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Everything you need to know about the LongMill MK2 48×30 and Extension Kits

One of the most common requests for future upgrades is the ability to increase the size of the machine. With the implementation of the improved extrusion design on the X-axis from the LongMill MK2 platform, it is now possible to extend the X-axis to have a working travel of 48 inches without impacting overall rigidity and performance.

Increasing the X-axis to 48 inches allows users to pass full 48in or 4ft wide materials through the middle of the machine, as well as overall increasing the usable area that the machine can cut.

At the time of writing, both the MK2 48×30 machine and Extension Kit is a work in progress. Parts and designs have not been finalized, and shipping and completion times are estimated. We’ve had a LOT of people request to place an order for these new products, just like our LongMill MK2’s, so we’ve decided on opening up pre-orders ahead of time. Opening up pre-orders will help us to judge demand and help us get an idea of the quantities to produce for each item. 

If you wish to place a pre-order for these items, please note that we have extended lead times for all items, and shipping/delivery times may change without notice. We will keep customers update to these changes through our regular blog and social media updates.

Please read this post completely, as it provides information about ordering, to-do’s, FAQs, pricing, and more.


Please note that all USD amounts are based on conversion from our CAD prices and may change based on the exchange rate.

The LongMill MK2 48×30 consists of a full LongMill CNC machine with a working area of 48in x 30in. This would be the kit to get if you don’t already have a LongMIll and want to jump straight to the larger size. This kit will be priced at $2300CAD or $1800USD.

The Extension Kit provides the T12 Lead Screw, extended X-Axis Rail, Y-Gantries, drag chain, and wiring to increase the width of the machine. The base price for the kit will cost $650CAD or $520USD.

Users may need to purchase additional items to adapt their version of their machine along with the Base Extension Kit.

For MK2 users, only the base extension kit is needed, as the MK2 XZ gantry and other hardware can be reused.

For MK1 users who wish to use their stock MK1 XZ gantry, an additional hardware kit to adapt the T12 ACME nut and drag chains will be needed and will be priced at $45CAD or $35USD.

For MK1 users who wish to upgrade their XZ gantry to the latest MK2 design, the XZ gantry assembly will be priced at $220CAD or $170USD which comes with a fully assembled XZ gantry assembly, aluminum motor mount, and Z motor. MK1 users will not need the hardware kit mentioned above if they are using the MK2 gantry.

Where to order

Extension Kits on an existing machine (LongMill MK1 or MK2):

Upgrade on a pre-ordered LongMill MK2:

LongMill MK2 48×30 Kits:

If you have a pending MK2 12×30 or 30×30 order you want to upgrade

Payments to upgrade pending LongMill MK2 pre-orders can be made directly on our website ( Instructions and additional info can be found on the order page.

Please note that upgrading will delay the shipment of your order to June/July. If you wish to receive your 12×30 or 30×30 machine first, then upgrade later, please order the Base Extension Kit instead.

Please also note that your order will be shipped based on the order of when they are placed. You will lose your place in the line for the 12×30 and 30×30 machines and will need to rejoin the line for the extension kits and larger 48×30 machines.

Changes made

X-Axis Rail Design

One of the main developments that make this possible project is the stiffer X-axis rail. One of the main issues with working with a longer axis is that the overall rigidity of the machines decreases as the rail gets longer. To solve this issue, a stiffer rail needs to be used to provide a high level of performance. The new X-axis rail provides up to 50% more torsional rigidity over the original MK1 rails, which means that the extended versions of the LongMill will perform equally or better than the outgoing MK1 30×30 machines.

T12 Lead Screw System

Due to screw whip, T8 lead screws found on the 12×30 and 30×30 machines are limited to how fast they can turn. Above around 5000mm/min, or around 2500RPM, screw whip on a 30×30 machine becomes enough to cause excess vibrations and whip to cause issues with cutting.

To counteract this, we are using 1450mm T12 lead screws, which use a 12mm diameter over a 8mm diameter lead screw, which has 2.25x more cross-sectional area. We’ve tested the T12 lead screw system at over 7000mm/min or 3500RPM with acceptable amounts of whip. 

A T12 lead screw vs T8 lead screw

The T12 lead screw system also implements new larger flange bearings, T12 anti-backlash blocks and T12 ACME locking nuts as well, to accommodate the larger lead screw.

A T12 nut next to a T8 nut

6001ZZ vs 6008ZZ bearings

Development to-dos

Wiring extensions

We are currently working on making extensions for motor, inductive sensor, and router plug cables, as well as to the overall wire management to accommodate the longer amount of travel.

Beta testing and in house testing

As we continue to design, we’ll be working with beta testers as well as internally to do testing. Thank you to the over 250 people who signed up for beta testing. Our beta testing signup is closed.

Packaging design

Due to the size and weight of the larger machines, we’ll need to 1) develop new packaging 2) split packages up. A full 48×30 machine will weigh more than the weight limit for most couriers, which means that 48×30 kits will ship in two shipments. We need to create a tracking system that makes it easy to track multiple shipments at a time.

With regards to the extension kits, we’re also in the process of working on the packaging for the kits as well. 


Pre-orders placed today should expect orders to start shipping in June or July. We’re doing our best to get everything done for this new product, but want to give ourselves enough time to have everything tested and sorted out before shipping. We have also been facing supply shortages and slower than normal shipping times for most items, and want to provide ourselves with ample time to work around the ever-changing landscape of supply chain. Customers should note and expect that there may be delays that may push this timeline further. Customers may cancel their order without penalty at any time before it ships for a full refund.

We’ve received our first batch of parts for the 48×30 and extension kits, but are still waiting on lead screws and bearings to arrive by sea. These parts are expected to arrive at the end of February.

There are a couple of parts that are still in progress and have not been ordered, including:

  • Y gantry plates
  • Extended wiring
  • Packaging

Additional development is required to be done before release which includes:

  • Resources
  • Software updates

We are expecting the process of ordering and receiving these additional items to take between 8-12 weeks. 


Will the Extension Kit work for my older machine (MK1)?

Yes, the Extension Kit will work with any generation of machine. The Y gantry plates will come with different hole patterns to work with both the angle aluminum Y rails and the MK2 Y rails.

Prototyping for the MK1 Gantry on the MK2 machine

When will the new kits ship?

Customers should prepare to wait until June or July for their machines or extension kits to ship. Orders will be shipped out based on the order of when they are placed. 

I have a LongMill MK2 pre-ordered. Can I upgrade to the 48×30?

Yes, you can upgrade by paying the difference. We would note that if you change to the 48×30, your machine will be shipping in June or July instead. Please upgrade through this product page:

When do you take payment?

We require full payment for all pre-orders. Payment is taken at the time of order.

What’s the difference between the MK1 and MK2 XZ Gantries?

The MK1 XZ gantries are the assemblies used in the MK1 LongMill machines. We generally refer to the LongMills that use angle aluminum rails as MK1 as they have the overall same structure within that generation. MK2 XZ gantries are used in LongMill MK2s, which use custom aluminum rail profiles. 

MK1 XZ Gantry Assembly
MK2 XZ Gantry Assembly

Although overall both designs are very similar, the MK2 version of the XZ gantry puts the Z motor on top of the motor mount with spacers and couplers, similar to the X and Y-axis of the machine, simplifying assembly. The motor mount is also made from CNC’ed aluminum, which improves overall rigidity and precision in that area. 

Since the hole spacings for the v-wheels are the same between the two gantries, both can be adapted to work with each other with additional brackets and hardware. In regards to the MK2 rails, however, the overall integration of the new XZ gantry is simpler and requires fewer parts than the MK1 XZ gantry, but we will be providing the additional hardware as a kit to make either option compatible.

Will there be a 48×48 version?

At this current time, no. There are a couple of engineering and logistical challenges extending the Y-axis. One of the biggest reasons is that it is difficult to purchase a 6ft x 6ft sheet which the machine would have to sit on at the 48×48 version. Part of the reason we chose a 48x30in working area is because the machine can sit on a 4ft x 6ft sheet (basically a cut down 4ft x 8ft sheet). To accommodate a 48×48 version, we would need to build a custom table as well, which is currently not a priority in development.

For customers who are looking for 48×48 size machines, please feel free to read about the AltMill in our blog ( There is no set expected release date for the AltMill, but it is likely to be in the middle to end of this year.

Are the rails on the MK1 and the MK2 Extension Kits the same?

Yes, they are the same. The base Extension Kit works for both the MK1 and MK2, and additional optional hardware can be purchased separately depending on the configuration you want to use.

How do you test performance and rigidity on the new machines?

Testing is generally done using a combination of applying forces to the machine and measuring changes using dial indicators, as well as general real-world testing. We want to make sure that users will be able to drive their machines as fast and hard as they do with our smaller versions so that compromises don’t need to be made for the 48in versions of the machine.

So with that in mind, any feeds and speeds you were using with your current LongMill shouldn’t need to change.

What does “T12” mean?

“T12” is a general term to refer to threaded rods or leadscrews with a 12mm diameter. So a T8 lead screw (the one we use for the LongMill 30×30 for example) has an 8mm diameter. We generally refer to other hardware, such as the T12 Delrin Anti-Backlash Nuts with the T12 in the name to clarify the size differences between different block sizes.

What is the overall footprint of the machine once it has been extended?

We are still working on finalizing the designs for the extension kits, so these numbers may vary, but we expect foot-to-foot dimensions to be around 62.5in by 43in. We recommend having extra space around the machine for other items and attachments. 

Will there be any tramming system built into the machine? Is it possible to tram the machine?

For the uninitiated, tramming is the process of making sure your spindle or router is perpendicular to the X and Y rotational axis of your machine. If you have ever seen small ridges on a part, especially with surfacing, it may be due (but not limited to) to the small variations in the tram of the machine. 

In some CNC routers, a tramming plate is used to adjust the angle of the router to the motion of the machine. This is usually attached to the Z-axis, and allows the router to tilt left and right to adjust.

The LongMill will not come with something like this. A big part of the reason is that we are concerned that it will affect the overall simplicity and integrity of the machine by using additional components to add a feature that we believe may overcomplicate the process for most beginners.

For almost all users, tramming should not be an issue. A properly assembled and tuned LongMill will be in-tram enough for the large majority of users and provide excellent results. While the new LongMill does not have custom plates to assist with the tramming, it should be easier to adjust the angle of the X-axis now as the four bolts on each side of the rail should allow users to adjust the rail and retighten to change the angle. The process for adjusting the rotation of the router in the Y direction remains the same (adjusting the four bolts at the back of the router or the eight M3 screws attaching the Z-axis to the linear guide blocks). 

Also worth noting, the new saw process and QA process for actually cutting the aluminum rails have been greatly improved, which means that rail components will fit together more accurately, reducing the need for tramming except in extreme circumstances.

The long and short of it is that, although the LongMill does not come with a built-in tramming system, the combination of the improved design and stricter cutting and QA processes should reduce the need for tramming to be done. For users who wish to manually tram, adjustments should be easier to make compared to the previous generation, but still require loosening, retightening, and checking tram with proper tools for higher degrees of alignment.

One of our engineers showing off the extrusion measuring tool

Will there still be continued support for the MK1 LongMills?

Yes, we’ll still be supporting the MK1 machines and any previous version of our products. Because most parts, such as Delrin Anti-backlash nuts, router mounts, V-wheels, linear guides, bearings, and control boards are cross-compatible, we will be a reliable source for consumables and replacement parts. Parts such as rails, gantries, and brackets that are made custom for the LongMill MK1 will be available until we run out. We don’t expect many people to need to replace these parts as they are the most robust parts of the machine overall.

Both the MK1 and MK2 also share the same software, which means that any resources for the LongMill will apply to any generation of machine. New content produced using the MK2 will translate in terms of concepts for the MK1 as well.

Users will also be able to find free CAD and other documentation for all versions of the LongMill here:

Why don’t you make the Y-axis rails longer instead of the X?

While making the Y-axis rails longer may technically make the machine more rigid as the rails are supported to the bed and not as prone to deflection, it eliminates one of the key benefits of having a wider X-axis, which is the ability to pass materials through the center of the machine. This is a trade-off we’ve decided to make, and we feel that there is little to no difference in actual day-to-day cutting between the different configurations.

At this time, we are not planning on releasing a longer Y-axis for the LongMill.