Ko te whakakoi he tukanga whakaoti tika e whakamahia ana i roto i te hangarau huri hei whakapai ake i te tika o ngā āhuatanga me te kounga o te mata o ngā poka mīhini. I roto i te tukanga, ka kawea ngā kōhatu whakakoi ki roto i te pa o te mata o te mea mahi. Mā tēnei taunekeneke ka tangohia ngā wāhi teitei moroiti—e mōhiotia ana ko ngā pūwāhi pokanoa—i waenganui i te mata tapahi o te kōhatu whakakoi me te mata o roto o te mea mahi. Mā te tango rauemi tonu me te pumau, ka āta rite haere te mata, ka hua ake he whakaoti tino tika me te maeneene e hiahiatia whānuitia ana i roto i ngā tono hangarau tika.
Ko ngā kōhatu whakakoi, e kiia ana ko ngā kōhatu hinu i roto i ngā mahi ahumahi, he mea hanga mai i ngā momo rauemi whakakoi i runga i ngā whakaritenga miihini. Ko ngā mea whakakoi e whakamahia whānuitia ana ko te taimana, te nitride boron cubic (CBN), te alumina kua whakakotahitia (te waikura konumohe), me te karawaka silicon. Ka tīpakohia ia rauemi i runga i te pakeke o te mea mahi, te mutunga o te mata e hiahiatia ana, me te āheinga miihini o te rauemi e tukatukahia ana. Ko ngā mea whakakoi tino pai pēnei i te taimana me te CBN e whakamahia ana mō ngā tono pakeke-teitei, tino tika rānei, ko te alumina me te karawaka silicon e whakamahia whānuitia ana mō ngā whakaotinga whānui.
He maha ngā painga matua o te tukanga whakakoi. He tino tika te mahi miihini, ā, he tino pai te kounga o te whakaotinga o te mata. He pai mō te whānuitanga o ngā rauemi me ngā āhuahanga, inā koa ngā mata porotaka o roto. He iti noa te wā e hiahiatia ana mō te tango rauemi ki te whakataurite ki ētahi atu tikanga huri, ā, he kaha tōna kaha ki te whakatika i ngā hapa āhuahanga o te kōhao pērā i te whakapiko, te rerekētanga porowhita, me te ngaru o te mata. Nā ēnei āhuatanga ka waiho te whakakoi hei tukanga whakaotinga nui i roto i te hanga tino tika.
I tīmata te whanaketanga o te hangarau whakakoi i te tīmatanga o te rautau 20 i te Hononga o Amerika, i reira ngā kamupene pēnei i a Barnes me Micromatic i whai wāhi paionia. I tere te whakamahi i te hangarau i roto i ngā whenua ahumahi tae atu ki Tiamana, te United Kingdom, me Hapani, inā koa mō ngā tono whakaoti rango miihini. I te tau 1924, i whakaurua mai ngā tikanga whakawhānui waipēhi mō te whakakoi i ngā kōhatu, e āhei ai te kaha tango rauemi me te whakapai ake i te ngāwari o te tukanga. I taua wā anō, ka tīmata te puta mai o ngā pūnaha ine aunoa, e tohu ana i te wāhanga wawe o te aunoatanga i roto i te hangarau whakakoi.
I te tau 1938, i puta ake ētahi atu whakapainga me te whanaketanga o ngā pūnaha whakahaere whāngai matatau ake, i taea ai te whakahaere pai ake i te tere whakawhanui o te kōhatu me te utu mō te kakahu o te taputapu. Nā tēnei i tino whakapai ake te ōritetanga me te tika o te mīhini. I te tau 1952, i whakaurua mai ngā pūnaha whakawhanui hiko kua utua katoatia, e tohu ana i tētahi atu taahiraa nui ki te aunoatanga, te tika ake, me te pumau o te tukanga i roto i ngā mahi whakakoi ahumahi.
Ahakoa te haere tonu o te ahunga whakamua o te hangarau, kei te noho tonu te āputa i waenga i ngā taputapu whakakoi matatau o te motu me te ao i roto i ētahi wāhanga. Kei roto i ēnei ko ngā pūnaha whakamatao me te tātari, te tika o te whakahaere pāmahana, me te hoahoa taputapu tino tika. He pānga tika ēnei āhuatanga ki te kounga o te mata, te roa o te ora o ngā taputapu, me te pumau o te miihini whānui, ā, kei te noho tonu hei wāhanga matua mō te whanaketanga tonu i roto i te umanga.
He whānui te whakamahinga o te whakakoi i ngā rāngai ahumahi maha, tae atu ki te hanga waka, ngā tarakihana me ngā motopaika, te hangarau moana me te rererangi, ngā taputapu mīhini, me te hanga taputapu hōia. Ko ngā whakamahinga noa ko ngā raina rango miihini, ngā poka porowhita me te tuku tika, ngā kōhao rango waipēhi me te hau, ngā whare pouaka me ngā whare motuka, ngā tinana papu, tae atu ki ngā oko ātete-kakahu tino tika pērā i ngā oko pū. Me whai tika te āhua o ēnei wāhanga katoa, me te tino pai o te mata.
I ngā tau tata nei, kua noho te whanaketanga o ngā kōhatu whakakoi hei kaupapa matua mō te whanaketanga hangarau. Nā te pikinga ake o te whakamahinga o ngā taimana hangai me ngā mea whakakoi CBN kua tino pai ake te mahi me te whai huatanga. E whakaatu ana ngā raraunga ahumahi neke atu i te 92% o ngā tukanga whakakoi hou e whakawhirinaki ana ki ngā kōhatu whakakoi taimana, ki ngā kōhatu whakakoi CBN rānei, e whakaatu ana i te nekehanga mārama ki ngā rauemi mahi teitei.
He maha ngā painga nui o ngā kōhatu whakakoi tino kaha, tae atu ki te roa o te ora mahi, te iti o te utu tukatuka whānui, te iti o te rakuraku mata, te iti o te whakaputanga wera huri, me ngā tauira mata whakawhiti-whatu pumau me te ōrite. Nā ēnei painga ka tino pai mō ngā tono hangahanga teitei e tino hiahiatia ana te ōritetanga me te tika.
He rerekē anō hoki te hanga o ngā kōhatu whakakoi i runga i te pūnaha whakakoi. Ko ngā kōhatu tino whakakoi pērā i te taimana me te CBN ka hangaia mā te whakamahi i te tukanga whakakoi matao, te whakakoi wera rānei. Ko te whakakoi matao ka whakamahia ngā pokepoke whakarewa i raro i te pēhanga teitei mai i te 400 ki te 500 MPa, ka roa te ora o te pokepoke me te pumau o te hanganga. Ko te whakakoi wera, i tetahi atu ringa, ka whakamahia ngā pokepoke karāti i raro i te pēhanga iti iho i te 15 ki te 20 MPa, me ngā pāmahana whakakoi iti iho me te tiaki pai ake i te kaha whakakoi, ahakoa he nui ake te whakamahinga o te pokepoke.
Ko ngā kōhatu whakakoi alumina me te silicon carbide tuku iho i roto i ngā momo tuatahi i whakawhanakehia, ā, kei te whakamahia whānuitia tonutia i ēnei rā. Heoi, he iti iho ngā herenga o ēnei pūnaha whakakoi-kotahi mō te urutau me te mahi, inā koa i te tukatuka i ngā rauemi uaua ki te mīhini. Ki te whakatauritea ki ngā taputapu whakakoi-kotahi, he iti ake te ngāwari me te whai hua i roto i ngā tono matatau.
Me whiriwhiri ngā kōhatu whakakoi i runga i ngā āhuatanga tukatuka motuhake. Mō ngā pane whakakoi e mānu ana, me whakarite te roa o te kōhatu kia pumau te tukatuka me te arataki tika i roto i te poka. Mō ngā pane whakakoi āhua-mānu, pakari rānei, inā koa i roto i ngā tono poka poto, he iti ake te hiranga o te arataki-ake, e āhei ai te whakamahi i ngā kōhatu poto. I roto i te miihini poka matapo, me teitei ake te tika o te tauutuutu, ā, me āta tupato kia kore ai e pā te pānga ki te mata o te pito ka kino pea te kōhatu. I roto i ēnei take, ko te roa o te kōhatu he mea hanga kia tata ki te whā ngā wā o te whānui o te whiu mangere.
Haunga te roa, me whiriwhiri te maha me te whānui o ngā kōhatu whakakoi kia rite ki te pakari o te taputapu me te pumau o te tukanga. I roto i ngā rohe miihini e whakaaetia ana, mā te whakanui ake i te whānui o te kōhatu ka taea te whakapai ake i te pai o te tapahi me te ōritetanga o te mata. Ko ētahi atu mea matua hei whiriwhiri ko te rauemi o te mea mahi, te whānui me te hohonu o te poka, te whakaotinga mata e hiahiatia ana, me ngā āhuatanga o te mīhini whakakoi e whakamahia ana. Mā ēnei tawhā ka whakatau ngātahi i te mahi whānui me te whai huatanga o te tukanga whakakoi.