Gauge for Prusa MK3/MK4 Nylock / silicone tube bed leveling mod

thingiverse

This gauge uses the handle of the hex key as the pointer to a scale showing the elevation change of the heat bed screw in increments of 0.01 mm. After looking at similar gauges, I wanted something that uses less material and has no moving parts. Prusa's automatic mesh bed leveling creates a perfectly uniform first layer on the build plate, but "level" doesn't equal "flatness". Flatness becomes important if you need to join the surfaces of two parts that were on the build plate. Then flatness imperfections become evident. The usual way to compensate for flatness imperfections is to replace the eight metal spacers around the edge of the heat bed with Nylock nuts, leaving the metal spacer in the center. Then, using Octoprint or Pronterface to get a 7×7 array of bed elevation data, adjust the screws to minimize the measured differences from the center, then lock the screws in place with the Nylock nuts. A better way is to use Daniel Schweinert's [silicone tube bed level mod](https://www.schweinert.com/silicone-bed-level-mod-prusa-mk3/) (see also the [YouTube video](https://www.youtube.com/watch?v=OP1xzEKhHDg)). Basically, you replace the 6 mm metal spacers with 10 mm lengths of silicone tube as compression spacers, again leaving the metal spacer in the center. Then there's no need to get under the heat bed to tighten nuts; simply tighten the screws against the compressed silicone spacers. The silicone tubing should be 8 mm outer diameter and 3 mm inner diameter. ### Operation 1. Insert the short end of the hex key into the gauge on the side labeled UP or DOWN, depending on the direction you are adjusting the screw. 2. Insert the short end of the hex key into the screw head. 3. Position the gauge so the handle of the hex key points at 0. 4. Turn the hex key the desired amount. The number scale represents incrememtns of 0.01 mm.