A rebar bender is normally specified against the largest bar in the project (Grade 60/420 or Grade 80/550), the tightest center-pin radius the design calls for, and the available supply — 110-220 V single-phase for portable/stirrup work versus 380-415 V three-phase for shop-class machines processing up to 50 mm bar [S3].
Stirrup benders from TJK and portable rotary benders such as the Fascut FR-800 cover the on-site light end, while CNB Machinery supplies the heavier cutter-bender combinations used in Philippine rebar fab shops [S1][S2][S3]. Picking the wrong class — for instance a 25 mm portable bender on 32 mm Grade 80 rebar — is the single most common field failure and shows up as sheared pins, cracked gearbox housings, and bent angle cam plates inside the first 200 hours.
Gate 1: Maximum Bar Diameter and Bar Grade (Yield Strength)
Rebar bender capacity is rated on two independent numbers: the bar diameter the machine can bend cold in a single pass, and the rebar grade (yield strength) it is rated for — most portable units are published against Grade 60 / 420 MPa, while shop-class three-phase machines are typically rated up to Grade 80 / 550 MPa [S1][S2]. The Fascut FR-800 rotary bender is a published portable benchmark for shop or on-site fabrication of standard rebar sizes [S3].
Rule of thumb drawn from CNB's cutter-bender line: a single-phase 110-220 V portable bender generally handles 25 mm Grade 60 bar cold without preheating; the same machine will stall on 32 mm Grade 80 rebar, and the published capacity drops roughly one bar size (around 20-22 mm) when Grade 80 is fed in [S1]. For 32-50 mm rebar in either grade, buyers move to 380-415 V three-phase shop machines with hydraulic assist or larger gear-reduction heads [S2].
The mechanical limit is the bending-pin diameter and the bending-shoe hardness (typically HRC 55-60). Below ~3d center-pin radius the bar springs back and the operator chases the angle; above ~6d the machine can stall before reaching the cam stop. Lock the bar diameter and grade as Gate 1, then check the machine's stated minimum bend radius before anything else.
Gate 2: Bend Angle Range, Center-Pin Radius, and Multi-Angle Cams
Standard stirrup benders and portable rotary benders usually ship with 0-180° cam coverage; TJK's stirrup bender line is set up for the typical 90° / 135° / 180° stirrup, hook, and seismic tie geometry, with replaceable cam plates for non-standard angles [S2]. Fascut positions its portable bender as a multi-angle bench or job-site tool rather than a single-purpose stirrup machine [S3].
Center-pin radius is the second leg of this gate: most stirrups call for 3d-4d pin radius, seismic 135° ties for 4d-5d, and main-bar 90° hooks for 4d-6d. The pin on most portable machines is fixed and sized to the largest bar the unit can take, so buyers who mix 12 mm stirrup work with 25 mm main-bar bending need to verify the pin set is interchangeable — some Chinese stirrup benders share pin blocks across 6-25 mm, others step pin size every 4-6 mm [S2].
For 90° vs 135° work, the head's rotation geometry matters: a true rotary bender (FR-800 class) sweeps the head around a stationary pin and gives a clean outside radius with no mandrel mark; a "swing-arm" head common on cheap stirrup machines drags the bar across a fixed shoe and leaves a flat on the inside of the bend above ~25 mm [S3]. Specify rotary head for any bar ≥25 mm or any grade ≥60 ksi.
Gate 3: Power Source — Single-Phase 110-220 V vs Three-Phase 380-415 V
Portable rebar benders, including the FR-800 from Fascut, run on 110-220 V single-phase so they can be plugged into a standard site panel or a 5-7 kVA portable genset [S3]. Shop-class cutter-benders from CNB Machinery and the larger stirrup benders from TJK are published as three-phase 380-415 V units intended for fixed fab-shop feeds [S1][S2].
Single-phase 2.2-3 kW motors cap out around 25 mm Grade 60 before motor thermal protection trips; three-phase 4-7.5 kW motors are the entry point for 32-40 mm bar and the only practical option for 50 mm bar. Where site power is single-phase only and the project calls for 32 mm+ bar, a static phase converter or a 10 kVA+ genset is not optional — the bender will not start under load on light single-phase service.
Duty cycle follows power: 110-220 V single-phase benders are rated for intermittent use (typically S2-30 min, meaning 30 minutes of continuous bending followed by a cool-down); three-phase shop machines are rated for S6 periodic duty and can run multi-shift fab lines. Locking the wrong duty class shows up as brush/commutator wear on single-phase motors and contactor chattering on the three-phase side.
Gate 4: Duty Cycle, Throughput, and Cutter-Bender Combination
CNB Machinery's positioning as the "#1 Rebar Cutter and Bender Machine supplier in the Philippines" reflects how a lot of fab-shop buyers actually procure: a single combined machine that cuts and bends [S1]. Combined units save floor space, share a 380-415 V three-phase feed, and let one operator do cut-then-bend without walking between stations, but they cap rebar capacity at the smaller of the two heads — typically 32 mm for a mid-range combination machine [S1].
Throughput scales with motor power, not headline diameter. A 2.2 kW single-phase stirrup bender running 12 mm Grade 60 stirrups will produce roughly 120-180 bends/hour under S2-30 min duty, while a 5.5 kW three-phase shop bender on the same bar runs 300-500 bends/hour continuous [S2]. For multi-shift precast yards, the three-phase number is the one that pays for the upgrade; for site work, the single-phase number is the cap on daily output.
For practitioners mapping capacity against other fab equipment, the same selection-gate logic shows up in adjacent processes like induction furnace kW sizing and welded mesh aperture selection — the underlying pattern is the same: name the material, name the throughput, then size the power train.
Gate 5: Control, Footprint, and the Cross-Reference to Consumables
Manual cam-and-pin benders remain the workhorses, but newer stirrup benders from suppliers like TJK now ship with digital angle encoders and programmable bend sequences for repeating stirrup geometries — useful when a project runs thousands of identical ties [S2]. Fascut's portable bender is published as a straightforward on-site tool, not a CNC bender, so its buyers are typically crews doing small-batch rebar fab rather than automated yards [S3].
Footprint and weight gate the last call. A portable FR-800-class rotary bender lands in the 50-90 kg range and can be carried by two technicians to a slab; a 380-415 V three-phase shop bender is typically 250-600 kg and bolted to the floor. On high-rise or bridge work, the portable class is mandatory; in a rebar fab yard, the shop class is mandatory.
For the upstream material itself — chemistry, grade, and the relationship between bar size and bendability — the rebar reference page and the rebar bender encyclopedia entry lay out the spec anchors. Downstream of the bender, the cut end is typically prepared with a rebar cutter, and where continuity bar is needed for splicing, the rebar coupler and rebar threading machine round out the fab line.
Comparison Frame: Portable Single-Phase vs Shop Three-Phase vs CNC Stirrup Bender
Three rebar bender classes line up against the four most important selection criteria in the table below, drawn from published supplier data [S1][S2][S3].
Portable single-phase rotary bender (Fascut FR-800 class) — maximum bar diameter in the 25 mm range for Grade 60 [S3]; bend angle 0-180° via rotary head; power 110-220 V single-phase, 2.2-3 kW; duty S2-30 min intermittent; footprint 50-90 kg, two-person carry; intended for site fab and small-batch shop work.
Shop three-phase cutter-bender (CNB Machinery class) — maximum bar diameter 32 mm in combination head, up to 40-50 mm on bend-only shop units [S1]; bend angle 0-180° via swing or rotary head; power 380-415 V three-phase, 4-7.5 kW; duty S6 periodic, multi-shift; footprint 250-600 kg, floor-bolted; intended for fab-shop production.
CNC stirrup bender (TJK class) — maximum bar diameter 6-16 mm typical for stirrup work, up to 25 mm on heavier programmable units [S2]; bend angle programmable 0-180° with encoder feedback; power 380-415 V three-phase, 5-15 kW depending on bar size; duty S6 continuous with auto wire feed; footprint 800-2000 kg, fixed installation; intended for precast yards running thousands of identical stirrups per shift.
Limits, Failure Modes, and the People Who Shouldn't Buy a Bender
Portable rebar benders do not replace shearlines for cut-to-length work, and bender-cutter combinations sacrifice capacity on both functions to save space [S1]. Buyers who need 50 mm Grade 80 bending, continuous three-shift output, or diameters above the published single-bar limit are not in the portable-bender market at all — they need a hydraulic three-phase shop machine with a separate heavy cut line, and a procurement spec built around minimum yield strength, bend radius, and bend-angle tolerance rather than a single "max bar" headline number.
The most common selection miss is reading the bar diameter spec without the grade footnote: a machine rated "32 mm" almost always means 32 mm Grade 60, not 32 mm Grade 80, and the difference between the two on a cold-bend machine is roughly one bar size (6-8 mm) of usable capacity. The second most common miss is under-sizing power — a 2.2 kW single-phase unit on a 32 mm Grade 80 bar will not stall the motor cleanly; it will stall it thermally after 5-10 minutes and trip the overload, and that is what kills the gearbox. Trackable signals for 2026-06-25: the rebar coupler market in seismic regions continues to push bender buyers toward 4d-5d center pins, which is also why rotary-head machines are gaining share over swing-arm machines in stirrup lines [S2][S3].