Breakout force is how hard the machine can push the bucket teeth through material.
It's the spec that determines whether an excavator digs hard clay and hardpan or bounces off it — and it's frequently overlooked in favor of dig depth and tonnage.
A machine with plenty of depth but insufficient breakout force is frustrating in hard ground. It'll get there eventually, slowly.
Two Different Forces
Manufacturers publish two, and they mean different things.
Bucket breakout force (bucket curl force). Generated by the bucket cylinder curling the bucket. The higher of the two numbers, and it's what does the work when you're digging into a face or a bank — the initial penetration.
Arm force (dipper/stick force). Generated by the arm cylinder pulling the arm inward. Lower, but it's what pulls the bucket through material once it's in the cut, and what matters for long sweeping passes.
Both matter, for different parts of the digging cycle. A machine with strong bucket force and weak arm force penetrates well but drags poorly.
Units are typically pounds-force (lbf) or kilonewtons (kN).
What Drives It
Cylinder size and hydraulic pressure. Force is pressure times cylinder area. Bigger cylinders and higher system pressure produce more force.
Geometry. The mechanical advantage of the linkage. Manufacturers optimize this, and it's why two machines with similar cylinders can differ.
Machine weight. Not directly — but a machine that can generate more force than it weighs enough to resist just pushes itself around. Force and weight have to be matched.
Where It Matters
Hard clay and hardpan. The most common real-world test.
Rocky and stony ground. Penetration through and around rock.
Frozen ground. Winter work.
Compacted fill. Old road base, construction fill, and anything that's been driven on for years.
Root-bound soil. Cutting through root mass.
Where it matters less: loose soil, sand, sandy loam, and already-disturbed material. In easy digging, most machines in a class perform similarly and depth and reach dominate.
The Long Arm Trade-Off
Worth knowing when you're spec'ing.
A long-arm configuration adds dig depth and reach — and typically reduces breakout force, because you've increased the lever arm the cylinders are working against.
If you need depth, that's the trade. If you dig hard material, a standard arm with more force may serve you better than a long arm you can't push through the ground.
Comparing Machines
Compare within class. A 5-ton machine will out-dig a 2-ton machine; that's not informative.
Compare both numbers — bucket and arm force. A machine strong in one and weak in the other digs unevenly.
Ask what configuration the figure is for. Standard vs. long arm, and what bucket.
Consider it alongside weight. Force without the weight to resist it means the machine lifts itself instead of digging.
Bucket Selection Affects Digging Too
Breakout force is the machine's contribution. The bucket is the other half.
Narrower buckets concentrate force on less material — they penetrate hard ground far better than wide ones. If you're struggling in hard material, a narrower bucket often helps more than a bigger machine.
Tooth condition matters. Worn, rounded teeth dramatically reduce effective penetration. Sharp teeth are the cheapest performance upgrade available.
Tooth style — penetration teeth for hard digging, general-purpose for mixed work.
Bucket type — a digging bucket penetrates; a grading bucket doesn't and isn't meant to.
FAQ
Which number matters more, bucket or arm force?
Bucket force for initial penetration into a face. Arm force for pulling through the cut. Both matter; look at both.
Is more always better?
Within reason. Force has to be matched to machine weight — an over-powered machine pushes itself around instead of digging.
Does a long arm reduce it?
Typically yes. You trade force for reach.
How do I compare across brands?
Same class, same configuration, both figures. Units should be consistent — watch for lbf vs. kN.
My machine won't dig hard clay. Is breakout force the problem?
Possibly. Check bucket width and tooth condition first — a narrower bucket and sharp teeth frequently solve it without a bigger machine.
What about ripper attachments?
A ripper tooth concentrates all the force on a single point, which penetrates material a bucket can't. Useful in hardpan, frozen ground, and light rock.
Does this apply to mini skid steers?
Loaders publish breakout force too, though it functions differently — it's about curling a bucket full of material rather than penetrating a face.