Installation of M20 foundation bolts requires precision and adherence to strict guidelines. The bolts must be positioned accurately to ensure proper alignment with the equipment they will secure. After the concrete sets, the bolt's threaded end is exposed, allowing for the attachment of machinery or structural elements through nuts and washers After the concrete sets, the bolt's threaded end is exposed, allowing for the attachment of machinery or structural elements through nuts and washers
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Figure 1: O.D. (outside diameter) wall material
The shaft on which the oil seal is mounted has to be ground to a rough surface finish. The shaft also should be hardened to prevent grooves forming on the shaft when the pressure is exerted by the spring on the seal. The area where the seal is fitted also has to be ground to prevent grooves that tend to wear out the lip of the oil seal faster than normal.
As type C with dust lip
The perfect remedy for this is to use oil seal materials that are rated for the temperature of your application. Also, ensure that the elastomer is free from volatile constituents like waxes, plasticizers, etc.
Metal cased design
Oil Seal in Motor:

For a more detailed discussion of seal types and type codes, please see the following:
Oil seals in any size, material or quantity
If you follow the above instructions, the oil seals should work properly. Also watch the video below for an example of the installation process.