How to read a linear guide datasheet
2026-11-06
# How to read a linear guide datasheet
A linear guide datasheet carries twenty or more columns. Four of them decide whether the size is correct. The rest are there so the mounting drawing closes — important, but they do not choose the size for you.
This is the order to read it in.
The four numbers that choose the size
1. Dynamic load rating C. The load at which 90% of a batch reaches 50 km of travel (100 km for roller types). This is the number you put into the life formula. It is not a maximum, it is a reference point.
2. Static load rating C0. The load at which the permanent deformation at the most stressed contact equals one ten-thousandth of the ball diameter. This one is effectively a limit — the peak load the block should ever see should not exceed C0, and for anything with shock it should stay well under it.
3. Block length L. Needed for rail sizing: rail length = stroke + L + 2 × end distance E. Get this wrong and the rail will not fit, no matter how correct the load rating is.
4. Block height H and width W. These decide whether the block physically fits the machine, and whether an existing mounting face can be reused.
Everything else on the sheet — H1, N, B, B1, L1, K1, G, M, H2, H3 — is there to draw the mounting. Read them when you draw, not when you size.
What the moment columns mean
MR, MP and MY are permissible static moments about the three axes: roll, pitch and yaw. They are given in kgf·m or N·m, and the unit matters more than the number.
A block loaded at the end of a long arm sees a moment, not just a force. The check is fs = M0 / M, using the same safety factor you applied to the load. If a customer reports a block failing in a way that looks like the rail is bending, check the moment columns before assuming the guide is faulty.
Where the units bite
Two traps on Chinese and Taiwanese datasheets:
- Miniature series often publish load in kgf, not kN. MGN and MGW sheets typically head the column
C[kgf]. Reading 140 as 140 kN instead of 140 kgf overstates capacity by a factor of ten and produces a badly undersized choice. - Moment is published in kgf·m on some sheets, kgf·mm on others. A factor of 1000 between two documents that both look authoritative.
Before quoting anything from a sheet, read the unit row. We write kgf with the kN equivalent in brackets for this reason.
The preload and accuracy rows
These are not numbers, they are specifications with ranges:
- Accuracy: C, H, P are interchangeable grades. SP and UP are matched-set only.
- Preload: Z0 and ZA are interchangeable. ZB is matched-set only.
- The same letter means different force on different series. On HG, ZA is 0.05–0.07C. On EG it is 0.03–0.05C. Quote it as
ZA (HG, 0.05–0.07C)or the customer will not get the force he specified.
A five-minute check
Given a customer's load, stroke and machine width:
- Pick the size from the mounting dimensions first — H and W — because that is the constraint you cannot change.
- Check C0 against the peak load with the safety factor: 1.0–3.0 for smooth running, 3.0–5.0 with shock.
- Check C against the equivalent working load in the life formula.
- Check the moment columns for any block at the end of an arm.
- Read rail length off the block length plus the end distances.
If the four constraints pass, the guide is right. If the customer wants more rigidity, go up one size before going up one preload — a size step buys roughly half again the load rating, and preserves life.