Ein '''hydrostatisches Gleitlager''' ist ein Lager, das im Hydrodynamischen Gleitlager vermieden, nämlich der beim Anfahren und Auslaufen durch die Mischreibung verursachte hohe Gleitwiderstand und damit verbundenen Verschleiß des Lagers. 

thumb|290px|Komponenten eines hydrostatischen Gleitlagers.<br />Bild: MT Aerospace AG, AugsburgIm Bild sind auf der Innenseite der Lagerbuchse die Schmiermitteltaschen zu erkennen, die durch radiale Bohrungen den Lagerspalt laufend mit Schmiermittel versorgen. Es handelt sich um ein keramisches Lager mit einer Buchse aus faserverstärkter Keramik als Reibpartner aufgeschrumpft.

Hauptanwendungsgebiete der hydrostatischen Gleitlager, welche als Linear- oder Rotationslager (Axial- oder Radiallager) gebaut werden können, sind hochpräzise Mess- und Bearbeitungsmaschinen. Die Funktion beruht darauf, dass mittels einer externen Druckversorgung (Pumpe oder Gasdruckbehälter) fortwährend der flüssige oder gasförmige (Luftlager) Schmierstoff  über Einlasskanäle in Kammern (Schmiermitteltaschen) zwischen den Lagerflächen gepresst wird und diese dadurch stets durch einen dünnen Schmierfilm voneinander getrennt sind. Dadurch tritt Reibungsverlust nur durch die Scherkräfte der Flüssigkeit auf, die proportional zur Geschwindigkeit sind, mit der sich die Lagerflächen gegeneinander bewegen. Der Reibungskoeffizient ist damit sehr niedrig. Im Grenzfall verschwindender Relativgeschwindigkeit laufen hydrostatische Lager daher praktisch reibungsfrei; ein Stick-Slip-Effekt tritt nicht auf, da kein direkter Kontakt zwischen den Lagerflächen stattfindet. Dies ermöglicht hochgenaue Positionsregelungen im Sub-Mikrometerbereich.

thumb|Crankshaft, [[babbit metal, plain bearing shells]]
''A mechanical'' '''bushing''' is a cylindrical lining designed to reduce friction and wear inside a hole, or constrict and restrain motion of mechanical parts.

== Bushing types ==

One type of bushing is the "threaded insert", a hardened metal insert with a threaded fixing hole which allows one assembly to be fixed to another by means of a nut and washer on the other side of the fixed material. Such inserts are usually fitted into sheet material by a tool which operates on a similar principle to riveting; alternatively, some rivets can themselves incorporate a bushing.

=== Plain bearings ===
A typical plain bearing is made of two parts. For example, a rotary plain bearing can be just a shaft running through a hole. A simple linear bearing can be a pair of flat surfaces designed to allow motion (for example, a drawer and the slides it rests on).

Plain bearings may carry load in one of several ways depending on their operating conditions, load, relative surface speed (shaft to journal), clearance within the bearing, quality and quantity of lubricant, and temperature (affecting lubricant viscosity). If full-film conditions apply, the bearing's load is carried solely by a film of fluid lubricant, there being no contact between the two bearing surfaces. In this condition, they are known as fluid bearings. In mix or boundary conditions, load is carried partly by direct surface contact and partly by a film forming between the two. In a dry condition, the full load is carried by surface-to-surface contact. 

Plain bearings are relatively simple and hence inexpensive. They are also compact, light weight, straightforward to repair and have high load-carrying capacity. However, if operating in dry or boundary conditions, plain bearings may wear faster and have higher friction than rolling element bearings. Dry and boundary conditions may be experienced even in a fluid bearing when operating outside of its normal operating conditions, e.g., at startup and shutdown.

A common plain bearing design utilizes a hardened and polished steel shaft and a soft bronze bushing. In such designs the softer bronze portion can be allowed to wear away, to be periodically renewed.  

Plain 'self-lubricating' bearings utilize porous journals within which a lubricant is held. As the bearing operates and lubricant is displaced from the bearing surface, more is carried in from non-wear parts of the bearing.  Dry plain bearings can be made of a variety of materials  including PTFE (Teflon), graphite, graphite/metal (Graphalloy) and ceramic. The ceramic is very hard, and sand and other grit which enter the bearing are simply ground to a fine powder which does not inhibit the operation of the bearing.

==== Solid polymer types ====