CNC Maintenance 🛠️


Doing regular maintenance on your LongMill is quick and easy and ensures that your machine runs at the top of its game for many years.

Adjusting the tension on your Delrin anti-backlash nuts

The LongMill comes with four Delrin anti-backlash nuts that allow users to reduce backlash and compensate for wear over time. For more information about backlash and how it can affect the precision of your machine, check out this awesome page here: 

  1. Check if you have backlash in your machine by pushing each axis back and forth. If you can feel the machine move, even though the lead screws are stationary, you may need to tension your nut.
  2. Use an allen key to reach each of the tensioning screws. Photos of the locations for each screw are below. Start by very lightly turning the screw and checking for play. Note that overtightening your nut can cause premature wear, and you should only need a very small amount of tension to remove the backlash from your system. Also note that once the delrin nut is worn excessively, then the head of the M5 bolt could start to rub or bind against the lead screw and cause damage to it. Backlash nuts are consumable, so if they are excessively worn then they should be replaced.

Left Y-axis

Right Y-axis



Adjusting your eccentric nuts

The eccentric nuts allow users to adjust the tension on the Delrin v-wheels to bring them closer or further away from the edge of the rail. The wheels need to grip the edge firmly, while still allowing the machine to move smoothly.

Eccentric nut at its highest position.

Eccentric nut at its lowest position.

One simple way to check if your v-wheels have the right amount of preload is to check if you can turn the wheel with your fingers. Your wheel should be on tight enough that it should be difficult to use your fingers to turn them, but not tight enough that they do not rotate when you move the axis back and forth.

We recommend checking the tension on your v-wheels on a regular basis.

Checking for the tension on the Delrin v-wheels.

Cleaning your rails

Over time, your rails may accumulate dust. Dust that lands on the rails and gets rolled over by the Delrin v-wheels can stick onto the edges of the rails. We recommend regularly cleaning off this gunk with a small brush or a plastic scraper.

Black dirt on the edges of the rail.

Checking for loose fasteners

To mitigate fasteners from coming loose over time on the LongMill, we use nylock nuts wherever we can. That being said, fasteners can start to come loose over time. We recommend retightening fasters on a regular basis.

Some key areas to check:

  • Set screws on all couplers, pulleys, and the ACME lock nuts
  • M8 screws along the Y-axis rail.
  • M8 screws holding the X-axis rail and Y-axis plate.
  • M5 screws mounting the Z-axis motor to the steel plate.
  • M5 screws on the X and Y-axis
  • M3 screws on the XZ gantry

Maintaining your Linear Guides

Although the frequency of lubricating your linear guides may vary depending on the type of cutting you do and the frequency of use, we would recommend doing this procedure every 20-30 hours. However, if you experience any grinding noises or roughness in your gantry, we recommend doing this procedure more often.

  1. Wipe your linear guides with a clean cloth, paper towel, rag, or shop towel to remove any dust that may have accumulated on your linear guides. Move your Z-axis up and down if needed.
  2. Apply a liberal of machine oil or grease to your linear guides. Move your Z-axis up and down to ensure that the bearings inside have a chance to get coated Most general-purpose lubrication options should suffice. However, it is not recommended to use dry lubricants or anything with particulates such as graphite in the lubricant.

Here are some links to more into about lubrication:

We believe that most general-purpose lubricants such as the 3 in 1 oil should suffice since the linear guides are used in a relatively low speed, low load application.