Straight Stainless Steel Wire 0.15-12mm - Straightness and Cut Length
Stainless Steel Straight Wire 0.15-12mm
,Straight Stainless Steel Wire Cut Length
,Stainless Steel Straight Wire High Straightness
What Straight Means in Millimetres: Controlling Straightness in Stainless Cut Lengths
Straight wire without a number is a description, not a specification. Two suppliers can both ship straight lengths that look identical on a pallet and behave differently on an automatic feeder, because one holds 1 mm of bow per metre and the other holds 3. This page sets out how straightness is defined, measured and lost, so the requirement can be written into an order.
A Straightness Claim Needs a Length and a Number
Three expressions are used in trade, and they are not interchangeable:
- Bow over a stated length. The maximum deviation from a straight line measured over 1 m, with the bar resting on a flat surface. Written as 1 mm per metre, for example.
- Total indicator reading. The bar is rotated in V-blocks and a dial gauge records the swing. TIR reflects both bow and ovality, so it is always larger than the bow value.
- End straightness. The deviation over the first 100 - 200 mm, which decides whether the end enters a guide bush or a welding torch without catching.
As a working scale for stainless cut lengths: 2 mm per metre is commercial, 1 mm per metre is a precision supply, and 0.5 mm per metre is high precision and usually implies grinding or a second straightening pass. Whichever value is agreed, the measuring method and support arrangement should be written next to it, otherwise buyer and mill will measure different numbers on the same bundle.
How Straightness Is Measured
- Surface plate and feeler gauge. The simplest shop-floor check: roll the bar on a plate, find the maximum gap, and record the gap over the stated length.
- V-blocks and dial gauge. Gives TIR over the full length and separates bow from ovality if readings are taken at several stations.
- Laser scan. Used where 100% inspection is required; records the full profile rather than a sample, which is the only way to catch a single bent piece inside a bundle.
Where Straightness Is Lost
- Residual stress from drawing. Uneven reduction around the section, die misalignment or an oval pass leaves the wire with a built-in curve that appears as soon as tension is released.
- Straightening parameters. Roller straightening is not pulling the wire straight; it imposes alternating bends so that residual stress is redistributed. Roll pitch, penetration and roll angle decide the result, and excess penetration marks the surface while leaving the exit curvature uneven.
- Cutting. Shearing displaces material at the cut and can bend the last 20 - 50 mm. Sawing and laser cutting leave a straighter end but add burr or a heat-affected zone.
- Bundling and transport. Thin wire bends under its own weight. Bundles strapped at wide intervals, or stacked without support, arrive curved even when they left the plant within tolerance.
- Heat treatment. Uneven cooling or a coil that was not free to move during annealing can set a permanent cast into the length.
Diameter Changes the Problem
Below 1 mm, stiffness is low enough that handling dominates: a 0.5 mm straight length can be bent by its own weight over a 2 m span, so short cut lengths or coil supply are the practical answer. Between 1 mm and 6 mm, roller straightening gives good control and this is where cut lengths are most commonly specified. Above 6 mm, the straightening force rises sharply, roll marking becomes a surface risk, and the answer is a larger roll diameter with lower penetration over more passes rather than more pressure.
Cut Length and End Quality
Standard cut length tolerance is plus or minus 1 mm; plus or minus 0.5 mm requires a dedicated stop or a servo feed and should be quoted as such. End condition matters as much as length: a sheared end has a collapsed edge and a burr that catches in feeders, collets and weld torches. Where the part is fed automatically or welded without preparation, specify deburred or chamfered ends and state the burr limit rather than leaving it to visual judgement.
Inspection Items
| Item | Method | Typical value |
|---|---|---|
| Bow over 1 m | Surface plate and feeler gauge | 1 mm/m precision grade |
| TIR over full length | V-block rotation with dial gauge | 2 mm max |
| Cut length | Steel rule or laser measurement | plus or minus 1 mm |
| End burr | Visual or profile projector | No sharp burr, deburred on request |
Wire Specification
| Parameter | Specification |
|---|---|
| Material | 201, 304, 304L, 316, 316L, 410, 430 |
| Diameter | 0.15 - 12 mm |
| Form | Straight lengths 1 - 6 m, or cut to order |
| Straightness | 0.5 - 2 mm per metre, by supply grade |
| Cut length tolerance | plus or minus 1 mm standard; plus or minus 0.5 mm on request |
| Temper | Soft annealed or light drawn |
| Surface | Bright, bright annealed or soap coated |
| Standard | ASTM A580, GB/T 4240, or agreed equivalent |
What to Put on the Order
- Straightness as a number over a stated length, plus the measuring method.
- Cut length and its tolerance band, with the end condition named.
- Diameter with tolerance, since a change in diameter changes both stiffness and straightening behaviour.
- Bundle weight and strapping pitch, especially for wire below 2 mm.
- Packing method for transport, if the parts will be fed directly from the bundle.
- Temper and surface, because both affect how the part behaves in the next operation.
Straightness is one of the few properties that can be inspected with a flat plate and a feeler gauge, so there is no reason to accept it as an adjective.
