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AltMill MK2 4×4

Name: AltMill MK2 4x4
Brand: Sienci Labs Inc.
SKU: AM4X4MK2
Availability: InStock
Rating: 4.76 (262 reviews)

Rated 4.76 out of 5 based on 262 customer ratings

(262 customer reviews)

$4,290.00

The AltMill is the pinnacle of hobby CNCing, bringing industrial-level precision to a price point and ecosystem for both beginners and advanced users. The AltMill MK2 4×4 is your go-to CNC when time, performance and precision are crucial for production-level reliability.

The AltMill MK2 4×4 comes with a standard 80mm spindle mount only. It does not come with a spindle, which must be purchased separately.

Ontario. Canada Customers: Starting April 29th, we’ll be pausing sales for all sizes of AltMill. Please read further on specific plans for each machine – ESA Compliance.

Lead Time: 1 week

Description

Highlights:

Production level cutting speeds (approx. 600 inches/minute)
Closed loop motor system on all three axis to auto-correct positioning and auto-stop when necessary (reliable for production style work)
Requires little maintenance during project production
Advanced, production-style features including Y-axis auto-squaring; limit switches by default; and tram adjustment capabilities
Cuts materials ranging from hardwoods to plastics, foams, composites, aluminum – even steel
Support for 80mm spindles and routers
49″ x 49″ working area with a max Z-height of 5.5″
Footprint of 59″ wide and 62″ deep

Lead times
This product has a potentially long waitlist, relative to demand and seasonality. For more info on expected shipping and delivery times, please see our Order Status page.

Additional information

Weight	76 lbs
Dimensions	38 × 11 × 12 in
Include Spindle and Dust Shoe Kit	Include Spindle and Dust Shoe Kit, Machine Only
origin-criterion	C
Lead time	1 week

What's Included

Included with your AltMill MK2 4×4

SLB-EXT controller and emergency stop
48 Volt Power Supply
Partially pre-assembled rigid frame
Inductive sensors for homing
Sturdy metal legs with the ability to add 4ft wide shelving underneath

***Not included with your AltMill MK2 4×4***
Check out our recommended products tabs for an ideal set up, but note the following ARE NOT included with your order:

Computer or laptop
Spindle
End mills or bits
T-tracks
Waste board (e.g. MDF 2ft x 4ft sheet)
Set of metric Allen keys, standard bits or drill for assembly

***Some photos may contain items for illustrative purposes, such as spindles, caster wheels, t-tracks, or additional shelving. There may also be cosmetic differences between the machine in the photo and the production version of the AltMill.

Specifications

Specifications

Rigid frame and linear motion design using HGR15 linear guides and ball screws on all axis mounted to a custom-designed, machined aluminum extrusion
Closed loop stepper motors for over 600IPM
Support for 80mm spindles and routers
49″ by 49″ working area with a max Z-height of 5.5″
Inductive sensors for homing included
Sturdy metal legs with the ability to add 4ft wide shelving underneath
Footprint of 59″ wide and 62″ deep

Must Have Add-on: 1.5kW, 2.kW Spindle or 2.2kW ATC Spindle

Unlock the full potential of your AltMill with a 1.5W or 2.2KW ER Spindle and Dust Shoe Kit, or, an Automatic Tool Changer Spindle Kit

Each 1.5KW ER20 Spindle & Dust Shoe Kit comes with:

80mm Dust Shoe
ER20, 80mm, 1.5KW 110V Air-Cooled Spindle
110V, 1.5KW, 3-Phase VFD
AC power cable and 5m spindle power cable
ER20 1/8″, 1/4″, 3/8″and 1/2″ collets (one of each)
Data cable to connect to the AltMill/SLB-EXT controller for remote speed control

Each 2.2KW ER20 Spindle & Dust Shoe Kit will come with:

80mm Dust Shoe
ER20, 80mm, 2.2KW 220V Air-Cooled Spindle
220V input, 2.2KW, 3-Phase output VFD
NEMA 6-15P AC power cable and 5m spindle power cable
ER20 1/8″, 1/4″, 3/8″and 1/2″ collets (one of each)

Each ATC Spindle Kit comes with:

2.2kW ATC Spindle
ATC Spindle Mount
Enclosed 2.2kW VFD and Mount Adapter
Clear Cut Dust Shoe
Tool Length Sensor
ATC Expansion Board for an SLB-EXT Controller
2.2kW VFD NEMA 6-15P Power Cord
10m Length 8mm Air Line Tubing
Male ¼” NPT to 8mm Air Line Push Fitting
ER20 Collet Wrench

**Each ATC Spindle Kit comes with a variety of tool holders, collets or racks (or no rack.) Read for more details.

Recommended Add-ons & Accessories

FAQs

Choosing an AltMill vs a LongMill

Payment
Full Payment is required at time of purchase to get your order into the Queue. We ship on a first-come, first-served basis. If you choose local pick-up, you are subjected to the queue order and cannot get your machine quicker.

Power Requirements
AltMill with the 1.5kW spindle. We recommend allocating 2x 15A, 110V/120V circuits — one for the spindle, the other for the machine and a computer.

The AltMill consumes 500W and runs off a 48V 10A power supply, 110-120 volt circuit
The 1.5KW Spindle Kit consumes 1500W at max load, 110-120 volt circuit

AltMill with the 2.2kW spindle. We recommend allocating 1x 15A, 110V/120V & 1x 20A, 220/240 Circuit — one for the spindle, the other for the machine and a computer.

The AltMill consumes 500W and runs off a 48V 10A power supply, 110-120 volt circuit
The 2.2KW Spindle Kit consumes 2000W at max load, 220-240 volt circuit

If you live in a country with 220V/240V power you must use a transformer to convert to 110V/120V.

To solely run the machine, you need a rating above 500W
To run the machine and a 1.5kW spindle, you need a rating of 2000W

AltMill Power Supply Specifications: Input: 100-130 VAC 50/60 Hz, 7-54 Amps, Output: 48 VDC 10 Amps, 480 Watts

3rd Party Spindles – I would like to source my own spindle, what should I be aware of?

For spindles 2.2KW or above, you will need to install extra 220VAC wiring
The AltMill comes with an 80mm spindle mount, we do not have larger diameter mounts at the moment
The VFDs that may work with our controller are: Huanyang v1, Huanyang P2A, Yalang YL620, H-100, and GS20, however they are not plug-and-play — read this article for further information

Warranty

The AltMill has a 1-year warranty once it arrives at your door.

We want you to have a great experience with your machine, so if any parts are found to be missing or damaged, please email us. We will ensure that you receive the support you need to restore your AltMill to operating condition or provide a full or partial refund.

You may cancel an order if it has not shipped yet, please contact us if you wish to do so. We do not accept returns for AltMills that have already shipped.

General Warranty and Limits of Service:

Effective August 1, 2026:

Throughout this policy the words “we”, “us” and “our”, or “Sienci Labs” will be used to refer to Sienci Labs Inc. herein and “AltMill” or “machine” will refer to Sienci Labs’ Sienci AltMill. Additionally, the words “you”, “your”, “user”, and “operator” will refer to the original purchaser/customer, user, or viewer of any of the products or media provided by or through Sienci Labs.

Sienci Labs Inc. (the “Company”) grants the AltMill (the “Product”) a standard warranty within Canada and the US to the original customer to be free from missing parts, defects in material, and defects in workmanship for a period of three-hundred-sixty-five (365) days from the date of receipt by the original purchaser. Sienci Labs Inc. will ensure that the appropriate support is provided to the original customer to restore the AltMill to operational condition or provide a full or partial refund under the sole discretion of the Company.

This warranty does not cover damage due to improper use or assembly, lack of maintenance, normal wear and tear, or modifications to the AltMill which are not produced or authorized by the Company. Consumables such as cutting tools and sample or stock materials which may have come with your AltMill are not included in this warranty.

This warranty will become void if the operator does not follow the Safety Warnings and Guidelines, uses the Product for illegal purposes, intentionally causes damage to the Product, or transfers the Product to another owner.

The original customer must contact Sienci Labs Inc. within three-hundred-sixty-five (365) days of receiving their order to make a warranty claim to be eligible for warranty service. Proof of purchase, tracking number, email address, or other material will be used to confirm the original purchasing date and the identity of the original customer. If damage was due to shipping, original packaging materials must be kept in the original received condition. Photos, videos, written descriptions, and other items may be requested to assess and validate a warranty claim.

In the case Sienci Labs Inc. requires the original parts to be returned, the customer is solely responsible for packing all items securely. Damage incurred during return shipping will not be covered by the warranty. A method of payment such as a credit card may be requested by Sienci Labs Inc. to cover shipping costs or damaged items if Products are not eligible for warranty service.

Instructions & Assembly

New CNC users, Read these Resources to Ensure a Successful Start. When assembling the AltMill, use the Resources as well as the Assembly video for a successful start.
Assembly Overview & Detailed Instructions
About Your AltMIll
AltMill Prep before it Arrives
How to Choose Design Software

Videos

Shipping

This product has a lead time. View current lead times.
Our products are subject to the USMCA and are not affected by the 35% tariff on Canadian goods. Read how we are handling the situation.
We will be shipping to US customers with UPS option only.

262 reviews for AltMill MK2 4×4

4.8

Based on 262 reviews

5 star	84	84%
4 star	9	9%
3 star	3	3%
2 star	0	0%
1 star	1	1%

Rated 3 out of 5

James S. (verified owner) – September 1, 2026

Had to get the kead screw replaced at kess than 3 months old. Peak construction season here so havent had time to install it yet. Dont know if it will fix the issue. Not at all happy with that experience. Back and forth with tech help yielded no helpful suggestions. Tried calling 3 or 4 times, no answer or return calls. Finally had to go to the forums and ask how to get ahold of a human to talk with someone. Had to reach back out to find out how the issue was going to be handled. On the good, you guys did replace the lead screw for free and promptly once reminded. VERY disappointed in the customer service quality and response times and thats part of why I went with the altmill.

(0) (0)
Rated 5 out of 5

Kevin Hair (verified owner) – August 26, 2026

I love my new Altmill 4×4. Set up was easy with the videos. Customer support has been great and very quick responses. The XYZ auto zero is a must have.

(0) (0)
Rated 5 out of 5

patrick b. (verified owner) – August 26, 2026

Packaging is excellent. Pretty easy to assemble. Allen tools are a bit sloppy and strip bolt heads pretty easily. Use better tools if you have them.

(0) (0)
Rated 5 out of 5

frank hays (verified owner) – August 25, 2026

assembly instructions were excellent

(0) (0)
Rated 5 out of 5

Camille Patch (verified owner) – August 25, 2026

One big problem though, the xyz probe needs a code tweak. I’ve crashed it a couple of times because I forgot to select the corner I was using. The speed that the head moves at is waaaaaay to fast during this operation, especially since I have to hold the block down. Very dangerous and frustrating. Also, the stop button on the screen doesn’t work during this time, so I have to run to the big red button.

(0) (0)
Rated 5 out of 5

JAMES B. (verified owner) – August 21, 2026

Amazing CNC, reliable and accurate

(0) (0)
Rated 5 out of 5

William Scrote (verified owner) – August 17, 2026

I upgrade from the LongMill mk2 30×30. It was a good machine to learn CNCing on. The Altmill 4×4 mk2 is a whole other level. It moves quicker, completes jobs faster and gives a better quality finish than the LongMill mk2. Not having used any other brand of CNC machine I can not compare brands from other companies. But, since my experience of learning on the LongMill mk2 was invaluable for learning how to CNC on a beginners machine I chose to upgrade to the Altmill Mk2 and have not been disappointed.

(0) (0)
Rated 5 out of 5

ERNEST Phillips (verified owner) – August 17, 2026

well thought out assembly. went smoothly

(0) (0)
Rated 5 out of 5

Marc McAteer (verified owner) – August 17, 2026

A wonderful machine

(0) (0)
Rated 4 out of 5

Travis (verified owner) – August 15, 2026

Overall the machine is great. When running at faster speeds the machine will shake when changing directions. Some additional supports in the legs may help with this.

(1) (0)
Rated 5 out of 5

andy s. (verified owner) – August 14, 2026

Price seems reasonable for the rigidity of the machine. It was easy to set up based on the video. There were a few things that are outdated on the video that I had to figure out but overall I used the video over the written instructions. I did call but left a message and your team called back but did figure out what I needed to do. So far experience has been good and I have able to make a few things so far.

(0) (0)
Rated 4 out of 5

Gordon Stephenson (verified owner) – August 6, 2026

Functionally, everything is top tier and I honestly couldn’t be happier. I was a CNC machinist in my career, and have had plenty of CNC routers over the years. I can confidently say the altmill will be my last, I’m that confident in it’s longevity.
Mechanically there are minor issues I’m still figuring out, the most annoying is the motor placement for the Y axis. I’ve spent hours trying to align the motors to make them run quiet, including beating the mounting plates with a 1lb rubber mallet like they owe me money. A LOT of money.
They still refuse to align.
My next step is a file.

(1) (0)