Tig yog txheej txheem machining uas lub cuab yeej txiav tshem tawm cov khoom siv los ntawm kev sib hloov ua haujlwm; nws yog ib daim ntawv ntawm tshuab dhos machining. Cov txheej txheem cia siab rau kev sib koom ua ke ntawm qhov kev sib hloov ntawm lub workpiece thiab txoj kab los yog curvilinear txav ntawm cov cuab yeej txiav. Los ntawm kev sib pauv hauv cov cuab yeej xws li laum cov khoom, cov khoom sib tsoo, lossis cov reamers, kev ua haujlwm zoo li drilling thiab counterboring tuaj yeem ua tau. Tig yog tsim rau kev tsim khoom xws li shafts, discs, thiab tes tsho, thiab muaj peev xwm ntawm machining nto ntawm kiv puag ncig-suav nrog rau sab hauv thiab sab nraud cylindrical nto, kawg ntsej muag, conical nto, thiab threads. Raws li machining precision, cov txheej txheem yog categorized rau hauv ntxhib tig (IT11 qib) thiab tiav tiav (IT10–IT7 qib); Cov txheej txheem tshwj xeeb muaj xws li daim iav tig, uas ua tiav qhov roughness qhov tseem ceeb ntawm Ra 0.04-0.01 μm, thiab zoo nkauj tig, uas tsim cov qauv ornamental. Cov txiaj ntsig tseem ceeb ntawm cov txheej txheem suav nrog qhov tseeb ntawm qhov chaw siab, kev txiav txim siab ruaj khov, tsim nyog rau kev ua tiav cov hlau tsis yog{11}}ferrous hlau, thiab cov cuab yeej geometry yooj yim.
Kev hloov pauv ntawm lub tshuab dhos pib nrog tib neeg thaum ub - cov khoom siv fais fab. Xyoo 1797, tus kws tshaj lij Askiv Askiv Henry Maudslay tau tsim lub hauv paus rau lub tshuab dhos niaj hnub los ntawm kev tsim cov hlau lead- ntsia hlau- tsav tsheb, thaum xyoo 1845, tus neeg tsim khoom Asmeskas Stephen Fitch tau tsim lub tshuab dhos turret, txhim kho lub peev xwm automation. Hluav taws xob lub cev muaj zog tau nthuav dav nyob rau hauv lub xyoo pua 20th, ua raws li kev nce qib ntawm cov kev pab cuam -tswj technology nyob rau hauv 1950s thiab kev loj hlob sai ntawm CNC (Computer Numerical Control) lathes nyob rau hauv 1970s, tag nrho cov uas tau tsav nruam kev txhim kho nyob rau hauv machining precision thiab efficiency.
