Castors.

What are Castors?

Castors, also known as castor wheels or wheel castors, are wheels mounted in a housing that fixes to the underside of equipment, and they make up the largest part of Accu’s Castors & Wheels range, with options for almost any load, floor and environment. Each castor combines a top plate, bolt hole or threaded stem for fixing, a fork that holds the axle and a wheel with a tread suited to the floor, while swivel versions add a bearing head that lets the whole fork rotate. That simple assembly turns a static piece of equipment into something one person can push, steer and park, from small castors on a 25 kg instrument case to transport frames carrying 1,440 kg per castor.

Much of the range is listed against European castor standards: EN 12528 for furniture, EN 12530 for institutional settings, EN 12532 for industrial equipment moved at up to 4 km/h and EN 12533 for industrial equipment moved at 4 km/h to 16 km/h. They are used throughout manufacturing, logistics, engineering workshops, laboratories and food and pharmaceutical production, on everything from furniture and trolleys to machine bases and heavy transport frames.

How Castors Work

Once fixed through its top plate, a single bolt hole or a threaded stem, a castor passes the load down its fork to the axle, where the wheel turns on a plain, roller or ball bearing. On a swivel castor, the head above the fork turns on a ball race and the axle is set a short distance behind the swivel axis, so a push in any direction swings the wheel round to follow it. Fixed versions have no swivel head and simply roll straight, which is why most trolleys combine the two, while brakes lock the wheel or, on total lock versions, the wheel and swivel head together. The tread then decides how the castor feels: hard polyamide rolls easily under heavy loads, polyurethane balances load capacity with floor protection and rubber cushions shocks and runs quietly.

A 540 kg mobile hydraulic power unit in a press shop is a good example, moved between machines across sealed concrete with steel floor plates. Shared between three castors in contact, the load is 180 kg each, inside the 200 kg rating of a 125 mm castor with an injection moulded polyurethane tread. The handle end runs on braked swivel castors that steer the unit and lock it while hoses are connected, with a fixed pair at the opposite end keeping it straight between machines. The polyurethane treads roll over the floor plates without damaging the sealed concrete, where a polyamide wheel would clatter over the plates and a solid rubber tread of the same size would be overloaded.

Materials Castors Are Made From

Every castor in Accu’s range combines a metal or polyamide housing with a wheel of engineering-grade polymer or elastomer, often on a metal centre, matched to the load, floor and conditions it will work in:

• Steel: Pressed steel housings from light to extra-heavy-duty, blue passivated or zinc plated for corrosion protection.
• Stainless Steel: Housings for wet, washdown and corrosive areas.
• Cast Iron: The material behind the strongest castors in the range, used for forged housings and wheel centres rated up to 1,440 kg.
• Aluminium: Rigid wheel centres beneath polyurethane and elastic rubber treads.
• Rubber: Solid, elastic, natural and synthetic rubber treads that cushion shocks and run quietly, including non-marking versions.
• Rubber - TPR: Thermoplastic rubber treads on lighter-duty models.
• Plastic - Nylon: Solid polyamide wheels with very low rolling resistance, from 14 mm compact wheels to 1,440 kg heavy-duty wheels.
• Plastic - PUR: Injection moulded and cast polyurethane treads that balance load capacity with floor protection.
• Plastic - PP: Light polypropylene wheels and wheel centres for light duty castors.
• Plastic - Phenolic: Rigid black phenolic wheels for loads of 100 kg to 150 kg and thermoset wheels for heat up to 280 °C.
• Plastic - TP: Tough black wheels on stainless steel housings.

Sizes & Types of Castors Available

Accu’s range of castors is available in a wide variety of sizes, fixings and load ratings, from small castor wheels for furniture and apparatus to large castor wheels for heavy transport:

• Wheel Diameter (D): 14 mm to 200 mm.
• Wheel Width (T): 13 mm to 50 mm.
• Mounting Height (H): 17 mm to 250 mm.
• Approximate Load Capacity: 25 kg to 1,440 kg.
• Static Load Capacity: 50 kg to 2,400 kg.
• Castor Type: Swivel Castor or Fixed Castor.
• Braked/Unbraked: Braked or Unbraked.
• Fixing Type: Bolt Hole Fixing; Rectangular Plate; Square Plate, 60 x 60 mm; Rectangular Plate, EN R42, 105 x 85 mm; Rectangular Plate, EN R43, 137 x 105 mm.
• Thread Size: M10 x 25 to M12 x 30.

Not every combination exists across that range. Rubber treads stop at 450 kg, so heavier loads need polyurethane or polyamide wheels, while threaded stem versions stop at 100 mm wheels and 120 kg and bolt fixing castors at 125 mm wheels and 200 kg. Anything with a mounting height of 70 mm or less is rated up to 75 kg. When a tread wears, many of these castors can be refreshed with replacement rubber castor wheels from the Castors & Wheels range rather than replaced outright.

If the equipment never needs to roll and simply has to stand level, check out Accu’s range of machine feet instead.

FAQ

Q: Is it casters or castors?

A: Both are correct and describe the same product. Castor is the usual British spelling and caster the American one, so caster wheels and castor wheels are used interchangeably in catalogues and drawings. Accu uses the British spelling throughout its UK range, and a specification calling for large caster wheels is asking for exactly the same thing as one calling for large castor wheels.

Q: What is the definition of a castor?

A: A castor is a wheel mounted in a housing, usually a fork with a top plate, bolt hole or threaded stem, that fixes to the underside of a piece of equipment so it can be rolled rather than lifted. Swivel versions rotate through 360 degrees to steer, fixed versions only roll in a straight line and braked versions can be locked in place. The term covers the complete assembly, while the wheel on its own is usually called a castor wheel, and replacement wheels are listed separately.

Q: What are the types of castors?

A: They are usually grouped by how they move, what they are made of and what they carry. In Accu’s range, Swivel Castors and Fixed Castors cover movement and Castors With Brakes cover locking. By material there are Rubber Castors, Plastic Castors, Stainless Steel Castors and Cast Iron Castors, while Heavy-Duty Castors carry 500 kg to 1,440 kg and Low Profile Castors keep mounting heights to 70 mm or less for light duty castors on compact equipment. Spare castor wheels and ball transfers are covered in the wider Castors & Wheels range.

Q: How do I choose the right castor?

A: Start with the load: add the equipment’s weight to its heaviest payload and divide by three on a four-castor frame, since an uneven floor rarely lets all four bear at once. Next, match the wheel to the floor, with polyamide for easy rolling on smooth concrete, polyurethane for sealed or painted floors and rubber where quiet, cushioned running matters. Then consider the environment, choosing stainless steel for washdown or corrosive areas and heat-resistant wheels for high temperatures. Finally, pick the fixing and layout, usually a braked swivel pair and a fixed pair, with a top plate for heavier loads or bolt fixing castors and threaded stems for lighter frames.

Bespoke Castors Manufacture.

High precision, bespoke manufacture of Castors to customer specification. State of the art facilities specialising in both small batch prototyping and large scale manufacture.