THKHSR25CA1SSLM Guide Carriage Block, Size 25 for 23 mm Rail, 36 mm Height, Four-Row 45° Ball Contact, C 27.6 kN, GK Interchangeable Series, Block Only

Product Description

What this part is

This is a THK LM Guide carriage block, model HSR25CA — a four-way equal-load linear bearing block running on a 23 mm wide HSR size-25 LM rail. HSR is THK’s flagship full-ball linear guide series: four rows of balls at a 45° contact angle, giving equal load capacity downward, upward and to both sides.

Block only — and why that is fine here:
This is the block on its own, with no LM rail. Ordinarily that would be a problem: THK marks standard LM Guide blocks and rails with matching serial numbers and states that “an LM rail and LM blocks used in combination must have the same serial number,” because preload and running parallelism are set as a pair.

This part carries the (GK) designation, which changes that. THK’s GK series exists specifically so blocks and rails can be bought separately — in THK’s words, the GK series “features a lineup of interchangeable LM blocks and LM rails that can be combined freely as long as they have the same model number.” Fit this block to any HSR25 GK rail of matching accuracy and preload grade and you have a correct assembly. That is what makes a bare block a genuine spare rather than an orphan.

Decoding the designation

HSR — four-way equal-load full-ball LM Guide series25 — size, corresponding to a 23 mm wide railCA — block type: flanged, tapped mounting holes, mountable from top or bottom1 — THK’s coding field for the number of LM blocks used on the same rail. Not a pack quantity, which is the usual misreadingSS — end seal plus side seal. Note SS is not “double seal” in THK’s scheme: DD is double seal, UU is end seals onlyGK — the interchangeable block-only / rail-only series

Published dimensions and ratings

Assembly height M: 36 mmBlock width W: 70 mmBlock length L, with UU or SS seals: 83.1 mm; block body L1: 59.5 mmBlock mounting hole pattern B x C: 57 x 45 mm; taps 6 x M8Mating rail width W1: 23 mm (±0.05); rail height M1: 22 mmRail hole pitch F: 60 mm; hole d1 x d2 x h: 7 x 11 x 9 mmBasic dynamic load rating C: 27.6 kNBasic static load rating C0: 36.4 kNStatic permissible moment MA: 0.324 kN·m (one block) / 1.8 kN·m (two blocks)Static permissible moment MB: 0.324 kN·m (one block) / 1.8 kN·m (two blocks)Static permissible moment MC: 0.366 kN·m (one block)Rolling elements: four rows of balls, 45° contact angle, full complement with retainer platesBlock mass: 0.59 kg; rail mass 3.3 kg/mGrease nipple: B-M6F; maximum rail length 3000 mmAccuracy grades available: Normal, H, P, SP, UP. Preload grades: Normal, C1, C0

What the 45° contact angle buys you

The four-row 45° geometry is the reason to choose HSR over a cheaper two-row guide. With the contact lines at 45°, capacity is identical in all four radial directions and moment stiffness is symmetrical — so you can mount the rail on a wall, inverted or vertically with no derating, and a single block resists roll, pitch and yaw rather than needing a partner block to react them.

The trade is friction and speed. A full-complement ball guide has balls contacting each other in the circulation path, which runs warmer and noisier at high speed than a caged-ball design. For fast, light duty a caged-ball series is smoother; for heavy, shock-loaded, orientation-agnostic duty HSR is the correct family.

Reading the moment figures correctly

MA and MB are quoted for one block and for two blocks on the same rail, and the two-block value is roughly five times the single-block value rather than double. Two blocks spaced along a rail react a moment as a couple between them, so capacity scales with their spacing. Size a single-block axis on the one-block column — using the two-block figure overstates your design by about five times.

Interchange guidance

Cross-references: HSR25CA1SS, HSR25CA1SS(GK), HSR-25-CA1-SS, HSR25CA1UU, HSR25CA, HSR 25 CA, HSR25-CA1-SS-GK. Related block types in the same size: HSR25A, HSR25B, HSR25C, HSR25R. Adjacent sizes: HSR20CA, HSR30CA.

Central Surplus also stocks THK HSR30CA1SS (eight on hand) and HSR30B1SS blocks, plus SR35W and SHW21CA blocks — useful if you are re-blocking a machine with mixed rail sizes from one source.