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Shopping for a hydraulic oil press means running into three numbers on every spec sheet: MPa, tonnage, and cake surface pressure. They sound interchangeable, suppliers quote them inconsistently, and it is easy to pick the wrong machine by chasing the biggest figure. This guide explains what each number actually tells you as a buyer — and which one really separates one model from another — so you can read a spec sheet with confidence. (If you want the full physics and the force calculation behind it, see our deep dive on MPa, tonnage and real output.)
The three numbers, in plain terms
System pressure (MPa) is how hard the hydraulic system pushes, per unit area. Megapascals measure the oil-system pressure inside the machine. Almost every commercial hydraulic oil press runs at around 60 MPa — it is a property of the hydraulic system, not a feature one model has over another.
Tonnage (tons of force) is the total downward force the machine can apply. It comes from the system pressure multiplied by the area of the cylinder — so a bigger cylinder at the same 60 MPa produces more tons. A 325 model delivers about 325 tons of real pressing force, a 500 model about 630 tons. Tonnage tracks the size and capability class of the machine.
Cake surface pressure (MPa/cm²) is the one buyers overlook and the one that matters most for results. It is how much of that force actually lands on the seed cake, spread over the barrel’s cross-section. The same tonnage on a smaller barrel gives higher surface pressure — and surface pressure is what squeezes oil out of hard or stubborn material. This is the number that genuinely separates models.
Why you should not shop on MPa alone
Because nearly all hydraulic presses sit at about 60 MPa system pressure, comparing models on MPa tells you almost nothing — they are all roughly the same. A supplier advertising “60 MPa!” as a selling point is quoting a number that every competitor also hits. What changes between a small shop press and a 630-ton industrial unit is cylinder size, barrel size and therefore tonnage and cake surface pressure. Read past the MPa headline to those figures.
Many machines also use a dual-pressure system with two gauge settings — a lower setting (around 55 MPa) for the start of the cycle and a high setting (around 60 MPa) to finish. That is normal and good: it lets the press ramp up gently and hold full pressure safely. It is not a reason to rank one machine over another.
Cake surface pressure across our range
Here is how tonnage and cake surface pressure scale across the models, at the same ~60 MPa system pressure. Notice the surface pressure climbing as you move from retail shop machines to industrial cold-press units — that climb, not the MPa, is what buys you the ability to press harder seeds and squeeze cakes drier:
| Model / class | Pressing force | Cake surface pressure | Typical use |
|---|---|---|---|
| KHOP small press | small-frame | retail-scale | Sesame oil shops, fresh-oil retail |
| 300 (hot press) | 300 tons | 25 MPa/cm² | Workshop hot pressing |
| 325 (hot press) | 325 tons | 27 MPa/cm² | Workshop hot pressing, most popular |
| 355 (cold press) | 370 tons | 31 MPa/cm² | Entry cold press |
| 400 (cold press) | 410 tons | 34 MPa/cm² | Mid cold press |
| 426 (cold press) | 500 tons | 42 MPa/cm² | Higher-yield cold press |
| 480 (cold press) | 600 tons | 50 MPa/cm² | Industrial cold press |
| 500 (cold press) | 630 tons | 53 MPa/cm² | Top industrial cold press |
The 100 kg batch trap
A common spec-sheet claim is “390 mm chamber = 100 kg per batch.” Treat that as the theoretical maximum, not your working batch. In real professional production the practical charge is smaller, because you need room to load, to let oil drain and to unload the cake cleanly, and because over-packing the barrel lowers cake surface pressure and hurts yield. When you compare machines, ask for the realistic working batch and cycle time, not just the headline chamber rating — that is the number that predicts your daily output.
So what actually determines yield?
Pressing force is necessary but it is not the whole story. Real oil yield depends on cake surface pressure for the material you press, how well the seed is cleaned and (for hot pressing) cooked, the moisture content, and a steady, held pressure cycle rather than a quick squeeze. A well-matched 325 will out-yield a poorly run larger machine on the right material. The takeaway: a professional press is not about who prints the highest MPa — it is about matching tonnage and surface pressure to your seed and running a proper cycle.
How to read a spec sheet, quickly
Skim the MPa — it should be around 60, and that is all it needs to be. Then look at tonnage to place the machine’s size class, and cake surface pressure to judge how well it will press your specific material: higher surface pressure for hard kernels and dry cakes, moderate for soft seeds like sesame. Finally, confirm the realistic batch size and cycle time. Match those to your oilseed and your target daily output, and the right model usually picks itself.
FAQ
Is a higher MPa machine better?
Not on its own. Almost all hydraulic oil presses run at around 60 MPa, so MPa rarely separates models. Look at tonnage and cake surface pressure instead.
What is the difference between tonnage and cake surface pressure?
Tonnage is the total force the machine applies; cake surface pressure is how much of that force lands on the seed cake per cm². The same tonnage on a smaller barrel gives higher surface pressure, which presses harder material more effectively.
Why do two gauges show different pressures?
Many presses use a dual-pressure system — a lower setting (~55 MPa) to start the cycle gently and a high setting (~60 MPa) to finish. It is normal and helps the machine hold full pressure safely.
Can the machine really press 100 kg per batch?
That is usually the theoretical maximum. Real working batches are smaller to allow loading, oil drainage and cake unloading, and to keep surface pressure high. Ask the supplier for the realistic batch and cycle time.
Which number should I focus on when buying?
Confirm MPa is around 60, use tonnage to gauge the machine class, and use cake surface pressure to match the press to your material. Then check the realistic batch size and cycle time.
Tell us your oilseed and we’ll match the numbers
Shengshi Hecheng builds hydraulic oil presses across the full range — small Korean-type shop machines, 300/325 hot-press workhorses and 355–500 industrial cold-press units. Send us your oilseed, your target daily output and whether you are hot or cold pressing, and we’ll recommend the tonnage and cake surface pressure that fit — and tell you plainly which spec-sheet numbers matter for your case and which to ignore.
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