Kev taw qhia ntawm cov hniav thoob excavator
Cov hniav thoob ntawm cov excavators yog cov khoom siv tseem ceeb ntawm

cov khawb av. Lawv zoo ib yam li cov hniav tib neeg. Lawv yog

cov hniav sib xyaw ua ke uas muaj lub rooj zaum hniav thiab ib lub hniav

lub hau, uas txuas nrog los ntawm ib lub pin shaft. Txij li thaum qhov hnav tawm

ntawm cov hniav thoob yog lub hau hniav, tsuas yog hloov lub hau.