Before requesting a quote for linear guides, document more than the rail size and length. A supplier can make a much better recommendation when the request includes the application’s moving mass, payload, mounting orientation, center of gravity, rail and block arrangement, stroke, speed, acceleration, external forces, required life, accuracy, rigidity, environment, lubrication needs, and finished rail dimensions.
The most useful RFQ answers four basic questions:
What is moving? → How is it loaded? → How must it perform? → What physical rail and carriage configuration will fit the machine?
THK’s current selection methodology follows the same engineering logic: define operating conditions, select a preliminary guide type, calculate loads on the individual blocks, determine equivalent load, check static safety, calculate life, evaluate rigidity and accuracy, and then address lubrication and environmental conditions.
For buyers, maintenance teams, and machine designers, that leads to one simple rule:
The more application information you provide before requesting a linear-guide quote, the less likely you are to receive a part that merely fits dimensionally but is wrong mechanically.
The Linear Guide RFQ Checklist
Before contacting a supplier, try to gather:
manufacturer or preferred brand
existing part number, if replacing a guide
rail size and series, if known
number of rails
number of carriages per rail
block style
rail length
required stroke
mounting orientation
moving mass and maximum payload
center-of-gravity location
rail spacing
block spacing
speed
acceleration/deceleration
process or external forces
required accuracy
required rigidity or allowable deflection
preload requirement, if known
expected operating life or duty cycle
operating environment
lubrication method
sealing or contamination-protection needs
corrosion or special material requirements
rail mounting-hole pitch and end dimensions
quantity
whether rails need custom cutting
You may not know every item.
That is fine.
But understanding why each item matters makes it much easier to collect the information that will actually influence selection.
1. Is This a New Application or a Replacement?
This should be the first piece of information on the RFQ.
New Application
For a new machine, the supplier may need to help determine:
guide family
nominal size
number of rails
number of blocks
preload
accuracy class
finished rail length
Replacement Application
If replacing an existing guide, provide:
manufacturer
complete rail part number
complete carriage part number
photographs
dimensional measurements
quantity
If the original system is discontinued, include as much information from the old guide as possible.
Linear Automation USA specifically offers interchange assistance for discontinued linear systems in addition to stocking profile rails and carriages.
2. Provide the Complete Part Number
If a part number exists, do not provide only:
“Size 25 rail.”
A complete linear-guide model number can encode characteristics such as:
series
nominal size
carriage style
number of blocks
seals
preload
accuracy
rail length
options
The exact coding system depends on the manufacturer.
Therefore:
never decode one manufacturer's guide using another manufacturer's part-number system.
If possible, photograph the entire marking on both:
carriage
rail
3. Identify the Preferred Manufacturer
If your machine already standardizes on a brand, include it.
Linear Automation USA currently supplies profile-rail products from brands including SBC, WON, and Ewellix/Schaeffler-related solutions. (Linear Automation USA)
If you are open to an equivalent replacement, say:
“Equivalent/interchange acceptable.”
That gives the supplier more flexibility.
But remember:
nominal rail size alone does not establish interchangeability.
A replacement may also need to match:
rail width and height
carriage dimensions
mounting-hole locations
reference geometry
preload
accuracy
load capacity
4. What Is the Mounting Orientation?
Specify whether the guide is:
horizontal
vertical
wall mounted
inverted
inclined
This information can change both loading and lubrication.
THK formally distinguishes horizontal, inverted, wall, vertical, and slant mounting and warns that non-horizontal orientation can affect whether lubricant reaches the raceways as intended.
So do not simply write:
“Two size-25 rails.”
Write something like:
“Two parallel size-25 profile rails mounted vertically.”
That is much more useful.
5. What Is the Moving Mass?
Provide the approximate total moving mass.
Include:
moving table
tooling
fixtures
motors mounted on the moving assembly
workpiece
maximum payload
For gravity:
W = m × g
where:
W = weight force
m = mass
g ≈ 9.81 m/s²
For example, a 250 kg moving assembly represents approximately:
2,453 N
of gravitational force.
But that still does not tell us how much load reaches each carriage.
6. Where Is the Center of Gravity?
This is one of the most frequently missing pieces of RFQ information.
The supplier needs to know whether the payload is:
centered
offset sideways
elevated above the guide plane
cantilevered beyond the blocks
Why?
Because:
M = F × d
A relatively modest load with a large offset can create a large moment.
THK specifically includes center-of-gravity position, thrust position, working-load direction, acceleration, stroke, speed, and guide arrangement among the variables needed to calculate applied block loads.
A useful sketch showing the CG can be more valuable than a paragraph of explanation.
7. How Far Apart Are the Rails?
For a two-rail system, provide the approximate:
rail center-to-center spacing
This dimension strongly affects resistance to roll moment.
In a simplified two-rail system:
moment-induced rail load shift = Mroll / S
where:
Mroll = roll moment
S = rail spacing
Greater rail spacing generally reduces the reaction required to resist the same roll moment.
If you are requesting help selecting the rail size, this geometry can materially affect the recommendation.
8. How Far Apart Are the Blocks?
Also provide longitudinal:
block center-to-center spacing
Block spacing helps establish resistance to:
pitch
yaw
For a simplified support pair:
moment-induced load shift = M / L
where:
L = block spacing
Do not simply state:
“Four blocks.”
A four-block system with blocks clustered together behaves very differently from one with a large rectangular support footprint.
9. How Many Rails and Blocks Will Be Used?
Specify the proposed arrangement.
Examples:
1 rail / 1 block
1 rail / 2 blocks
2 rails / 2 blocks each
2 rails / 3 blocks each
This affects:
load distribution
allowable moment
rigidity
required rail length
THK's engineering methodology calculates applied load on individual blocks rather than assuming that total machine load divides evenly by the number of carriages.
10. What Is the Required Stroke?
Stroke means the actual travel required by the moving assembly.
Do not confuse:
stroke
with:
rail length.
A rail generally needs additional length for:
carriage length
block spacing
end allowance
A useful preliminary relationship is:
Rail Length ≈ Required Stroke + Carriage-Group Footprint + End Allowance
So if you need:
1,500 mm travel
you may need significantly more than:
1,500 mm of rail.
11. What Finished Rail Length Do You Need?
If the machine has already been designed, provide the finished rail length.
For custom-cut rail, also provide the mounting-hole requirements.
Linear Automation USA currently offers cut-to-size rail processed locally, making finished rail geometry an especially useful item to define during the quote process.
12. Provide Mounting-Hole Pitch and End Dimensions
Profile rail mounting holes normally follow a repeating pitch.
A finished rail can be represented conceptually as:
L = G1 + nP + G2
where:
L = total rail length
P = mounting-hole pitch
G1 = distance from one rail end to first mounting hole
G2 = opposite end distance
n = number of pitch intervals
If replacing an existing rail, these dimensions can be critical.
Do not assume two rails of equal nominal length automatically have identical hole placement.
13. What Is the Maximum Speed?
Provide maximum travel velocity.
For example:
1.5 m/s
is much more useful than:
“fast.”
Speed can influence:
guide family
lubrication
sealing
heat generation
required travel life
But speed alone is not enough.
14. What Is the Maximum Acceleration?
Acceleration can be more important than top speed.
Dynamic force is:
F = m × a
Suppose the moving mass is:
300 kg
and acceleration is:
5 m/s²
Then:
F = 1,500 N
If the center of gravity is offset from the guide system, that inertial force also creates moment.
THK's applied-load procedure explicitly includes acceleration/deceleration generated during machine starts and stops.
15. What External Forces Act on the Machine?
Include forces caused by:
cutting
pressing
drilling
grinding
clamping
robotics
material handling
belt tension
actuator reaction
State:
magnitude
direction
point of application
if known.
A 500 N force acting directly through the guide center is different from the same 500 N force acting 500 mm away.
16. Is Shock or Impact Expected?
Tell the supplier if the machine experiences:
impact
vibration
rapid reversals
hard stops
repeated starts/stops
rough material transfer
Manufacturer life methodologies may account for vibration and impact rather than treating every application as perfectly smooth operation. THK, for example, provides load-factor guidance for varying speed, vibration, and impact conditions.
Describe the real machine rather than the ideal machine.
17. What Service Life Do You Need?
If possible, provide:
hours/day
days/week
cycles/minute
stroke
expected machine life
THK's load-calculation inputs specifically include stroke, reciprocation frequency, average speed, and required service life.
This is more useful than saying:
“It needs to last a long time.”
For a production machine, you might state:
16 hours/day, 5 days/week, 20 cycles/minute, 1,000 mm stroke, 10-year design objective.
That creates a usable engineering target.
18. What Accuracy Does the Machine Require?
Do not simply write:
“high accuracy.”
Where possible, define requirements such as:
positioning accuracy
repeatability
straightness
running parallelism
Accuracy class can influence:
cost
availability
rail manufacturing limits
installation requirements
THK notes that maximum manufactured rail lengths can become restricted where a high degree of precision is required.
19. What Rigidity or Deflection Is Acceptable?
For precision machinery, the guide may be sized by rigidity before it is limited by basic load capacity.
If possible, provide a target such as:
maximum allowable tool-tip deflection = 20 μm
instead of simply:
“needs to be rigid.”
Rigidity is especially important for:
machine tools
grinding
inspection
precision assembly
cantilevered tooling
20. Do You Need a Particular Preload?
If you know the required preload class, include it.
If you do not, provide the application information and let the guide selection determine it.
THK states that radial clearance/preload materially affects running accuracy, rigidity, and load behavior, and recommends selecting the appropriate clearance according to application conditions.
Do not specify maximum preload simply because it sounds more precise.
21. What Is the Operating Environment?
Tell the supplier whether the guide will operate around:
metal chips
abrasive dust
coolant
water
washdown
chemicals
high humidity
cleanroom requirements
elevated temperatures
This can influence:
seals
scrapers
lubricant
surface treatment
material
THK places contamination protection, lubrication, and corrosion prevention explicitly within the final environment-selection stage.
22. How Will the Guide Be Lubricated?
Specify whether the machine uses:
manual grease
centralized grease
oil lubrication
another approved method
Also consider grease-fitting accessibility.
This matters especially for:
vertical
wall-mounted
inverted
applications because lubrication-port position can be orientation-dependent. THK specifically asks for mounting orientation and grease-nipple or piping-joint position when ordering.
23. Do You Need Special Seals or Scrapers?
In contaminated environments, indicate whether there is:
dust
swarf
chips
coolant
abrasive material
The supplier can then determine whether available options include additional:
seals
scrapers
lubrication accessories
rather than quoting a bare standard carriage.
24. Do You Need Corrosion Resistance?
If the application is exposed to:
moisture
chemicals
food-processing washdown
outdoor conditions
mention that before the quote.
Do not assume the standard product material and surface condition will be appropriate.
25. What Carriage Style Fits the Machine?
If packaging is already fixed, specify whether you require:
flanged block
non-flanged/slim block
standard-length block
long block
low-profile configuration
Provide existing mounting dimensions where relevant.
Block style affects both:
physical fit
load/moment capability
so it should not be treated only as a cosmetic preference.
26. Provide a Drawing Whenever Possible
One simple dimensioned sketch can answer dozens of questions.
Show:
rails
blocks
payload
center of gravity
rail spacing
block spacing
stroke
force directions
major offsets
It does not need to be a finished CAD drawing.
Even a clear hand sketch can prevent misunderstandings.
27. For Replacement Guides, Send a Nameplate or Part-Number Photo
Photographs are especially useful for obsolete or unknown systems.
Photograph:
carriage marking
rail marking
entire guide
mounting arrangement
rail cross section
surrounding machine
If the marking is difficult to read, take:
close-up photo
angled photo
wider context photo
Linear Automation USA specifically offers interchange services for discontinued systems, making identification information particularly valuable.
28. State the Quantity
Specify separately:
number of rails
number of blocks
For example:
2 rails, 4 blocks total
is better than:
“Need two linear guides.”
That phrase could mean:
two rails
two rail/block assemblies
two complete axes
Avoid ambiguity.
29. State Whether Rail Cutting Is Required
If you need custom rail, provide:
quantity
finished length
hole pitch if known
end dimensions if required
Linear Automation USA currently states that custom-cut rails are processed at its local warehouse.
That can make the RFQ much more specific than simply ordering stock rail and cutting it later.
30. State Whether an Equivalent Is Acceptable
For replacement applications, say whether you require:
exact OEM
or whether:
engineered equivalent/interchange is acceptable.
That can make a major difference when the original guide is:
obsolete
unavailable
experiencing long lead times
But an interchange should be confirmed against the complete system geometry and requirements—not nominal rail size alone.
A Better Linear Guide RFQ Example
Instead of:
Need price on two 25 mm linear rails, 6 feet long.
A much more useful request would say:
New horizontal automation application. Two parallel profile rails with two carriages per rail. Moving mass approximately 180 kg including maximum payload. Rail spacing 500 mm; block spacing 400 mm. CG approximately 150 mm above the rail plane and centered between rails. Required stroke 1,500 mm. Maximum speed 1.2 m/s and acceleration 3 m/s². No major process force. Approximately 10 cycles/minute, 16 hours/day. Standard industrial environment with moderate dust. Normal industrial accuracy is acceptable. Please recommend SBC, WON, Schaeffler/Ewellix equivalent as appropriate and quote custom-cut rails with four carriages.
Now the supplier can actually engineer around the application.
Linear Automation USA's Perspective
At Linear Automation USA, one of the biggest problems we see with linear-guide quote requests is that the buyer often begins with:
“I need a size 25 rail.”
That tells us much less than people realize.
We would rather know:
What is the machine doing?
From there, we can work backward toward the appropriate:
series
rail size
carriage
rail length
preload
accuracy
options
For a new application, some of the most valuable information is:
mass + center of gravity + rail spacing + block spacing + stroke + speed + acceleration + mounting orientation
For a replacement, some of the most valuable information is:
complete part number + photographs + rail dimensions + carriage dimensions + hole pattern
And for a custom-cut rail, we want:
finished rail length + mounting-hole geometry
Linear Automation USA supplies profile rails and carriages from SBC, WON, and other supported linear-motion product lines, provides locally processed custom-cut rails, and can assist with discontinued-system interchange applications.
Our rule is:
Do not request a linear guide quote with only a rail size. Give the supplier enough information to understand the machine, the load, the motion, and the finished geometry.
Printable Linear Guide Quote Checklist
Before submitting your RFQ, gather as many of these as possible:
InformationWhat to ProvideApplicationNew machine or replacementManufacturerPreferred/current brandPart numberComplete rail and block numbersMounting orientationHorizontal, vertical, wall, inverted, inclinedMoving masskg or lbMaximum payloadkg or lbCenter of gravityX/Y/Z offset or sketchNumber of rails1, 2, etc.Blocks per rail1, 2, etc.Rail spacingCenter-to-centerBlock spacingCenter-to-centerRequired strokemm or inchesRail lengthFinished lengthSpeedMaximum travel speedAccelerationMaximum acceleration/decelerationProcess forcesMagnitude, direction, locationShock/vibrationNone, moderate, severeDuty cycleCycles/minute and hours/dayRequired lifeHours, cycles, or yearsAccuracyRequired class/performanceRigidityAllowable deflection if knownPreloadIf specifiedEnvironmentDust, chips, coolant, cleanroom, etc.LubricationManual, centralized, oil, etc.ProtectionSeals, scrapers, coversCorrosion resistanceYes/no/special environmentBlock styleFlanged, slim, long, etc.Rail hole pitchPFirst-end dimensionG1Opposite-end dimensionG2QuantityRails and carriages separatelyDrawing/photosAttach whenever possibleEquivalent acceptable?Yes/no
You do not need every line completed before contacting a supplier.
If several items are unknown, say:
“Need application assistance.”
That is far better than guessing.
Frequently Asked Questions
What Information Do I Need to Order a Linear Guide?
At minimum, identify the rail/carriage series or describe the application, required rail length, number of blocks, and quantity. For proper engineering selection, also provide payload, CG, orientation, spacing, stroke, speed, acceleration, forces, duty cycle, and environment.
What If I Do Not Know the Linear Guide Part Number?
Provide photographs and measurements of the existing rail and carriage, along with information about the machine.
Can a Supplier Select a Linear Guide From Payload Weight Alone?
Not reliably. Center-of-gravity offsets, acceleration, external forces, and rail/block geometry determine the loads on individual carriages.
Do I Need to Know the Preload Before Requesting a Quote?
Not necessarily. If preload has not already been specified, provide the rigidity, accuracy, loading, and application information needed to select it.
Should I Specify Rail Length or Stroke?
Ideally both. Stroke is the machine's required travel; rail length also includes the carriage footprint and appropriate end geometry.
Do I Need the Rail Mounting-Hole Pattern?
It is especially useful for replacement and custom-cut rails because total rail length alone does not define mounting-hole position.
Should I Include Mounting Orientation?
Yes. Orientation affects load calculations and can affect lubrication configuration.
Should I Send a Drawing?
Yes. A simple dimensioned drawing showing rails, blocks, payload, CG, stroke, and forces can dramatically improve the quality of an application review.
Can I Request an Equivalent for an Obsolete Linear Guide?
Yes, but dimensional similarity alone is insufficient. The proposed interchange should be checked for mounting geometry, load capacity, accuracy, preload, and other relevant specifications.
Ready to Request a Linear Guide Quote?
For the fastest application review, send:
part number or application description + photos/drawing + mass + CG + orientation + rail/block spacing + stroke + speed + acceleration + rail length + quantity
Then include any:
accuracy
rigidity
environmental
lubrication
requirements that matter to the machine.
Contact Linear Automation USA for application assistance, custom-cut rail, or help identifying a replacement profile-rail system.
Recommended Reading
How to Choose the Right Linear Guide Rail
Start with the overall engineering selection process before narrowing the application to a specific rail and carriage.
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How to Size a Linear Guide for an Industrial Application
Learn how load, moments, static safety, life, and rigidity determine guide size.
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How to Calculate Load on a Linear Guide
Understand why payload alone does not determine individual carriage loading.
Publishing note: Replace the temporary homepage link with the final article URL.
How to Select Linear Rail Length
Calculate rail length from required stroke, carriage footprint, end allowance, and mounting-hole geometry.
Publishing note: Replace the temporary homepage link with the final article URL.
How to Read a Linear Guide Part Number
Learn what information may be encoded in a manufacturer's rail and carriage model numbers.
Publishing note: Replace the temporary homepage link with the final article URL.
How Mounting Orientation Affects Linear Guide Selection
Understand horizontal, vertical, wall, inverted, and inclined mounting before finalizing the guide.
Publishing note: Replace the temporary homepage link with the final article URL.
Linear Guide Load Ratings Explained
Review C, C₀, static safety, and fatigue-life considerations before comparing candidate guides.
Publishing note: Replace the temporary homepage link with the final article URL.
Sources & Technical References
THK — LM Guide Selection Criteria
Provides the engineering selection sequence covering operating conditions, applied block load, equivalent load, static safety, average load, nominal life, rigidity, accuracy, lubrication, contamination, and corrosion.
THK — Applied Load
Provides the application inputs needed for load calculation, including moving mass, force direction, center-of-gravity position, guide arrangement, velocity, acceleration, stroke, duty cycle, and required life.
THK — Setting Conditions
Documents horizontal, inverted, wall, vertical, and inclined mounting conditions and explains why mounting orientation must also be considered when configuring lubrication.
THK — Notes on Ordering
Useful when preparing the actual order because it addresses order units, mounting orientation, lubrication-port location, options, and maximum manufactured rail lengths.
THK — Predicting Rigidity and Selecting Preload
Explains why radial clearance and preload must be selected from application requirements rather than treated as a generic specification.
Linear Automation USA
Current information on Linear Automation USA's profile-rail inventory, custom-cut rail processing, and discontinued-system interchange assistance.