A precision cleaver scores the glass with a diamond or carbide blade while holding it under slight tension, so the crack runs straight across and leaves a mirror end. A good cleave is required for every fusion splice, mechanical splice and splice-on connector. Bad cleaves show up as chipped edges, lips, hackle or angled faces on the splicer screen and get rejected before arcing.
Third bad cleave in a row, rotate the blade a position and clean the pads before you waste more fiber.
Blade position matters: cleavers have a numbered wheel, and rotating to a fresh position fixes most runs of bad cleaves.
Related terms
Cleave angle
How far a cleaved fiber end deviates from a perfect right angle to the fiber axis, in degrees.
Strip, clean, cleave
The three-step fiber prep routine done before every splice or splice-on connector.
Fusion splice
A permanent joint made by melting two cleaved fiber ends together with an electric arc.
Fusion splicer
The instrument that aligns two fiber ends, welds them with an electric arc and estimates the splice loss.