Ọzọkwa, ọrụ anyị na-enye njikwa mgbawa dị mma iji hụ na a na-egwupụta ya nke ọma, nke na-enweghị nkwụsị. Iwepụ mgbawa dị irè na-egbochi mkpọchi mgbawa, na-ebelata ihe egwu nke mmebi ngwaọrụ na oge nkwụsị. Atụmatụ a na-eme ka arụmọrụ zuru oke nke ihe mgbochi oghere miri emi nke BTA nke ZJ clamp nwere ike ịrụ ọrụ, na-eme ka ọ dị mma maka ọrụ igwe dị elu.
Ọ na-eji agụba ndị a kpụchara akpụcha nke e si mba ọzọ ebubata, nke nwere arụmọrụ nhazi dị elu, mgbanwe agụba dị mma, ojiji ogologo oge nke ahụ ịkpụcha ihe, obere oriri ngwaọrụ na njirimara ndị ọzọ. Ọ nwere ike ịhazi ígwè carbon, ígwè alloy siri ike, ígwè anaghị agba nchara, wdg.
Otu n'ime ihe ndị pụtara ìhè nke ngwaahịa a bụ sistemụ ịgba mmiri BTA (Boring and Trepanning Association), nke na-eme ka a hụ na a na-agba mmiri nke ọma ebe a na-ebelata ịma jijiji ma na-eme ka mma oghere dịkwuo mma. Nke a na-eme ka ọ dị mma maka ngwa ndị chọrọ ezigbo nkenke, dịka ụlọ ọrụ ụgbọ elu na ụgbọ ala.
Tinyere nke a, igwe ZJ nke nwere ihe mkpuchi miri emi nke BTA nke a na-akpọ ZJ na-enyekwa ezigbo mmiri oyi iji hụ na okpomọkụ na-agbaze nke ọma n'oge a na-egwu olulu. Njirimara a na-egbochi oke okpomọkụ ma na-agbatị ndụ ngwaọrụ, na-ebelata ọnụ ahịa ma na-eme ka arụmọrụ dịkwuo mma.
| Nkọwapụta igwu mmiri | Ejiri osisi arbor mee ya | Nkọwapụta igwu mmiri | Ejiri osisi arbor mee ya |
| Φ28-29.9 | Φ25 | Φ60-69.9 | Φ56 |
| Φ30-34.9 | Φ27 | Φ70-74.9 | Φ65 |
| Φ35-39.9 | Φ30 | Φ75-84.9 | Φ70 |
| Φ40-44.9 | Φ35 | Φ85-104.9 | Φ80 |
| Φ45-49.9 | Φ40 | Φ105-150 | Φ100 |
| Φ50-59.9 | Φ43 |
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