A machine can only make accurate parts if it is properly aligned.

As machines wear out, not only do the way surfaces become rough, the angles change. A slide that hangs from a column wears the bottom way surfaces faster than the top ways, because of how a slide applies leverage to a column when it hangs. This effect causes the ways on the slide to go out of square with the ways on the column. Machines that do most of their movement in one area wear more in just that area, causing a slide to be loose in the exact position where tight precision is most needed. As machine ways wear the inaccuracies are compounded, a loose table is attached to a loose cross slide that is attached to a loose knee... If you simply tighten them up then the machine will seize when you try to move the machine into a position where it is less worn, because the ways do not wear evenly.

Uneven wear of slide ways is why complete realigns are necessary. A good realign starts from the ground up to eliminate compounded errors. The machine base is leveled and its ways are scraped flat and parallel to each other. A granite surface plate is used as a reference for flatness. Using a very thin layer of dye and carbide scrapers, the flatness of a surface plate is transfered to metal by rubbing the two surfaces together and scraping the high spots. This process affects angle as well as flatness, one part of the way may be scraped more than another part in order to change the angle.

Some rebuilders try to cut costs by only grinding the slide surfaces, not scraping them, or scraping them only superficially. But when the ways are not scraped, the angle and squareness of the sliding surfaces are not matched to each other. Grinding only makes each separate surface flat, it does not make the parts fit together as a whole. Proper alignment requires scraping, because the parts must fit together with extreme precision. Attention to detail is essential, or the machine may make parts that are out of tolerance in terms of length, squareness, and finish.

Studwell rebuilders have experience with the subtle issues of precise machine alignment. If the ways of a machine appear to be low in the center on an unusually cold morning, we know to work on another part of the machine until measurements can be taken at a stable temperature. If the machine has been leveled recently, we know that false measurements are possible until stresses in the casting have settled. We can read high spot patterns and know which spots to scrape, and which to temporarily ignore, in order to achieve a certain angle change. After we scrape a way it distributes weight evenly over flat and well lubricated contact areas, adding to the longevity of the machine. Our experience at paying attention to the details of machine alignment enable us to bring worn out machine tools back to the levels of accuracy they had when they were new.