Device for measuring projection size and drawing line on arc surface

The utility model relates to a device for measuring a projection size and drawing a line on an arc surface. The device comprises a scaleplate, a drawing rod, a positioning rod, sliding blocks and a sleeve, wherein the scaleplate is connected with the drawing rod and the positioning rod respectively by using the sliding blocks and screws; a line drawing pen is fixed on the drawing rod through the sleeve and another screw; and scale lines are formed on the scaleplate and used for reading a distance size between the drawing rod and the positioning rod during measurement of a drawn line. The special point is that the size of the drawn line can be measured by the scales on a line drawing device; during line drawing, an angle between two drawing arms and the size of the drawn line are not changed, so that the line drawing precision is improved; and the end A of the drawing rod 2, the end B of the positioning rod 3 and two ends C and D of the scaleplate 1 can be lengthened by a standby scaleplate 7, the sleeve 5 and the screws 6 according to an actual size of a product, so that the device can be used by engine products in different specifications, and a fixture is universal.