Cutting Force: Static vs Effective at the Blade
Cutting force is the number every buyer compares and the one most often misunderstood. Two shears with the same rated tonnage can take completely different material, because the rating describes the hydraulic system while the cut happens at the blade — and the distance between those two facts is where sizing mistakes live. This article separates the two numbers, with the Q91-315 as the reference class, and gives you the rule that connects force to material.
The Two Numbers
Static force is the theoretical maximum the hydraulic cylinders can generate with the shear stationary — the headline number in every brochure. It is a real number, measured and verifiable, and it describes the system rather than the cut.
Effective force is what actually reaches the material at the blade during a real cycle. It is lower than the static figure — always — because of leverage through the blade carrier, the speed of the stroke, the material’s own resistance, and the frame’s deflection under load. Two machines with identical static ratings can deliver materially different effective force, and the difference is in the structure rather than in the badge.
Why the Structure Decides the Effective Force
The gantry design’s advantage is precisely here. A portal frame anchored in a foundation distributes the reaction force of every cut across four columns and an upper beam — the load spreads through the structure, deflection stays small, and the effective force at the blade stays close to the static figure through the stroke. A frame that carries reaction through a different path deflects more, and deflection is lost force: the blade works harder for the same cut, cycle times stretch, and the wear bill arrives early.
This is why the same “500 ton” on two different designs is not the same specification. The number is the hydraulic system’s capability; the structure decides how much of it reaches the blade, shift after shift. Read the frame, then the number — and the design guide covers how the four structures differ.
The Rule That Connects Force to Material
The working rule for demanding scrap: your shear’s static force should be roughly one and a half to two times the yield strength demand of the material you cut. That ratio is not a formula to compute — it is a sanity check that keeps buyers honest about what a class can take. A machine sized exactly to its material works at the edge of its band every shift; a machine with headroom works in the middle, where blade life and cycle time live.
The published boundary rows exist because we have already done that arithmetic per class. The Q91-315 carries 30 mm continuous and 50 mm occasional; the Q91-630 carries 60 mm and 80 mm. Those figures are the effective-force answer, expressed as material rather than as tons — which is why they, and not the force rating, are the rows to size against.
What This Means for Your Sizing
Three practical consequences follow:
Compare boundary rows, not force badges. Two 500-ton machines on different designs are different machines. The continuous plate figure is the effective-force answer in material terms, and it is the row that describes what the machine takes on your feed.
Size to the continuous row. The continuous rating is the daily diet; the occasional rating is what the week allows. A machine sized to its occasional rating works at the edge of its band every shift, and the edge is where blade life and cycle time go to die.
Declare the material, not the tonnage. “I need a 500-ton shear” is a less useful sentence than “my heaviest routine piece is a 60 mm I-beam and my weekly plate runs to 45 mm.” The first is a badge; the second is a specification, and the quotation answers it with a class rather than a number.
The Honest Conversation
When a buyer asks “is 315 ton enough,” the honest answer is always about material rather than about force. Send the three heaviest pieces from a normal month with their cross-sections, the plate thickness that shows up weekly, and the daily tonnage — and the written recommendation names the class whose effective force matches your feed, whether that is the 200 or the 400. The class comparison covers the ladder, and the quotation comes back within two business days.
The Structure Comparison
The same static force on different structures delivers different effective force, and the comparison is visible in the published boundary rows. Our gantry range publishes continuous plate figures per class — 30 mm at the Q91-315, 60 mm at the Q91-630, 170 mm at the flagship — because those figures are the effective-force answer expressed as material. A competitor quoting the same tonnage on a different structure has to publish different boundary rows, and the rows are the honest comparison.
This is why the design question comes before the tonnage question. The design guide covers how the four structures carry reaction force differently, and the boundary rows are where that difference becomes a number you can size against.
The Sizing Method
The method that connects force to your feed has three steps. First, describe the material — cross-sections and frequencies, not tonnage. Second, find the class whose continuous row covers the heavy tail with headroom, applying the rule from the force-and-material guide. Third, check the frequency — weekly heavy events size for the heavier class, monthly ones keep the lighter class viable with the right blade configuration.
Three steps, an afternoon, and the answer is a class rather than a guess. Send the material description with your inquiry and the written recommendation names the class whose effective force matches your feed — whether that is the 200 or the class above the one you asked about.
The Force Question, Answered
The force question — is this tonnage enough — has exactly one reliable form, and it is a material question. Describe the feed: the three heaviest pieces from a normal month with cross-sections, the plate thickness that shows up weekly, the daily tonnage, the shift pattern. The answer that comes back is a class, and the class is justified by the boundary rows rather than by the badge. The comparison guide covers the ladder, and the rule guide covers the headroom check.
The force question in its badge form — “is 315 ton enough for my yard” — cannot be answered reliably by anyone, including the factory, because the answer depends on the material and the material has not been described. The first job of any good quotation conversation is therefore to convert the badge question into the material question, and that conversion is what the published range exists to support.
The Force as a Material Question
The force rating is a real number describing a real capability, and it is the wrong question. The right question is what the machine takes on your feed, and the answer is the boundary rows — the continuous and occasional plate figures that express effective force as material. Every honest sizing conversation converts the badge question into the material question before it answers anything.
Send the material description and the answer comes back as a class. The published range carries the boundary rows per class, and the comparison guide walks the ladder the answer points into.
Buyer FAQ
Why do two shears with the same tonnage cut different material?
Because the static rating describes the hydraulic system while the cut happens at the blade, and the structure between them decides how much force arrives. Frame deflection is lost force, and the designs differ.
What is the effective force?
What reaches the material during a real cycle — lower than the static figure because of leverage, stroke speed, material resistance and frame deflection. The published boundary rows are the effective-force answer expressed as material.
What ratio should static force have to my material?
Roughly one and a half to two times the yield strength demand for demanding scrap — a sanity check rather than a formula. A machine sized exactly to its material works at the edge of its band every shift.
Which row should I size against?
The continuous plate figure. It is the daily diet the machine holds its numbers on; the occasional rating is what the week allows, and sizing to it buys half the published blade life.
How do I describe my material for a recommendation?
Cross-sections and frequencies, not tonnage: the three heaviest pieces from a normal month, the weekly plate thickness, and the daily tonnage. That is a specification, and the quotation answers it with a class. Describe the feed rather than the tonnage, and the answer that comes back is a class justified by boundary rows rather than by a badge — the conversion from badge question to material question is the first job of any good quotation conversation. Describe the feed rather than the tonnage and the answer comes back as a class justified by boundary rows — the conversion from badge question to material question is the first job of any honest quotation conversation.