Linear Guide (LM Guide) Life Calculator — Rated Life, Hours & Static Safety (ISO 14728-1)

Because nothing has been given to judge the life against. A rated life is a number, not a verdict: 15 km and 5,000 km look identical to a tool with no requirement to compare them to. The calculator therefore treats the fatigue life and the static safety check as two INDEPENDENT checks — the life is only judged once you enter a required travel distance, and the static check is only judged once you enter the static rating C0 and the peak static load P0. A green PASS means both were supplied and both were met; passing one of them never green-lights the other. A target life of 0 is not an acceptance criterion and is ignored.

Three sources, named separately rather than folded into one claim. The rated-life FORM is ISO 14728-1, the standard for the rated life of linear motion rolling bearings. The modifying factors (fH hardness, fT temperature, fC contact, fW load/speed) and the 50 km ball reference distance are THK catalog convention layered on that standard, not ISO clauses — which is why the headline figure is THK's MODIFIED nominal life L10m and the unmodified ISO L10 is reported beside it. The STATIC safety factor belongs to ISO 14728-2, whose scope is the basic static load rating, the static equivalent load and the static safety factor; its factored form and acceptance floors are THK General Catalog A1-64. Every one of these attributions is stated on the result and in the PDF report.

The basic dynamic load rating C is defined as the load giving a specified reference life, and that reference distance is a convention. ISO 14728-1 itself uses 10⁵ m = 100 km for BOTH element types; the 50 km figure for ball guides is the Japanese and Taiwanese catalog convention (THK, HIWIN, NSK, NB, MiSUMi), while Bosch Rexroth and Schaeffler publish ball ratings on the ISO 100 km basis. The rating you read from a catalog is on one of those two bases, so the life formula must use the matching one — mixing them changes the life by a factor of two. THK gives the conversion as C100 = C50 / 1.26 for balls and C50 / 1.23 for rollers, so the 50 km rating is always the larger number. The calculator states the basis it used on every result.

Lh = L × 10⁶ / (2 × ℓs × n₁ × 60), where L is the nominal life in km, ℓs is the stroke length in mm, and n₁ is the number of reciprocations per minute. The factor of two accounts for the block travelling the stroke in both directions each reciprocation. Provide the stroke and frequency and the calculator returns the life in hours alongside the kilometres.

The static safety factor fS = (fH·fT·fC·C0)/P0 compares the (factored) static load rating against the peak static or moment load. Below about 1 the raceway can be permanently indented (brinelled), which the tool flags as a failure. THK's guideline for LM guides (General Catalog A1-64, Table 10) is a minimum of 2 without vibrations or impacts and 5 with them; the calculator will not accept a floor below 2, because a factor of 1 is the onset of indentation rather than a margin. The load factor fW is not applied to the static check, and the static rating itself is defined by ISO 14728-2.

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