There are two types of marble rulers: marble rulers and I-shaped marble rulers, which are mainly used to measure the straightness and flatness of workpieces and equipment installation. It can also be used to check the flatness and straightness of machine tool worktables, guide rails, and work. Suitable for industrial production and laboratory measurement work.

The main mineral components of granite are trace amounts of magnetite, with a black color and structure. After billions of years of aging, the texture is uniform, the stability is good, the strength is high, and it can be maintained under heavy loads. The marble ruler is made from underground rock layers, and after billions of years of natural aging, its shape is extremely stable, without worrying about deformation due to conventional temperature differences. The marble ruler has undergone rigorous physical testing and selection of granite material, which has fine crystallization and a hard texture. Due to its non-metallic nature, granite has no magnetic reaction and no plastic deformation. Therefore, it has good accuracy retention.

Testing method for straightness of marble ruler

Verticality of the side of the marble ruler to the working surface

Place the marble ruler on a flat surface and align the dial gauge seat with a division value of 0.001mm through a standard round rod on a standard right angle ruler. Then, in the same way, place the dial gauge holder tightly against one side of the marble ruler, and the reading of the dial gauge is the perpendicularity error of that side. Similarly, detect the perpendicularity error of the other side and take the larger error value

Parallel marble ruler contact point area ratio

Apply display agent to the working surface of the inspected marble ruler, and grind it onto a cast iron flat plate or marble ruler with an accuracy not lower than its precision. Clearly display the contact points on the working surface of the inspected marble ruler. Then use a transparent thin plate (such as a glass plate) with 200 small squares of 2.5mm x 2.5mm engraved within a range of 50mm x 25mm, and place it at any position on the working surface of the inspected marble ruler. Observe the proportion of the area containing contact points in each square in sequence (in units of 1/10). Calculate the sum of the above ratios and divide by 2 to obtain the ratio of the contact point area of the detected area.

Parallel marble rulers are supported by equal height blocks at the standard support marks 2L/9 from both ends of the marble ruler, and appropriate inspection bridge slabs are selected based on the length of the working surface of the marble ruler (generally 8-10 steps, with a span between 50 and 500mm); Then place the bridge deck on one end of the marble ruler and fix the reflector or level on the bridge deck; The bridge deck is gradually moved from one end of the marble ruler to the other end according to the span, and the reading at that position is taken from an autocollimator with a scale of 1 "(or 0.005mm/m) or an electronic level with a scale of 0.001mm/m (a composite level with a scale of 0.01mm/m can be used for a first level marble ruler with a working face length greater than 500mm, and a frame level with a scale of 0.02mm/m can be used for a second level marble ruler) for each span moved; The difference between its large and small values is the straightness error of the marble ruler working face. The straightness error of any 200mm on the working surface can be determined by selecting 50mm or 100mm bridge slabs and inspecting them within any 200mm using the above method.

The parallelism between the upper and lower working surfaces of the parallel marble ruler, as well as the parallelism between the working surface and the lower support surface

When a suitable flat plate is not available, it is allowed to place the side of the marble ruler on a supporting surface and measure the height difference of the marble ruler using a lever micrometer with a division value of 0.002mm or a gauge with a division value of 0.002mm.