Cast iron tri-square, mainly used for the inspection and scribing of the right-angle of various parts and also used for the perpendicularity measurement of relevant surfaces of parts during the installation and maintenance of equipment.
| Specification (mm) | Perpendicularity Between Adjacent Measuring Surface | Flatness and Straightness of Measuring Surface | Flatness and Straightness of Datum Surface | ||||||
| Accuracy Grade (μm) | |||||||||
| 0 | 1 | 2 | 0 | 1 | 2 | 0 | 1 | 2 | |
| 150×100 | 4 | 8 | 16 | 1.5 | 2.5 | 5 | 2 | 4 | 8 |
| 300×200 | 6 | 11 | 22 | 2 | 4 | 7 | 3 | 6 | 11 |
| 400×300 | 7 | 12 | 25 | 2 | 4 | 8 | 3.5 | 7 | 12 |
| 500×350 | 8 | 15 | 30 | 2.5 | 5 | 10 | 4 | 8 | 15 |
| 630×400 | 9 | 18 | 35 | 3 | 6 | 12 | 4.5 | 9 | 18 |
| 800×500 | 10 | 20 | 40 | 3 | 7 | 14 | 5 | 10 | 20 |
| 1000×630 | 12 | 25 | 50 | 4 | 8 | 16 | 6 | 12 | 25 |
| 1250×800 | 15 | 30 | 60 | 5 | 10 | 20 | 8 | 15 | 30 |
| 1600×1000 | 18 | 38 | 70 | 6 | 12 | 24 | 10 | 18 | 35 |
| 2000×1250 | 22 | 46 | 80 | 8 | 15 | 30 | 12 | 22 | 40 |
| Specification (mm) | Perpendicularity Between Adjacent Measuring Surface | Flatness and Straightness of Measuring Surface | Flatness and Straightness of Datum Surface | ||||||
| Accuracy Grade (μm) | |||||||||
| 0 | 1 | 2 | 0 | 1 | 2 | 0 | 1 | 2 | |
| 150×100 | 4 | 8 | 16 | 1.5 | 2.5 | 5 | 2 | 4 | 8 |
| 300×200 | 6 | 11 | 22 | 2 | 4 | 7 | 3 | 6 | 11 |
| 400×300 | 7 | 12 | 25 | 2 | 4 | 8 | 3.5 | 7 | 12 |
| 500×350 | 8 | 15 | 30 | 2.5 | 5 | 10 | 4 | 8 | 15 |
| 630×400 | 9 | 18 | 35 | 3 | 6 | 12 | 4.5 | 9 | 18 |
| 800×500 | 10 | 20 | 40 | 3 | 7 | 14 | 5 | 10 | 20 |
| 1000×630 | 12 | 25 | 50 | 4 | 8 | 16 | 6 | 12 | 25 |
| 1250×800 | 15 | 30 | 60 | 5 | 10 | 20 | 8 | 15 | 30 |
| 1600×1000 | 18 | 38 | 70 | 6 | 12 | 24 | 10 | 18 | 35 |
| 2000×1250 | 22 | 46 | 80 | 8 | 15 | 30 | 12 | 22 | 40 |
