As part of developing my own 3D printer firmware, I also keep an eye on what is happening in other firmware. One feature that is causing confusion in the Marlin community is the junction deviation setting. Up until recently, Marlin used the jerk method (hence forth referred to as "archaic jerk") it inherited from Grbl for computing corning speed (junction velocity). With the option now in Marlin to use junction deviation instead of jerk, there are many people who want to know what are good settings for junction deviation to insure they get reasonable movement while printing. In this post I will give an equation for converting the jerk values into junction deviation and my derivation of this equation.