Take the cage out of a ball bearing and you can fit more balls into the same outline. That single change is the whole of the full complement (also called max type) design, and it is one of the most misunderstood choices in bearing selection — usually reduced to "more balls, more load" without the other half of the sentence.
This article covers what the extra balls actually buy, what they cost, and how to tell which side of the trade your application sits on. The worked example is the DW6, a metric double row angular contact design we developed to a customer drawing.
What the cage is actually for
A cage does not carry load. Its job is to keep the rolling elements apart and evenly spaced. That sounds minor until you remove it.
In a caged bearing, each ball is separated from its neighbours by cage material. Balls only ever touch the raceways. In a full complement bearing, the balls touch each other — and at the contact point between two adjacent balls, the surfaces are moving in opposite directions.
| Caged | Full complement | |
|---|---|---|
| Ball count in a given envelope | Lower — cage occupies space | Highest the geometry allows |
| Ball-to-ball contact | None | Yes, sliding in opposition |
| Static load capacity | Baseline | Higher — load shared over more contacts |
| Radial stiffness | Baseline | Higher |
| Friction and heat at speed | Lower | Higher |
| Practical speed range | Wider | Narrower — moderate speeds |
| Assembly | Standard | Needs a loading route for the balls |
That "sliding in opposition" row is the one people skip. It is the source of every drawback below.
The worked example: 24 balls in a small envelope
The DW6 is a double row, extra-wide, full complement angular contact design. Its published outline is small:
| Item | Value |
|---|---|
| Bore | 9.525 mm (0.3750″) |
| Outside diameter | 26.988 mm (1.0625″) |
| Outer ring width | 27 mm |
| Inner ring width | 30.18 mm |
| Balls | 4.763 mm (3/16″) — 12 per row, 24 total, no cage |
| Rows | 2, angular contact |
Twenty-four balls inside a bearing 27 mm across. A caged version of the same outline would carry noticeably fewer, because the cage needs wall thickness between every pocket and clearance to the ring shoulders. In a small bearing that wall thickness is a large fraction of the available circumference — which is exactly why full complement construction is most attractive at small sizes and least attractive at large ones.
What you gain
Static capacity and stiffness
Load entering the bearing is shared across the balls in the loaded zone. More balls in that zone means more contacts sharing the same force, lower contact stress at each one, and less deflection under load. For a mechanism where the bearing must not move measurably under a heavy but slow load — a linkage, a pivot, a clamping mechanism — that stiffness is often the whole reason for the design.
Envelope efficiency
This is the real driver. Full complement construction is chosen when the outline cannot grow. If you can make the bearing bigger, you generally should — a larger caged bearing will beat a smaller full complement one on almost every metric. Full complement earns its place when the housing is already fixed and the load requirement went up.
What you give up
Speed
At every ball-to-ball contact, two surfaces slide against each other in opposite directions. That is pure sliding friction, not rolling, and it scales with speed. The result is heat generated inside the bearing, in a location that is difficult to cool. This is why full complement designs are specified for slow, oscillating or intermittent motion — control linkages, rocker arms, pivots, adjustment mechanisms — and why a continuously running high-speed application should use a cage.
Predictability of ball behaviour
A cage keeps balls evenly distributed at all times. Without one, the balls are free to bunch up as the bearing turns, particularly under light load or when the load direction reverses. Spacing becomes a consequence of operating conditions rather than a designed-in guarantee.
Assembly complexity
You cannot push a full complement of balls past the ring shoulders — there is no gap left to work with. On the DW6 the solution is machined into the rings: a small, rounded loading notch is ground into both the inner and the outer ring shoulder at one position. The two notches face each other, forming an assembly window through which the balls are loaded, then distributed around the raceways.
Notch geometry is a real design variable, not a detail. A wide slot is easy to load through and takes more of the shoulder away; a small, carefully radiused scoop keeps more of the shoulder intact and disturbs the raceway less. Ours are specified as small-radius scoops.
How to choose
Work through these in order — the first "yes" usually settles it:
- Can the envelope grow? If yes, use a larger caged bearing. Full complement is a solution to a space constraint.
- Is the motion continuous and fast? If yes, use a cage. Ball-to-ball sliding will generate heat you cannot get rid of.
- Is the motion slow, oscillating, or intermittent, under high load? This is full complement territory.
- Is stiffness under static load the governing requirement? Full complement is favoured.
- Does the bearing need to be very quiet at speed? Prefer a cage — uncontrolled ball spacing works against you.
What to send us if you are unsure
The construction choice is usually decided by the application, not by preference. Send outline dimensions plus:
- Speed, and whether motion is continuous, oscillating or intermittent
- Load magnitude and direction — radial, axial, or combined, and whether it reverses
- Duty cycle — how much of the time the bearing actually turns
- Temperature and environment
- Whether the housing envelope is fixed or has room
We review feasibility and propose a construction with the reasoning attached, rather than quoting a catalogue number back at you.
FAQ
Does a full complement bearing really carry more load?
It has higher static load capacity in the same envelope, because more balls share the load. Dynamic rating and service life depend heavily on speed and lubrication, where the cageless design is at a disadvantage.
Why can't full complement bearings run fast?
Adjacent balls touch, and at that contact the two surfaces move in opposite directions. That is sliding friction, and it generates heat inside the bearing that rises with speed.
How do the balls get in without a cage?
Through paired loading notches — small rounded scoops ground into the inner and outer ring shoulders that face each other and form an assembly window.
Do loading notches weaken the bearing?
They remove shoulder material at one position, so notch size and radius are design decisions. A small, well-radiused notch preserves more shoulder and disturbs the raceway less than a wide slot.
Is full complement cheaper because there is no cage?
Not reliably. You save a component but add more balls and a notch-grinding operation. Cost follows the whole process chain, not the parts list.