Reading a Shaped Wire Section Drawing: 5 Numbers That Set the Price | ERQI WIRE

Two sections with the same name and roughly the same size can differ in price by half. The reason is always on the drawing, in five numbers that buyers rarely look at as a set. Reading them before you send the enquiry tells you what the quote will be — and which of your numbers is buying something you do not need.

1. Circumscribed circle

The smallest circle that contains the section. This is the dimension the mill actually works from, because it sets the die bore and the number of drawing passes. A section inside a 4 mm circle is one family of dies; 8 mm is another, with heavier equipment and different pass counts.

It is also the honest way to compare two offers. “3 mm shaped wire” can mean a 3 mm flat, a 3 mm height or a 3 mm circumscribed circle — three different products. Quoting by circumscribed circle removes the ambiguity, which is why our own pages lead with it. The logic is laid out in sections, not gauge.

2. Tolerance on the functional faces

This is the biggest single lever on price, and the one most often over-specified. Tight tolerance (±0.02 mm and below) requires gauge control, more frequent in-process checks and more scrap. Applied to the whole section, it is expensive. Applied only to the face that mates, it is affordable — and the part works identically, because fit is decided by that face alone.

Look at your drawing: if every dimension carries the same tight tolerance, you are paying for precision on faces nobody measures in assembly. What the tolerance number means covers how to re-place those calls.

3. Corner radius

Sharp corners are the quiet cost line. A die cutting sharp corners wears faster and needs more frequent correction, so the price carries die life. Broken corners — typically 0.1–0.3 mm — extend die life, draw more smoothly and change nothing about a part that seats in a groove.

Where the corner is functional — a seal lip, a locating edge — keep it sharp and expect to pay for it. Everywhere else, a radius call saves money and improves consistency.

4. Section area

In square millimetres, this is what turns a section into kilos. For stainless, weight per metre is the area times 7.93 times 0.001 — a 12 mm² section runs about 0.095 kg/m. Three consequences:

• Price basis. Wire is priced per kilo, so the section area decides the price per metre before any processing.
• Coil economics. A 250 kg coil of a 12 mm² section is over 2.6 km; the same coil in a 2 mm² section is more like 15 km. Coil weight and coil length are not interchangeable, and quoting one when you meant the other is a classic error.
• Handling. Heavy sections need bigger reels and stronger take-off; light sections need care against tangling. Both affect packing, which affects price.

5. Length and delivery tolerance

If you buy cut lengths rather than coils, the drawing needs a length tolerance and a deburring requirement. ±1 mm cut and deburred is a secondary operation; ±5 mm saw cut is nearly free. Straightness belongs here too — a residual bow figure per metre, set to your guide spacing rather than to a number copied from an old drawing.

Putting the five together

A drawing that reads well for quoting looks like this: circumscribed circle stated, functional faces marked with the tight tolerance, all other dimensions commercial, corners broken to 0.2 mm except the one that seals, section area noted (or calculated), and delivery form specified with length tolerance and straightness. That drawing gets a firm number in one round.

The section families themselves are on the profile wire sections page, the standard sizes with drawings on the drawings page, and the quote structure — tooling, sample, batch, secondary operations — on custom profile wire. Send the drawing and we will mark up which of the five numbers is costing you money.