How to Cut Linear Guide Rail to Length

Oct 27

Linear guide rail can be cut to a custom length, but cutting profile rail correctly requires more planning than simply measuring the desired length and making a cut. The rail is a precision component with hardened raceways, regularly spaced mounting holes, defined end dimensions, and surfaces that the carriage depends on for smooth motion. Before cutting, determine the finished rail length, mounting-hole pitch, desired distance from the rail ends to the first and last mounting holes, and whether the resulting rail will still provide enough length for the required carriage travel.

The basic rule is:

Plan the finished rail geometry first, cut the rail second, and carefully finish and clean the cut end before putting the rail into service.

For many industrial applications, having the supplier provide the rail already cut to the required length is preferable to field cutting. Linear Automation USA provides custom-cut profile rail processed locally, allowing rail length and mounting-hole geometry to be addressed before the rail reaches the machine.

Can Linear Guide Rail Be Cut to Length?

Yes. Linear guide rail is commonly supplied in standard or longer lengths and can be provided in application-specific lengths.

However, profile rail is not ordinary mild-steel bar stock. Depending on the manufacturer and guide family, the rail incorporates hardened precision raceways that interact directly with the rolling elements inside the carriage.

The goal is therefore not merely to create a shorter piece of steel. The finished rail must still provide:

the required usable travel
appropriate mounting-hole locations
usable end dimensions
an undamaged raceway
a clean finished cut
proper mounting and alignment

The exact rail construction, standard lengths, maximum manufactured lengths, hole pitch, and recommended end dimensions are manufacturer- and series-specific.

Determine the Required Rail Length Before Cutting

Start with the machine's required stroke.

The rail normally needs to be longer than the stroke because the carriage or carriage group occupies physical space on the rail.

A useful preliminary relationship is:

Rail Length ≈ Required Stroke + Carriage-Group Footprint + End Allowance

For a single carriage:

Lrail ≈ S + B + 2E

where:

S = required stroke
B = carriage length
E = desired end allowance

If two blocks are mounted on each rail, account for the entire carriage group rather than the length of one block.

If block center-to-center spacing is D and each block has length B, the approximate carriage-group footprint is:

Bgroup ≈ D + B

The preliminary rail length then becomes:

Lrail ≈ S + Bgroup + 2E

This establishes how much physical rail the axis requires before mounting-hole geometry is considered.

Example: Calculating Rail Length Before Cutting

Suppose an automation axis requires:

1,000 mm usable stroke
two blocks per rail
250 mm overall carriage-group footprint
40 mm end allowance at each end

The preliminary rail length would be:

1,000 + 250 + 80 = 1,330 mm

That does not automatically mean you should mark the rail at exactly 1,330 mm and cut it.

The next step is to determine how that dimension works with the mounting-hole pattern.

Check the Mounting-Hole Pitch Before Making the Cut

Profile rail normally has mounting holes positioned at a repeating pitch.

A useful way to represent the geometry is:

L = G1 + nP + G2

where:

L = finished rail length
G1 = distance from one end of the rail 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 between the first and last mounting holes

This relationship is extremely important when cutting rail.

Suppose your rail has a 60 mm mounting-hole pitch. An arbitrary cut may leave:

a mounting hole extremely close to the rail end
an unnecessarily large unsupported end section
unequal end dimensions
a mounting pattern that no longer matches the machine

A few millimeters of adjustment to the finished rail length may produce a much better mounting-hole arrangement.

Why G1 and G2 Matter

Manufacturers commonly specify recommended or standard end dimensions for their rails.

THK, for example, publishes rail-length tables showing:

standard rail lengths
standard mounting-hole pitch
end dimensions
maximum rail lengths

THK also warns in its technical documentation for applicable guide families that as the rail end dimensions become larger, that portion of the rail becomes less stable and accuracy may be negatively affected.

That means you should not treat the area between the final mounting hole and the rail end as irrelevant.

Ideally, the cut should create sensible end geometry rather than leaving a long unsupported section of rail.

Equal End Dimensions Are Often Desirable

When the machine design permits it, a balanced mounting-hole layout can provide a clean rail configuration.

For example:

G1 = G2

This centers the mounting-hole pattern within the finished rail length.

However, equal end dimensions are not a universal requirement.

A replacement machine may require a particular:

G1
G2
overall length

to match existing mounting holes.

The correct geometry is the geometry required by the machine and permitted by the selected rail system.

Use the Manufacturer's Dimensional Table

Before cutting any rail, identify:

Manufacturer
Rail series
Nominal rail size
Mounting-hole pitch
Standard end dimensions
Finished rail length
Required G1 and G2

Do not assume that two different size-25 rails use identical mounting-hole geometry.

Even guides with similar nominal sizes can have different:

rail widths
rail heights
mounting-hole diameters
counterbores
hole pitches
end dimensions

Always use dimensional information for the exact guide family.

Use a Rail-Cut Calculator When Available

Linear Automation USA's resource center includes a Linear Rail Cut Calculator designed around the relationship between:

brand
rail size
mounting-hole pitch P
buffer/end dimension B
total rail length L
requested first-hole dimension G1

This type of calculator is useful because it allows the mounting-hole pattern to be planned before the physical cut is made.

The objective is to answer:

If I cut this rail to this length, where will the first and last mounting holes end up?

That question should be answered before cutting.

Profile Rail Is Hardened

One of the biggest differences between cutting linear guide rail and ordinary structural steel is hardness.

The raceway surfaces must withstand repeated rolling contact from:

balls
rollers

under substantial contact stress.

Consequently, linear guide rail should be treated as a precision hardened component rather than ordinary steel bar.

This affects both:

cutting-tool selection
post-cut finishing

The exact hardness profile and material treatment vary by manufacturer and series, so the safest practice is to follow the manufacturer's machining guidance where available.

What Should You Use to Cut Linear Guide Rail?

The appropriate cutting process depends on:

rail size
material
hardness
available equipment
required finish
production quantity

Industrial suppliers processing rails routinely may use dedicated equipment appropriate for hardened rail.

For field or machine-shop cutting, the important requirement is to use a method capable of cutting the selected hardened material without damaging the remaining precision rail.

Do not assume that a general-purpose blade intended for mild steel is appropriate.

Abrasive Cutting

Abrasive cutting can cut hardened material and is therefore one possible shop method.

However, it creates concerns including:

heat
sparks
abrasive debris
burrs
surface contamination

The rail must be firmly supported and the cut should be made without allowing excessive heat to affect a large region of the rail.

Afterward, the cut end requires careful finishing and cleaning.

Saw Cutting

Appropriate industrial sawing equipment may also be used when the blade, machine, feeds, and speeds are suitable for the rail material and hardness.

The important distinction is:

“Can this saw cut steel?” is not the right question.

The question is:

“Is this cutting system appropriate for this specific hardened linear-guide rail?”

If there is uncertainty, have the rail cut by the supplier or a machine shop experienced with hardened precision components.

Do Not Use the Carriage as a Cutting Fixture

Remove or move the carriage well away from the cutting area before machining the rail.

Cutting generates:

metal particles
abrasive particles
grinding dust
heat

None of these belong inside the recirculating rolling-element system.

Protect the remaining rail and carriage from contamination throughout the process.

Support the Rail Properly

Long profile rail can flex while being handled.

Before cutting:

support the rail securely
prevent vibration
keep the cut area accessible
avoid clamping directly against critical raceway surfaces
prevent the rail from falling or twisting when the cut completes

For a long rail, support both sides of the cut.

Do not allow the cutoff section to hang unsupported and tear away as the cut finishes.

Mark the Finished Length Carefully

Measure from a known rail end and confirm:

total finished length
G1
G2
hole pitch

before marking.

Then measure again.

A useful shop rule is particularly appropriate here:

Measure twice, verify the mounting-hole pattern, then cut once.

Once hardened profile rail has been shortened, the removed length cannot be put back.

Protect the Raceway Surfaces

The carriage rolls directly against precision raceways on the rail.

Avoid:

vise damage
hammer marks
grinder contact
scratches
welding spatter
clamp damage

on the functional rail surfaces.

If clamping is necessary, use appropriate protective fixtures or soft jaws positioned so they do not damage the precision surfaces.

Make the Cut Square

A reasonably square end makes the finished rail:

easier to handle
easier to measure
easier to install

For a standalone rail, the cut face itself normally is not the carriage's rolling surface, but poor cutting can still create burrs or damaged material extending into functional areas.

Do not allow the cutting process to damage the raceway at the rail end.

Deburr the Cut End

After cutting, the end will usually require deburring.

Remove:

sharp edges
loose material
burrs

without grinding into the precision raceway.

This requires restraint.

The objective is not to reshape the rail end aggressively.

It is to produce a clean, safe edge without changing the functional geometry of the guide.

Add a Small Protective Edge Break Only Where Appropriate

A freshly cut rail can have extremely sharp edges.

A controlled edge break can make handling and installation safer.

However:

do not aggressively chamfer or grind the raceway surfaces.

The rolling elements depend on those surfaces.

When in doubt, use the manufacturer's finishing recommendation or have the rail professionally processed.

Clean the Rail Thoroughly

After cutting and deburring, remove all:

steel particles
abrasive dust
chips
grinding residue

Pay particular attention to:

raceways
mounting holes
counterbores
rail ends

Do not allow cutting debris to enter the carriage.

After cleaning, restore the appropriate corrosion protection or lubrication to exposed functional surfaces as required by the guide manufacturer.

Be Careful With the Carriage at a Newly Cut End

Depending on the guide design, the carriage may contain recirculating rolling elements that should not simply be allowed to run off the rail.

THK specifically warns for certain LM Guide models that rolling elements can fall out if the block is removed from the rail, and manufacturer handling devices may be supplied for that reason.

As a general practice:

do not run a carriage off the end of a rail unless the manufacturer's procedure specifically permits it and the appropriate transfer or retention method is being used.

Also ensure the machine has appropriate mechanical travel limits so the carriage cannot unintentionally leave the rail during operation.

Do Not Cut Through a Mounting Hole Without Planning for It

An arbitrary cut can intersect:

a counterbored mounting hole
a tapped hole
another rail feature

That may leave an undesirable partial hole at the end.

This is another reason to calculate the mounting-hole pattern before choosing the final cut location.

Often a small change in rail length produces a much cleaner result.

Example: Planning a Cut Around Hole Pitch

Suppose a rail uses:

P = 60 mm

mounting-hole pitch.

You initially want:

L = 1,330 mm

Rather than immediately cutting at 1,330 mm, calculate where the mounting holes will fall.

If the resulting G1 or G2 is undesirable, you may determine that a slightly different finished length gives:

better end spacing
more symmetrical mounting
easier installation

The machine design should determine whether that length adjustment is acceptable.

This is why rail cutting should be treated as a geometry problem before it becomes a machining operation.

Cutting Two Parallel Rails

If the machine uses two parallel rails intended to have identical lengths, do not independently approximate the cuts.

Specify and verify:

identical finished length
identical mounting-hole pattern
appropriate end dimensions

Label the rails after cutting so the installation team knows their intended positions if they are application-specific.

Cutting Replacement Rail

Replacement applications require additional care.

Before cutting a replacement, measure the original rail for:

total length
width
height
hole pitch
hole diameter
counterbore
G1
G2

Also identify:

manufacturer
series
rail size
carriage part number

Do not assume that a rail with the same nominal size can simply be cut to the old length and installed.

Interchangeability must be established separately.

Can You Drill New Mounting Holes in Linear Rail?

This should not be treated like drilling ordinary steel.

Because the rail may be hardened and the mounting-hole geometry contributes to proper installation, adding holes can require specialized machining.

If the existing machine has a nonstandard mounting pattern, better options may include:

ordering appropriately machined rail
modifying the machine mounting plate
using an engineered adapter arrangement

depending on the application.

Do not casually drill additional holes into a hardened precision rail without confirming that the manufacturer or qualified machining process supports the modification.

Can You Cut a Rail Shorter After It Has Been Installed?

Physically, this may sometimes be possible, but it is generally better to remove the rail or otherwise protect the machine before cutting.

Cutting in place can expose:

carriages
lubrication
actuators
sensors
electronics

to metal and abrasive debris.

It also makes it more difficult to:

support the rail
produce a controlled cut
deburr
clean the rail thoroughly

Whenever practical, perform rail cutting before final installation.

Does Cutting the Rail Change Its Load Capacity?

Simply shortening an otherwise properly manufactured rail does not automatically change the catalog load rating of the carriage.

However, the finished system can change if cutting affects:

mounting-hole support
carriage travel
block spacing
usable rail length
rail mounting

For example, shortening the rail so much that two blocks must be positioned closer together can reduce the system's leverage against pitch or yaw moment.

So while the carriage's catalog rating may not change, the machine geometry can.

Does Cutting Affect Accuracy?

A properly executed cut at the rail end does not inherently change the precision of the entire raceway.

But poor cutting practices can.

Potential problems include:

raceway damage
excessive heat
burrs
debris
poor mounting-hole geometry

Accuracy also depends on the rail's installation.

THK publishes model-specific standard and maximum rail lengths and notes that maximum available length can vary with accuracy requirements.

For precision applications, consult the guide manufacturer or supplier before making substantial modifications.

What About Very Long Rails?

If the required rail length exceeds the manufacturer's maximum one-piece length, cutting is not the solution.

The application may require:

jointed rails
a different guide family
manufacturer consultation

Do not assume that several independently cut rail pieces can simply be butted together to create a precision joint.

Jointed rails require properly prepared ends and an installation strategy appropriate for the selected guide.

Should You Cut Linear Rail Yourself or Order It Cut?

For a maintenance department or machine shop with suitable equipment and experience, cutting rail may be practical.

But for a new machine or replacement where the finished dimensions are already known, ordering the rail cut to length has several advantages:

correct finished length
planned mounting-hole geometry
less shop labor
less risk of damaging raceways
less contamination
easier installation

This is especially attractive when only a few rails are required.

Linear Automation USA's Perspective

At Linear Automation USA, we view cutting linear guide rail as a precision planning operation first and a cutting operation second.

The question should not begin with:

“Where do we put the saw?”

It should begin with:

“What finished rail geometry does the machine actually need?”

Before processing a rail, we want to know:

manufacturer
rail series
nominal size
required stroke
number of carriages
block spacing
finished rail length
mounting-hole pitch
required end dimensions

Once those are established, the rail can be planned around the machine instead of forcing the machine to accommodate an arbitrary cut.

Linear Automation USA supplies profile rail systems from Schaeffler, SBC Linear, and WON Linear, with custom-cut rail processing available for applications requiring specific finished lengths.

Our rule is:

Calculate the stroke, carriage footprint, mounting-hole pattern, and end dimensions before cutting the rail. Never choose the cut location from overall length alone.

Linear Guide Rail Cutting Checklist

Before cutting, confirm:

Exact manufacturer and rail series
Nominal rail size
Required usable stroke
Carriage or carriage-group footprint
Required finished rail length
Mounting-hole pitch P
Desired G1
Resulting G2
Cut does not intersect an unwanted mounting feature
Cutting equipment is suitable for the rail material
Rail is securely supported
Raceway surfaces are protected
Carriage is protected from cutting debris
Cut end will be deburred carefully
Entire rail will be cleaned before use
Final length and hole geometry will be verified before installation

If you cannot confidently verify those items, having the supplier cut the rail is usually the better option.

Frequently Asked Questions

Can You Cut Linear Guide Rail With a Saw?

Potentially, but the cutting equipment and blade must be appropriate for the material and hardness of the specific rail. Profile rail should not be treated like ordinary mild steel.

Can You Cut Linear Rail With an Abrasive Wheel?

Abrasive equipment can cut hardened material, but heat, debris, burrs, and raceway protection must be carefully controlled.

Is Linear Guide Rail Hardened?

Profile guide rails incorporate hardened precision raceways designed for rolling contact. The exact material and hardening method vary by manufacturer and guide family.

Where Should I Cut a Linear Rail?

Choose the finished rail length based on required travel and carriage footprint, then calculate the cut location using the mounting-hole pitch and desired end dimensions.

What Are G1 and G2?

They describe the distances between the rail ends and the centers of the first and last mounting holes. Terminology can vary by manufacturer, but the concept is important when planning a custom rail length.

Should G1 and G2 Be Equal?

They can be equal when a symmetrical mounting-hole pattern is desirable and the machine permits it, but they do not universally have to be equal.

Can I Cut Through a Mounting Hole?

Avoid creating an accidental partial mounting hole. Plan the cut around the hole pattern before machining the rail.

Do I Need to Deburr a Cut Linear Rail?

Yes. The cut should be carefully finished so no sharp burrs or loose material remain, while avoiding damage to the precision raceways.

Can I Grind the Raceway After Cutting?

Do not casually grind or reshape the precision raceway. Only remove material necessary to safely finish the cut end using a process appropriate for the selected rail.

Can I Drill Additional Holes in Linear Guide Rail?

Because profile rail may be hardened and requires precise mounting geometry, additional holes can require specialized machining. Confirm the modification with the supplier or manufacturer rather than treating the rail like ordinary bar stock.

Can I Cut Two Rails to the Same Length?

Yes. For a two-rail system, carefully match the finished lengths and mounting-hole geometry required by the machine.

Does Cutting Linear Rail Reduce Its Load Rating?

Shortening the rail does not inherently change the carriage's published basic load rating, but it can change system geometry, available block spacing, mounting support, and usable stroke.

Can I Join Two Cut Rails to Make a Longer Rail?

Do not assume ordinary cut rails can be butted together to create a proper jointed guideway. Applications exceeding one-piece rail limits should use a manufacturer-supported jointed-rail solution.

Is It Better to Order Linear Rail Already Cut?

For many industrial applications, yes. Supplier cutting reduces the risk of incorrect hole geometry, raceway damage, contamination, and shop rework.

Need Linear Guide Rail Cut to Length?

Before requesting custom-cut rail, provide:

manufacturer or preferred brand
rail series
nominal size
quantity
finished rail length
required stroke
mounting-hole pitch if known
desired end dimensions if critical
number and type of carriages

If the application is replacing an existing rail, also provide photographs and measurements of the original.

Contact Linear Automation USA for assistance selecting and specifying custom-cut profile rail.

Sources & Technical References

THK — Notes on Ordering

THK documents ordering considerations for LM rails, including maximum manufactured rail lengths and the fact that high-precision applications can impose additional length limitations.

THK — Standard and Maximum Lengths of LM Rails

THK's dimensional documentation illustrates how standard rail length, mounting-hole pitch, end dimensions, and maximum rail length are related for specific guide families. It also demonstrates why these dimensions must be checked for the exact rail model rather than generalized across all profile rails.