Bracket Thickness on a 150 kg Caster: What It Tells You and What to Require Instead

Why a quoted plate thickness does not prove the rating

Capacity is attributed to the rig, not the plate. One source ranks construction tiers by per-caster capacity — stamped steel kingpin 75–600 lb, drop-forged kingpin 600–1500 lb, welded kingpinless 1000–3500 lb, forged kingpinless 2000–6000+ lb.

And describes the rig as the part that fails first under shock load³. A 150 kg rating (about 330 lb) falls inside the stamped-steel band on that scale³.

Thickness rises with duty class in the sources that discuss it, but none publishes a thickness-to-capacity formula^11,16. What substantiates a rating is test protocol: a static hold at 150% of rated load for 24 hours, and more than 100,000 dynamic cycles at roughly 5 km/h watching axle and bracket fatigue¹⁸.

Safety-factor conventions are stated separately, at 2x, 4x and 5x depending on duty². So when you read a quote, treat the plate thickness as a description of how the bracket was built, not as the number that generates the rating.

Ask what construction tier it is and what test basis the 150 kg figure rests on.

What thickness to expect at 150 kg, and when to question a quote

Only one listing in this set states a bracket thickness at exactly 150 kg: a 100 mm polyurethane caster with a 3 mm bracket, 95x95 mm top plate and 11 mm bolt holes¹⁷.

That figure is a single product listing with no test standard or safety factor attached, so read it as an example of what the class looks like, not a target. Where it lands depends on which band you compare it to.

One supplier describes industrial-grade brackets as thickened stamped or welded steel plate at 3–5 mm, against 1–2 mm thin plate or plastic for household light-duty brackets, without attaching a load figure to the band¹¹.

Another publishes a duty ladder: 2–4 mm stamped plate for light indoor and service use, 5–6 mm for 280–420 kg per caster¹⁶.

| Reference point | Plate thickness | What it describes | |---|---|---| | 150 kg, 100 mm PU caster listing | 3 mm | Single product listing, no test basis stated¹⁷ | | Industrial-grade bracket band | 3–5 mm | Thickened stamped/welded plate,

no load figure attached¹¹ | | Household light-duty bracket | 1–2 mm | Thin steel plate or plastic¹¹ | | Light indoor / service duty | 2–4 mm | Stamped plate for smooth floors and light goods¹⁶ | | 280–420 kg per caster | 5–6 mm | Stamped,

hot-forged and welded plate¹⁶ | A 3 mm bracket therefore sits at the bottom of the industrial band and inside the light-indoor band at the same time¹⁷ (supplier-reported figure).

If your quote comes in below 3 mm for a 150 kg rating, that is worth a direct question about construction and test basis before you accept it¹⁷ (supplier-reported figure).

Specify construction tier and material grade, not thickness alone

Because the tier carries the capacity band, the tier belongs in the spec. Naming stamped, drop-forged, welded kingpinless or forged kingpinless tells the supplier which family you are buying from, and the published bands let you check the 150 kg figure sits inside it³.

How much a higher tier buys you is disputed. One aggregator table records a claim of 2–3x fatigue life for forging over a cast part alongside a statement that no comparative data exists for forged versus stamped brackets.

And lists maximum loads of 9,500 lb stamped against 30,000 lb forged kingpinless as contested items³⁵. Do not assume a thinner forged bracket equals a thicker stamped one at 150 kg; the sources give no grade-specific thickness allowance.

Material grade is a separate decision driven by environment rather than load. Stainless steel brackets and fasteners are specified for washdown and corrosive service in place of plated steel²³.

If your 150 kg caster runs in a wet or chemical-exposed area, that condition, not the thickness, should set the material callout.

Set the safety factor and test regime the rating must be substantiated against

A bare 150 kg number tells you nothing about how it was arrived at. The test regime one manufacturer describes is a static hold at 150% of rated load for 24 hours, checking for deformation or cracking, followed by more than 100,000 dynamic cycles at about 5 km/h to expose axle and bracket fatigue¹⁸.

Ask for results against that kind of protocol, or against the standard the supplier cites. Safety factor is a separate convention and the sources present it as one publisher's position rather than a mandate.

That source calls 2x the manufacturer marketing minimum, says it fails within 6–12 months under real duty, and puts 4x as the industrial standard for 3–5 year life². For 24/7 AGV duty the same source calls for a 5x factor on the dynamic rating plus fatigue verification at 1M+ cycles².

Note that the 150% static test and the 4x design convention are different quantities and cannot be compared directly^2,18. Decide which one your application needs and write it into the RFQ as a requirement, not an assumption.

Check wheel diameter and top plate before you accept the bracket

The bracket does not stand alone; it has to fit the wheel and the frame. One manufacturer maps light load under 150 kg to 3–5 in wheels and medium load of 150–500 kg to 4–6 in wheels⁹.

A 150 kg caster offered with a 100 mm (about 4 in) wheel sits on the boundary of those two bands, so confirm with the supplier which duty class they are claiming^9,17. Top plate is a separate dimension from fork thickness.

One source describes 1/4 in (about 6.35 mm) plate as standard for medium duty and 3/8–1/2 in for heavy duty, noting that thicker plates raise overall mounting height⁵. The 150 kg listing carries a 95x95 mm plate with 11 mm holes on 67x67 or 74x74 mm spacing¹⁷.

Match the bolt pattern to your frame before anything else. No source gives a numeric rule for how bracket size scales with wheel diameter, so the fit has to be checked against your own mounting holes rather than inferred.

Weigh a custom plate against a standard bracket

If the standard plate will not fit your frame, custom tooling is the alternative and it has a price. Custom plate tooling is quoted at $50–$300 per caster with a 15–30 day lead time.

And one source puts it as worth doing for production runs over 50 units, with a weld-in or bolt-on adapter preferred for one-offs⁶. The same source reports custom mount plates running about 5% of orders by volume but 12% by revenue, averaging 21 business days for tooled orders⁶.

For a 150 kg caster the usual reason to go custom is a legacy bolt pattern, not the load. If your frame already takes a standard pattern, the tooling spend buys nothing on capacity.

What to verify before releasing the order

Ask for evidence that the bracket was built and tested as quoted, not just described. One manufacturer describes an ISO 9001:2015 system covering raw material incoming inspection, in-process dimensional verification and finished-product load testing to EN 840, BIFMA or customer-specified standards¹⁵.

Another states that not all manufacturers adhere to a common capacity standard, and that its own casters are tested to ANSI ICWM standards to substantiate issued capacity¹⁰.

• ✓Request the construction tier in writing: stamped, drop-forged, welded kingpinless or forged kingpinless
• ✓Ask for the load-test report behind the 150 kg figure, including static hold level and dynamic cycle count
• ✓Confirm the safety factor the rating assumes and whether it is on static or dynamic capacity
• ✓Get the plate thickness, top plate size and bolt pattern on the drawing, not just the catalog page
• ✓Ask whether the bracket material is plated steel or stainless, based on your environment
• ✓Request material certification and dimensional records for the plate thickness shipped

Where the sources disagree, and what to do about it

Three points in this evidence set stay contested. Keep both sides visible when you compare quotes, and resolve each with the supplier rather than picking the convenient number.

Before you request a quote

• Request the complete specification sheet with units, test conditions and configuration assumptions.
• Public sources do not settle this — put it to the supplier: no published load-versus-bracket-thickness table or formula from any source.
• Public sources do not settle this — put it to the supplier: no steel grade designation tied to a 150 kg bracket.
• Public sources do not settle this — put it to the supplier: no numeric rule for how bracket or plate size scales with wheel diameter.
• Request a written quote with price basis, MOQ, tooling, payment terms and production lead time.
• Public sources do not settle this — put it to the supplier: no lead time stated specifically for a standard 150 kg bracket.
• Public sources do not settle this — put it to the supplier: no bracket-specific dimensional or weld inspection protocol, and no source confirms EN 12530 or EN 12532 certification for a 150 kg bracket.