KIT Roughness samples "CALIBER" 1935

All surfaces around us have various roughnesses, which are divided into 14 classes, depending on the height of the surface microprofile.

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KIT Roughness samples "CALIBER" 1935
All surfaces around us have various roughnesses, which are divided into 14 classes, depending on the height of the surface microprofile.
To quantify roughness, Rz and Ra are used, which are correlated with each other:
Up to grade 6 roughness (including coarser) are correlated in a proportion of about 4: 1;
For roughness more (coarser) roughness, a 5: 1 ratio applies.
For quantitative control of roughness, profilometers and profilographs are used, which provide an error of 1 ... 5% (workshop and laboratory).
For the qualitative control of roughness in production, measures (samples) of roughness (comparison), rectangles with metal surfaces of the specified roughness are common.
50 years ago, roughness measures were made in the form of metal rectangles from various materials (cast iron, aluminum, copper) with control, processed accordingly (turning, grinding flat, grinding cylindrical, milling and others) with different heights of the microprofile (modern Ra and Rz, outdated roughness classes 4 ... 14).
Modern roughness measures are made using the technology of electroforming, when a thin galvanic coating of nickel and / or chromium is applied to the control surface of the plastic plate (formed in thermoplastics using the selected display of the appropriate roughness) (does not distort the pattern on the plastic surface).
Roughness measures are very popular in every production due to their ease of use:
Even an inexperienced worker can accurately distinguish roughness indicators with various machining methods;
The worst roughness (Rz 320 ... 80 microns or 1 ... 3 roughness classes) is obtained after casting and filing)
Rough roughness (Rz 80 ... 10 μm, or 3 ... 6 roughness classes) gives drilling;
Good roughness (Ra1.25 ... 0.32 microns or 7 ... 9 roughness classes) gives a reamer, grinding or scrapping;
Mirror roughness (Ra 0.63 ... 0.16 microns or 8 ... 10 roughness classes) is obtained after polishing or diamond turning;
The best roughness (Rz0.05 μm or 14 roughness class) is obtained after successive stages of grinding, polishing with final super-finish polishing with submicron abrasives.
The use of electroforming significantly reduces the cost of manufacturing roughness measures, but somewhat distorts the pattern of the roughness profile for various materials after various processing operations.
Metrological roughness samples are controlled using profilometers and profilographs.
In the "MICROTECH Museum of Industrial Tools" is a rare collection of roughness samples 1951:
40 roughness samples made of several non-ferrous metals after various machining methods (turning, drilling - reamers, cylindrical milling, face high-speed milling)
Four roughness classes (5 ... 8) for the specified materials with the corresponding technological processing modes.