THKLM50UULinear Ball Bushing, Sealed Both Ends, 50 mm Shaft x 80 mm Housing Bore x 100 mm Long

Product Description

What this part is

The LM50UU is a recirculating linear ball bushing — a cylindrical bearing that slides along a round shaft instead of rotating on one. It fits a 50 mm shaft, drops into an 80 mm housing bore and is 100 mm long.

What these specs mean in practice

How it works and why you would choose it. Inside the steel sleeve, rows of balls run in closed circuits: they roll along the shaft under load, then curve out of the load zone and return through a channel to start again. Because the balls recirculate, stroke length is limited only by the length of the shaft, not by the bearing — which is the fundamental advantage over a ball-screw nut or a short linear slide. The balls make POINT contact with the shaft, so friction is very low and the same in both directions, giving smooth motion at low speed without the stick-slip you get from a plain bronze bushing.

The trade-off is directly implied by that point contact: load capacity per bearing is modest compared with a profile-rail block, and all of the load passes through a few small contact spots, so the shaft must be a properly hardened and ground linear shaft. Run one of these on ordinary cold-drawn bar and the balls will brinell tracks into it within hours. It is also NOT self-aligning — the bushing and the shaft must be genuinely parallel, so on a two-post arrangement the posts must be bored and aligned properly, or one bushing will bind.

Decoding the designation

The UU suffix is the important part of the designation: it denotes SEALS AT BOTH ENDS. Sealed ends keep grit and swarf out of the ball circuits, which is what determines service life in a dirty environment — a linear bushing dies from contamination far more often than from fatigue. The seals also retain grease so the bushing holds its own lubricant. The cost is a little drag and slightly reduced usable stroke at each end of travel. Where the environment is clean and every gram of friction matters, the unsealed LM50 form is used instead.

Published ratings and mounting data

Built from 52100 chrome bearing steel, working range -30 to +80° C, weight approximately 1.58 kg. Typical duty is guide posts and die sets, vertical lift columns, pick-and-place pillars, tool-change slides and general machine axes running on round shafting.

Quantity and configuration

Sold as one bushing.

Interchange guidance

Also written LM-50-UU, LM-50UU, LM 50 UU and LM50-UU. Central Surplus also stocks the LM50U form of the same envelope — see that listing if you need the version without both-end seals.