Bosch Rexroth Ball Rail Systems: Accuracy Classes

Accuracy Classes and Their Tolerances

In ball rail systems, the ball runner blocks are available in six accuracy classes and the guide rails in five accuracy classes. For details of the available ball runner blocks and guide rails, refer to the "Part numbers" tables.

Key to Illustration

H = Height tolerance (µm)
A3 = Side tolerance (µm)
P1 = Parallelism offset (µm)
L = Rail length (mm)

Precision Manufacturing Ensures Interchangeability

Bosch Rexroth manufactures its ball guide rails and ball runner blocks with high precision, particularly in the ball track zone. This allows individual components to be replaced at any time. For instance, a ball runner block can be used without issues on various guide rails of the same size, and different ball runner blocks can be used on the same ball guide rail.

Ball Rail System: Steel, Aluminum, Resist NR, and Resist NRII

Tolerances and Maximum Differences for Steel/Aluminum Systems
Accuracy classes	Tolerances of the dimensions (µm)		Max. differences of dimensions H and A3 on one rail (µm)
Accuracy classes	H	A3	Max. differences of dimensions H and A3 on one rail (µm)
N	+100	±40	30
H	+40	±20	15
P	+20	±10	7
XP¹⁾	+11	±8	7
SP	+10	±7	5
UP	+5	±5	3

¹⁾ Ball runner block in accuracy class XP, ball guide rail with accuracy class SP.

Ball Rail System: Resist CR (Matte-Silver Hard Chrome Plated)

Tolerances and Maximum Differences for Resist CR Systems
Accuracy classes	Tolerances of the dimensions (µm)		Max. differences of dimensions H and A3 on one rail (µm)
Accuracy classes	Ball runner block/guide rail	Ball runner block/guide rail	Ball runner block/guide rail	Ball runner block/guide rail	Ball guide rail	Ball guide rail
	H	A3	H	A3	H	A3
H	+47/-38	+44/-39	+23	+19	18	15

Parallelism Offset (P1)

Parallelism offset P1 of the ball rail system in operation is measured in the middle of the runner block with ball rail systems without surface coating. In the case of Resist CR hard chrome-plated ball guide rails, the values can increase up to 2 µm.

The graph indicates that parallelism offset (P1 in µm) generally increases with rail length (L in mm). Lower accuracy classes (N, H) exhibit higher parallelism offsets compared to higher accuracy classes (SP, UP).

Tolerances for Combination of Accuracy Classes

Tolerances for Combinations of Accuracy Classes (µm)
Ball runner block	Ball guide rails
Ball runner block	N	H	P	SP	UP
N	Tol. H: +100	Tol. H: +48	Tol. H: +32	Tol. H: +23	Tol. H: +19
	Tol. A3: ±40	Tol. A3: ±28	Tol. A3: ±22	Tol. A3: ±20	Tol. A3: ±19
	Max. diff. H/A3: 30	Max. diff. H/A3: 30	Max. diff. H/A3: 30	Max. diff. H/A3: 30	Max. diff. H/A3: 30
H	Tol. H: +92	Tol. H: +40	Tol. H: +24	Tol. H: +15	Tol. H: +11
	Tol. A3: ±32	Tol. A3: ±20	Tol. A3: +14	Tol. A3: +12	Tol. A3: +11
	Max. diff. H/A3: 15	Max. diff. H/A3: 15	Max. diff. H/A3: 15	Max. diff. H/A3: 15	Max. diff. H/A3: 15
P	Tol. H: +88	Tol. H: +36	Tol. H: +20	Tol. H: +11	Tol. H: +7
	Tol. A3: ±28	Tol. A3: ±16	Tol. A3: ±10	Tol. A3: +8	Tol. A3: +7
	Max. diff. H/A3: 7	Max. diff. H/A3: 7	Max. diff. H/A3: 7	Max. diff. H/A3: 7	Max. diff. H/A3: 7
XP	Tol. H: +88	Tol. H: +36	Tol. H: +20	Tol. H: +11	Tol. H: +7
	Tol. A3: ±28	Tol. A3: ±16	Tol. A3: ±10	Tol. A3: +8	Tol. A3: +7
	Max. diff. H/A3: 7	Max. diff. H/A3: 7	Max. diff. H/A3: 7	Max. diff. H/A3: 7	Max. diff. H/A3: 7
SP	Tol. H: +87	Tol. H: +35	Tol. H: +19	Tol. H: +10	Tol. H: +6
	Tol. A3: ±27	Tol. A3: ±15	Tol. A3: +9	Tol. A3: +7	Tol. A3: +6
	Max. diff. H/A3: 5	Max. diff. H/A3: 5	Max. diff. H/A3: 5	Max. diff. H/A3: 5	Max. diff. H/A3: 5
UP	Tol. H: +86	Tol. H: +34	Tol. H: +18	Tol. H: +9	Tol. H: +5
	Tol. A3: ±26	Tol. A3: ±14	Tol. A3: +8	Tol. A3: +6	Tol. A3: +5
	Max. diff. H/A3: 3	Max. diff. H/A3: 3	Max. diff. H/A3: 3	Max. diff. H/A3: 3	Max. diff. H/A3: 3

Recommendations for Combining Accuracy Classes

For relatively large ball runner block distances and long strokes: Use a ball guide rail in a higher accuracy class than the ball runner blocks.
For small ball runner block distances and short strokes: Use ball runner blocks in a higher accuracy class than the ball guide rail.

Selection Criterion: Travel Accuracy

Perfected ball entry and exit zones in the ball runner blocks, along with optimized spacing of the mounting holes in the guide rails, provide very high travel accuracy with very low pulsation. This is particularly suitable for high-precision applications such as metal-cutting machining, measuring technology, high-precision scanners, and eroding technology.

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