Linear bearing

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Linear bearing


Linear bearings are used for low friction movements along a smooth rod.
Wikipedia Linear-motion bearing

A linear bearing provides low friction motion along a single axis. They are a little costlier than classical round ball bearings, but simpler to integrate in carriage design.


Not all Linear Bearings need lubrication Some bearings need lubrication to run smoothly. Use white lithium grease, tri-flow or 3-in-1 oil.

Don't use dry lubricants, PTFE-based greases or thick, high temperature greases like wheel bearing grease, because they may stop the bearing balls from circulating. Also don't use spray lubricants, as it contains an agent that helps it spray evenly but does no good to precision ball bearings.

Apply the lubricant inside the bearings. If you try and put it on the rod, the bearings just wipe it off.

Adafruit reports that some (but not all) linear bearings are packed in cosmoline (Wikipedia: cosmoline) to keep them from rusting. WD-40 works well for removing the sticky cosmoline."LM8UU bearings"


LM8UU linear bearings are the most common type of bearings used in RepRap/ Mendel / Prusa. The prefix "LM" denotes that the bearing is intended for linear motion, distinguishing it from rotation ball bearings. The number refers to the diameter of the shaft that the bearing will fit on. The suffix letter appears to refer to the design of the bearing. V and U appear to refer to types of bearing seals (V indicates a non-contact seal, and U indicates a contact seal), whereas Z indicates that the bearing has been shielded instead of sealed. Single letters indicate that the bearing is single sealed/shielded, whereas double letters (for example, "UU") indicate that the bearing has been double sealed/shielded.There are also many other types of bearings such as LMk8UU, LMKL8UU. For different length, there could be another prefix letter before seal prefix, say S for 'short' and 'L' for long. ex: LM8SUU or LM8LUU. Long bearings are used for stabilisation instead of doubling the bearing.

"SC10UU linear bearing blocks" are pillow blocks with a LM10UU linear bearing inside.

Common Linear Bearing Dimensions


Model Inner D. Outer D. Length
LM6UU 6 mm 12 mm 19 mm
LM6LUU 6 mm 12 mm 35 mm
LM8UU 8 mm 15 mm 24 mm
LM8LUU 8 mm 15 mm 45 mm
LM8EUU 8 mm 16 mm 25 mm
LM10UU 10 mm 19 mm 29 mm
LM10LUU 10 mm 19 mm 55 mm
LM12UU 12 mm 21 mm 30 mm
LM12LUU 12 mm 21 mm 57 mm
LM16UU 16 mm 28 mm 37 mm

Pillow blocks

Model Inner D. Outer D. Length
SCS8UU 8 mm 35 mm 30 mm
SC10UU 10 mm 35 mm 40 mm