Cutting system
Rotary heads
Three round heads on a plate, each with a cutter turning under a slotted cap. The heads float independently and the plate floats under them, which is the whole idea: rather than your hand hunting for the right angle, the appliance keeps finding it as you move. Everything this system is good at and everything it cannot do follows from that one arrangement.
Cross-section, not to scale
The mechanism
How it cuts
- Each head is a slotted cap sitting over a circular cutter that spins underneath it.
- Hair drops through a slot and is cut against the inside edge of the cap, so the thickness of the cap decides how close the cut can be.
- The heads pivot separately on a plate that pivots as well, spreading pressure across three points instead of concentrating it under one.
- The motion is circular. Small overlapping circles, worked slowly, rather than strokes in one direction.
What follows for a face
Consequences
- A jaw with real shape in it
- The floating heads follow the curve without any decision from the hand holding them, which is why this arrangement is the usual first suggestion for a face that is not flat anywhere.
- Hair growing several ways at once
- A circular motion meets hair from every side in turn, so a patch that changes direction halfway does not need a change of technique to go with it.
- Drawing an edge along a cheek
- The heads are round and the plate is wide, and no part of that geometry produces a straight line. It is why these appliances almost all carry a separate pop-up trimmer bolted to the back.
- Hair that has been left a week
- Slots accept hair up to a certain length. Past it, hair lies across the slots instead of dropping into them, and the appliance buffs the surface without cutting much of anything.
- A scalp
- The same floating action that suits a jaw suits a skull, and several appliances quoted on this site are sold for both. The difference is time under the hand rather than a difference in method.
Zones it suits
Keeping it working
- The cap and the cutter under it are a matched pair. They wear together and the maker sells them together, which is why a single replacement cutter is rarely offered on its own.
- Hair packs under the caps rather than falling out of them. Whatever the listing says about rinsing, the heads come off at intervals and the dust gets tipped out.
- Reassemble each cutter into the cap it came out of. Mixing them across three heads is a common way to make a working appliance feel blunt.
Common errors
Pressing to get closer
The floating plate bottoms out, the heads stop following the face, and the pressure lands on skin instead of on hair.
Let the weight of the appliance do it and make a second pass instead of a harder one.
Working in straight strokes
Round heads dragged in a line meet each hair from one direction only, and everything lying the other way survives the pass.
Work in small circles and let the overlap catch what a single direction misses.
Starting on a long beard
Hair bridges the slots, the caps ride across the surface of it, and a long session produces nothing but a slightly flattened beard.
Take the length down with a comb and a trimmer first, then let the heads do the last part.
Shuffling cutters between caps
Each pair has worn into itself, and a swapped pair cuts worse than either did before the swap.
Clean one head at a time and put each cutter back where it came from.
Cautions
- StopTwo things mean stopping rather than taking one more pass. Skin that is broken, raised, sore or already inflamed, which is a doctor’s call and not something to draw a blade across. And a line so far out of true that a shorter setting only chases it, which is a barber’s. Neither of them improves by carrying on.
- StopA shaver or a trimmer belongs to one person. Shaving injures skin at a scale too small to notice, and whatever sits on the blade goes into that injury.
- NoteReplacement foils, cutters and heads come from the list printed in the appliance’s own documentation. A part that seats is not the same as a part the maker names.
Where to look next
- Rotary Shavers
The appliances built on this arrangement, including the ones sold for a head as well as a face.
- Foil heads
The other full-face system, and the one that answers the opposite set of questions.
- Cheeks and jawline
The area this geometry was designed around, and where the floating plate earns its keep.
- Neckline
Where hair changing direction stops being an idea and starts being a daily problem.