Classification of Fits

Classification of Fits Points : Asa Classification of Fits 1. Loose fit (class 1) large allowance Loose fit give for extensive freedom with embraces definite fit where correctness is not essential, for example machined fits of agriculture and mining machinery. Controlling device for textile, marine work, rubber, candy with bread machinery, common machinery of a like grade several ordinance materials. 2. Free fit (class 2) liberal allowance It is planned for operation fits by speeds of 6f.600 r.p.m. or above with journal pressure of 40 kg/km2 or over for example engines, dynamos, several machine tool parts with various automotive parts. 3. Medium fit (class 3) medium allowance Medium fit is working for running fits, below 600 r.p.m. and with journal pressure below 40 kg/cm2, also for sliding fits with other extra accurate machine tools with automotive parts. 4. Snug fit (class 4) Zero Allowance Sung fit is the adjoining fit that can be assemble through hand and require work of extensive precision. It must be used where no traceable shake is allowable and where moving parts are not intended to move freely below load. 5. Wiring fit (class 5) zero to negative allowance Wiring fit is also identified as a “trunking fit” with it is practically metal to metal. Assembly is generally selective and not identical. 6. Light fit (class 6) slight negative allowance Light fit is necessary to collect these fits, with element are extra or less eternally assembled, for example the fixed ends of studs of pulleys, gears, rocker arms etc and these fits are use for drive fits in thin section or extremely long fits in other sections rocker arms and so on. 7. Medium force fir (class 7) negative allowance Extensive pressured is necessary to assemble these fits’ with parts are considered stable assembled. These fits are use in fastening car wheels, locomotive wheels, armatures of dynamos with motors and crank disc to their axle or shafts are also use for shrink fits on medium section or long fits. 8. Heavy force and shrink fit (class 8) considerable negative allowance This fit is use for steel holes where the metal able to be extremely stressed with no above its elastic limit. These fits reason extreme stress for cast iron holes: Shrink fits are use where heavy force it’s practical, as no locomotive wheel tires, heavy crank discs of large engines and so on.