THKSR35W1SSRadial-Biased LM Guide Carriage Block, Size 35 for 34 mm Rail, 48 mm Height, 90° Contact Angle, C 60.4 kN, GK Interchangeable Series, Block Only

Product Description

What this part is

This is a THK LM Guide carriage block, model SR35W — a four-row linear bearing block running on a 34 mm wide SR size-35 LM rail. The SR series differs from THK’s HSR series in one respect that decides whether it suits your design: the raceway geometry is arranged for a 90° contact angle rather than 45°.

Why SR and not HSR — the 90° contact angle:
This is the specification that matters most and it is the one nobody publishes plainly. In the SR series the ball contact lines are set at 90°, which biases the block’s capacity strongly toward radial load — downward load, in a normal horizontal installation — at the expense of symmetry.

Compare the published moment figures for this block: MA is 0.785 kN·m but MB is only 0.482 kN·m. In the HSR series those two are equal, because 45° geometry is symmetrical. Here they are not, and that asymmetry is the whole design intent: the SR series is for applications where the load is predominantly downward and you want maximum radial capacity per millimetre of block height. At 60.4 kN dynamic from a 48 mm tall block, the SR35W is considerably stronger radially than an HSR of comparable height.

The practical rule: if your load is mostly vertical and downward — a heavy table, a vertical machining centre saddle, a press slide — SR gives you more capacity for the space. If the rail is mounted on a wall, inverted, or loaded from unpredictable directions, use HSR instead, because SR’s reduced upward and lateral capacity will bite you.

Block only — and why that is fine here:
This is the block alone, with no LM rail. Normally that is a problem: THK serial-number-matches standard blocks to their rails 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 resolves it. THK’s GK series exists precisely so blocks and rails can be bought separately — the GK line “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 to any SR35W GK rail of matching accuracy and preload grade and the assembly is correct.

Decoding the designation

SR — THK’s radial-biased LM Guide series, 90° contact angle35 — size, corresponding to a 34 mm wide railW — block type, bolts mounted from above. Note THK does not describe SR-W as a “wide type” despite the letter; the companion type is SR35V1 — THK’s coding field for the number of blocks used on the same rail. Not a pack quantitySS — end seal plus side seal. 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: 48 mmBlock width W: 70 mmBlock length L, with UU or SS seals: 111 mm; block body L1: 79 mmBlock mounting hole pattern B x C: 50 x 50 mm; taps 4 x M8 x 12 mm deepMating rail width W1: 34 mm (0 / −0.05); rail height M1: 27.5 mmRail hole pitch F: 80 mm; hole d1 x d2 x h: 9 x 14 x 12 mmBasic dynamic load rating C: 60.4 kN (radial)Basic static load rating C0: 81.8 kNStatic permissible moment MA: 0.785 kN·m (one block) / 4.27 kN·m (two blocks)Static permissible moment MB: 0.482 kN·m (one block) / 2.65 kN·m (two blocks)Static permissible moment MC: 1.08 kN·m (one block)Rolling elements: four rows of raceways, 90° contact angle, full complement with retainer platesBlock mass: 1.2 kg; rail mass 6.4 kg/m; maximum rail length 3000 mmAccuracy grades: Normal, H, P, SP, UP. Preload grades: Normal, C1, C0

Do not cross-read the SR35V figures

The SR35V shares a table line with the SR35W in THK’s catalogue and its numbers are materially lower — C 40.9 kN, C0 46.7 kN, block length 77.6 mm, mass 0.8 kg. Those are a different block. Every figure published above is the W-type column.

Interchange guidance

Cross-references: SR35W1SS, SR35W1SS(GK), SR-35W1-SS, SR-35V/W, SR35W, SR 35 W, SR35W1UU, SR35W1SSGK. Companion block type in the same size: SR35V. Adjacent sizes: SR30W, SR35TB. Note the moment values are quoted for one block and two blocks, and the two-block figure is roughly five times the one-block figure rather than double, because two blocks react a moment as a couple across their spacing — size a single-block axis on the one-block column.

Central Surplus also stocks THK HSR25CA, HSR30CA, HSR30B and SHW21CA blocks from the same source.