Ukuphotha kwensimbi, okubuye kwaziwe ngokuthi ukuphotha noma ukuphotha, kuyinqubo yokusebenza kwensimbi ehlanganisa ukuzungezisa idiski yensimbi noma ishubhu ku-lathe kuyilapho ufaka ingcindezi ngethuluzi ukuyilolonga ibe yifomu oyifunayo.Inqubo ivamise ukusetshenziselwa ukwakha ubujamo obuyisilinda noma obuyindilinga njengezitsha, amavase, nezibani zezibani, kanye namajiyometri ayinkimbinkimbi njengama-hemispheres nama-paraboloid.
Ngesikhathi sokuphotha kwensimbi, idiski yensimbi noma ishubhu iboshelwa ku-lathe futhi ijikeleziswa ngesivinini esikhulu.Ithuluzi, elibizwa ngokuthi i-spinner, libe selicindezelwa phezu kwensimbi, liyenze igeleze futhi ithathe isimo sethuluzi.I-spinner ingabamba ngesandla noma ifakwe ku-lathe.Inqubo iphindaphindwa izikhathi eziningi, futhi umumo ulungiswa kancane kancane ngephasi ngayinye kuze kube yilapho kutholakala ifomu lokugcina.
Ukuphotha kwensimbi kungenziwa kusetshenziswa izinhlobonhlobo zezinsimbi, okuhlanganisa i-aluminium, ithusi, ithusi, insimbi engagqwali, ne-titanium.Ivamise ukusetshenziselwa ukwenziwa kwezingxenye zezimboni ze-aerospace, izimoto, nezibani, kanye nezinjongo zokuhlobisa nezobuciko.