After two decades shipping shiny die-cast housings from my foundry to four continents, I’ve learned that what ruins a margin isn’t alloy price—it’s the freight class scribbled on that yellow bill of lading.
A carton that looks innocent in my warehouse can morph into a wallet-draining beast once an LTL terminal re-weighs, re-measures, and re-classes it. Let me walk you through the rules, the math, and the sneaky cost traps—plus the tricks I use to keep freight auditors from drinking my profit.
Freight Class 101: From NMFC Code to Dim-Weight Surcharges
The U.S. National Motor Freight Classification (NMFC) system drops every product into one of 18 classes—60 (dense bricks) to 400 (feather-light balloons). Class hinges on four levers: density, stowability, handling risk, and liability.
Aluminum castings usually travel under codes 32355 or 32360, but ribbed heat-sinks or mixed-kit cartons can bump higher. Mis-declare and carriers will “courtesy re-class” your freight—and your invoice.
Density Calculation for Die-Cast Components
Before a single forklift moves, I grab a tape, a scale, and this formula:
Density (lb/ft³) = Weight (lb) ÷ [Length × Width × Height (in) ÷ 1 728]
A finned LED housing weighs barely 4 lb, yet boxed in bubble wrap it occupies 0.12 ft³—density 33 lb/ft³, landing in Class 125 instead of Class 70. Multiply that by fifty cartons and the surcharge dwarfs alloy scrap.
Mapping Common Die-Cast Parts to Freight Classes
| Part Type & Example | Avg. Density (lb/ft³) | Likely Class | NMFC Code | Shop Notes |
|---|---|---|---|---|
| Gearbox housing, 4 kg | 75 | 70 | 32360 | Compact cube, easy pallet block |
| LED heat-sink, 2 kg | 35 | 125 | 32355 | Fins = air volume; watch voids |
| Pump manifold, 6 kg | 85 | 65 | 32360 | Dense lump, survives stack |
| Auto bracket kit, mixed SKUs | 40 | 110 | 133300 | Carton voids push class up |
How Freight Class Translates into Dollars per Kilometer
Carriers price LTL lanes on a class multiplier. Class 70 rides the base rate. Class 125 jumps to 1.5 ×, and Class 175 can hit 1.9 ×. On a Charlotte → Chicago lane at US $2.10 base, a 1 000 lb pallet of Class 70 castings costs about US $2 100; the same pallet at Class 125 balloons to US $3 150—enough to wipe out any early-payment discount you squeezed from me.
Packaging Tricks to Drop a Class and Save 10 – 20%
- Nest & rotate brackets so flanges interlock, doubling density without metal-to-metal scratches.
- Custom tri-wall cartons sized to the part—not left-over 18″ cubes—boost density and survive drop tests.
- Shrink-wrap blocks tame loose‐fit boxes and stop terminals from “re-measure & re-bill” games.
- Foam inserts only at pinch points; full shells look pretty but ship air.
Result: my HVAC customer shaved Class 110 down to 85 and pocketed 15 % freight savings overnight.
Accessorials That Sneak Onto Your Invoice
- Lift-gate service at a plant dock with no ramp
- Residential or limited-access surcharges for rural distributors
- Re-weigh / re-measure fees when carton labels lie
- Detention at pickup because pallets weren’t staged on time
Each can add US $50–150, and none appear on the carrier quote until it’s too late to argue.
Case Snapshot — Cutting East-Coast LTL Spend by 18%
A Connecticut HVAC OEM moved two pallets of finned coolers weekly. We redesigned the carton to sandwich fins back-to-back, density climbed from 38 lb/ft³ to 62 lb/ft³, freight class dropped from 110 to 85, and monthly LTL spend fell US $1 200. Extra cardboard cost US $40. CFO called it “found money.”
Checklist for Your Next RFQ or Routing Guide
- Lock exact weight & dims before carriers quote; avoid “subject to change.”
- Confirm the NMFC code with the carrier’s rating desk in writing.
- Negotiate density-based exceptions if you feed the lane > 3 loads/month.
- Design cartons that clear fork-pocket height but stay under 1.2 m to dodge dim-weight tiers.
Tick these boxes and freight auditors will hunt prey elsewhere.
Freight class is the stealth tax on aluminum castings—get it right, and your landed cost looks as good as your alloy quote. Get it wrong, and forklifts haul away your profit. Need a quick density audit or packaging sketch? Send dims and photos to yongzhucasting@gmail.com—I’ll reply faster than a pallet jack can turn a corner.
Quick FAQ
Will U.S. terminals re-class ocean pallets I pre-labeled?
Yes, if dims or density look fishy. Always build some class cushion.
Do mixed-material kits change NMFC code?
Often—they fall under “Articles, NOI.” Verify before shipping.
Does adding corner foam raise freight class?
Only if it lowers density below the class breakpoint; measure after packing.
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Zhejiang Yongzhu Casting Technology Co., Ltd.
Location: Zhejiang, China
Company type: Manufacturers, Producers, Wholesalers
Year Founded: 2004
Main Products: Aluminium die casting, Mold Making, Die Casting, Sand Casting, Gravity Casting
Leading Chinese producer Yongzhu Casting is formerly known as Hangzhou Higer Metal Products Co., Ltd., was established in 2004.
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