in static-safety evaluation.

Preload

Intentional internal bearing load.

They are related in the engineering calculation, but they are not the same specification.

Does Preload Increase Load Capacity?

Do not treat preload as a method for increasing catalog load rating.

The manufacturer specifies C and C₀ for the guide.

Preload changes:

internal load distribution,
rigidity,
deflection behavior.

It can also add to the loading that must be considered when calculating life.

If the application needs substantially more load capacity, consider:

larger carriage,
long carriage,
additional blocks,
larger nominal rail size,
different guide architecture.

Preload and Service Life

Preload must be considered in fatigue-life analysis because the rolling elements carry an internal load even before the external working load is applied.

THK specifically states that when an LM Guide is used with its medium-preload C0 condition, service life must be calculated while considering the magnitude of preload. THK — Service Life With Preload Considered

Schaeffler likewise states that higher preload creates additional rolling-element loading and reduces basic rating life.

This creates a fundamental tradeoff:

more preload → more rigidity

but potentially:

more preload → less fatigue-life margin

when everything else remains unchanged.

Preload and Friction

Schaeffler identifies preload as one of several variables influencing frictional force in monorail guidance systems, along with:

load,
travel velocity,
rolling-element recirculation design,
lubricant,
temperature,
misalignment,
seals.

Schaeffler — Technical Pocket Guide

Therefore:

higher preload generally means the drive must overcome more internal resistance.

Preload and Motor Sizing

In a highly preloaded multi-block system, bearing resistance may become meaningful in:

actuator sizing,
servo sizing,
low-force positioning.

The drive calculation should consider the complete resistance of:

guide system,
seals,
ball screw or belt,
payload,
acceleration.

Do not select preload independently of the motion system.

Preload and Heat

Greater rolling resistance can contribute to additional heat generation, particularly in:

high-speed,
high-duty-cycle,
heavily preloaded

applications.

Heat can then affect:

lubricant behavior,
dimensional stability,
machine accuracy.

For demanding applications, use the manufacturer's speed, lubrication, preload, and thermal guidance together.

Preload and High-Speed Motion

High-speed automation creates an important tradeoff.

High preload may provide excellent rigidity.

But a high-speed axis may prioritize:

low resistance,
low heat,
low drive force.

The appropriate preload may therefore be lower than what would be selected for a heavy machining axis.

Preload and Machine Tools

Machine tools often benefit from higher preload because:

cutting forces change,
rigidity is critical,
vibration can occur,
deflection directly affects machining performance.

THK specifically associates its medium-preload C0 condition with applications such as:

machining centers,
lathes,
milling machines,
boring machines.

But even in machine tools:

maximum available preload is not automatically correct.

Life and friction still matter.

Preload and Precision Automation

Precision automation may use light or moderate preload to reduce internal movement while avoiding unnecessary resistance.

This can be useful for:

precision XY stages,
inspection machinery,
robotics,
measuring equipment.

THK's application guidance associates light preload with several of these machine types.

Preload and Packaging Machinery

General packaging equipment may not require substantial preload if:

loading direction is predictable,
vibration is low,
two rails are used,
low resistance is desirable.

This is one reason the correct preload should come from machine requirements rather than a blanket rule.

Preload and Single-Rail Systems

A single rail can experience:

radial loads,
reverse-radial loads,
lateral loads,
moments.

THK specifically identifies single-rail configurations as one condition where light preload may be useful.

The exact permissible moments and preload still need to be checked for the selected guide.

Preload and Two-Rail Systems

Two parallel rails create a wider support footprint.

If:

loads are predictable,
vibration is limited,
machine precision requirements are moderate,

a lower-preload or clearance condition may sometimes be appropriate.

But two rails do not automatically eliminate the need for preload.

The actual application controls.

Preload and Moment Loads

Moment loading is another reason preload can matter.

A moment changes the load carried by different rolling contacts.

Preload keeps opposing rolling contacts engaged and can reduce displacement as the moment changes direction.

For large moments, however, preload should not substitute for good machine geometry.

Improve:

rail spacing,
block spacing

where practical.

Preload Cannot Fix Poor Rail Spacing

Suppose a wide moving platform has a large roll moment but the two rails are extremely close together.

Increasing preload may make the guides locally stiffer.

But it does not create the same mechanical leverage as increasing rail spacing.

For roll:

geometry often matters more than preload.

Preload Cannot Fix Poor Block Spacing

The same principle applies to pitch and yaw.

Two blocks spaced farther apart can create greater moment leverage.

Heavy preload should not be used to compensate for an unnecessarily small support footprint.

Preload and Vibration

Preload can improve behavior under vibration by maintaining controlled rolling contact and reducing internal movement.

Both THK and Schaeffler identify preload as important where:

vibration,
impact

are present.

But severe shock loading must still be addressed through:

static safety,
correct guide size,
machine structure.

Preload and Reversing Motion

Reversing axes are another useful example.

When an axis rapidly changes direction:

acceleration changes sign,
inertial forces reverse,
bearing reaction forces shift.

A preloaded guide can respond more rigidly because the rolling contacts are already engaged.

This can be valuable in:

pick-and-place,
precision positioning,
CNC feed axes.

Preload and Ball Guides

Ball-type profile guides commonly use controlled ball/raceway interference to establish preload.

The exact preload range depends on:

guide family,
nominal size,
manufacturer.

Do not assume every ball guide offers the same preload options.

Preload and Roller Guides

Roller guides can also be preloaded.

Because roller systems can provide extremely high rigidity, preload selection becomes particularly important in applications where:

machine stiffness,
machining performance,
deflection

are critical.

THK's current caged-roller documentation, for example, includes rigidity testing under a specified C0 preload condition. THK — Caged Roller LM Guides

Is Preload Factory Set?

For many profile rail systems, yes.

THK states that the clearances of most of its LM Guide models are adjusted to the specified condition before shipment and therefore do not require the user to perform an additional preload adjustment. THK — Selecting a Radial Clearance

This is an important practical point.

Do not assume preload is something an installer should manually “tighten into” a standard recirculating profile rail carriage.

Specify the correct configuration when ordering.

Can You Adjust Preload After Installation?

It depends on the bearing architecture.

Some precision rail-guide designs use external adjustment methods.

For example, Schaeffler's precision rail-guide documentation discusses defined preload created through arrangements such as:

set screws,
adjustment bars,
wedges

for certain precision guide systems.

That is different from a typical factory-preloaded recirculating profile rail carriage.

Always follow the design-specific manufacturer procedure.

Preload vs. Unintentional Installation Stress

A very important distinction exists between:

intentional bearing preload

and:

unwanted assembly stress.

A guide may become difficult to move because:

rails are misaligned,
mounting surfaces are not flat,
two rails are not parallel,
the table twists the carriages,
fasteners distort the assembly.

That is not beneficial preload.

It is installation error.

Binding Is Not Preload

If a guide becomes dramatically harder to move after tightening the machine table, do not immediately conclude:

“The preload increased.”

Investigate:

rail parallelism,
mounting-surface flatness,
carriage alignment,
table flatness,
bolt sequence.

A properly specified preload is controlled by the bearing design.

Binding from misalignment is uncontrolled.

Why This Matters With Two Rails

Two parallel rails can overconstrain a machine if installed inaccurately.

Suppose each rail runs smoothly individually.

After both rails are bolted to one rigid table, resistance increases dramatically.

Possible causes include:

rail parallelism error,
height mismatch,
yaw misalignment.

Increasing preload would not solve that problem.

It could make the system even less tolerant of error.

Higher Preload Can Demand Better Mounting

As rigidity increases, the guide system can become less forgiving of geometric installation errors.

A highly rigid preloaded guide mounted to an inaccurate base may develop unintended internal loads.

Therefore, high-preload applications often require correspondingly good:

base flatness,
rail parallelism,
shoulder accuracy,
assembly technique.

Preload and Accuracy Class Should Be Selected Together—but Separately

A precision machine may require both:

high accuracy class,
suitable preload.

But they should be chosen for different reasons.

Use:

accuracy class to control geometric manufacturing tolerances.

Use:

preload to control internal clearance and rigidity.

This distinction is fundamental to proper linear-guide specification.

Preload and Standard vs. Long Blocks

A long carriage can provide greater:

load rating,
permissible moment,
local stiffness.

That does not mean it automatically has greater preload.

A standard block and long block can potentially be ordered with comparable preload classes depending on the manufacturer.

Carriage length and preload are separate specifications.

Preload and Rail Size

Nominal rail size also does not define preload.

size 15,
size 25,
size 45

guide may each be offered in multiple preload conditions.

Choose size from:

load,
life,
moment,
rigidity,

then select the appropriate preload for the guide and application.

Preload and Flanged vs. Non-Flanged Blocks

External carriage shape does not determine preload.

Both:

flanged,
non-flanged

blocks may be available with different preload specifications.

Do not infer preload from carriage appearance.

How Much Preload Should a Linear Guide Have?

There is no universal percentage or class that is correct for every linear guide.

The appropriate preload depends on:

guide manufacturer,
guide series,
rolling-element type,
external load,
vibration,
shock,
moment load,
required rigidity,
speed,
required life,
mounting accuracy.

Manufacturer guidance should control the final selection.

A Practical Preload Selection Framework

Step 1: Determine the Machine's External Loads

Calculate:

gravity,
acceleration,
process forces,
moments.

Step 2: Determine Required Rigidity

Ask:

How much guide deflection can the machine tolerate?

Step 3: Evaluate Vibration and Shock

More demanding environments may justify additional preload.

Step 4: Evaluate Moment Loading

Consider:

pitch,
yaw,
roll.

Step 5: Improve Machine Geometry First

Optimize:

rail spacing,
block spacing,
center-of-gravity position.

Step 6: Select the Guide Architecture

Choose:

ball,
roller,
size,
block length,
block count.

Step 7: Review Manufacturer Preload Classes

Use the exact series documentation.

Step 8: Check Friction and Drive Requirements

Confirm that the selected preload does not create unacceptable running resistance.

Step 9: Calculate Life With Preload Where Required

Do not ignore the internal preload contribution.

Step 10: Verify Mounting Accuracy

Ensure the structure can support the rigidity level selected.

Step 11: Specify Accuracy Separately

Do not confuse preload with precision grade.

Step 12: Document the Complete Part Number

Include the correct:

preload,
accuracy,
seal,
block,
rail

configuration.

Preload Selection Matrix

Machine ConditionPreload DirectionPredictable load, low vibrationLower preload may be sufficientLowest possible running resistanceLower preload favoredSingle railLight preload often worth evaluatingModerate moment loadLight/moderate preload may helpPrecision positioning structurePreload often usefulReversing loadPreload can improve rigidityVibration/impactGreater preload may be justifiedHeavy machiningMedium/higher preload often consideredMaximum service life priorityAvoid unnecessary preloadHigh-speed, low-force axisAvoid excessive preloadPoor mounting surfacesCorrect structure before increasing preload

This table is conceptual.

Use the selected manufacturer's actual preload recommendations.

Example 1: Packaging Axis

Application:

two rails,
predictable load,
low vibration,
moderate accuracy,
high cycle rate.

A low-preload or normal-clearance configuration may minimize resistance while providing adequate performance.

Example 2: Single-Rail Robot Axis

Application:

one profile rail,
overhung payload,
reversing motion,
moment loading.

Light preload may improve rigidity and reduce internal movement.

THK specifically identifies single-rail and overhung/moment-loading conditions among applications for light preload.

Example 3: CNC Machine Tool

Application:

cutting forces,
vibration,
high rigidity requirement,
precision-machined base.

A medium-preload guide may be appropriate depending on the exact guide system and life calculation.

Example 4: High-Speed Pick-and-Place

Application:

light payload,
very high acceleration,
low required drive force.

Excessive preload could add unnecessary resistance and moving-system losses.

Use only enough preload to satisfy rigidity and motion requirements.

Example 5: Four-Block Precision Table

Application:

two rails,
two blocks per rail,
precision motion,
rigid table.

Preload may improve system stiffness, but:

block matching,
rail parallelism,
mounting-surface accuracy

become especially important.

Example 6: Large Roll Moment

Application:

wide platform,
high center of gravity,
significant lateral acceleration.

Do not simply increase preload.

First evaluate:

lowering the center of gravity,
increasing rail spacing.

Those changes can reduce the underlying carriage reaction loads.

Then select preload.

Common Linear Guide Preload Mistakes

Mistake 1: Assuming More Preload Is Always Better

Higher preload adds internal load and resistance.

Mistake 2: Confusing Preload With Accuracy

They are separate specifications.

Mistake 3: Confusing Preload With Load Capacity

Preload does not replace C or C₀.

Mistake 4: Ignoring Preload in Life Calculations

Medium or high preload can materially affect internal bearing loading.

Mistake 5: Using Preload to Compensate for Poor Machine Geometry

Improve rail spacing, block spacing, and center-of-gravity location first.

Mistake 6: Assuming Preload Codes Are Universal

They are manufacturer specific.

Mistake 7: Assuming Binding Means High Preload

Binding can indicate misalignment.

Mistake 8: Increasing Preload on Poor Mounting Surfaces

High rigidity can make installation errors more consequential.

Mistake 9: Specifying Heavy Preload for Every Precision Machine

The correct level depends on the complete application.

Mistake 10: Replacing a Carriage Without Checking Preload

A physically compatible block can still have the wrong internal clearance.

Linear Automation USA's Perspective

At Linear Automation USA, we treat preload as a rigidity-setting decision with consequences—not as a performance upgrade that should automatically be maximized.

The question should not be:

“What is the highest preload available?”

It should be:

“How much preload does this machine need to control deflection without creating unnecessary internal load, friction, and life penalty?”

We first look at the machine itself:

load,
moments,
acceleration,
vibration,
block arrangement,
rail arrangement,
center of gravity,
required rigidity.

If the problem is a large roll moment, we would rather investigate:

rail spacing,
center-of-gravity height

before attempting to solve everything with preload.

If the problem is a large pitch moment, we evaluate:

block spacing,
carriage length.

If the problem is basic load capacity, we evaluate:

rail size,
block count,
block style.

Then preload becomes part of the final optimization.

For precision machinery, we also separate:

preload from accuracy class.

A guide can be manufactured to very tight geometric tolerances and still require the appropriate preload to achieve the desired rigidity.

For replacement applications, the preload code deserves the same attention as:

manufacturer,
series,
nominal size,
carriage dimensions,
accuracy grade.

A replacement carriage that physically fits the rail but has substantially different preload can change:

running resistance,
rigidity,
deflection,
calculated life.

Linear Automation USA supplies industrial profile rail systems from Schaeffler, SBC Linear, and WON Linear, along with application, identification, replacement, and cut-to-length support.

Our rule is:

Use enough preload to achieve the rigidity the machine needs—but no more than the application can justify.

Frequently Asked Questions

What Is Preload in a Linear Guide?

Preload is an intentional internal load between the rolling elements, carriage, and rail that reduces internal clearance and increases rigidity.

Why Are Linear Guides Preloaded?

Primarily to reduce internal movement and deflection under changing external loads.

Does Preload Increase Rigidity?

Yes. Increasing preload generally increases guide rigidity.

Does Preload Increase Friction?

Greater preload generally increases running resistance because the rolling elements carry more internal load.

Does Preload Reduce Linear Guide Life?

Higher preload can reduce calculated fatigue life because it creates additional rolling-element loading. The effect must be included in the appropriate manufacturer life calculation.

Is More Preload Better?

No. The correct preload is the minimum appropriate level that satisfies the machine's rigidity and operating requirements.

Is Preload the Same as Accuracy?

No. Preload controls internal clearance and rigidity. Accuracy class controls manufacturing geometry and tolerances.

Is Preload the Same as C₀?

No. C₀ is the basic static load rating. Preload is intentional internal bearing load.

What Is Negative Clearance?

Negative clearance describes an interference condition in which the rolling elements are intentionally loaded against the raceways. This is the basis of preload in many profile rail systems.

Is Zero Clearance the Same as Preload?

Not necessarily. Manufacturer terminology and specifications must be checked.

What Preload Should I Use?

Select preload from the exact manufacturer's guidance based on rigidity, vibration, moment load, speed, life, and machine configuration.

Is Preload Good for a Single Linear Rail?

It can be. THK identifies single-rail configurations as one condition where light preload may be useful.

Is Preload Good for CNC Machines?

Often, because machine tools can require high rigidity under changing cutting forces. The exact class still requires engineering evaluation.

Is Preload Good for High-Speed Automation?

Sometimes, but excessive preload can add unnecessary resistance and heat. Balance rigidity against speed and drive requirements.

Is Preload Factory Set?

For many recirculating profile rail systems, yes. THK states that most of its LM Guide clearances are adjusted to the specified condition before shipment.

Can I Adjust Linear Guide Preload Myself?

Do not assume so. Typical factory-preloaded profile rail carriages should be ordered with the correct clearance/preload specification. Some specialized precision guide architectures use adjustable preload mechanisms.

Can Misalignment Feel Like Preload?

Yes. Excessive running resistance can result from rail or carriage misalignment rather than intentional preload.

Should Replacement Blocks Have the Same Preload?

Where preload affects the machine's required rigidity, friction, or accuracy behavior, the original specification should be identified and preserved or an engineered alternative selected.

Need Help Selecting the Right Preload?

For a new application, record:

guide manufacturer or preferred series,
moving mass,
external loads,
pitch/yaw/roll moments,
acceleration,
speed,
stroke,
block count,
block spacing,
rail spacing,
required rigidity,
required life,
desired accuracy,
vibration/shock conditions,
mounting orientation.

For a replacement, provide:

manufacturer,
complete carriage number,
complete rail number,
preload or clearance code,
accuracy code,
nominal size,
photographs,
carriage dimensions,
rail dimensions,
rail length,
quantity.

Contact Linear Automation USA with this information when you need help identifying or evaluating an industrial profile rail replacement.