Castor Mounting Types: Plate, Stem, Insert Stem, Bolt Hole — How to Choose

When buyers spec a new piece of equipment, they spend hours picking the right wheel diameter and load rating. Then they bolt on whatever castor fixing their supplier happens to stock and find out six months later that the castor either will not fit the machine frame, or pulls out under load, or cannot be replaced without drilling a new hole.

The mounting type is not an afterthought. It is the interface between your equipment and the wheel, and it decides how hard the castor is to fit, how much load it can hold, and how easy it is to swap out later. This guide walks through the four mounting types you will actually find on industrial casters — top plate, threaded stem, insert stem, and bolt hole — and which one belongs on your equipment.

What Is a Castor Mounting, Exactly?

The mounting is the part of the bracket that attaches the whole castor to your equipment frame. A castor wheel with the same diameter, same load rating, same bearing, made by the same factory, will perform completely differently depending on how it is bolted to the machine. A loose mounting turns a smooth-rolling wheel into a wobbling one. An undersized stem pulls out. A plate that does not match your hole pattern means a trip back to the drill press.

There is no “best” mounting. There is only the mounting that matches your frame, your load, and your service cycle.

The Four Main Castor Mounting Types — Side by Side

Mounting Deep Dive

1. Top Plate — The Heavy-Duty Default

A top plate is a flat steel plate welded to the top of the swivel bracket, with four bolt holes. You bolt the whole plate to the underside of your frame. This spreads the load over four bolts and a wide contact area, which is why it carries the highest load rating of any mounting. It is the standard choice for any castor over 150 kg per wheel, and for anything that rolls on rough concrete.

The catch: your frame must have a flat, rigid surface big enough for the plate, and you must drill four holes on a fixed pattern. On our EH08 heavy-duty series, the plate measures 114 × 100 mm with an 84 × 71 mm hole pitch and 11 mm bolt holes — that is the layout you would spec into your frame drawing.

2. Threaded Stem — For Cabinets and Benches

A threaded stem is a bolt sticking up out of the top of the bracket. It screws into a tapped hole on the frame, or through a clearance hole with a nut underneath. Threaded stems are lighter and cheaper than plate mounts, and they let you mount a castor on a thin leg or a tubular frame where a plate would not fit. The tradeoff: a single bolt is a single point of failure. On heavy loads, a threaded stem can wobble or pull loose unless you lock it with a nut or a Nyloc.

Stem sizes you will see on industrial casters: M8 (light duty), M10 (medium), M12 (heavy), M16 (extra heavy). Match the stem diameter to the load — an M8 stem on a 200 kg wheel is asking for trouble.

3. Insert Stem (Grip Neck) — For OEM Frames

An insert stem is a smooth (unthreaded) tube that presses into a pre-drilled hole in your frame. It usually has a small groove or a ring near the top that locks into the hole once pressed. This is the fastest mounting to install on a production line — no nuts, no threads, just drill and press. It is the standard choice for office furniture, retail racks, and light industrial carts where the frame tube is thick enough to hold a press-fit hole.

The limit: insert stems are rated for lighter loads than plates, because a press-fit hole cannot hold the same shear load as four bolts. Over 150 kg per wheel, move up to a plate or a bolt-hole mount.

4. Bolt Hole — When You Cannot Weld a Plate

A bolt-hole castor has a single vertical hole up through the center of the swivel leg. You run a bolt up through your frame and tighten it into the castor. This is common on pallet jacks, hand pallet trucks, and equipment bases where the frame is a thick steel plate and you cannot weld a castor bracket on top. It is cleaner-looking than a plate, but the single bolt carries the whole shear load, so size the bolt to the load.

Mistakes Buyers Make With Mounting Types

1. Specifying the right wheel but the wrong mounting. Two casters with the same wheel can come in plate, stem, or bolt-hole versions. Confirm the mounting on the inquiry, not just the wheel diameter.
2. Drilling the frame to fit the castor, not the other way around. If your frame has a standard hole pattern, ask the factory to match it — most plate mounts can be bent to a non-standard hole pitch at low cost.
3. Using a threaded stem on a heavy load. A 200 kg wheel on an M10 stem will wobble. Move up to a plate mount.
4. Forgetting the hole diameter. Plate mounts come with different bolt hole sizes (9 mm, 11 mm, 13 mm). Specify the bolt size you intend to use.
5. Mixing mounting types on one cart. It is possible, but it makes replacement a headache. Stick to one mounting type across all four wheels.

How to Choose — A Quick Decision Flow

1. Is the load over 150 kg per wheel? Yes → top plate. That is the heavy-duty default.
2. Is the equipment a cabinet, bench, or light stand under 150 kg per wheel? Yes → threaded stem (M8–M12).
3. Is this an OEM product you will manufacture in volume, with pre-drilled frame holes? Yes → insert stem, fastest to assemble on the line.
4. Is the frame a thick steel plate and you cannot weld a bracket on top? Yes → bolt-hole mount.

Worked Example

A 700 kg industrial machine base, factory-made in runs of 50 units per year. Four wheels → 700 ÷ 4 = 175 kg per wheel. Add 30% safety margin → 227 kg per wheel. The load is well into plate-mount territory — a threaded stem would wobble, an insert stem would pull out. The frame is a welded steel base with a flat underside. Pick a 5 inch (125 mm) iron-core PU wheel on a 114 × 100 mm top plate, with an 84 × 71 mm hole pitch and 11 mm bolt holes — exactly the layout on our EH08-11-125S-402. The machine designer drills four 11 mm holes on the 84 × 71 mm pitch into the frame drawing, and the castor bolts straight on.

How Globe Caster Helps

Globe Caster — Foshan Global Caster Co., Ltd, Guangdong, China — has been making casters and castors since 1988. Our 156,000 m² facility runs in-house stamping, injection molding and PU pouring. We stock top-plate, threaded-stem, insert-stem and bolt-hole mounts across our light, medium and heavy series, and we can bend a plate to your non-standard hole pattern at low tooling cost. 600+ standard SKUs in stock, 30-day lead time on catalog items, 12-month warranty, ISO 9001 and ISO 14001 certified.

Send us your frame drawing or a sketch of the mounting hole pattern. We will tell you whether our standard plate fits, or whether we can modify the hole pitch to match your frame — before you cut any tooling.