When replacing or retrofitting a linear motion system, identifying the correct runner block is only half the battle. You must also match the exact specifications of the underlying track. Like their runner blocks, Bosch Rexroth Profiled Guide Rails use a highly structured, 10-digit alphanumeric part number system (e.g., R1605 7 0 3 31).
Understanding codes like R1605 versus R1645 tells you the rail's mounting style, material, accuracy grade, and cover option. This technical guide breaks down the full part number structure so you can source the exact replacement rail you need.
1. The Prefix & Rail Type (Digits 1–5)
The first letter and subsequent four numbers explicitly dictate the physical mounting profile, material composition, and fixing method of the linear rail.
- The Letter "R": Stands for Rexroth.
- The Second & Third Digits ("16"): Identifies a standard ball rail system. (An R18 prefix signifies a heavy-duty roller rail system).
- The Fourth & Fifth Digits (Mounting & Material Geometry): This identifies how the rail mounts to your machine bed and what it is made of:
05(R1605): Standard steel rail designed for mounting from above (bolted down from the top).07(R1607): Standard steel rail designed for mounting from below (bolted up through the bottom of the machine bed via threaded blind holes).45(R1645): Corrosion-resistant, hard chrome-plated steel rail (Resist CR) for harsh or high-humidity environments.19(R1619): Wide ball rail system variant designed for high torsional torque handling. [1]
2. The Size Code (Digit 6)
The sixth digit determines the physical width of the guide rail in millimeters. This must match the size of your runner block perfectly.
1= Size 15 rail width8= Size 20 rail width2= Size 25 rail width7= Size 30 rail width3= Size 35 rail width4= Size 45 rail width [1]
Example: An R1605 2... configuration denotes a standard top-mounting rail in a Size 25 footprint.
3. The Cover Option & Hole Cap Geometry (Digit 7)
The seventh digit specifies how the counterbored mounting holes are protected to prevent debris from entering the runner block.
0(Plastic Caps): The mounting holes are plugged using standard plastic caps. This is the most common, cost-effective industrial standard. [1]3(Steel Cover Strip): The rail features a smooth, continuous stainless steel cover strip that snaps or slides over the entire length of the rail. This eliminates all pockets where debris can settle.6(Wedge Profile): Features specialized caps or strips optimized for high-vibration applications.
4. Accuracy Grade (Digit 8)
The eighth digit defines the spatial variation and travel tolerance thresholds of the component. Because Rexroth components are modular, you can match a higher accuracy rail with a lower accuracy block if needed. [1]
4(Accuracy Class N): Normal accuracy. Used for material conveyor systems and basic packaging machinery.3(Accuracy Class H): High accuracy. The baseline standard for precision pick-and-place and material handling.2(Accuracy Class P): Precision grade accuracy. Engineered for high-end CNC machining centers and laser cutters. [1, 2, 3, 4, 5]
5. Segment Style and Length Formatting (Digits 9–10)
The final two digits tell the factory whether the rail is a standard standalone piece or part of a multi-section linked system.
31/61: Standard single-piece rail configuration.32/62: Composite, multi-section rail. This indicates the total required length is too long for a single rail piece (typically over 4 meters) and will arrive in precisely matched segments numbered for sequential installation. [1, 2]
Quick Reference Rail Decoding Table
+---------------+---------------------+-----------+-------------------------+-----------------+
| Part Code | Rail Mounting Style | Rail Size | Cover Strip / Cap Type | Accuracy Class | +---------------+---------------------+-----------+-------------------------+-----------------+
| R1605 703 31 | Top-Mounting Steel | Size 30 | Standard Plastic Caps | H (High Class) | | R1645 232 31 | Chrome-Plated Resist| Size 25 | Stainless Cover Strip | P (Precision) | +---------------+---------------------+-----------+-------------------------+-----------------+
Sizing and Ordering Your Rails Digitally
When ordering a replacement rail, you must provide the exact length in millimeters alongside the 10-digit part number (e.g., R1605 204 31, Length: 1200mm). To quickly verify your exact end-hole spacing calculations (E₁ and E₂) so you do not accidentally cut through a mounting hole: [1]
- Launch the Linear Motion Technology Selector to input your desired rail type, required length, and structural hole spacing metrics.
- Load your physical configuration into the Linear Motion Designer (LMD) software application to double-check structural bending resistance and simulate how various rail coatings hold up under heavy industrial workloads.
SEO Meta Data (For Website Implementation)
- Target Focus Keyword:
Rexroth linear guide rails - Secondary Keywords:
R1605 guide rail,Bosch Rexroth rail part number,linear rail nomenclature,top mounting linear guide,profiled rail systems. - Meta Description: Replacing a linear track? Read our guide on decoding the Bosch Rexroth linear guide rail part number structure to correctly cross-reference R1605 and R1645 systems. [1]
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