On this page
- Plate Casters: Complete Industrial Buying Guide (Load, Size and Mounting Explained)
- Quick Answer: How to Spec a Plate Caster
- Plate Size Chart by Duty Class
- Bolt Hole Pattern Reference
- Load Rating Math for Plate Casters
- Wheel Material Selection for Plate Applications
- Swivel vs Rigid Configuration on 4-Caster Carts
- Spec Sheet Template: 10 Data Points for RFQ
- Frequently asked questions
- Related Engineering Tools & Guides
Choosing plate casters comes down to load, wheel material, mount style, and duty cycle.
- Match capacity per caster to your total load divided by 3 (one caster may be airborne)
- Polyurethane and rubber wheels favor floor protection; phenolic and steel favor heavy capacity
- Top-plate or stem mount is dictated by the equipment, not preference
- CasterHQ stocks Albion, Hamilton, P&H, Colson, Faultless, and Durastar from Mansfield, Texas
- Call 844-439-4335 for fitment help on any non-standard caster
Plate Casters: Complete Industrial Buying Guide (Load, Size and Mounting Explained)
A plate caster is an industrial caster with a rectangular mounting plate that bolts to the underside of a cart, fixture, or piece of equipment. Plate casters are the default industrial mounting type in North America and carry the widest range of load ratings, wheel materials, and rig constructions. Correct plate caster specification comes down to four decisions: plate size and bolt pattern, load rating per caster, wheel material and diameter, and rig construction (swivel vs rigid, kingpin vs kingpinless). This guide walks OEM engineers and MRO buyers through every decision point with ICWM-referenced load tables and a spec-sheet template.
In this guide
Quick Answer: How to Spec a Plate Caster
Spec a plate caster in four decisions, in order: plate size and bolt pattern (to match the mounting surface), load rating per caster (with 33% safety factor), wheel material and diameter (matched to floor), and rig construction (swivel vs rigid, kingpin vs kingpinless based on duty cycle). Every other detail (brake type, thread lock, zerk fitting) is a refinement, not a gate.
- Plate size determines load rating range. 2.5x3.625 in plate tops out at ~350 lb. 4.5x6.25 in goes to 2,500+ lb.
- Bolt pattern must match the mounting surface. Use an adapter plate if not.
- Load per caster = (gross weight / 3 effective corners) x 1.33 safety factor.
- Default industrial wheel: 95A polyurethane on steel hub, 5-8 inch diameter.
- Typical cart: 2 swivel + 2 rigid for straight tracking, 4 swivel for omnidirectional.
Engineer tip: Always spec by plate size AND bolt pattern AND load rating. Supplier SKUs look similar across sizes. A 4-inch plate with the wrong bolt pattern is a $40 caster that becomes a $400 mounting rework.
Plate Size Chart by Duty Class
Plate caster mounting plates fall into five common duty classes by plate size. The plate size drives the maximum load rating, the rig gauge, and the wheel diameter options.
- Light duty: 2.5 x 3.625 in plate. 100-350 lb capacity. 2-4 inch wheels.
- Medium duty: 3.625 x 5 in plate. 300-800 lb capacity. 3-5 inch wheels.
- Heavy duty: 4 x 4.5 in plate. 500-1,400 lb capacity. 4-6 inch wheels.
- Extra heavy duty: 4.5 x 6.25 in plate. 1,000-2,500 lb capacity. 5-8 inch wheels.
- Super duty / institutional: 5.25 x 7.25 in and larger. 2,500-10,000+ lb.
| Duty Class | Plate Size | Typical Wheel | Load Range |
|---|---|---|---|
| Light | 2.5 x 3.625 in | 2-4 in | 100-350 lb |
| Medium | 3.625 x 5 in | 3-5 in | 300-800 lb |
| Heavy | 4 x 4.5 in | 4-6 in | 500-1,400 lb |
| Extra Heavy | 4.5 x 6.25 in | 5-8 in | 1,000-2,500 lb |
| Super Duty | 5.25 x 7.25 in+ | 6-12 in | 2,500-10,000 lb |
Bolt Hole Pattern Reference
Bolt hole patterns vary by manufacturer within each plate size. The most common patterns are documented in the table below. Always verify the pattern dimensions with the manufacturer spec sheet before ordering.
- Patterns are measured on center, long side first then short side.
- Slotted plates allow for some alignment tolerance on retrofits.
- Adapter plates bridge mismatched patterns but add 1/4 in to the caster stack height.
- Hole diameter matches bolt size: 3/8 in bolt = 7/16 in hole typical.
- Industrial standard bolts are Grade 5 or Grade 8. Grade 2 is not industrial.
Procurement tip: When replacing casters on existing equipment, measure the bolt pattern in both dimensions with calipers. Do not trust nominal plate size. The difference between 2.5 x 3.625 and 2.625 x 3.75 is one unusable caster.
Load Rating Math for Plate Casters
Plate caster load rating math follows the same 3-corner rule as all industrial casters. For a 4-caster cart, divide gross loaded weight by 3, not 4, then multiply by 1.33 safety factor to get the minimum required caster rating.
- Static load: rated capacity at rest on level floor.
- Dynamic load: capacity while rolling. Typically 25-40% lower than static.
- Shock load: 2-3x static at expansion joints and dock plates.
- Safety factor: 1.33 minimum (ICWM). 1.5-2.0 for aerospace, defense, medical.
- Never rate at nameplate capacity. Nameplate is the failure point, not working load.
Load rule: If the cart gross loaded weight is 2,400 lb on 4 plate casters, minimum required per caster is (2,400 / 3) x 1.33 = 1,064 lb. Round up to 1,100 lb or 1,200 lb ICWM-rated plate casters.
Wheel Material Selection for Plate Applications
Plate casters accept every industrial wheel material. Selection follows floor condition and chemistry, not plate type. Polyurethane on steel is the default. Phenolic for heat. Cast iron for maximum load.
- 95A polyurethane on steel hub: Default 600-2,500 lb. Sealed concrete, general industrial.
- 80A-85A polyurethane: Coated floors, ergonomic push reduction, 600-1,500 lb.
- Phenolic: 600-5,000 lb. Bakery, paint line, forge, up to 475F continuous.
- Cast iron: 1,000-10,000 lb. Max load on sealed concrete. Never on coated floors.
- Mold-On rubber: 200-1,000 lb. Quiet, ergonomic, coated-floor safe.
- Pneumatic: 250-1,000 lb. Outdoor and rough surface.
Swivel vs Rigid Configuration on 4-Caster Carts
Four-caster cart configurations fall into three common patterns: 2 swivel + 2 rigid diagonal (straight tracking), 2 swivel + 2 rigid in line (predictable steering), and 4 swivel (omnidirectional). Each has ergonomic, tracking, and safety trade-offs.
- 2 swivel front + 2 rigid rear: Most common. Straight tracking at speed, steering at the front. Best for production and assembly.
- 4 swivel: Omnidirectional. Tight spaces and parts-bin carts. Harder to control at speed.
- Diagonal (2 swivel, 2 rigid on opposite corners): Stabilizes tracking on long carts. Less common.
- 6-caster configurations: 2 fixed center + 4 corners on long carts. Requires center-raise geometry.
- Powered tow: Typically 4 rigid + towbar, or 2 swivel + 4 rigid with kingpinless swivel rigs.
| Configuration | Best For | Drawback | Typical Cart |
|---|---|---|---|
| 2 swivel + 2 rigid (front/rear) | Straight tracking | Larger turning radius | Production carts |
| 4 swivel | Omnidirectional | Hard to control at speed | Parts-bin carts |
| Diagonal | Long-cart tracking | Unusual, harder to source | Custom platforms |
| 6-caster center raise | Long carts, stability | Complex geometry | Carts over 8 ft long |
| Powered tow | AGV / continuous | Kingpinless required | AGV platforms |
Spec Sheet Template: 10 Data Points for RFQ
A compliant plate caster RFQ captures 10 data points. Any RFQ missing these fields produces quotes that are not comparable and not defensible in audit.
- Plate length x width (measured)
- Bolt hole pattern on center, both dimensions
- Hole diameter
- Load rating required per caster
- Wheel diameter
- Wheel material and durometer
- Bearing type
- Rig construction (swivel kingpin, swivel kingpinless, rigid)
- Brake type (top lock, total lock, none)
- Overall mount height (from floor to top of plate)
RFQ reality: Plate casters with missing bolt-pattern data are the most common cause of wrong-part shipments in industrial procurement. Always verify with calipers before ordering.
Key takeaways
- Plate casters are the default industrial mounting type in North America.
- Four decisions drive selection: plate size and pattern, load rating, wheel material, rig construction.
- Plate size drives load rating range. 2.5x3.625 tops at 350 lb. 4.5x6.25 reaches 2,500+ lb.
- Load math: gross weight / 3 effective corners x 1.33 safety factor = minimum rating.
- 10-point spec sheet captures everything needed for a compliant RFQ.
Frequently asked questions
What are the standard plate caster sizes?
Five duty classes: light (2.5 x 3.625 in), medium (3.625 x 5 in), heavy (4 x 4.5 in), extra heavy (4.5 x 6.25 in), super duty (5.25 x 7.25 in and larger). Each class carries a characteristic load rating range.
How do I measure a plate caster bolt pattern?
Measure on center, long side first then short side, with calipers. Nominal plate size is not enough. The difference between 2.5 x 3.625 and 2.625 x 3.75 will make the caster unusable.
Can I use adapter plates for mismatched bolt patterns?
Yes, adapter plates bridge mismatched patterns but add 1/4 in to overall mount height. Check clearance and stability before using. Adapter plates are a legitimate engineering solution for retrofits, not a shortcut to skip bolt pattern verification.
What load rating should I specify for my cart?
Gross loaded cart weight divided by 3 (not 4, because of 3-corner rule on uneven floors), times 1.33 safety factor. Example: 2,400 lb cart = 800 lb x 1.33 = 1,064 lb minimum per caster. Round up to 1,100 or 1,200 lb ICWM-rated.
Should I use 2 swivel + 2 rigid or 4 swivel?
2 swivel front + 2 rigid rear for straight tracking and production carts. 4 swivel for tight spaces and omnidirectional parts-bin carts. Longer carts benefit from diagonal or 6-caster center-raise geometry.
Do plate casters need ICWM certification?
Functionally yes, even though ICWM is voluntary. OEM engineers in aerospace, defense, medical, and heavy industry spec ICWM in 85%+ of RFQs because it is the only consistent load-rating methodology. Without it, load numbers are not comparable across suppliers.
Spec Your Plate Casters in One Call
Send plate size, bolt pattern, load target, and floor type. We return an ICWM-rated plate caster spec and a signed spec sheet within one business day.
References & Standards Cited
- Institute of Caster and Wheel Manufacturers (ICWM) Load Rating Standards
- ANSI MH28.1 Industrial Grade Steel Shelving
- ASME B30.1 Jacks, Industrial Rollers, Air Casters
- ISO 22878 Castors and Wheels Terminology and Test Methods
- CasterHQ plate caster RFQ analysis, 2022-2026
- Standard industrial plate caster bolt-pattern reference manual
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Shop All CastersCall 844-439-4335Jordan Wilson
Founder of CasterHQ.com. Works directly with engineers, MRO buyers, and procurement teams across material handling, healthcare, food service, aerospace, and OEM. CasterHQ stocks Albion, Hamilton, P&H, Colson, Faultless, and the in-house Durastar series from a Texas warehouse and retrofits OEM fitments from dimensional drawings when brands discontinue parts.