Why second & Fourth angle projection does not exist? ( only 1 st angle & 3 rd angle projection exists) ?

Answer 1

They exist, they are just not practical for visualizing 3D geometry.

Most people have trouble with 1st and 3rd angle (2nd and 4th would be front and back "views" given a "side" projection).

Answer 2

in the beginning of the 2d and 4th and 5th and 6th could all be interchanged with the 1st ..the assumption of view is consistent with convention that we've desperate the superb,front,returned,left,proper,superb and backside. because of the fact that those are in basic terms relative to the object and to no longer the drawing you may still as easily carry out an isometric view on any attitude with an analogous accuracy or for that count all 6 attitude named perspectives. the universal way of the clothier seeing the section is putting on a table in its frequent resting state. very frequently FEA (finite factor prognosis) is utilized to an outstanding style, which by making use of the way makes use of an analogous 6 named perspectives. understanding which way is up or particularly drawing the section in its meant place of use is lots greater appropriate as there is way less confusion in the assembly of complicated machines. even although if we took the dis-ambiguous piece like a pencil the superb view isn't important.on the different hand to make cube that's paramount for the CNC operator to maintain on with the 6 edge rule...because of the fact the onset of excellent modeling the are many greater view purposes rather in the hollow good physique varieties or in our case the view from interior the piece finding out at an interference in good condition. solid luck in the Craft ....Merry Christmas....From the E..