THKHSR30B1SSLM Guide Carriage Block, Size 30, Four-Through-Hole Flange Type, 28 mm Rail, 45° Four-Way Equal Load, End and Side Seals — Block Only, No Rail

Product Description

What this part is

This is a THK LM Guide carriage block, model HSR30B — a four-way equal-load linear bearing block that runs on a 28 mm wide HSR size-30 LM rail. HSR is THK’s flagship full-ball linear guide: four rows of balls arranged at a 45° contact angle, so the block carries equal rated load in all four directions — radial, reverse-radial, and both lateral.

The B type is the through-hole flange block — check this before you order:
Within a single HSR size, the block types differ in one thing that decides whether the part bolts to your table: the mounting holes. They are not interchangeable mountings, even though they share the same envelope and the same rail.

HSR30B — this part. Four ø9 mm through holes through the flange, on a 72 x 52 mm pattern, taking M8 bolts. THK’s own detail-specification page for HSR 30B gives the block mounting direction as bottom-surface mount.HSR30A — same envelope, but the flange is tapped (6 x M10 on 72 x 52 mm) instead of drilled through.HSR30CA — the C-family block, tapped 6 x M10 and mountable from either the top or the bottom face.HSR30R — a narrowed block, 60 mm wide rather than 90 mm, with 4 x M8 x 10 mm deep taps on a 40 x 40 mm pattern.

All four ride the identical HSR30 rail and carry the identical load ratings. So if you are replacing a block on an existing machine, the ratings will not tell you whether you have the right one — count the holes and measure the pattern. A B-type block cannot be substituted for an A or CA unless you are prepared to re-drill or re-tap the table.

Block only — and why that is fine here:
This is the block on its own. No LM rail is supplied. Ordinarily that 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 the LM blocks used with it must carry the same serial number — preload and running parallelism are set as a pair, so a standard block separated from its rail is out of specification.

This part carries the (GK) designation, which changes the answer. THK’s GK series exists specifically so that blocks and rails can be bought separately: the GK line offers interchangeable LM blocks and LM rails that can be combined freely provided they share the same model number. Fit this block to any HSR30 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.

Condition — what is and is not on this piece:
This is a new open-box block. Two items are absent and are not supplied: there is no grease nipple (zerk) fitted and no locking bolt. The missing nipple is not a defect — the greasing hole is a semi-standard specification on the HSR series, so THK machines it to order and blocks legitimately ship without a fitting. The correct nipple for size 30 is B-M6F, a standard stock item. Budget for one if you intend to plumb a lubrication line to this block.

Decoding the designation

HSR — THK’s four-way equal-load full-ball LM Guide series30 — size, corresponding to a 28 mm wide railB — block type: flanged with four through holes, as above1 — THK’s coding field for the number of LM blocks used on the same rail. This is a model-number field, not a pack quantity — the usual misreadingSS — end seal plus side seal. Note SS is not “double seal” in THK’s scheme: DD is double seal and UU is end seals onlyGK — the interchangeable block-only / rail-only series

Published dimensions and ratings

Assembly height M: 42 mmBlock width W: 90 mmBlock length L, with UU or SS seals: 98 mm; block body L1: 70.4 mmMounting hole pattern B x C: 72 x 52 mm; four ø9 mm through holes (dimension H)Flange dimensions: t 18 mm, T 9 mm, T1 10 mm; block shoulder K 35 mm; N 7 mm; E 12 mmMating rail width W1: 28 mm (±0.05); rail height M1: 26 mm; W2 31 mmRail mounting hole pitch F: 80 mm; hole d1 x d2 x h: 9 x 14 x 12 mmBasic dynamic load rating C: 40.5 kNBasic static load rating C0: 53.7 kNStatic 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 platesBlock mass: 1.1 kg; rail mass 4.8 kg/mGrease nipple specification: B-M6F (not fitted to this piece); UU seal resistance 7.80 NService temperature: −15 to 80 °C; standard grease AFB-LFRadial clearance grades offered: Normal, light preload C1, medium preload C0Accuracy grades offered: Normal, H, P, SP, UPRail mounting-hole cap: C8; maximum standard rail length 3000 mm (2520 mm in stainless)

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° to one another, capacity is identical in all four radial directions and moment stiffness is symmetrical. In practice that means you can mount the rail on a wall, inverted or vertically without derating, and a single block resists roll, pitch and yaw rather than needing a second block to react them. The circular-arc groove geometry also gives the HSR a self-adjusting characteristic, so a degree of mounting-surface error is absorbed rather than translated into rough running.

The trade is friction and speed. A full-complement ball guide has balls touching one another 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 — heavy-cutting machine tools are THK’s stated home for HSR — this is the right family.

Reading the moment figures correctly

MA and MB are quoted both for one block and for two blocks in close contact on the same rail, and the two-block figure is roughly five times the one-block figure rather than double. Two blocks spaced along a rail react a moment as a couple between them, so the capacity scales with the spacing rather than simply adding. Size a single-block axis on the one-block column: substituting the two-block figure overstates what the design can carry by about five times.

Fitting notes

Beyond the missing nipple noted above, an inner seal is available on sizes 30 and above as an option beyond the standard end and side seals, and any added contamination-protection accessory increases the overall block length L above the 98 mm quoted. If you are fitting into a tight stroke envelope, check the accessory length increment rather than assuming 98 mm.

Because the balls are held by retainer plates, this block will not shed its balls if it is slid off a rail — a genuine practical advantage over miniature HSR sizes and over some competing guides.

Interchange guidance

Cross-references and alternative renderings of the same part: HSR30B1SS, HSR30B1SS(GK), HSR30B1SSGK, HSR-30B1-SS, HSR30-B1-SS, HSR 30 B1 SS, HSR30B, HSR-30-B, HSR30B1UU. Same size, different mounting: HSR30A, HSR30CA, HSR30R. Same block in stainless: HSR30BM. Long block, same cross-section and higher rating: HSR30LB (C 48.9 kN, C0 70.2 kN). Adjacent sizes: HSR25B, HSR35B.

Other manufacturers offer size-30 profile-rail blocks in a comparable envelope, but Central Surplus has not verified a specific competitor interchange for this listing. The full published dimensions above are given precisely so you can compare against what is on your machine before ordering.

Central Surplus also stocks THK HSR25CA1SS and HSR30CA1SS blocks (eight of the latter on hand), plus a second HSR30B1SS. If you need a matched pair of HSR30B blocks for one axis, both are available from the same source.