Ball screws classified as “double nut” appear to be aptly named. However, what seems to be a simple distinction varies from one vendor to another. Let’s clarify the true definition of a double nut and the unique features of Steinmeyer designs.
Taken literally, a double nut is composed of two separate nuts that are more or less identical. The purpose of this design is to preload the two nuts against each other and achieve two-point contact on the balls. Preload eliminates play and helps build additional stiffness, keeping the nut centered on the shaft. While there are many ways to achieve preload, Steinmeyer defines double nuts as those that have two-point contact. This makes sense as it describes the double nut from a performance point-of-view, regardless of the design details.
The main design challenge involving double nuts is how to join them. Various solutions have been developed around the industry to solve this issue, but most require complex joining with spacers, shims, fitting keys, pins, and setscrews. We believe in a simpler approach.
Steinmeyer’s patented UNILOCK coupling system avoids complicated hardware by using a special epoxy. It is proven to deliver a robust connection of the two nut halves, making our double nut nearly as compact and stiff as a single-piece design. It also prevents radial slippage of the two halves, so that the UNILOCK double nut cannot be misaligned. The coupling is rugged and absolutely tight to prevent the loss of lubricant.
Contact our motion control engineers to learn the benefits of UNILOCK for your application.