Everything you need to get to for starting CNCing with your LongMill

One of the most common questions we get from folks looking to order a LongMill is “What should I get with it?”. This article and video are designed to help you walk through everything you need.

The average order value for customers first purchasing a LongMill and accessories in the past 12 months is approximately $2850CAD or $2190USD, which means that for most customers, you can easily get a complete setup for under $3000. These numbers represent the total value of the order, which includes the machine, as well as most other accessories such as the software, router, endmills, a dust shoe, touch plate, and other items. You should allocate a few hundred dollars for other items that you may or may not have in your shop already, such as a bench, computer, and vacuum.

Here is the breakdown of the most popular items that customers order along with their LongMill by percentage.

The LongMill

If it’s your first time getting into hobby CNC, you might be a little intimidated by what you need to get started. This video is designed to cover everything you need to have in your shop.

Your first, and largest purchase is going to be the machine itself. The LongMill Benchtop CNC is a capable option for hobbyists who are looking for a lot of functionality found on more expensive machines but in a more budget-friendly package. Depending on the size, you can get a LongMill for around $1800 to $2300CAD or around $1400USD to $2000USD, which makes it one of the least expensive options for the size.

While there are cheaper and more expensive machine options out there, we believe our specific machine is best suited for customers who:

  • Are looking to do this as a hobby, with some interest in production and business work
  • Need high-quality resources and support
  • Willing to make a small compromise in cutting speed but still be able to produce the same type of work as more expensive machines

Our main goal as a company is to make CNC accessible to everyone. This comes down to a number of commitments to our customers and products:

  • To make products that are affordable for the average hobbyist
  • Provide resources, support, and instructions so that we can make sure our customers can be successful in using our products.

We feel that customers not only choose the LongMill because it is an affordable option, but because we created a helpful and supportive community around our products.

If you’re not sure what size to choose, we recommend considering the working areas of each version of the machine, and determining what size fits in your shop as well as can do the type of projects that you’re interested in doing.

Router or Spindle

The base LongMill kit does not come with a router, since we wanted to let customers choose which router they want to use with their machine. The LongMill can work with several different palm routers, but the one that is the most popular and the one we recommend is the Makita RT0701, as it’s inexpensive, readily available, and has more than enough power for general woodworking use. You can order this directly through us, or at most local hardware stores.

The LongMill also can be retrofitted with an aftermarket spindle, and we provide 71 and 80mm router mounts for larger spindles, however, due to cost and complexity, we only recommend this upgrade to experienced customers. More information about routers and spindles can be found in our resources.

End Mills and Bits

You’ll also need to get some end mills and bits to start off your CNCing journey.

Assuming you have a Makita router, you’ll mostly be using ¼” shank tools, or if you get either the ¼” to ⅛” adapter, or the ⅛” Precision Collet, ⅛” shank tooling as well.

We provide dozens of different bit options and packs on our store. If you’re not sure what to get, we recommend checking out one of the End Mill Sets, such as the Signmakers Set and Machinist Set.

If you’re starting out for the first time, I recommend the Starter End Mill Set, which comes with all of the bits that we think you’ll need and a collet adapter. The Starter End Mill set, which we recommend for first-time users, is about $45USD or $60CAD, and come with 9 different bits and accessories.

Prices for bits vary a lot, especially when you get into high-end tools, but for the average user, you should expect to pay a few dollars for smaller tooling, and up to around 20 dollars for a larger bit.


The last thing you must get for your CNC is a bench and spoiboard. This is just a large surface you can put your machine on. It should be noted that the surface should be as flat and strong as possible, since any flex or irregularity may show up in your cuts as well. Some people will make a bench from scratch, which can cost $100s of dollars, but even an old sturdy desk or dining room table can work as well.

Some different ideas and inspirations can be found in our resources.

You’ll also need a spoil board or wasteboard, which acts as a consumable surface for your projects to sit on. We recommend ¾” MDF, as its cheap, readily available, and dimensionally stable. You should be able to buy a 4×8 sheet and cut it into 2-3 wasteboards for about $60.

Computer and Software

There are two main pieces of software you’ll need with your CNC machine. First is the gcode sender. We build gSender as a feature-filled, powerful sender specifically for the LongMill. This program lets you send jobs, change settings, control your machine, and integrate with accessories like the touch plate and inductive sensors. Best of all, it’s completely free!

There are other gcode sending software, such as UGS and Openbuilds Control, but we think you should use gSender.

I recommend checking out our resources where we talk about different CNC software (Broll of scrolling through the resources, https://resources.sienci.com/view/lmk2-choosing-software/ or checking out our video on software to help you choose which software to get.

If you want to read about our thoughts on Free vs Paid software, we recommend reading our article on the topic.

Dust Collection

CNCing can be really messy, which makes dust collection an important part of your setup. 

At our shop, we use a Rigid Shop Vac and Dust Deputy, both of which can be purchased for about $200. This sort of set up will be more than capable for hobby CNC dust collection use.

To help clean up dust while cutting, we have the Dust Shoe, a $60USD, $75CAD attachment which goes on the front of the machine to suck up dust while your job is cutting. This particular one works with the 2.5in hose from the Rigid Vac perfectly.

Work Holding

To keep parts from flying out while cutting, you’ll need some form of work holding. Certain methods, such as using screws or hot glue, are very inexpensive and are easy to use. 

Some users will set up a t-track table on their wasteboard which allows you to use t-clamps and ¼” bolts to have a fast and adjustable system for workholding. A full set costs about $100USD or $125CAD.

I should note what makes our t-tracks unique is that they use ¼”-20 bolts rather than t-bolts which are harder to find, so that you can buy different size bolts from the hardware store if you want to make your own t-clamps.

There are a lot of workholding options, so I recommend checking out our resources page for different options.

Touch Plate and Inductive Sensors

When starting your job, the LongMill needs to have a set origin point. You must choose a starting point for the machine to start from, and it will perform the movements sent by the computer from that point, in relation to the starting point.

The important thing is to setting the starting point. You can choose the starting point manually by just jogging the machine to the place you want to start and “Zeroing” the machine, but we’ve created the touch plate to help semi-automate the process.

We currently have a simple touch plate for around $30, and a more advanced AutoZero touch plate for around $100. 

Additionally, you can add limit or homing switches to your machine. These are sensors that are set up at specific corners of your machine so that you can return the machine to a specific position over and over again (Broll of homing). For the LongMill, when you shut off your machine, it does not remember the specific position relative to itself, and so by having a specific homing position to return to, you can use this to reference the positions of the machine automatically. For example, if you want to set up a job in the same position over and over again, you can home your machine and find the origin of the part relative to the home position after you’ve shut your machine off.

You can get an inductive sensor kit for about $50-60 dollars from our store, however, we generally recommend this to only advanced users, since the setup and process for using it can be complicated, and we generally recommend users who are already familiar with their CNC machines to use it.

Other Accessories

The LongMill also is compatible with other accessories, like the Vortex Rotary Axis and LaserBeam add-ons that provide additional functionality. Over the past few years, we’ve developed these add-ons to plug and play with the LongMill. We plan, over time, to continue to create new add-ons and accessories that help our customers do more things.

For a full list of other add-ons and accessories you can get with your LongMill make sure to check out our add-ons section in our store (https://sienci.com/product-category/addons/mk2-addons/).

Maintenance Items

The LongMill requires some regular maintenance which is easy and straightforward to do. Recommended maintenance checks can be found in our resources.

There are only two consumable items, the Delrin Ant Backlash Blocks and Delrin V-Wheels which we recommend replacing every 1500-2000 hours, roughly once a year of regular use. Some customers choose to have them on hand just in case.


I hope this helps answer the “what should I get with my LongMill” question we get all of the time. If you have any other questions, please feel free to reach out!

General Tips on LongMill Troubleshooting

Hey everyone, it’s Andy here. Over the past few years, we’ve welcomed many thousands of CNC users into our community. Of course, with any electro-mechanical machine, some degree of troubleshooting is to be expected.

For the first year and a half since the launch of the LongMill, I had taken on the large majority of troubleshooting from customers directly through email. This was an excellent experience for me as it opened my eyes to observe almost all of the issues that were possible, as well as giving me the chance to learn and communicate with customers better. Even to this day, I am regularly checking on customer tickets and working with our support team to tackle new or more complicated support issues, although it’s typically no longer my day-to-day role.

What has been interesting to see over this period of time has been not just how we collect data and information about issues over time, but also our understanding of the human nature of users when it comes to identifying and troubleshooting issues.

One of the things we’ve come to recognize is that there are a number of misconceptions to address in terms of troubleshooting the LongMill. This article covers some of my personal recommendations for helping you troubleshoot issues on your LongMill.

Our custom dashboard tracking what types of tickets we receive and the frequency of certain issues

Tip 1: Listen and look at your machine carefully

Simply listening and looking at what your machine is doing can help a lot in identifying problems. Is the machine making a weird sound? Do you hear the motors stalling? Is the machine stopping and starting irregularly? Is there a component that is slipping? Making a close observation can help identify the cause of an issue.

It’s important to note that the large majority of issues for the LongMill are mechanical. This means that for most issues, you can physically, hear, or feel issues. A few extra tips for this tip:

  • Jog your machine manually on each axis and check for smooth motion. I recommend running at the highest speed for each axis as stalling is more likely at higher speeds
  • Run your project in the air. Look for any irregularities and odd behavior.
  • Try turning lead screws and moving your gantries by hand. This can help identify looseness or binding.

Tip 2: Most issues are simple issues

The large majority of issues are caused by something simple. Always start with simple fixes first before trying something more drastic. This will save you time and give you statistically the best chance in fixing your issue.

99% of issues that our users have can be found in the Common Issues and Fixes section of our resources. I encourage everyone to read through it carefully as it covers everything that we know that may help you solve your issues. This section is updated regularly with new issues and fixes when they are found.

From my experience, users often have a tendency to jump to the conclusion that if they run into an issue, it’s a rare, complicated, or unknown issue. Sort of like being a…LongMill hypochondriac? This means that many people try to troubleshoot their issues in the wrong place and become frustrated with the machine, rather than checking the most simple reasons for issues. For example, you’d be surprised at how many people reach out to us because their machine won’t work at all because they just never turned on the machine in the first place.

Tip 3: Mechanical and electrical issues happen randomly. Software issues happen exactly the same way over and over again.

The main differentiator between a mechanical and electrical issue versus a software issue is that mechanical and electrical issues seemly happen at random and software issues happen the same way over and over again.

While mechanical and electrical issues can be caused over time by loose fasteners and connectors, wear and tear, and power fluctuations which can happen seemly randomly, software works in a series of exact pieces of code that is rigidly defined. While double-checking firmware settings and reinstalling gSender can help eliminate those as being the issue, if your issue seems random, it’s more likely to be a mechanical issue and updating or reinstalling gSender will not help.

I sometimes joke to Chris that many users use gSender as a scapegoat, as many pin their issues on gSender when they aren’t sure what’s going on. I suspect it’s because its easy to blame something that people don’t feel as comfortable with (aka the software). Sometimes it feels like gSender is messing something up randomly, however, the reality is that the vast majority of issues come from something mechanical.

If you are running into issues with gSender, additional help and documentation can be found here: https://resources.sienci.com/view/gs-feedback/.

Tip 4: Static and EMF cannot cause a machine to lose steps

It is a common misconception that static and EMF can cause a machine to stall or lose steps. The main symptom of static and EMF is a complete disconnect between your machine and CNC. Issues caused by static and EMF will likely cause your machine to disconnect or stop completely. Additionally to note, due to the high draw of tools such as routers and dust collectors, its easy to mistake brown-outs for static and EMF, even though they are completely separate problems.

If your machine is losing position or steps randomly, it’s best to check out the mechanics of the machine first, as static and EMF does not cause the machine to lose its position. Use the process of elimination by turning on and off different tools and dust collectors in your shop while running your machine to identify the culprit.

Tip 5: Let us help you

Don’t forget that our technical support team is here to help answer any questions and help tackle technical issues. Sending us a message with detailed information, videos, and photos of your issue through our Contact Us page.

When you send a ticket, you’re talking to:

  • One of our team members or engineers who designed a certain part of the machine
  • Someone with hundreds, if not thousands of hours of CNC experience
  • The whole technical support team, as tickets and information can be shared between all members

We also use tickets to collect data and improve the quality of our products and make adjustments to our resources.

Reaching out directly to our technical support team is typically the fastest and most reliable way to solve technical issues.

A note from Jason Kent, our Customer Support Manager

Provide as much information as possible. Information such as recent changes or updates made to the machine or software is useful to include.  When reaching out for customer support, please add images or videos relevant to the issue. While family photos are cute, images of the issue help us to diagnose your problem faster.


Tip 1) Observe the mechanics of your machine carefully, such as the sound and the movement, as mechanical issues are the most common in LongMills.

Tip 2) It’s statistically more likely that an issue is caused by something simple. Always troubleshoot by checking basic things first. Troubleshooting guides in our Resources contain fixes for 99% of issues around the LongMill and are regularly updated.

Tip 3) Understand that if the problem happens randomly, it’s most likely a mechanical or electrical issue. Software does not cause random problems.

Tip 4) Static and EMF does not cause stalling or missing steps. Static and EMF causes the machine disconnects or to stop completely.

Tip 5) Don’t forget to reach out to us directly! We can help too!

Maintaining Linear Guides

Hi everyone. This post about maintaining the linear guides on your LongMill. We’ve had a couple of people report to us that they’ve had their Z-axis get stuck or become rough especially when they have been running over a long period of time.

I and another customer who has experienced this issue have been investigating the cause of this for a few weeks and doing more research to help customers prevent their linear guides from sticking.

I’ll just fill everyone in on our recommendation for maintaining your linear guides to ensure they work flawlessly for every cut. If you want to hear more about what we’ve done to look into linear guide maintenance, scroll down past this section to read more.

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:

  • https://www.thomsonlinear.com/en/support/tips/what-should-be-used-to-lubricate-linear-bearings
  • https://www.hiwin.com/pdf/lubricating_instructions.pdf

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.

These instructions are now a part of our Machine Maintenance page on our Resources.

Jumping into our other findings

One of our customers had reported having their Z-axis linear bearings seize several times, and with the help of this customer, we have investigated the issues further. Initially, this had been a fairly uncommon issue, with only 3 tickets in our system pertaining to these parts as well as a small number of users reporting this issue on our Facebook group so it hadn’t been top of mind for us to investigate. However, I guess it’s better to sort potential problems out than let them sit and percolate forever.

Based on research, the main reason for failure for linear guides is lack of lubrication. This is what I suspect happens.

  • Linear guides get coated with dust from regular use. This dust either sticks to the lubricant already on the guides and either falls off taking lubricant with it, the guides push it off, or the user wipes off dust and lubricant.
  • The chance of the ball bearings in the guide seizing goes up either due to the resistance between the balls rubbing against each other or dust making their way into the guide

To replicate the issue I first cleaned all of the grease and debris from a spare ZX gantry using brake cleaner. This provided a situation where the linear guides would have no lubrication. Then the guides were coated in MDF dust and were moved back and forth.

Although I was not able to create a complete failure of the bearings, were was a noticeable increase in friction, and over a longer period, I suspect that the bearings would be able to be coaxed into seizing.

After this testing, I applied machine oil to the guides as discussed in the section above and the linear guide returned to its original smooth movement. I believe that cleaning and relubricating the linear guides can return seized linear guides back to life, and maintaining them should ensure smooth operation for the years to come.

I hope that adding this helps improve the LongMill’s reliability and ensure that everyone’s machine keeps chugging along great!

Launching our own T-Track clamping system

Hey everyone, I’m excited to share something Kelly and I, and the rest of the Sienci team have been working on for the last couple of months. We know that many of our customers use T-Track extrusion as a clamping/workholding system for their LongMills and other CNC machines, and we’ve learned that folks have been coming up with their own solutions based on what’s available to them.

Well, we’ve created our own that serves as an excellent option for affordable and high-quality T-Track extrusion.

You can order them here:  https://sienci.com/product/t-track/ ‎

Universal 1/4-20 hex bolt compatibility

One of the key features to highlight about this new t-track system is that the profile is designed to use 1/4-20 hex bolts rather than T-Bolts that are often used in other T-Slot extrusions.

This means:

  • You can easily find and buy 1/4-20 bolts for cheap
  • You can find lots of different lengths and related 1/4-20 hardware that you can use to make your own clamps

If you want to make your own clamps/need some inspiration, check out https://www.thingiverse.com/thing:4537983

Kelly designed some hold down clamps

Hi everyone. I just wanted to share some news on a new project/product we have been working on for the last couple of weeks. We are working on a new T-track work holding system to add to our host of accessories!

In the meantime, one of our awesome engineers, Kelly, has created a simple hold-down clamp design that can be used for all sorts of CNC stuff. We are also sharing the link so that you can copy and modify the design to fit your needs: https://cad.onshape.com/documents/4002cf32491a7a7a17c84759/w/f9f2dc06d2e8375fa2fb89a3/e/cd612c44ade33406e8df06a6

If you want to download the STL files, we also posted the design on Thingiverse: https://www.thingiverse.com/thing:4537983

We’ve designed these clamps to be made from plywood and use standard 1/4-20 hardware. Knobs can be 3D printed or milled as well.

As mentioned before, we are currently working on our own t-track as well. One of the biggest selling points of the new extrusion will be designed to fit the head of standard 1/4-20 hex bolts, which means that you can find the bolts you need for any of your workholding needs from your local hardware store. No special hardware needed!

We are expecting to have t-tracks available for purchase in the next month or so!

Things to consider when making a longer LongMill

One of the most frequently asked questions is “Can you make a bigger version of the LongMill?” Well the short answer may be “yes”, but there are many other considerations that you should to consider.

Screw whip

Screw whip, or “whip” refers to when a rotating rod wobbles or flexes, which is exacerbated by the length of the rod, the speed of the rotation, or how off balance the rod is. The LongMill 30×30 uses a 8mm diameter steel leadscrew that is approximately 1030mm long. At the speeds that the NEMA 23 motors turn at and the length of the lead screw are such that the effect of a properly assembled machine are minimally affected by whip.

When you start to go longer in lead screw length, the effects of whip become more pronounced to the point where you will either need to increase the diameter of the screw or use a lower motor speed, both of which present different challenges and downsides.

There are different lead screw designs that can be used for this application, but may need modification with bearings, mounting feet, couplers, and motor mounts.

Motor speed

For practical purposes, it is best for the machine’s speed to increase proportional to the size of the machine. For context, the Mill One with a work area of around 258mm x 185mm has a maximum speed of 1800mm/min. The LongMill on the otherhand, comes has a maximum speed of 4000mm/min, more than double the speed of a Mill One but also significantly larger.

It is important for a machine to offer faster speeds to accommodate for a larger size machine as doing large jobs at a slow speed would take forever. Typically, you can run a LongMill 2.5x the speed of a Mill One, which means that a project that takes 30 minutes to do on a LongMill would take 1 hour 15 minutes to complete.

If you want to run the machine faster, you will likely need to provide more power to your motors as well. You can do this by increasing current and voltage supplied to your stepper motors, which may also need upgrading your power supply and motors to support the changes.

Luckily the LongBoard controller can support higher voltages and current with a larger power supply, but you will still need to consider upgrading the stepper motors (rated for up to 2.8A).

Rail rigidity

The longer your rails are, the more flex you’ll have if you don’t fully support or reinforce the rail. While the Y-axis is easy to do, as all you need are more feet to support the rail, you may want to consider adding additional reinforcement to their X-axis rail which is a free-floating part.

Without modifying the rails, you may experience more deflection, which will need to be combated by decreasing your cutting speeds.

The other consideration to make is how straight and parallel your rails are. Aluminum extrusion is relatively straight due to the process used to manufacture them. However, deviance in straightness increases the longer your rails are. This also applies when considering if your rails are skewed as well.

For some deep dive into rail design and FEA, make sure to check out this post on the forum: https://forum.sienci.com/t/making-a-stiffer-3×3-angle-gantry/693/5


A larger machine cost more to ship, as there are restrictions on how large shipments by courier can be. This can vary region and country, which limits the ability to transport the parts for the machine, which is why we don’t offer longer rails for the LongMill. That being said, you can typically find 2×2″ and 3×3″ angle aluminum from most metal supermarkets as it is a standard material.


We believe that the sizes offered for the LongMill are optimal in terms of price, performance, and usability. However, we encourage folks to build their own machines if they choose to, which is why we provide all of our design files open and updated for free: https://sienci.com/dmx-longmill/open-source-and-modifications/

On the other hand, there are a lot of things that need to be considered in terms of building a longer version of the LongMill which can add to the cost and complexity of the machine. There’s a reason why costs can go up exponentially as size goes up as well. There is also a strong case to be made to avoid expanding this design without significant modification or purchasing a pre-made, larger machine as well.

For those who want to do larger pieces without modifying their machines, consider looking at putting your materials in diagonally, or using “tiling“.

We hope you enjoyed this read, or even inspired you to mess around with our LongMill design. In any case, we hope you share with the community what you learn and what you build.

Surfacing the Wasteboard on Your Longmill

Want to learn to surface your wasteboard?

  1. Surfacing your wasteboard helps level the surface in relation to your machine. This means that if you have bumps or uneven surfaces on your wasteboard, or if your wasteboard is higher on one side that the other, surfacing will even out and flatten the board.
  2. Cleans off old marks and scars, leaving you with a new, clean surface to glue, clamp, and mount your workpiece.

Check out our newest video that covers how on Youtube:

For more info and surfacing code for all LongMills, visit our resources page: https://sienci.com/dmx-longmill/surfacing-the-wasteboard/

Check out these new instructables on modding your Mill One

Troy, a.k.a tmbarbour has put out some really cool instructables on adding some new functionality to the Mill One! You might know him from his Add Homing Switches to a Sienci Mill One CNC project, and he’s made some other cool changes to his machine.

Easy Z Axis Probe for Your CNC Router

This instructable walks you through adding a Z axis probe to the Mill One using the built in pins on the CNC V3 Shield. This makes it a lot easier to automate the process of finding the Z height of your workpiece.

Add an Arduino-Based Optical Tachometer to a CNC Router

Knowing the RPM of your spindle can help you get more consistent results out of your Mill One. Not only that, it’s a cool little add on that’s fairly inexpensive and fun to make. Troy’s instructable covers everything you need to know to make your own.

Sienci Mill One Air/Oil Mist Coolant System

There’s been talks and photos of different coolant systems on the Sienci Mill One Group over the last few months, but this is the first full guide I’ve seen on setting it up on a Mill One. Check it out here: https://www.instructables.com/id/Sienci-Mill-One-AirOil-Mist-Coolant-System/

So why a coolant system? Well, when it comes to cutting aluminum, one of the biggest challenges is to keep the end mill from clogging with aluminum chips that weld themselves due to the heat created by friction. Aluminum has a fairly low melting point, making it a material susceptible to this.

There are a few methods to make sure you don’t damage your end mills. One is to make sure that the chips you’re creating are large enough to carry the heat created away from the cut. This is where using a single flute aluminum bit works well, since the single, large flute creates larger chips than what a 2 flute or a 4 flute would typically do. This works great with most jobs, and typically you won’t reach those temperatures. However, with long jobs that can take several hours, some sort of cooling is nice to have.

Andrey’s method of using a mist coolant system is commonly used in industry on large, industrial machines. It uses a blast of air, mixed with a stream of vaporized coolant, pointed toward the end mill to lubricate and cool the part and the tool. Unlike flood cooling, which uses a stream of liquid coolant that sprays at the tool, mist cooling requires far less coolant, and if properly set up, a lot less messy.

If you’ve had this mod in mind for your Mill One, check it out!



What is backlash?

With any screw driven mechanical positioning system, there is often some degree of slop or “backlash“, including the one used in the Mill One. To explain further, backlash occurs when there is a gap between the threads of the nut and the lead screw and the nut is allowed to move within the gap which is present. With most people, the level of precision that the Mill One provides is more than enough, but for those who want to push their machine further, or want to need their Mill One extremely high precision work, this is an important topic to discuss.

We tested the backlash on our ACME nuts by attaching a dial indicator to the Mill One’s gantry and running the gantry back and forth. We chose a point to call zero on the dial indicator, and moved the gantry past zero, moved it back, then moved back even more, and then moved it forward again. The gap between the zero and where the needle landed was our backlash. A better explanation can be found here: http://www.cncexpo.com/MeasuringBacklash.aspx

We tested this way for both a brand new stock ACME nut, as well as after running for many cycles. We ran the gantry back and forth for about 8 hours, with an additional load simulated by using bungee cords as to wear the nut as far as possible.

The results of this test, are as follows:

  • Brand new stock ACME nut: 0.001″ or less in backlash
  • Stock ACME nut after 2-3 hours: 0.002″to 0.003″ in backlash
  • Stock ACME nut after 6 hours: 0.003″ in backlash
  • Stock ACME nut past 8 hours: 0.003″ in backlash

Based on these results, we can see that the backlash of the ACME nut had gone from just under 0.001″ to around 0.003″. Just to put that into perspective, 0.003″ is approximately the thickness of a sheet of paper. For most projects, this is a great level of precision. But for something like PCB milling, where the width of each trace can be less than 0.006″, 0.003″ is a big number.

Over the last few months we have been testing anti-backlash nuts on the Mill One, which “preloads” two sides of the ACME nut to eliminate the gap which causes backlash. Using the same tests, the anti backlash nuts manage decrease backlash to less than 0.001″, greatly improving its accuracy. This resulted in parts coming out with much better dimensional accuracy, with tolerances of +/-0.002″ (0.05mm) or better being easily achievable.

Here’s an example of a test cut we milled from some brass:

Because of these good results and since the upgrade is simple to do and fairly inexpensive, we have created kits to allow users to install their own anti backlash nuts. You can order a kit here: https://sienci.com/product/anti-backlash-nut-kit/. We’re really happy to make this upgrade available to let users take their projects to the next level. We will continue to do tests with the anti backlash nuts with a variety of projects, so make sure to check out the blog to find out more!