THKLM Guide Carriage Block, Size 30 for 28 mm Rail, 42 mm Height, Four-Row 45° Ball Contact, C 40.5 kN, GK Interchangeable Series, Block Only

Product Description

What this part is

This is a THK LM Guide carriage block, model HSR30CA — a four-way equal-load linear bearing block that runs on a 28 mm wide HSR size-30 LM rail. The HSR series is THK’s flagship full-ball linear guide, with four rows of balls arranged at a 45° contact angle so the block takes equal load in all four directions: down, up, and both sides.

Block only — and why that is fine here:
This is the block on its own, with no LM rail. That normally matters a great deal, because THK marks standard LM Guide blocks and rails with matching serial numbers and states plainly that “an LM rail and LM blocks used in combination must have the same serial number.” A standard block separated from its rail is out of specification, because preload and running parallelism were set as a pair.

This part carries the (GK) designation, and that changes the answer. THK’s GK series exists specifically to be sold as separate blocks and separate rails: in THK’s own 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.” So a GK block is a legitimate standalone item — fit it to any HSR30 GK rail of the same accuracy and preload grade and it is a correct assembly.

Decoding the designation

HSR: THK’s four-way equal-load full-ball LM Guide series.

30: size, corresponding to a 28 mm wide rail.

CA: block type, flanged, with tapped mounting holes, mountable from the top or the bottom.

1: the number of LM blocks used on the same rail. This is a THK coding field, not a quantity of items in the box.

SS: end seal plus side seal plus inner seal. SS is not “double seal” in THK’s scheme; double seals are DD, and UU is end seals only.

GK: the interchangeable block-only / rail-only series.

Published dimensions and ratings

Assembly height M: 42 mm.

Block width W: 90 mm.

Block length L, with UU or SS seals: 98 mm. Block body L1: 70.4 mm.

Block mounting hole pattern B x C: 72 x 52 mm.

Block taps: 6 x M10.

Mating rail width W1: 28 mm (±0.05). Rail height M1: 26 mm.

Rail mounting hole pitch F: 80 mm. Hole d1 x d2 x h: 9 x 14 x 12 mm.

Basic dynamic load rating C: 40.5 kN.

Basic static load rating C0: 53.7 kN.

Static permissible moment MA: 0.599 kN·m (one block) / 3.1 kN·m (two blocks).

Static permissible moment MB: 0.599 kN·m (one block) / 3.1 kN·m (two blocks).

Static permissible moment MC: 0.652 kN·m (one block).

Rolling elements: four rows of balls, 45° contact angle, full complement retained by retainer plates.

Block mass: 1.1 kg. Rail mass: 4.8 kg/m.

Grease nipple: B-M6F. UU seal resistance: 7.80 N.

Service temperature: −15 to 80 °C. Standard grease: AFB-LF.

Maximum rail length: 3000 mm. Rail hole cap: CV8.

What the 45° contact angle buys you

The four-row 45° geometry is the whole point of the HSR series and it is worth understanding before you compare it against a cheaper two-row guide. Because the contact lines sit at 45°, the block’s capacity is the same in all four radial directions and its moment stiffness is symmetrical. Practically, that means you can mount the rail on a wall, upside down, or vertically without derating, and a single block resists roll, pitch and yaw rather than needing a second block to react them.

The trade is friction and speed. A full-complement ball guide like this has balls touching each other in the circulation path, which generates more heat and noise at speed than a caged-ball design. If your duty is high-speed and light, a caged-ball series is quieter; if it is heavy, shock-loaded and orientation-agnostic, HSR is the right family.

Note on the two moment values

MA and MB are given both for one block and for two blocks on the same rail, and the two-block figure is roughly five times the single-block figure — not double. That is because two blocks separated along a rail react a moment as a couple between them, so the capacity scales with the spacing rather than simply adding. If you are sizing a single-block axis, use the one-block column; substituting the two-block figure will overstate what your design can carry by a factor of five.

Interchange guidance

Cross-references: HSR30CA1SS, HSR30CA1SS(GK), HSR-30-CA1-SS, HSR30CA1UU, HSR30CA, HSR 30 CA, HSR30CA1SSGK. Related block types in the same size, differing only in flange and bolt direction: HSR30A, HSR30B, HSR30R. Larger and smaller sizes: HSR25CA, HSR35CA.