Table Mounting 📐


The LongMill is designed to be mounted to a flat surface which is provided by the user. This could be as simple as a single sheet of material, or as intricate as a multi-piece torsion table with t-tracks and threaded inserts. This helps to:

  1. Save on the cost of shipping. For example, a 4’x4’ piece of 3/4” MDF shipped often costs over a hundred dollars in shipping and is very easy to damage during transit. Instead, you can usually find a full 4’x8’ sheet of 3/4” MDF for under $60 at your local lumber or hardware store.
  2. Give users flexibility to choose the size and material of the wasteboard to match their needs.

Suitable Wasteboard & Table

There are two factors to consider for your setup:

  1. The table / mounting surface itself: this needs to be relatively flat to properly mount the machine to and it should be relatively sturdy as well
  2. The wasteboard: this is the cutting area of the machine that you place material within and will get worn out over time. This will get flattened and occasionally re-flattened by your LongMill to ensure any material you cut is parallel to the machine. Ideally this should be removable. If you want to pass larger material through the cutting area you should also ensure the wasteboard is the same size as the machines cutting area otherwise it’ll leave a lip when you flatten it out

The easiest setup that we recommend is a flat, clean piece of 3/4” MDF to act as both your mounting surface and your wasteboard, as shown at the start of this section. This is because 3/4” MDF is quite stiff and is readily accessible in 4’x4’ and 4’x8’ sizes from most big-box hardware stores or a lumber store. Any similar piece of thick, flat material would also suffice.

A higher-quality setup will have both a flat surface that your machine mounts to as well as a removable surface that you can cut away at to ‘re-flatten’ after it starts to show some wear. You can see some examples of this above, one with a spare piece of MDF as the wasteboard and another with added ‘foot risers’ to maintain the LongMill’s tall cutting height. These sorts of setups can sometimes be made out of a single sheet of 4’x8’ MDF as shown below. Feel free to see more inspirational example setups by our community members here:

Machine Dimensions

When getting ready to mount your LongMill the mounting surface will need to be at least the same size or larger than the space the feet take up, known as the ‘foot base’. In addition, some parts of the machine extend outside the foot base like the stepper motors, so leave enough space around your mounting surface to account for this ‘total machine outline’.

Each MK2 model (12×30, 30×30 and 48×30) is designed to generally fit on a 2’×4’, 4’×4’ and 4’x6’ surface respectively. The diagrams below show a more detailed view for each model where the red represents the travel / cutting area and the blue shows the hanging features outside the foot base.

The control box is also something you should plan for. It has buttons on its top to Play, Pause, and Stop the machine which some users prefer having access to though these are also accessible via gSender. It also has a USB input on the left side, motor and other I/O on the right side, and the power input on the back side. Normally the control box will plug in on the left side of the machine (unless you mirrored assembly to put it on the right side) and you can have it sitting on the table or screwed to the side or underside.

Mounting your LongMill

There’s a simple step-by-step process you can follow to ensure that your machine is mounted securely and accurately. Ensure your computer is connected to your machine so that you can move it around between steps. You can use the wood screws provided (#8 x 1”), or use your own mounting hardware depending on your setup. Either way, a drill with a long Robertson driver or a bit extender works best to reach all the holes when you begin screwing the feet into place.

Gently place your LongMill on the mounting surface roughly where you want it. Usually you’ll want to have a reference ‘straight edge’ on the right and front of your surface to align the machine to; whatever best suits your setup. In this case we’re using a 4’x4’ MDF sheet as a combination mounting surface and wasteboard which we had cut to 42 inches to better fit in a car. We’ll be mounting it in the middle offset from the factory edges and have the electronics box sit off to the side.

Start by moving the machine all the way to the front by jogging in the Y-axis on your control software. Keep moving forward until you hear a grinding coming from the motors on both sides to confirm that your machine is all the way forward on both sides. After this you can jog backward slightly.

First we’ll be mounting the whole right-side of the machine into place. Each foot has two primary holes for mounting (red circles) and the steel end feet have a backup set (orange circles) built-in to allow you to make adjustments in case you find that you made a mistake later on.

Start with the steel end feet using 2 screws per foot and ensuring they’re aligned to where you want your machine to be. If you’d like to pre-drill the holes to avoid shifting around that’s an option as well.

Next screw in the middle feet on the right side. Don’t ream down as hard on the plastic feet as you did on the steel ones.

At this point the right side of your machine will be fully secure. When mounting the left side, we’ll want to ensure it’s mounted parallel to the right side and also that the back feet are aligned to each other. You can see in the diagram below why mounting the rails both parallel and in-line is important to ensure the CNC isn’t overly stressed and also cuts how you expect it to.

Checking for ‘squareness’ can happen many different ways depending on your tools at hand. For example, if your right side was attached 90° to your table front, then make another 90° mark for the left side to reference using a straight edge and a carpenter’s square. If you have a friend to help you, the steel end feet also have a small notch built-in that can allow you to run a measuring tape under the X-rail from the top left to bottom right foot and top right to bottom left foot. Adjust the left side until these two measurements are equal and that’ll ensure your machine is mounted square.

A third option is to use the ‘XY Squaring’ tool that’s built into gSender. This tool is probably too fancy for most people but it’s one of the most accurate ways to check the squaring on your machine. You can read how to use it here if you’re interested and then come back to continue assembling once you’re done:

Once you feel confident in the foot placement, drive the first screw into place on the front left foot:

Then jog your machine to the rear and drive in another screw on the back left foot:

Now double-check that everything is looking correctly aligned before completing the mounting. At this point if there seems to be an issue don’t sweat it, the second set of holes on the steel end feet will allow you to make small changes in how the machine is mounted. Once you’re happy, jog the CNC roughly to the middle and finish securing the remaining foot holes:

Followed by the second screw for each foot. Once complete, congrats! Your machine should now be fully secure and square to its mounting surface.

Mounting the Rest

With the machine mounted, take a once-over on the rest of your setup and see if there’s anything else you’d like to fasten down before you start on your first project:

  1. Control box: If you don’t think you’ll be using the on-board control buttons feel free to mount the box out of the way. The box has 8 mounting holes available allowing you to place it anywhere and in any position you wish. Just keep in mind access to its inputs and outputs in case you need to do troubleshooting or upgrades down the road.
  2. Power supply: The body of the power supply comes with 4 mount points. Screw it down out of the way and be mindful that it gets a little hot to the touch while it’s providing power to your machine.
  3. E-stop: the e-stop button is meant to be your ‘oops button’ so place it somewhere that will always be easy to access in an instant whenever something goes wrong. If you undo the 4 screws holding the e-stop body together you’ll see that there are holes to attach wood screws through the black bottom so you can mount it to any surface and reassemble the e-stop once you’re done. If you wish to place it further from the machine, extending it’s wires is quite straightforward by unscrewing the green connector and either using a soldering iron or a crimpable wire extender to lengthen it out.
  4. Motor cables: an easy way to tidy up motor cables is to drill holes with a spade or forstner bit right where the cables dangle down at both the rear Y-axis motors and where the remaining wires come out of the drag chain. This will allow you to run the wires on the underside of the table with tie mounts or even bent nails and keep your table surface nice and tidy.

Steps Forward

You’re finished assembling your LongMill! Take a picture 📷 and pat yourself on the back for arriving here. People come from many backgrounds and pick up a LongMill so whether getting to this point took you an hour or a couple days we’re sure your LongMill will be very happy with the new home you’ve given it.

In the next section we’ll walk you through the basics of using your new CNC and cutting out your first projects. Afterwards you’ll assemble any add-ons you purchased with your MK2 and see how they benefit your CNC workflow, as well as dive into the MK2 Handbook – your bible on using your machine.

We really hope you enjoy using your LongMill MK2 Benchtop CNC in the days, weeks, and months to come. Remember that CNC routers are an amazing tool that you can use for whatever you like, and that the point of the LongMill and its community is to offer you resources and support so that you can be confident in using your CNC to make what you imagine. Good luck and happy making!

-The Sienci Labs team

Move on to the next page where you’ll get to carve out your first project ⭛