a variety of mast bearings

This publication is an attempt to explain a little more about Fork Truck Mast Bearings.

A glossary of terms can be found at the bottom of this page.

What makes a Mast Bearing different from a standard bearing?

A Mast Bearing needs three attributes not always found together on a standard bearing.

  1. The outer ring is usually very thick so as to take high loads without distortion.
  2. The bearing has to be of a non-separable design - that is the inner ring and outer ring must stay together (unlike, for example a standard cylindrical roller N; NU; NJ series)
  3. The bearing needs to have good seals as many fork trucks operate in dirty environments.

What information do I need to get from my customer?

  1. The brand of the fork truck.
  2. The fork truck manufacturer's part number (usually in the parts book issued with each fork truck) or any part number marked on the bearing and any maker's mark.
  3. The dimensions as ID x OD x IW/OW.
  4. The type of bearing i.e ball, roller, or needle.
  5. Some idea of the cross section profile i.e where is the big radius, a taper on the OD - see the illustrations in Type Drawings and our glossary of terms (below) to help you.

What if I can not get all of this information?

Get as much as you can (including a photo if possible) and contact us. We will do our best to help.

Parts of a Typical Fork Truck Mast Bearing:

typical mast bearing

Back to Fork Truck Mast Bearing Index

Glossary of terms relevant to Fork Truck Mast and Carriage bearings:

BORE - see ID (Inner Diameter)

CAGE- device holding balls, needle rollers or cylindrical rollers apart between inner and outer rings.

CHAMFER - short straight line connecting 2 points across the corner of a bearing (to remove sharp corner).

CYLINDRICAL ROLLER - roller bearing using steel rollers that are less than 3 times their diameter in length. e.g. a roller 3 x 5 is a cylindrical roller but a roller 3 x 9 is a needle roller.

ENDCAP- Cap that blanks off one end of the bore of the bearing.

FULL COMPLEMENT - bearing without cage. Usually higher loadings than caged type bearing of same size and type.

ID - Inside diameter of bearing - see drawing above.

INNER RING - smaller of the two rings that form the bearing.

INNER WIDTH - The measurement through the inner ring. See drawing above.

IW - see Inner Width

NEEDLE ROLLER - roller bearing using steel rollers that are more than 3 times their diameter in length. e.g. a roller 3mm x 9mm is a needle roller but a roller 3mm x 5mm is cylindrical roller.

OD - Outside Diameter of bearing. If the bearing tapers on the OD then measure both largest and smallest diameters. See also Taper.

OUTER RING - larger of the two rings that form the bearing.

OUTER WIDTH - the measurement across the outer ring - see drawing above.

OW - see Outer Width

RADIUS - part of a circle around corner of bearing ring connecting outer surface and side surface - see drawing above.

SEAL- usually natural rubber or nitrile rubber seal on sides of bearing to retain grease and to exclude dirt.

SIDEPLATE - usually steel plate with circlips or O-rings inset to seal bearings and to exclude dirt.

SPHERED OD - outer of bearing has a part of circle starting at one corner and finishing at the other. Radius is usually big and sphere sometimes difficult to detect. Use straight edge of ruler across OD of bearing.

TAPER - A long straight line connecting two points on the outside surface of the bearing. Commonly, we use this to mean one of the running surfaces of the outer ring, which will run in or on the mast channel. Do not confuse with Chamfer.

SPECIAL BEARING MANUFACTURE - Most of the bearings illustrated in this brochure are made by us in the UK using state of the art CNC machines and micro-processor technology. We are therefore well capable of producing bearings for applications other than fork trucks. Please call us if you think we may be able to help.