What are the three types of marking datum?

1, based on two mutually perpendicular planes (or straight lines);

2. Based on two mutually perpendicular center lines;

3, based on a plane and a center line.

According to the drawings and technical requirements, the process of drawing machining boundaries or drawing points and lines as benchmarks on blanks or semi-finished products is called scribing.

The basic requirements of marking are clear and symmetrical lines and accurate size and position. Because the scribing has a certain width, the accuracy is generally required to reach 0.25-0.5 mm It should be noted that the machining accuracy of the workpiece can not be completely determined by scribing, but by measurement during machining.

Extended data:

The main function of the tag

1, to determine the machining allowance of the workpiece, so that the machining has obvious size restrictions.

2. In order to facilitate the clamping of complex workpieces on the machine tool, the correct positioning can be found by marking.

3, can timely find and deal with unqualified blank.

4. When the error of the blank is not big, the method of borrowing and marking can be used to remedy it, so as to improve the qualified rate of the blank.

Marking tools are classified by purpose.

1, benchmark tools, including marking flat plate, square box, V-shaped iron, triangle iron, bending plate (right angle plate) and various indexing heads.

2. Measuring tools, including steel ruler, height ruler, vernier caliper, universal angle ruler, square ruler and steel tape for measuring long dimensions.

3. Drawing tools, including drawing needle, drawing disk, height cursor, drawing gauge, drawing card, leveling ruler, curve board, hammer, sample punch, etc.

4. Auxiliary tools, including pads, jacks, C-shaped chucks and fixtures, as well as wood strips and lead strips that are driven into the holes of workpieces during centering and rounding.

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