To order cut-to-length linear rail correctly, provide the exact rail series and size, required finished length, quantity, carriage configuration, mounting-hole requirements, and any critical end dimensions. If the application is new rather than a direct replacement, also provide the required stroke, number of blocks, block spacing, mounting orientation, and basic load information so the finished rail length can be checked against the machine geometry before it is cut.
The most important point is that cut-to-length rail should not be ordered from overall length alone.
A supplier needs to understand how that requested length relates to:
mounting-hole pitch
distance from each rail end to the nearest mounting hole
required carriage travel
carriage-group footprint
maximum manufactured rail length
accuracy requirements
whether the rail must match an existing mounting pattern
THK’s current ordering documentation confirms that LM rail length, mounting orientation, lubrication configuration, supported options, and maximum manufactured length are all model-specific ordering considerations. THK also recommends that special rail lengths maintain appropriate G and g end dimensions because excessively large unsupported end sections can reduce stability and negatively affect accuracy.
The basic rule is:
Order the rail from the complete finished geometry, not simply from a tape-measure length.
What Does Cut-to-Length Linear Rail Mean?
Cut-to-length linear rail is profile rail supplied at a finished overall length selected for a particular machine or application.
Instead of purchasing a stock rail and shortening it later, the customer provides the required dimensions and the supplier processes the rail before shipment.
This can reduce:
field cutting
handling
contamination risk
incorrect end dimensions
shop labor
installation delays
For a well-defined application, receiving the rail at the correct finished length can make installation substantially easier.
Start With the Exact Rail Manufacturer and Series
The first thing to provide is the exact rail identification.
For example:
manufacturer
guide family
nominal rail size
rail part number, if known
Do not simply request:
“25 mm linear rail.”
Nominal size alone does not define:
rail width
rail height
mounting-hole pitch
mounting-hole diameter
counterbore
accuracy
compatibility with the carriage
Different manufacturers and guide families can use different dimensions even when the nominal size is similar.
A better request would be:
SBC SBI size 25 rail
or:
replacement rail for existing carriage part number XXXXX
The more specific the identification, the less chance of receiving an incompatible rail.
If It Is a Replacement, Provide the Existing Part Number
For replacement applications, provide the complete markings from both:
rail
carriage
if available.
Also include photographs.
Photograph:
entire rail
rail markings
block markings
rail cross section
mounting holes
surrounding machine
If the existing system is obsolete, those details can help determine whether an equivalent or engineered interchange is available.
Do not assume that matching the rail width and length is sufficient to establish interchangeability.
Specify the Finished Rail Length
Provide the required finished overall rail length.
For example:
1,840 mm finished length
is much better than:
about six feet
Precision rail should be specified using an exact finished dimension.
If the machine was designed in inches, an inch dimension can be provided, but profile rail is commonly dimensioned in millimeters, so confirm the converted value before ordering.
For example:
72.000 in = 1,828.8 mm
Do not casually round that to 1,830 mm if the rail must match an existing machine.
Finished Length and Required Stroke Are Not the Same Thing
If the machine is still being designed, do not determine rail length from stroke alone.
A useful preliminary relationship is:
Rail Length ≈ Required Stroke + Carriage-Group Footprint + End Allowance
The blocks occupy physical rail length.
If two carriages are used on each rail, the carriage group may occupy several hundred millimeters beyond the required travel.
For example:
required stroke = 1,200 mm
carriage-group footprint = 300 mm
total end allowance = 100 mm
Preliminary rail length:
1,200 + 300 + 100 = 1,600 mm
That 1,600 mm should then be checked against the mounting-hole pattern before it becomes the final order length.
Specify the Mounting-Hole Pitch
Profile rail normally has mounting holes spaced at a regular pitch.
The pitch is commonly represented as:
P or F
depending on the manufacturer.
For example:
mounting-hole pitch = 60 mm
This is one of the most important dimensions when ordering custom rail because the mounting holes do not reposition themselves when the rail is shortened.
The finished cut determines how much rail remains beyond the first and last mounting holes.
Understand the End Dimensions
A useful representation of the finished rail is:
L = G1 + nP + G2
where:
L = finished overall rail length
G1 = distance from the first rail end to the first mounting-hole center
G2 = distance from the final mounting-hole center to the opposite rail end
P = mounting-hole pitch
n = number of pitch intervals
Manufacturers may use different notation.
THK commonly identifies the end dimensions as G and g and publishes recommended values for specific rail models. THK warns that excessively large values make the unsupported end section less stable and can adversely affect accuracy.
This is why the exact finished length should be checked against the rail’s hole pattern before the order is released.
Do G1 and G2 Have to Be Equal?
No.
A custom rail can have unequal end dimensions when the machine requires them.
For example:
G1 = 20 mm
G2 = 35 mm
may be appropriate for an existing machine base.
For a new machine, a more symmetrical arrangement may be convenient, but symmetry is not a universal requirement.
What matters is that the end dimensions are:
intentional
mechanically appropriate
compatible with the mounting plate
Give the Supplier the Existing Hole Pattern for Replacement Rail
If the replacement rail must bolt directly onto an existing machine, provide:
overall rail length
mounting-hole pitch
first-hole end dimension
last-hole end dimension
hole diameter
counterbore diameter and depth if relevant
A drawing is ideal.
This eliminates one of the most common replacement problems:
correct rail length, wrong mounting-hole locations.
Example of a Good Cut-to-Length Rail Order
Instead of writing:
Need two size-25 rails, 60 inches long.
Provide:
Quantity: 2 rails
Manufacturer/series: SBC SBI size 25
Finished length: 1,520 mm each
Mounting-hole pitch: 60 mm
Required first-hole dimension: 20 mm
Matching end pattern on both rails
Two carriages per rail
Horizontal application
Required stroke: 1,150 mm
Please confirm finished hole geometry before cutting.
That gives the supplier enough information to catch a potential geometry problem before the rail is processed.
How the Hole Pattern Can Change the Best Length
Suppose you initially request:
1,500 mm rail length
and the rail uses:
60 mm mounting-hole pitch
The supplier may calculate that the resulting end dimensions are undesirable.
A nearby finished length such as:
1,480 mm
or:
1,520 mm
might create much better support at the rail ends while still providing the required stroke.
This is exactly why it can be helpful to provide both:
desired rail length
required stroke
If the exact overall dimension is not critical, the supplier may be able to recommend a nearby length that works better with the hole pattern.
Say Whether the Overall Length Is Critical
This is a valuable RFQ detail.
State either:
Finished length is fixed and cannot change
or:
Finished length may be adjusted slightly to optimize mounting-hole end dimensions
Those are very different requests.
For a replacement rail, exact overall length may be mandatory.
For a new machine, a small change may be harmless and could produce a better rail configuration.
State the Quantity Clearly
Specify:
number of rails
number of carriages
separately.
For example:
2 rails, 4 carriages total
is clearer than:
2 linear guides
because “two guides” can mean different things to different buyers.
If you need multiple rails at the same finished length, say so explicitly.
Specify Whether Both Rails Must Be Identical
For a two-rail machine, it is usually useful to state:
Both rails identical finished length and hole pattern
if that is the requirement.
If the rails differ, provide each rail separately:
Rail A: 1,500 mm
Rail B: 1,620 mm
Do not assume the supplier will infer the machine configuration.
Provide the Number of Blocks Per Rail
If the rail length has not yet been finalized, the number of blocks matters.
A rail carrying one short block needs less carriage footprint than a rail carrying:
two standard blocks
two long blocks
three blocks
The supplier needs the complete carriage group to determine whether the requested rail length will support the required stroke.
Provide Block Spacing
For two blocks on each rail, provide the block center-to-center spacing if known.
For example:
block spacing = 300 mm center-to-center
This matters because the block group consumes rail length.
It also affects moment resistance.
Do not shorten the rail by moving blocks closer together without checking the mechanical consequences.
Provide the Required Stroke
Even when you already know the rail length, include the required stroke if possible.
The supplier can then perform a simple sanity check:
Will the block arrangement actually travel the required distance on this rail?
This can catch specification mistakes before material is cut.
Specify the Mounting Orientation
State whether the rail will be:
horizontal
vertical
wall mounted
inverted
inclined
This may not change the saw-cut dimension directly, but it can affect the complete guide order.
THK’s current ordering guidance specifically requires mounting orientation to be communicated because it can affect grease-nipple or lubrication-piping position.
If you are ordering:
rails
carriages
lubrication accessories
as one assembly, orientation is worth including.
Specify the Carriage Style
Include the carriage model or style if known.
Examples include:
flanged
non-flanged
standard length
long block
low-profile
Carriage length affects the minimum rail length required for a particular stroke.
A long carriage may require substantially more rail than a standard block.
State the Accuracy Requirement
If you need a particular accuracy grade, include it.
This becomes especially important with long rails.
THK specifically states that where a high degree of precision is required, limits can apply to the maximum manufactured rail length.
Do not assume that a rail length available in a standard accuracy grade is automatically available at the same length in every precision grade.
State the Preload if It Is Part of the Complete Order
Preload generally applies to the carriage/rail assembly rather than the cut dimension alone.
If you are ordering a complete matched guide system, provide the required preload class if known.
If it is not known, provide enough application information to select it:
payload
rigidity requirement
accuracy requirement
speed
machine type
Do not arbitrarily specify the highest preload.
Check Maximum One-Piece Rail Length
Before ordering a very long rail, verify that the selected family can be manufactured in the requested one-piece length.
Maximum rail length varies by:
manufacturer
guide series
nominal size
accuracy grade
THK’s current dimensional tables demonstrate this clearly. For example, some models have maximum lengths much shorter than 3,000 mm, while others are available to approximately 3,000 mm depending on model and accuracy.
There is no universal:
“All profile rails are available in 3-meter lengths.”
What If the Required Rail Is Too Long?
If the requested rail exceeds the maximum one-piece length, the application may require:
manufacturer-supported jointed rail
another guide family
revised machine geometry
THK specifically identifies jointed rails as an option for certain guide families when required length exceeds the published maximum.
Do not simply order two independent pieces and assume they can be butted together.
A proper jointed rail system must preserve the rolling path across the joint.
Do You Need Jointed Rail? Say So Up Front
For a long axis, include:
Required total guideway length: 4,500 mm
rather than:
Need two 2,250 mm rails
if your real intention is for a carriage to travel continuously across both pieces.
Those are completely different applications.
The supplier needs to know whether:
the pieces are separate rails
or they must form one continuous jointed guideway
Specify Whether the Rail Must Match an Existing Machine
For replacement applications, say:
Must match existing mounting pattern
if that is critical.
Also provide a drawing or dimensions.
This tells the supplier not to substitute a nearby “better” custom length without approval.
Send a Dimensioned Drawing When Possible
A simple rail drawing can show:
finished overall length
hole pitch
G1
G2
hole size
quantity
For an application-level review, add:
block locations
required stroke
rail spacing
payload
A drawing eliminates ambiguity and creates a record that both buyer and supplier can confirm before cutting.
A Photograph Can Help With Replacement Rail
If the existing rail is still installed, include photographs showing:
rail end
mounting holes
carriage
markings
full installation
Place a ruler or scale in the image when dimensions are difficult to communicate.
Photographs should supplement actual measurements rather than replace them.
What If You Do Not Know the Hole Pitch?
If you know the exact rail model, the supplier may be able to determine it from manufacturer dimensional data.
If the rail is unidentified, measure the distance:
center-to-center between adjacent mounting holes
Do not measure from:
edge to edge
unless you then convert that measurement correctly.
Center-to-center pitch is what matters.
What If You Do Not Know G1 or G2?
Measure from the rail end to the center of the nearest mounting hole.
Repeat on both ends.
If the rail is still installed and exact measurement is difficult, provide:
photos
overall length
hole pitch
number of mounting holes
The geometry can often be reconstructed.
Count the Mounting Holes
For replacement rail, include the number of mounting holes.
This provides another useful check against:
total length
pitch
end dimensions
If your dimensions suggest 18 holes but the original rail has 19, something should be rechecked before cutting.
Confirm Units
Always state units.
Write:
1,500 mm
rather than:
1500
or:
59.055 in
rather than:
59.055
Mixed metric and imperial dimensions are a common source of manufacturing errors.
A clean RFQ should use one unit system wherever practical.
Do Not Round Critical Dimensions
If replacing an existing rail measured at:
1,828.8 mm
do not automatically order:
1,830 mm
unless the machine has clearance for the difference.
The same applies when converting inch dimensions to metric.
Determine whether the dimension is:
nominal
approximate
exact
and communicate that.
Specify Tolerance if Overall Length Is Critical
For ordinary industrial rail, the supplier may already have a standard cutting tolerance.
If your machine requires something tighter, specify it and confirm that it is achievable.
For example:
Finished length 1,500 mm, overall length critical to existing enclosure clearance. Please confirm achievable cut tolerance.
Do not assume a precision rail automatically means the cut end is held to an unspecified ultra-tight length tolerance.
Ask for Confirmation Before Cutting When Geometry Is Critical
For expensive or unusual rails, request:
Please confirm final length, hole count, pitch, G1 and G2 before processing.
This is particularly useful for:
replacement rails
nonstandard lengths
long rails
expensive precision grades
multiple identical rails
A short confirmation can prevent costly scrap.
Should You Order the Rail and Carriages Together?
Often, yes, particularly for:
matched guide sets
preload-sensitive applications
higher-accuracy systems
replacement assemblies
Whether rail and blocks are interchangeable within a product family depends on the manufacturer and specific configuration.
Follow the manufacturer's ordering rules for the exact system.
THK, for example, documents specific ordering units and model-number configurations for different LM Guide families.
Should You Order Extra Rail Length and Cut It Later?
Sometimes that makes sense for:
maintenance inventory
prototyping
machines whose final geometry is not yet fixed
But once the finished machine dimensions are known, supplier-cut rail may be preferable.
Ordering excess length creates additional:
cutting work
contamination risk
measuring
deburring
handling
If the final dimension is already established, there may be little advantage to doing that work later.
A Complete Cut-to-Length Linear Rail RFQ
Here is a practical format you can copy when requesting a quote:
Application: New machine / replacement
Manufacturer:
Rail series:
Nominal size:
Rail part number:
Carriage part number:
Quantity of rails:
Quantity of carriages:
Finished rail length:
Required stroke:
Mounting-hole pitch:
G1 / first-hole end dimension:
G2 / last-hole end dimension:
Number of mounting holes:
Blocks per rail:
Block spacing:
Mounting orientation:
Accuracy grade:
Preload:
Lubrication requirement:
Exact OEM required or equivalent acceptable:
Drawing/photos attached: Yes / No
Can finished length be adjusted slightly to optimize hole geometry? Yes / No
If several specifications are unknown, add:
Please review application and recommend final configuration before cutting.
Example: Replacement Rail Order
A strong replacement RFQ might read:
We need two replacement profile rails for an existing machine. The current rail is SBC SBI size 25. Finished rail length is 1,840 mm. Hole pitch is 60 mm. First-hole center is 20 mm from the left end and last-hole center is 20 mm from the right end. Both rails must match the existing mounting plate exactly. Quantity is two rails and four matching carriages. Photos and drawing attached. Please confirm the rail model, final hole pattern, and finished length before cutting.
That is much more actionable than:
Need two 1,840 mm rails.
Example: New Machine Order
For a new machine:
Two parallel profile rails with two blocks per rail. Required travel is 1,500 mm. Block spacing is 300 mm center-to-center. Horizontal mounting. Approximate moving mass is 180 kg. We prefer SBC or WON and need cut-to-length rail. Please recommend the finished rail length and carriage configuration. Overall rail length can be adjusted slightly to optimize the standard mounting-hole pattern.
This gives the supplier freedom to select a sensible custom length rather than forcing an arbitrary dimension.
Common Cut-to-Length Ordering Mistakes
Ordering by Nominal Size Only
“Size 25” is not a complete rail specification.
Giving Only Overall Length
The mounting-hole geometry may not work.
Confusing Stroke With Rail Length
The blocks require additional rail.
Forgetting Block Spacing
The carriage group may not fit the assumed rail length.
Ignoring G1 and G2
The cut may leave poor end geometry.
Assuming the Supplier Knows the Existing Machine
Provide the dimensions or drawing.
Forgetting Quantity
Specify rails and blocks separately.
Mixing Inches and Millimeters
Use explicit units.
Rounding Replacement Dimensions
Small changes can affect fit.
Assuming Any Long Rail Can Be Supplied in One Piece
Maximum manufactured length is model-dependent.
Treating Two Rail Pieces as a Jointed Guideway
Continuous jointed rail requires a proper manufacturer-supported solution.
Forgetting Accuracy Grade
Precision requirements can affect maximum available rail length.
Ordering Before Confirming the Hole Pattern
This can turn an expensive rail into scrap.
Linear Automation USA's Perspective
At Linear Automation USA, we believe a cut-to-length rail order should answer three questions before the rail is processed:
What rail is it?
What finished geometry does the machine require?
Will that geometry actually support the required carriage travel?
For a straightforward custom rail order, the most important information is usually:
manufacturer + series + size + quantity + finished length + mounting-hole geometry
For a new application where the rail length has not yet been finalized, we also want:
stroke + number of blocks + block spacing + mounting orientation
That allows the finished rail length to be checked before material is cut.
Linear Automation USA supplies profile rail systems from SBC Linear, WON Linear, and other supported product lines, and provides cut-to-size rail processing for industrial applications.
Our rule is:
Do not order custom rail from overall length alone. Specify enough geometry that the rail arrives ready to fit the machine.
Frequently Asked Questions
What Information Do I Need to Order Cut-to-Length Linear Rail?
At minimum, provide the exact rail family and size, quantity, and finished length. For a reliable custom order, also provide mounting-hole pitch and critical end dimensions.
Do I Need to Know G1 and G2?
Not always, but they are very useful when the rail must match existing mounting holes or when the finished length is nonstandard.
Can the Supplier Calculate the End Dimensions?
Usually, if the exact guide family, rail size, finished length, and mounting-hole pitch are known.
Can I Order Linear Rail to an Exact Length?
Often, yes, within the supplier's processing capability and applicable product constraints. Confirm the required finished-length tolerance when it matters.
Can the Length Be Adjusted to Improve the Hole Pattern?
For a new machine, often yes. Tell the supplier whether slight dimensional adjustment is acceptable.
Can I Order Rail in Inches?
You can specify inch dimensions, but many profile rail systems use metric geometry. Confirm the exact converted finished length before processing.
Can I Order Rail Longer Than the Manufacturer's Maximum Length?
A manufacturer-supported jointed rail arrangement may be required. THK publishes model-specific maximum rail lengths and identifies jointed rails for certain applications exceeding those limits.
Does Accuracy Grade Affect Available Rail Length?
It can. THK specifically notes that high precision can impose maximum manufactured-length limitations.
Should I Order Carriages at the Same Time?
That can be beneficial, especially for a complete new guide system, preload-sensitive applications, or higher-accuracy configurations.
Can I Order a Replacement Rail Using Only the Existing Length?
You may be able to obtain a rail of the same length, but that does not establish mechanical interchangeability. Verify the guide family and mounting geometry.
What If I Do Not Know the Existing Rail Model?
Send clear photographs, dimensional measurements, and information about the carriage and machine installation.
Ready to Order Cut-to-Length Linear Rail?
For the fastest quote, provide:
rail manufacturer and series + size + quantity + finished rail length + mounting-hole pitch + G1/G2 if critical + required stroke + number of carriages
For replacement rail, include:
photographs
original part numbers
existing mounting dimensions
For a new application, include:
required stroke
block spacing
mounting orientation
basic payload information
Contact Linear Automation USA for custom-cut profile rail, application assistance, or replacement/interchange support.
Recommended Reading
How to Cut Linear Guide Rail to Length
Learn how rail cutting should be planned around hardened raceways, mounting-hole pitch, end dimensions, deburring, and cleaning.
Publishing note: Replace this temporary homepage link with the final published article URL.
Can Linear Rail Be Cut to Any Length?
Understand why custom length is limited by mounting-hole geometry, required travel, and manufacturer maximum rail length.
Publishing note: Replace this temporary homepage link with the final published article URL.
How to Select Linear Rail Length
Determine finished rail length from stroke, carriage footprint, block spacing, and end allowance.
Publishing note: Replace this temporary homepage link with the final published article URL.
Linear Guide Selection Checklist: What to Know Before Requesting a Quote
Gather the dimensions, operating conditions, and application information needed before requesting linear rail or carriage pricing.
Publishing note: Replace this temporary homepage link with the final published article URL.
Linear Guide Selection for Long-Stroke Applications
Learn when maximum one-piece rail length, accuracy, jointed rails, and machine alignment become major design factors.
Publishing note: Replace this temporary homepage link with the final published article URL.
Sources & Technical References
THK — Notes on Ordering
THK's current ordering guidance addresses order units, mounting orientation, lubrication location, supported options, and maximum manufactured rail lengths. THK also notes that high-precision requirements can impose additional rail-length limitations.
THK — LM Guide General Catalog
THK publishes model-specific standard rail lengths, mounting-hole pitches, G/g end dimensions, and maximum lengths. It also recommends maintaining appropriate end dimensions for special rail lengths because excessive unsupported rail ends can reduce stability and affect accuracy.
THK — Standard and Maximum Lengths of LM Rails
This model-specific dimensional reference demonstrates how finished rail length, mounting-hole pitch, end dimensions, maximum manufactured length, accuracy grade, and jointed-rail requirements interact.
Linear Automation USA — Resources
Linear Automation USA provides technical resources for specifying profile rail systems and planning custom rail dimensions.
Linear Automation USA
Linear Automation USA supplies industrial profile rails and carriages and supports custom-cut rail and replacement/interchange applications.