In this video we look at the accuracy of racks. Racks are commonly available from quality grade 4 through 10, with grade 4 being the most accurate. In this video Eric Megens explains what the quality class refers to and, what it explicitly doesn’t and why that makes racks from different suppliers hard to compare.
Rack accuracy: total pitch deviation
Grade 4 is the most accurate with a total pitch deviation of less than 20 micrometers per meter. This means that if a rack of 1 meter heats up by 1.5 degrees, this causes a pitch deviation of less than 20 micrometers.
At the same time, the quality of a gear rack says nothing about the after-treatment, the hardness and thus the feeding power. A grade 10 rack can provide more than twice the feed force than a more accurate grade 8 rack. This also makes it more difficult to compare rack suppliers because quality only relates to the total pitch deviation. And this is also often named at 300 or 500 mm.
Apex Dynamics has all the specifications and is also freely available via our website. Visit the straight or angled racks page and download the catalogue.