Frequently Asked Questions (FAQs)

Linear Motion Guide (LM Guide)

A.  Replacement & Interchangeability

1. Are PBH linear guides interchangeable with Hiwin?

Yes. Within matching series and size, PBH and Hiwin components are fully interchangeable — PBH blocks run on Hiwin rails, and Hiwin blocks run on PBH rails:

• PBH PGH..CA  ↔  Hiwin HGH..CA.
• PBH PGW..CC  ↔  Hiwin HGW..CC

  Tip:  If you are currently using Hiwin and want to try PBH as an alternative, you can test a PBH block on your existing Hiwin rail — no other changes needed.

2. Can PBH replace other brands such as THK, Bosch Rexroth, IKO, NSK, PMI, ABBA, or SBC?

In many cases, yes. However, for brands other than Hiwin it is safer to replace the rail and block together as a matched PBH set rather than cross-running individual components between brands.

3. How do I identify the right replacement, and what should I share with PBH?

Compare the following dimensions:

• Rail width and mounting hole pitch
• Block width and mounting hole distance
• Assembled height

If these match, PBH can usually supply a suitable replacement. To get a recommendation, share the brand name, part number, size, the dimensions above, and clear rail and block photos if available. A drawing or photo is often sufficient for PBH to suggest the correct model. 

B.  Selecting New Linear Guideway

 1. How do I select the correct linear guide for a new application?

Selection should be based on load (magnitude, direction, and distribution), travel length, available mounting space, number of rails and blocks, machine layout, and required smoothness and rigidity. A guide should always be selected as a complete system — size and load rating alone are not sufficient.

2. What is the difference between PGH..CA and PGW..CC, and which should I choose?

Both series are available in Normal (N) precision class. The main difference is block shape and mounting style:

In most corresponding sizes, dynamic load, static load, and moment load ratings are similar — so the choice is driven by mounting preference and machine layout rather than load capacity. Choose PGH..CA for a compact square block with tapped mounting; choose PGW..CC when through-hole mounting or easier assembly is preferred.

[ Insert diagram: PGH..CA (square block) vs PGW..CC (flange block) — photo or drawing showing both block types side by side ]

3. What are dynamic load, static load, and moment load ratings?

• Dynamic load rating — the load the guide can carry during continuous repeated motion over a long service life.
• Static load rating — the load the guide can withstand when stationary, or under shock or sudden force, without permanent deformation.
• Moment load — the turning effect when the load is offset from the block centre. Important for wide tables, overhanging loads, or uneven load placement.
• Proper selection must also account for number of rails and blocks, load distribution, mounting accuracy, shock or vibration, rail spacing, and an appropriate safety margin.

4. What sizes does PBH offer, and what are the load ratings?

PBH linear guides are available in Size 15, 20, 25, and 30. The table below shows the dynamic load rating (C) and static load rating (C₀) for each size in the PGH..CA series. PGW..CC ratings are similar in corresponding sizes.

C = dynamic load rating (for moving loads). C₀ = static load rating (for stationary or shock loads). Higher values mean the guide can handle heavier loads. For detailed dimensions and moment load ratings, refer to the specification sheet on each product page.

  Need help?:  Not sure which size you need? Share your load, travel length, and machine layout with PBH and we will recommend the right guide for your application.

5. Can you give a simple selection example?

Application: 50 kg horizontal load, 2 rails, 2 blocks per rail (4 blocks total), load placed centrally.

[ Insert diagram: Simple layout sketch — 2 rails, 4 blocks, 50 kg load shown centrally on top ]

Step 1 — Convert load to Newtons:

·  Total load  =  50 kg × 9.8  =  490 N

Step 2 — Distribute load across rails and blocks:

·  Load per rail  =  490 N ÷ 2 rails  =  245 N per rail

·  Load per block  =  490 N ÷ 4 blocks  =  122.5 N  =  0.12 kN per block

Step 3 — Check against rated load (starting from Size 15):

·  PGH15CA dynamic load rating  C  =  11.4 kN

·  Safety factor  =  C ÷ load per block  =  11.4 ÷ 0.12  ≈  93x  (guide can handle 93x the actual applied load)

·  Result: Size 15 is confirmed suitable. Safety factor is well above any practical requirement.

Step 4 — Choose block type based on mounting preference:

·  PGH15CA  —  square block, blind tapped holes, compact footprint.

·  PGW15CC  —  flange block, through holes, generally easier to install.

Load ratings for PGH15CA and PGW15CC at Size 15 are similar, so there is no performance difference between the two for this application. The choice is based entirely on how your machine is designed to mount the block.

C.  Mounting, Lubrication & Maintenance

 1. How should the rail be mounted?

Mount on a clean, flat, rigid, and properly machined surface. The rail must seat correctly against the reference edge. Burrs, dirt, paint build-up, or surface unevenness will affect accuracy, smoothness, and service life.

Tighten rail bolts gradually and evenly in sequence — random tightening can distort the rail. Never force, twist, hammer, or bend the rail into place. If the mounting surface or hole pattern is incorrect, correct that first.

  Important:  A poorly prepared surface is the single most common cause of guide problems. Always check the mounting surface with a straight edge before installation.

2. How should blocks be handled during installation?

Handle blocks carefully and keep them clean. Avoid removing blocks from the rail unnecessarily — careless removal can cause ball loss or internal damage.

3. How is parallelism achieved in a 2-rail system, and why does it matter?

Both rails must remain at a consistent distance from each other along the full length. Misaligned rails cause binding, rough running, increased friction, and reduced service life.

Mount one rail first as the reference rail, then align the second rail parallel to it. Check by measuring rail spacing at both ends and at intervals along the length. Use a dial indicator moving along the reference rail for greater accuracy. Final confirmation is smooth, drag-free movement through the full stroke with no tight spots.

[ Insert diagram: 2-rail parallelism check — measuring spacing at both ends and at intervals ]

4. Is lubrication necessary, and how often should it be done?

Yes. Lubrication is essential for smooth motion, reduced wear, corrosion protection, and longer service life. Grease lubrication is standard for most normal industrial applications.

As a general starting point under normal conditions, relubricate every 100 km of travel or every 3 months — whichever comes first. In dusty, high-speed, or high-duty environments, shorten this interval accordingly. Poor or neglected lubrication leads to higher friction, noisy running, accelerated wear, and rust.

  Tip:  Lubrication is the single most effective way to extend guide life. A guide that is properly lubricated will significantly outlast one that is not, even under identical load conditions.

5. What are the key dos and don'ts?

Do:

• Keep rail and block clean before and during installation.
• Mount on a flat, rigid, properly machined surface.
• Ensure correct alignment and parallelism in a 2-rail system.
• Tighten rail bolts gradually and evenly in sequence.
• Lubricate regularly at the recommended interval.
• Protect the guide from chips, dust, coolant, and moisture.

Do not:

• Mount on dirty, uneven, or unprepared surfaces.
• Force, hammer, or bend the rail into place.
• Run the guide without lubrication.
• Expose the guide to metal chips, coolant, or welding sparks.
• Remove the block carelessly from the rail.

6. What regular maintenance checks are recommended?

Check regularly for: smoothness of movement, unusual noise, lubrication condition, signs of rust or contamination, bolt tightness, and abnormal wear. Even a correctly sized guide will have a reduced service life if mounting, alignment, or lubrication are neglected. 
 

D.  Rail Length & Jointed Rails

1. What is the maximum single-piece rail length, and what if I need longer?

The maximum single-piece rail length is 4 metres. For longer travel requirements, two or more rail sections can be mounted end-to-end on the same base — this is called a butt joint or jointed rail arrangement.

[ Insert diagram: Butt joint arrangement — two rail sections mounted end-to-end with match marks shown ]

2. How should jointed rails be assembled?

Assemble rail sections according to the joint markings (match marks) provided. End-to-end alignment, height matching, and straightness are critical — any step or misalignment at the joint will cause the block to catch or run roughly. Once assembled, confirm smooth block transfer across the joint through the full stroke before putting the machine into service.

3. Are there any safety and usage considerations for jointed rails?

Yes. The following points must be observed:

• Do not stop the block at or near the joint under load. The joint is not a continuous bearing surface; resting load there long-term can cause localised wear or deformation.
• In high-speed applications, block transfer across the joint should occur at a controlled, moderate speed. Evaluate the joint transition carefully before running at full operating speed.
• Do not use a jointed rail arrangement where precise positioning is required at the joint location.
• If the block crosses the joint repeatedly, include joint alignment in your periodic maintenance checks to ensure it has not shifted over time.

E.  Troubleshooting

1. The guide is running rough or feels heavy. What should I check?

Check the following, in order:

• Parallelism — in a 2-rail system, misaligned rails are the most common cause of heavy running. Re-check rail spacing along the full length.
• Mounting surface — dirt, burrs, or unevenness under the rail can distort it and cause binding.
• Lubrication — dry or under-lubricated guides will feel stiff. Relubricate and test again.
• Contamination — metal chips, dust, or debris inside the block will cause rough motion. Clean and relubricate.
• Bolt tightness — over-tightened or unevenly tightened rail bolts can warp the rail. Loosen and re-tighten in sequence.

2. The guide is making unusual noise. What could be the cause?

• Metallic clicking or grinding — usually indicates contamination inside the block (chips, dust, or foreign particles). Clean and relubricate.
• Squeaking — typically caused by insufficient lubrication. Apply grease and run the block back and forth to distribute it.
• Rattling or looseness — check that the block is properly secured to the carriage plate and that rail bolts are tight.
• If noise persists after cleaning and relubrication, the balls or raceways may be damaged. Contact PBH for inspection or replacement.

3. I can see rust on the rail or block. What should I do?

Surface rust usually indicates insufficient lubrication or exposure to moisture or coolant. Clean the affected area, apply fresh grease, and run the block through the full stroke several times. Light surface rust caught early does not usually require replacement.

To prevent rust: maintain regular lubrication, protect the guide from coolant spray and standing moisture, and consider adding wiper seals or protective covers in harsh environments.

4. The block feels loose on the rail. Is it worn out?

Not necessarily. Some play is normal in standard (N) precision guides under no load — this is not a defect. Under load, the guide seats firmly. However, if there is noticeable play under working load, the raceways or balls may be worn. Contact PBH with the model number and a description of the issue for assessment.

5. The block does not slide smoothly after installation on a new machine. Why?

In most cases, this is a mounting or alignment issue, not a guide defect. The most common causes are:

• The mounting surface is not flat or properly machined.
• The two rails are not parallel to each other.
• The block mounting screws are pulling the block out of alignment with the rail.
• The guide has not been lubricated after installation.

Before concluding the guide is faulty, remove it from the machine, clean it, apply grease, and test it by hand on the rail alone. If it runs smoothly off the machine, the issue is with the mounting — not the guide.