Mechanical portable measuring instrument

A mechanical portable measuring instrument is technically characterized in that the measuring instrument comprises a supporting device, a positioning device and a measuring device, a linear guide rail pair 3 is mounted on a base 4 of the supporting device, and four adjusting nuts 1 are mounted on the lower end of the base 4; the positioning device comprises a positioning sliding block 8, four rail bearings 5 mounted at the bottom of the positioning sliding block 8 ensure the positioning sliding block 8 to move stably along the linear guide rail pair, a positioning base body 7 and two supporting base bodies 6 are mounted on the positioning sliding block 8, the measured piece can be radially positioned by a supporting bearing 9 and a positioning bearing 22; a sliding measuring base 18 of the measuring device can move along the oblique dovetail groove of an adjusting base 21 for adjusting the upper and lower measuring positions of a bracket body 14, a fixed measuring head 11 of the bracket body 14 is positioned