Crossarm Specifications: What to Put in Your RFQ

A specification for crossarms is only useful if it is unambiguous to someone who cannot see your project. Most disputes on this product do not come from bad manufacturing — they come from a drawing that could reasonably be read two ways, where the supplier read it the cheap way and the buyer read it the expensive way.

This is a practical specification checklist, written around what the standards actually require.

The three specification families you will meet

Suppliers will quote against whichever family your market uses, and the part can usually be built to any of them:

• ANSI C135.1 — Galvanised ferrous pole line hardware.
• ISO 1461 — Hot dip galvanised coatings on fabricated articles.

The mistake is to specify a standard reference without specifying the class or grade within it. If you write only the standard number, the supplier will quote the lowest class that satisfies it. Write the standard and the level you want.

Dimensional data that has to be on the drawing

For this product the critical dimensions are: lengths 1.2–2.4 m, hole spacing 300–450 mm, angle or channel section 8–12 kg per metre.

Three rules that prevent most dimensional disputes:

1. Give tolerances on every functional dimension, not just the nominal values. A nominal dimension with no tolerance is legally “as the supplier chooses”.
2. Say which dimensions are functional and which are cosmetic. Suppliers prioritise what you prioritise, and they cannot guess.
3. State the gauge or measuring method where a dimension is critical. Two inspectors with different methods will disagree about the same part.

Material and grade

The base specification is hot-dip galvanised steel angle or channel, or laminated wood. Grades commonly offered include:

• Q235 steel angle 63×63×6 mm
• Q345 for long spans
• glulam timber for utilities that still specify wood

Ask the supplier to state the grade on the quotation, not on an assumption. Grade substitution is the single most common silent cost reduction, and it is usually invisible in the finished part — a 201 stainless component looks exactly like a 304 one until the second winter.

Surface treatment

The usual finish for this product is hot-dip galvanised 70–85 µm; all holes punched before coating, never drilled after.

Two points worth writing into the order:

• A measured requirement, not a process name. “Hot-dip galvanised” is a process; “70 µm minimum, tested by coating mass on three parts per batch” is a requirement.
• What happens at cut edges and drilled holes, if any. These are where coatings are habitually broken and where corrosion starts.

Type tests and routine tests

These are different things and are frequently confused in quotations:

• Type tests qualify the design once. On this product: coating thickness at three points per arm; dimensional check of the hole pattern; load test of the centre mounting.
• Routine tests are run on every batch: visual inspection for bare edges.

Specify which type-test reports you want supplied as documents, and which routine test results must accompany each shipment. On a first order, ask for the type-test report before you place it.

The failure modes your specification should be closing

• Zinc starved inside the angle — no drainage path through the section, so molten zinc cannot flow — the inside of the angle rusts while the outside looks perfect
• Hole pattern drifting between batches — worn jigs; the arm then will not line up with an existing pole and needs field drilling, which destroys the coating

Each of these can be turned into one line in the specification. That is the real purpose of writing it out: not bureaucracy, but making the specific failure you are worried about somebody’s explicit responsibility.

A specification skeleton you can reuse

1. Scope: Crossarm to be supplied as cross arm, pole crossarm, bracket arm.
2. Dimensions and tolerances: lengths 1.2–2.4 m, hole spacing 300–450 mm, angle or channel section 8–12 kg per metre.
3. Material: hot-dip galvanised steel angle or channel, or laminated wood; grade Q235 steel angle 63×63×6 mm or better.
4. Standard: ANSI C135.1 — Galvanised ferrous pole line hardware; ISO 1461 — Hot dip galvanised coatings on fabricated articles.
5. Finish: hot-dip galvanised 70–85 µm; all holes punched before coating, never drilled after.
6. Tests: coating thickness at three points per arm; dimensional check of the hole pattern; load test of the centre mounting; visual inspection for bare edges.
7. Marking and packing: 20 pcs per bundle, steel-strapped; holes must not be blocked by strapping.
8. Inspection: pre-shipment, against this specification, with photo evidence and test records.

Related: the crossarm quality inspection checklist turns this specification into an inspection plan you can hand to a third-party inspector.