A Combined Punch and Shears is a dual-station fabrication machine that punches holes through plate or section steel on one side and shears bar, flat, or angle stock on the other, both driven from a single power frame. Machines like the Edwards 65-Ton Ironworker and Scotchman 6509-24M are the modern descendants. The purpose is to consolidate two high-tonnage operations into one footprint so a small fab shop can hole-punch and cut-to-length without owning a separate punch press and alligator shear. A 65-ton ironworker punches a 13/16" hole through 1/2" mild steel and shears 1/2" × 6" flat bar in under 4 seconds per cycle.
Combined Punch and Shears Interactive Calculator
Vary punch diameter, plate thickness, and clearance percent to size the die bore and see the punch-to-die gap animated.
Equation Used
The calculator applies the article rule that mild steel punch-to-die clearance should be about 8% of material thickness per side. The die bore equals the punch diameter plus two side clearances.
- Round punch and die.
- Clearance is radial clearance per side.
- 8% of material thickness per side is the mild-steel shop rule.
- Die bore is punch diameter plus twice the side clearance.
How the Combined Punch and Shears Actually Works
The machine is built around a single C-frame or twin-cylinder hydraulic frame that carries two work stations sharing one power source. On the punch side, a hardened punch is driven down through a die — the punch and die together create a controlled fracture across the workpiece, with the slug falling clear through the die bore. On the shear side, an upper blade descends past a lower blade and severs the bar by progressive fracture across the section. Both stations are operated by the same ram or by twinned rams fed from one pump, and a foot pedal selects which side cycles.
The geometry that matters most is punch-to-die clearance. For mild steel you want about 8% of material thickness on each side — punch a 20 mm hole in 10 mm plate and the die bore should be roughly 21.6 mm. Run the clearance too tight and you double the punching tonnage required, the punch wears in a few hundred cycles, and the slug welds itself into the die. Run it too loose and the hole edge tears, leaving a heavy burr and a fractured rather than sheared edge. On the shear side, blade clearance follows the same rule but the consequence of error is different — too much clearance and the bar twists as it cuts, leaving a rolled-over lip, too little and you flat-out stall the cylinder.
Failure modes are predictable. Punches snap when they hit a workpiece harder than their rated stock — punching A36 with a die set spec'd for it is fine, but try the same die on 4140 prehard and the punch shatters on the second hit. Shear blades chip at the corners when an operator cuts a section that exceeds the throat capacity, because the stock levers against the blade edge instead of bearing flat. And the hold-down stripper, which most operators ignore, is what keeps the plate from lifting with the punch on the upstroke — without it you get bent punches inside 50 cycles.
Key Components
- Hydraulic Power Unit: A single pump and reservoir, typically 5-15 HP on shop machines, supplies oil to one or two cylinders at 2,000-3,000 PSI. The Edwards 50-Ton runs a 5 HP pump at 2,300 PSI to develop 50 short tons at the punch ram.
- Punch Ram and Die Set: A hardened tool-steel punch (typically 60-62 HRC) drives into a matching die with 6-10% clearance per side for mild steel. Standard punch shanks are 7/8" or 1" diameter on most North American ironworkers.
- Shear Blades: Two opposed hardened blades — usually four-edged so they can be rotated as edges dull — sever flat bar, round bar, or angle. Blade clearance is set with shims and held to within 0.05 mm of spec for clean cuts in 1/2" plate.
- Hold-Down Stripper: A spring-loaded or screw-type clamp that pins the workpiece flat during the punch upstroke. Without functional stripper pressure of around 10-15% of punch tonnage, the punch lifts the plate and bends on retraction.
- C-Frame or Twin-Cylinder Frame: The structural backbone that carries both stations. A 65-ton machine frame is typically 1"-1-1/4" plate steel, stress-relieved after welding, with throat depth of 14-24" depending on model.
- Foot Pedal and Selector Valve: Routes hydraulic flow to either the punch ram or the shear ram based on operator selection. Most modern machines use a single pedal with mechanical interlocks preventing simultaneous activation of both stations.
Industries That Rely on the Combined Punch and Shears
The Combined Punch and Shears earns its place in any shop that fabricates structural steel, light plate, or bar stock in batch sizes too small to justify a CNC turret punch and a dedicated guillotine shear. The classic users are jobbing fab shops, ornamental ironworkers, agricultural equipment builders, and railing fabricators — anyone who needs to punch a bolt pattern and cut a piece to length on the same workpiece without re-setting on a second machine. The machine handles flat bar, angle iron, channel, and round stock up to roughly 1" in mild steel on a mid-size 65-ton frame, and it does so with no NC programming and no consumables beyond punches and dies.
- Structural Steel Fabrication: A jobbing shop using a Scotchman 6509-24M ironworker to punch 11/16" bolt holes in W6×15 column base plates and shear the gusset stock to length
- Ornamental Iron and Railings: A handrail shop running an Edwards 50-Ton to punch 3/8" picket holes in 1" × 1/4" flat bar and shear the bar to 42" balcony lengths
- Agricultural Equipment Manufacture: A mid-west implement builder using a Geka Hydracrop 80-S to fabricate plough frame brackets from 3/8" angle iron
- Trailer and Truck Body Building: A flatbed trailer fabricator using a Piranha P50 to punch tie-down hole patterns in 4" × 4" × 3/8" angle rub rails
- Heritage Blacksmithing and Restoration: A restoration shop using an antique Buffalo Forge No. 4 Combined Punch and Shears to reproduce period iron strap hinges with original-style punched eye holes
- Mining and Quarry Equipment Repair: An on-site repair crew using a portable Mubea KBL ironworker to fabricate replacement screen-deck mounting plates in the field
The Formula Behind the Combined Punch and Shears
The single most important calculation on a Combined Punch and Shears is the tonnage required to punch a hole, because that number tells you whether your machine can do the job, whether the punch will survive, and whether the slug will eject cleanly. The formula uses the perimeter of the hole, the material thickness, and the shear strength of the workpiece. At the low end of typical shop work — say a 1/2" hole through 1/4" mild steel — required tonnage runs around 6 tons, well inside the capacity of any 50-ton machine and the punch will last tens of thousands of cycles. At nominal mid-range work — a 13/16" hole through 1/2" A36 — you need about 32 tons, which is the bread-and-butter zone for a 65-ton machine. Push to the high end — a 1-1/16" hole through 3/4" plate — and you're at 64 tons, right at the edge of a 65-ton machine where punch life drops dramatically and you should slow the cycle to keep the oil cool.
Variables
| Symbol | Meaning | Unit (SI) | Unit (Imperial) |
|---|---|---|---|
| Fpunch | Punching force required | N | lbf or short tons |
| D | Hole diameter (or perimeter / π for non-round holes) | mm | in |
| t | Material thickness | mm | in |
| τs | Shear strength of the workpiece material (≈ 0.8 × tensile strength for mild steel) | MPa or N/mm² | psi |
Worked Example: Combined Punch and Shears in a sign-post fabrication shop in Ohio
A sign-post fabrication shop in Ohio is sizing the punch tonnage for a 13/16" hole through 1/2" A36 mild steel base plates on an Edwards 65-Ton Ironworker. They run 200 plates a shift and need to confirm the 65-ton frame has adequate margin and that the standard 60 HRC punch will hold up.
Given
- D = 13/16 (0.8125) in
- t = 0.500 in
- —s = 55,000 (0.8 × 68,000 psi tensile for A36) psi
Solution
Step 1 — at the nominal job (13/16" hole, 1/2" plate), compute the shear area around the hole perimeter:
Step 2 — multiply by shear strength of A36 to get nominal punching force:
That's 54% of the 65-ton machine's rated capacity — comfortable margin, punch life in the 15,000-25,000 hit range, oil stays cool over a full shift.
Step 3 — at the low end of typical work for this shop (1/2" hole through 1/4" plate):
This is a trivial load for the machine — the ram barely loads up, you'll hear the pump unload almost immediately, and a punch will go 50,000+ hits before regrinding. At the high end, a 1-1/16" hole through 3/4" plate:
That exceeds the 65-ton rating. The machine will either stall short of breakthrough or operate with no safety margin — punch life drops to a few hundred hits, the frame deflects measurably, and you should either step up to a Scotchman 9012-24M (90 ton) or pre-drill a pilot hole to drop required tonnage by 30-40%.
Result
Nominal punching force is 35. 1 short tons, well within the 65-ton machine's capacity. In practice the operator will feel a firm but unhurried hit with no frame shudder, and the slug will drop free through the die rather than sticking. Compare that to the low-end 10.8-ton load (effortless, near-silent pump cycling) and the high-end 68.8-ton load (over capacity — the machine groans, the cycle slows, and punch life collapses), and you can see the 65-ton frame is properly sized for the shop's bread-and-butter work but undersized for the heaviest jobs. If you measure higher actual tonnage than predicted, check three things: (1) the punch-to-die clearance — if it's tight, say 4% per side instead of 8%, your tonnage demand jumps 1.5-2×; (2) material certification — if the supplier sent A572 Gr 50 instead of A36, shear strength is 25% higher; (3) punch geometry — a flat-face punch needs the full calculated force, but a shear-angle punch (15° dish) cuts that demand by roughly 30%.
Combined Punch and Shears vs Alternatives
The Combined Punch and Shears competes against two single-purpose machines and against modern CNC equipment. The decision usually comes down to throughput, mix of work, and capital budget — a small jobbing shop wins with the combined machine, a high-volume sheet metal house wins with separate dedicated machines, and a structural plate shop with consistent geometry wins with CNC.
| Property | Combined Punch and Shears | Standalone Hydraulic Press Brake + Alligator Shear | CNC Plate Punch (Trumpf, Amada) |
|---|---|---|---|
| Capital cost (mid-size shop class) | $8,000-$25,000 | $15,000-$40,000 for the pair | $120,000-$400,000+ |
| Cycle time per hole/cut | 3-5 seconds | 3-4 seconds (no setup change penalty) | 0.5-1 second per hole, automated feed |
| Hole position accuracy | ±0.5 mm (manual layout) | ±0.5 mm (manual layout) | ±0.1 mm (CNC servo) |
| Maximum plate thickness (typical) | 3/4" mild steel on 65-ton class | 1" or more on dedicated press | 1"-1-1/4" on heavy CNC |
| Tooling change time | 2-5 minutes (manual punch swap) | 5-10 minutes per machine | Automatic turret, seconds |
| Setup overhead for short runs (10-50 parts) | Low — single machine, single setup | High — two machines, two setups | High — programming and nesting time |
| Operator skill required | Moderate — manual layout and feeding | Moderate — same per machine | Programmer plus operator |
| Footprint | ~20 ft² for 65-ton machine | ~50 ft² for the pair | 100-300 ft² with material handling |
Frequently Asked Questions About Combined Punch and Shears
Heavy bottom burr almost always points to a worn or chipped punch tip rather than wrong clearance. As the punch's leading edge dulls, it stops shearing cleanly and starts extruding metal into the die before fracture — the result is a rolled-over edge on the entry side and a heavy hanging burr on the exit side. Inspect the punch face under magnification. If you see a 0.1-0.2 mm radius where there should be a sharp 90° edge, the punch is done.
The other common cause is that your die has worn oversized. After 10,000+ hits the die bore opens up by a few thou, and the effective clearance walks past spec. Plug-gauge the die bore against the punch — if total clearance exceeds 18% of stock thickness, regrind or replace the die.
The deciding factor is hole-diameter to plate-thickness ratio. Below a ratio of 1.0 (hole smaller than plate is thick), you should drill — punching produces excessive distortion, the slug tends to jam, and punch life is poor. Between 1.0 and 2.0, punching is preferred but expect to use a pilot hole if you're above 80% of machine capacity. Above 2.0, punching is straightforward.
A practical rule on a 65-ton ironworker: if calculated tonnage exceeds 55 tons, either pre-drill a 1/4" pilot (drops required force by 30-40%) or use a shear-angle punch with a 15° dished face. Don't simply hope the machine will get through it — a stalled punch mid-stroke is a frame-deflection event you'll feel for the rest of the day.
This is almost always a hold-down problem rather than a blade problem. Angle iron sheared without proper support tries to rotate around its centroid as the upper blade descends, because the shear force isn't aligned with the section's principal axis. The leg furthest from the blade lifts and twists, producing the rolled-over edge.
Most ironworkers ship with a dedicated angle-shear station that holds the leg flat against a 90° fence — if you're feeding angle through the flat-bar shear, you're using the wrong station. Switch to the angle station and the cut comes out square. If your machine doesn't have a dedicated angle shear, fabricate a backup fence that supports the free leg within 5 mm of the cut line.
Spec sheets state tonnage at ideal conditions: fresh sharp tooling, 8% clearance, A36 mild steel, and full hydraulic pressure. Real-shop deviations stack quickly. A worn pump that's lost 10% of its rated pressure cuts available tonnage by the same 10%. Cold hydraulic oil on a winter morning thickens and slows ram speed enough that the punch dwells in the cut and effective force drops. And almost every shop runs material harder than nominal A36 — a heat of A572 Gr 50 needs 25% more force than the spec assumed.
Diagnostic check: install a pressure gauge on the punch cylinder port and read peak pressure during a known job. If you're hitting rated pressure but the punch still struggles, the problem is the workpiece or the tooling. If you can't reach rated pressure, the problem is the pump, relief valve, or oil.
The answer depends almost entirely on your job mix. If most of your work involves punching AND shearing the same piece — base plates, gusset plates, bracket stock — the combined machine wins on workflow because you don't reposition the workpiece between two machines. One layout, one operator station, one foot pedal.
If your work splits into long runs of pure shearing (cutting bar to length all day) and separate long runs of pure punching, two dedicated machines win because two operators can run them in parallel. The tipping point in most jobbing shops is around 3-4 operators — below that, the combined machine's workflow advantage dominates; above that, parallel throughput wins.
Premature punch breakage in the first 100 hits is virtually always a side-loading problem, not a tonnage or material problem. The punch is designed to see pure axial compression. Any lateral force — from a misaligned die, a bent punch shank, or a stripper that's clamping unevenly — bends the punch on each cycle and fatigue-cracks the shank.
Check three things in order: (1) punch-to-die concentricity with a dial indicator, must be within 0.05 mm TIR; (2) stripper plate flatness — if it's bowed or worn, it pushes the workpiece sideways during the upstroke; (3) punch shank straightness, especially on punches reground multiple times. A reground punch with a 0.1 mm runout will snap inside 200 cycles regardless of material grade.
You can, but with adjustments. 304 stainless has roughly 1.5× the shear strength of A36, so a hole that needs 30 tons in mild steel needs about 45 tons in stainless — and stainless work-hardens fast, so any rubbing in the die bore will gall. Use a tighter clearance (around 5-6% per side) and a slower ram speed.
Aluminium is the opposite problem. Shear strength is roughly 30% of mild steel, so tonnage isn't an issue, but the slug tends to stick in the die because aluminium gall-welds to tool steel under pressure. Open up the clearance to 12-15% per side and apply a wax-based punching lubricant. Don't use the same die set for both materials without thorough cleaning — aluminium pickup on the die wall will tear stainless and mild steel parts on subsequent jobs.
References & Further Reading
- Wikipedia contributors. Ironworker (machine). Wikipedia
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