Castor Types

The size of castors is generally denoted by the size of the wheel so although a 100mm castor is likely to be 127/130mm overall height, it is called a 100mm castor same applies to every diameter. This is standard throughout the trade.


In the main plate fitting. It is a rule of thumb (though exceptions do occur) that castors up to 125mm – so 80mm 100mm and 125mm will have rectangular top plates, 105 x 80 with 80 x 60 slotted bolt hole centres. 160mm, 200mm and occasionally 250mm will have 130 x 106mm top plates. Can differ slightly but bolt hole spacings are constant at 105 x 80 slotted bolt hole centres.

Industrial castors are also available in bolt hole fitting. Again, generally M12 especially in 80mm, 100mm and 125mm. Also in 150/160mm but these are also available in M16 and M20.

All industrial castors, plate and bolt hole come in swivel and swivel braked and in plate fixed but you can’t have fixed in bolt hole fitting.


There are a range of wheels for industrial castors. Black or grey rubber tyred on nylon or metal centres generally with needle roller bearing. Also white nylon/polypropolene/polyurethane on nylon P.P. centre, with plain bearing, roller bearing and ball bearing. Plain bearing denotes just running on the material in centre of wheel. These tend to be the most popular but polyurethane on cast iron centre and steel wheels are often used in heavy duty applications.


Mainly truck, trolley, bakery frames, small scaffold towers etc.


Most institutional castors are 50mm, 75/80mm, 100mm and 125mm. Larger diameters available but are rare. In zinc or chrome finish. Available in bolt hole fitting. Generally M10 or M12. Also plate fitting but, whereas industrial have standard bolt holes, institutional don’t. They are generally smaller plates than industrial but can be all sizes.

Bolt hole castors can have solid stems or expanding adaptors. These can be round or square, round being most popular. In 19mm and 22mm. Castors are available with combined swivel and wheel brakes (brakes the head of the castor as well as the wheel). Directional locks, which turns a swivel castor into a fixed castor.


Mainly grey T.P.R wheels ( T.P.R = Thermoplastic rubber) though polyurethane tyred and P.V.C tyred are not unusual.

Bearings Plain bearing, roller bearing and ball bearing. Also anti-static wheels are generally available.

MarketsMainly educational and catering equipment..


Many of the medical castors cross over with institutional but are nearly always chrome. But the main medical castors are now with glass filled nylon forks, some with stainless steel parts and some not. Polyurethane tyred twin wheel castors fall into this category mainly for patient lifters. Brakes and locking systems more or less as institutional but with an added three way locking system. Used mainly on hospital beds.


As per institutional types.


Walking aids such as frames (Zimmer) wheels only. Tea trolleys, mainly for care homes. Commodes, shower chairs etc.



S.W.B = combines swivel and wheel brake. Stops swivel and wheel.

BK = Generally as above but could also be just braking the wheel only.

B = Generally as above but could also be just braking the wheel only.

S.L.B = Side lock brake. Works off the axle. Only brakes the wheel.


Ex = Followed by ‘R’ for round. ‘Q’ for square. Followed by diameter

EXP = Followed by ‘R’ for round ‘Q’ for square. Followed by diameter.


S = Followed by dimensions. i.e 22 round x 75mm long etc. BUT

S.S = Is also used for stainless steel.


T.P.R = Thermoplastic rubber.

P.V.C = P.V.C Actually terminology too long.

A/S = Anti static. Generally specified for theatres.

P.U = Polyurethane. P.U.B = with roller bearing.

P.U.B.B = with ball bearing.

NY = Nylon. NYB = nylon roller bearing.

NYBB = nylon ball bearing.

P.P = polypropolene. Bearing refs the same. Please not nylon is often used when actually it is white P.P as they look the same.

G.R.T = Grey rubber tyred.

B.R.T = Black rubber tyred.T/G or sometimes just G. denotes threadguards.