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Central Surplus Bearing Finder
A faster way to search our bearing inventory Today we’re launching the Central Surplus Bearing
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3 in stock
Wide, low-profile caged-ball LM Guide carriage block for 37 mm wide rail — only 21 mm assembly height, 68 mm block width, four rows at 45°. Dynamic load 8.24 kN, static 12.8 kN. Block only, no rail supplied.
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| MFR / Brand | THK |
|---|---|
| MPN | SHW21CAN1SS |
| Model | SHW21CAN1SS(GK) |
| Type | Linear Bearing |
|---|---|
| Base Number | SHW21CA |
| Industry Terms | LM guide block, linear carriage, wide rail linear guide, low profile linear bearing, caged ball linear guide, LM block, SHW block |
| Housing Style | CA block type - flanged with tapped mounting holes, mountable from the top or the bottom |
| Mpn Variants | SHW21CA1SS, SHW21CAN1SS, SHW21CA1SS(GK), SHW21CAN1SSGK, SHW-21-CA1-SS, SHW 21 CA1 SS, SHW21CA1UU, SHW21CA, SHW-21 CA |
| Manufacturer Status | THK active catalogue series; GK interchangeable line current |
| Compatible With Replaces | Runs on THK SHW21 LM rail, 37 mm wide, 50 mm hole pitch. As a GK-series block it may be freely combined with any SHW21 GK rail of the same accuracy and preload grade. |
| Bearing Type | Linear motion guide carriage block, wide low-profile, four-way equal load, caged ball |
| Number Of Rows | 4 rows of balls |
| Part Number | SHW21CAN1SS(GK) |
This is a THK LM Guide carriage block, model SHW21CA — a wide, very low-profile caged-ball linear bearing block running on a 37 mm wide SHW size-21 rail. Four rows of balls at a 45° contact angle give four-way equal load capacity.
Why the SHW series exists — wide rail, low height, high MC:
The whole design premise is in the proportions. Assembly height is only 21 mm while the rail is 37 mm wide and the block 68 mm wide. In THK’s own words, “the Model SHW, which has a wide LM rail and a low center of gravity, is optimal for locations requiring compactness and a large MC moment rigidity.”
MC is the moment about the axis of travel — the rolling or twisting couple. Because the SHW’s raceways are spread far apart across a wide rail, a single SHW block resists that couple far better than a tall narrow block of similar capacity. MC is 0.229 kN·m against MA and MB of 0.0806 kN·m each, so roll resistance is nearly three times the pitch and yaw figures.
Where this pays: a single-rail axis carrying a wide, off-centre or cantilevered load. One SHW rail can replace two narrow rails, which saves the second rail, its machining, and the parallelism alignment between them. It is also the series for a low overall height budget — 21 mm total is very shallow.
Unlike THK’s HSR and SR series, the SHW uses a caged ball design: the balls are held in a synthetic cage so they never touch each other in the circulation path. Ball-to-ball contact generates most of the noise and heat in a full-complement guide, so a caged-ball block runs quieter and cooler, tolerates higher speed, holds grease in the cage pockets for longer relubrication intervals, and gives smoother, more consistent running friction. The trade is a slightly lower load rating for a given envelope, because the cage occupies space that balls could have.
This is the block alone, with no LM rail. 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.” This part carries the (GK) designation, and THK’s GK series exists specifically 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.” Any SHW21 GK rail of matching grade makes a correct assembly.
SHW: wide, low-profile caged-ball LM Guide series.
21: size, corresponding to a 37 mm wide rail.
CA: block type, flanged with tapped holes, mountable from the top or the bottom.
1: THK’s coding field for the number of blocks used on the same rail, not a pack quantity.
SS: end seal plus side seal. DD is double seal, UU is end seals only.
GK: the interchangeable block-only / rail-only series.
Assembly height M: 21 mm.
Block width W: 68 mm.
Block length L, with UU or SS seals: 59 mm. Block body L1: 43.6 mm.
Block mounting hole pattern B x C: 60 x 29 mm; taps 6 x M5; through-hole ø4.4 mm.
Mating rail width W1: 37 mm (0 / −0.05). Rail height M1: 11 mm.
Rail hole pitch F: 50 mm; hole d1 x d2 x h: 4.5 x 7.5 x 5.3 mm.
Basic dynamic load rating C: 8.24 kN.
Basic static load rating C0: 12.8 kN.
Static permissible moment MA: 0.0806 kN·m (one block) / 0.434 kN·m (two blocks).
Static permissible moment MB: 0.0806 kN·m (one block) / 0.434 kN·m (two blocks).
Static permissible moment MC: 0.229 kN·m (one block).
Rolling elements: four rows of balls, 45° contact angle, caged ball.
Block mass: 0.24 kg. Rail mass: 2.9 kg/m.
Standard rail lengths: 130, 230, 380, 480, 580, 780 mm; maximum 3000 mm.
Accuracy grades: Normal, H, P, SP, UP.
Grease nipple fitting size for size 21: PB1021B.
Cross-references: SHW21CA1SS, SHW21CAN1SS, SHW21CA1SS(GK), SHW-21-CA1-SS, SHW 21 CA, SHW21CA, SHW21CA1UU, SHW21CAN1SSGK. Related block type in the same size: SHW21CR. Adjacent sizes: SHW17CA, SHW27CA.
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A faster way to search our bearing inventory Today we’re launching the Central Surplus Bearing
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