Foot screw
Leveling foot or leveling screws serve an exact leveling of an object on the substrate ( measuring pillar , tripod head , bedrock).
Use in measuring instruments
Since a precise horizontal position is often necessary, especially with measuring instruments, they are often used here. To ensure sufficient accuracy and stability, they must be smooth, but have enough friction to prevent unintentional adjustment. In addition, little play and good turning handles (usually knurled screws ) are required.
The most common is the use of three foot screws at a distance of 120 °. With a level in the base of the measuring instrument, they allow leveling in 2 or (more precisely) in 4 steps:
- Bring in the level in the direction of the foot screws A and B.
- Turn by 90 °, insert the level with foot screw C
- If necessary, continue turning by 90 ° and halving the vial deflection by moving A and B in opposite directions
- and after another 90 ° the same with C.
The last two working steps are only required if the level has not yet been adjusted or if a higher level of accuracy is desired. Half of the deflection corresponds to the residual error of the setup, the other half to the adjustment error of the level (which can then be eliminated with its adjusting screw).
For special applications - such as fine measurements in mechanical engineering - the foot screws are also used to set the exact desired instrument height . In general, the working range of the foot screws is limited to a few millimeters.
Occasionally, measuring instruments also have two or four foot screws. The former z. B. when using a ball head , the latter when the opposite screws are to be set to "train and pressure".
Use in general mechanical engineering
But also with machines in general a horizontal installation is often necessary for an exact function.
In the past, wedges or other base plates were used that were placed under several points on the machine. Today, foot bolts are increasingly used. These have to be designed accordingly large, since they not only have to absorb the weight of the machine, but also the kinetic energy that arises when the machine is in operation. Since the screws represent a strong point load for the subsurface, metal plates are usually placed under it beforehand. Instead of pure metal plates, vibration dampers can also be used to ensure that the machine runs smoothly. In order to prevent loosening or loosening of the screws due to vibrations, a so-called lock nut is usually used.