THKHSR25A1KKC1LM Guide Block, Size 25 HSR, Square Flange, Four-Way Equal Load, Full Seal Package, C1 Light Preload

Product Description

What this part is

This is a THK LM Guide block: the moving carriage of a size 25 HSR linear guide, with its ball complement, retainers, end plates and seals.

A linear guide is a two-part product. The recirculating ball tracks close through the rail’s ground raceways, so the block runs on a THK HSR size 25 rail. This block suits adding a second or third carriage to an HSR25 rail already in service, or replacing a block that has been crashed or contaminated on a machine whose rail is still true. A complete new axis is built from this block plus an HSR25 rail cut to length.

Four-way equal load — the reason the HSR series exists:
The HSR is THK’s global-standard full-ball LM Guide, and its defining feature is the 45° contact geometry: four rows of balls arranged so the block carries the same rated load in all four directions — downward, upward (lift-off), and laterally from either side. It also takes moment loads about all three axes.

That matters more than it sounds. A profiled rail with unequal ratings has to be oriented so its strong axis faces the load, which constrains the machine design and makes vertical or inverted mounting awkward. A four-way equal load block can be mounted in any attitude — horizontal, on its side, upside down, on a wall — and behave identically. It is why HSR guides turn up in gantries, vertical axes, robot arms and anywhere the load direction changes as the machine moves. Being full-ball rather than caged-ball like THK’s SHS or SSR series, it is also the higher-rigidity, higher-capacity choice at a given size, at the cost of somewhat more noise and friction at speed.

Decoding the designation

HSR: THK full-ball LM Guide, four-way equal load type.

25: size 25. THK size codes correspond to a defined rail width and block envelope, so a size 25 block runs on a size 25 rail.

A: block type, the square flange block, mounted from above or below through the flange. THK’s other HSR block forms include B, R and LA/LB/LR variants with different flange shapes and lengths.

1: the number of blocks. This designation describes one block.

KK: THK’s full seal package. THK’s contamination-protection codes run from SS (end seals only) through UU (end seals plus side seals) to the KK/ZZ level, which adds inner seals for the most complete sealing THK offers on this series.

C1: THK’s radial clearance / preload designation. In THK’s LM Guide scheme, clearance is specified as Normal, C1 or C0, with C1 denoting a light preload rather than running clearance.

(GK): a bracketed suffix carried on this part, reproduced exactly as marked.

Why the KK seals and C1 preload are the two things to check:
The seal package is a genuine specification, not a trim level. Linear guides fail on contamination far more often than they fail on fatigue. A ball rolling in a ground raceway will tolerate an enormous number of cycles; a single hard chip carried into the ball track will indent the raceway and end the block’s accuracy immediately. KK is the top of THK’s sealing range for this series, which is why it is found on machine tools running coolant and chips, and on woodworking and grinding equipment where fine abrasive dust is the enemy.

C1 light preload changes the machine’s behaviour, not just its feel. A guide with running clearance has a small dead band: the carriage can move slightly before the balls take load, which shows up as lost motion on reversal and as vibration under changing load. A preloaded block removes that clearance, so the carriage responds immediately and holds position under cutting or accelerating load. The cost is higher friction, higher heat and a shorter calculated life at a given external load, because the preload itself is a permanent internal load. On a multi-block axis the blocks share a single preload class, since mixing classes on one rail loads the blocks unequally.

Published data

Series: HSR full-ball LM Guide, four-way equal load.

Size: 25.

Block type: A, square flange.

Blocks: 1.

Seal specification: KK, full seal package including inner seals.

Clearance / preload: C1, light preload.

Item weight: 1.30 lbs.

THK publishes exact block dimensions, load ratings and static moment ratings per designation in its LM Guide catalogue.

Quantity and configuration

One block. The matching rail is a THK HSR size 25 rail, ordered separately by length and accuracy grade.

Interchange guidance

Search forms include HSR25A1KKC1, HSR25A1KKC1(GK), HSR-25-A1KKC1, HSR25A1KK, HSR25A1, HSR25A, HSR25, HSR 25 A1 KK C1. Related THK designations at the same size: HSR25B (different flange form), HSR25R, HSR25LA and HSR25LB (long blocks, higher capacity), and the SS and UU seal variants of this same block. THK rails for size 25 are sold by length and by accuracy grade separately. Profiled rail geometry is proprietary: a block and rail must be the same manufacturer and the same series, so same-size blocks from other makers — NSK LH25 / LAH25, Hiwin HGH25 / HGW25, IKO LWH25, Rexroth R1651 size 25 — run on their own maker’s rails.