ʻO ke kuʻi ʻana i lokoke kalaiwa anaʻO ia ka paio ma waena o ʻelua metala o ka haku mele ʻokoʻa a me nā waiwai (alloys), ma waena o ka metala palupalu (mea hana) a me ka metala paʻakikī (make). Inā ʻaʻohe lubrication, ʻo ia ka friction pili o ʻelua ʻano kiʻi ʻoniʻoni metala ʻili; Ma lalo o ke kūlana lubrication, ʻo ka friction pili ma waena o ke kiʻi oxide ma nā ʻaoʻao metala ʻelua a me ka lubricating medium, a me ka friction ma waena o ka ʻili o ka papa o loko o ka mea hana, ʻaʻole i hoʻokahe ʻia a loaʻa ka ikaika adsorption nui. a ke piʻi aʻe nei ke kuʻekuʻe ma waena o ka lubricating medium a me ka ʻili o ka make a me ka friction maoli (contact).

Ma muli o nā hiʻohiʻona friction ma waena o ka blank a me ka ili hoʻopili make i kakaʻina forging, e loaʻa nā hopena i lalo:
(1) Piʻi ka ikaika deformation e 10% ma muli o ka friction, a piʻi ka hoʻohana ʻana i ka ikehu e like me ia;
(2) ʻO ka friction ke alakaʻi i ka deformation uneven o forgings, no laila ʻaʻole like ke ʻano o ka palaoa kūloko a me ka hana ʻana, a emi ka maikaʻi o ka ʻili;
(3) ʻO ka friction ke alakaʻi i ka hōʻemi ʻana o ke ʻano geometric a me ka pololei o ka dimensional o ka forgings, kahi e alakaʻi ai i ka ʻōpala o nā forgings ke hoʻopiha ʻole ʻia nā forgings;
(4) ʻo ke kuʻekuʻe e alakaʻi i ka ʻaʻahu ʻino ʻana o ka make a pōkole kona ola;
(5) ʻO ka hoʻonui ʻana i ke kūpaʻa kūloko kūloko o ka lua hiki ke hana i ka lua paʻakikī e hoʻopiha i ka metala me ka mālie a hoʻemi i ka helu hōʻole.
Hiki ke ʻike ʻia ʻo friction he pahi kaua ʻelua i kahana kalai, nona nā pono a me nā hemahema. No laila, pono e hoʻomalu pono ʻia ka friction i ka hana forging e hōʻoia i ka hana forging maʻamau.