A rebar straightener is a powered machine that removes coil set from reinforcing steel so the bar can be cut to length and used flat in a slab, beam, or welded mesh; classification is set by drive principle, diameter window, and line speed, with light coil lines at D6–D16 mm / 30–50 m/min and heavy bar at D16–D32 mm / 8–30 m/min [S4][S2].
The 2026 specification map breaks the category into three drive families (mechanical flywheel, servo-electric, hydraulic) and two integration patterns (standalone straightener vs straightener-cutter 2-in-1), with a 3-in-1 straightener-cutter-bender reserved for low-throughput factory lines running 4–14 mm bar at 500–900 m/min [S5]. For a primer on the machine class, see the rebar straightener encyclopedia entry; for the adjacent bar-prep category, see the rebar bender and rebar reference pages.
Drive Type Classification: Mechanical, Servo-Electric, Hydraulic
Mechanical flywheel straighteners are the workhorse class: 4–7.5 kW main motor, shear-pin or torque-limited overload, 5-roller geometry, throughput dominated by bar diameter, and quoted cycle speeds in the 30–60 m/min range for heavy 32 mm-class lines [S2][S5]. Servo-electric straighteners add closed-loop pinch-roll control at 3–5 kW per axis and win on 12–20 mm accuracy and noise, an advantage on tunnel sites that carry a 75 dB(A) night cap [S2].
Hydraulic straighteners are reserved for 32–50 mm heavy bar; they trade energy cost for a 15–25 kW draw but hold bar tension constant under fluctuating mill scale [S2]. On a tunnel yard the matching trio for a metro segment cage is straightener at 25 m/min, two-head bender at 12–15 bends/min, and a 32 mm-rated cut-off; mismatched throughputs leave the bender idle or the cutter starved [S2].
Diameter and Throughput Classes: Light Coil, Medium Bar, Heavy Bar
Light coil class is D6–D12 mm at 30–50 m/min, 1.5–3.0 kW servo drive, 0.8–1.5 t/h throughput, with mandrel slip held under 2 mm/m tolerance; medium bar at D12–D16 mm steps up to a 4.0–5.5 kW motor and 20–35 m/min line speed [S4]. Heavy fabrication at D16–D25 mm jumps to 5.5–7.5 kW with 15–25 m/min mandrel speed, and typically adds a two-roller pre-straightener upstream to prevent coil-set memory from surviving the cut-off shear.
For tunnel cages, line speed benchmarks stack as 8–16 mm at 30–50 m/min, 16–25 mm at 18–30 m/min, and 25–32 mm at 8–18 m/min; a 32 mm pass needs a 60–80 mm solid flywheel, smaller flywheels on heavy bars mark the surface and trip ultrasonic inspection at the rebar cutter station [S2]. Yards running both light coil and heavy bar usually pick a dual-mandrel machine with swappable 6–16 mm and 16–25 mm cartridges, because mandrel wear on a 6 mm bar accelerates sharply when the frame is sized for 25 mm [S4].
Straightening Principle: Rotor Geometry and Mandrel vs Crossed Rolls
A straightener uses 4–8 driven rolls in a zig-zag pattern to over-bend the bar in alternating directions, so the elastic coil-set is stretched out and the bar exits with residual bow inside roughly 1–2 mm/m, suitable for feeding a stirrup bender or cut-to-length saw [S5]. Mandrel radius of 3–5d (bar diameters) on the straightener sets residual camber under 1 mm/m, the threshold where the bar sits flat in a rebar jig without spring-back during cage assembly [S2].
Units that skip the mandrel and rely on crossed rolls alone are fine for stirrups but not for primary tunnel bars; a five-roller geometry at 8–32 mm and 30 m/min is the minimum credible specification for 2026 tenders, and cheaper three-roller units over-curve 25 mm+ bars so the residual camber shows up in the finished cage [S2]. The straightening process is by design destructive to surface condition: roll pressure on a 12 mm deformed bar past its yield point leaves micro-scratches and a measurable drop in ultimate tensile strength, which is why "little strength loss, good straightness and no scratch" is sold as a controlled-spec claim, not a default [S5].
Integration Pattern: Standalone, 2-in-1 Straightener-Cutter, 3-in-1 Lines
A rebar straightener-cutter integrates straightening and cutting into a single unit; after coiled rebars feed in, rollers straighten them automatically, then the hydraulic cutter shears to preset length in a fully automatic cycle, replacing two separate machines and saving floor space plus labor [S1]. Production data sheet example: YG-GTQ4-14 high-speed version has 4 kW traction, 4 kW cutting, 9 kW straightening, 4–14 mm round bar, 4–12 mm threaded bar, 35–55 m/min line speed, 850 kg machine weight; the frequency-conversion 2000-ton version scales to 15 kW traction, 5.5 kW cutting, 0–100 m/min line speed, 1100 kg [S1].
The 3-in-1 straightener-cutter-bender class, exemplified by the Okorder-spec unit with 4–14 mm scope, 500–900 m/min straightening speed, and 300–8000 mm auto-cut length, handles both bar-prep functions in one pass on factory cut-to-length lines; for site or workshop work, the straightener and rebar bender are usually bought separately because throughput math and operator skill floor diverge [S5]. For demolition sites where a handheld rotor is the right pattern, see Rebar Straightener Picks for Demolition: Handheld vs Bench Rotor.
Material Compatibility and Precision Grades
Multi-roll straighteners in the YGJ20 class cover OD 6–20 mm with yield strength up to 392 N/mm², roller throat 63 mm, roller length 90 mm, roller angle 25°–33° adjustment, line speed 44 m/min, precision ≤0.6 mm/m, allowed pre-bend ≤15 mm/m, 2×2.2 kW main motor, and Cr12Mo rollers in a 2-2-2-2-2 (10-roll) or 2-2-2-2-2-2 (12-roll) layout [S3]. Heavy pipe-and-bar rotor units such as the YGJ80A/YGJ80B class work 20–80 mm straightened pipe with ≤0.8 mm/m straightness, with customisation available for larger geometries [S6].
Material compatibility on these multi-roll lines covers carbon steel, stainless steel, copper, brass, aluminum, and titanium; the more rollers, the higher the straightness, which is why the 12-roll configuration is preferred for thin-wall tube and tight-tolerance bar [S3]. For comparison, the Senbo CNC automatic straightening-cutting machine targets 6–20 mm, ≤0.6 mm/m precision, 44 m/min line speed, with the same carbon-steel / stainless / copper / brass / aluminum material envelope [S3].
Comparison of the Three Drive Types on Selection Criteria
On cost, mechanical flywheel units are lowest, servo-electric mid-tier with 3–5 kW per axis closed-loop control, and hydraulic highest at 15–25 kW draw. On diameter window, mechanical covers 6–32 mm, servo-electric 12–20 mm sweet spot, and hydraulic 32–50 mm heavy bar. [S2]
On throughput, mechanical leads at the 30–60 m/min band for heavy bar; servo-electric leads on 12–20 mm accuracy and on noise compliance at a 75 dB(A) tunnel cap; hydraulic wins on bar-tension stability under mill-scale fluctuation [S2]. On maintenance, mechanical units carry the highest wear-part count (rollers, mandrel, shear pins), servo-electric units carry the lowest mechanical wear but the highest controls spend, and hydraulic units split the difference with periodic seal and pump service.
Bar Grade Coupling and Downstream Constraints
ASTM A615 plain billet steel is the dominant U.S. specification, with grade numbers (40, 60, 75, 80) denoting minimum yield strength in thousand psi: grade 40 = 40,000 psi (≈276 MPa) and grade 60 = 60,000 psi (≈414 MPa) [S4]. Rail-steel (A616) and axle-steel (A617) bars carry higher carbon and manganese and fall into the hard-to-weld category, so a straightener feeding a welding line downstream must hold straightness without work-hardening cracks at the mandrel contact arc.
For European tunnel projects, B500B and B500C per EN 10080 are the default grades, while ASTM A706 Grade 60 (weldable) is the U.S. equivalent when rebar couplers are specced rather than lap splices; a straightener that quotes a 500 MPa yield-retention certificate on 32 mm B500B is the bar to compare against, do not accept a generic "low-carbon bar" claim on the data plate [S2]. Mechanical coupler systems demand bar-end straightness within 0.5° over the threading length, which translates to a residual bow under 2 mm/m on the stock feeding the threading equipment; position couplers for non-rotatable bars are the most sensitive to helical twist left by the straightener [S4].
Selection Gates and Sourcing Signals
The three coupled selection decisions are the bar grade you will process (ASTM A615 grade 40, 60, 75, or 80), the diameter range on the cutting list, and the daily throughput the yard must clear, with straightness tolerance of ≤2 mm/m as the usual bid floor [S4]. For HVAC crews running rebar tie-rod and hanger-bar prep on a different logistics profile, see HVAC Rebar Straightener Selection: Motor, Diameter, Site-Logistics Map.
For electrical-installation yards threading conduit rebar and ground-rod stock, the 2026 spec map for electrical-installation rebar straighteners carries the matching diameter and motor band. Road-maintenance crews running mobile rotor units on small-batch coil should cross-check the road-maintenance rebar straightener spec map before locking procurement. Trackable signals for the next quarter: EN 10080 grade-B500C yield-retention certificates on 32 mm mandrel output, and dual-mandrel swappable-cartridge releases in the 6–25 mm band from at least one of the major Chinese OEM lines catalogued in the construction machinery and equipment index.