mill cnc conversion kit

A Comprehensive Guide To DIY Your Ideal CNC Mill Using A Conversion Kit

A conversion kit is the best way to make your manual mill CNC capable

If you own a machine shop with a manual mill, making it CNC capable with a conversion kit might be on your mind. And rightly so, since workshops of nearly all sizes are eyeing precision and speed with a CNC machine. 


You see, manual milling machines are not without limitations, and that can impact your business by affecting your workpiece quality. 




You can’t expect a manually operated milling machine to create all the workpieces in precisely the same shape and size. That’s because manual operations are prone to human error, something best reflected in the inaccuracy of manufactured goods. 


By switching over to CNC milling, you can easily overcome this problem, as automation eliminates the slightest chance of individual error. Also, the manufacturing process is aided by a computer program that provides high precision to your projects and gives them a competitive edge. 


But, when it comes to making your workshop CNC capable, the choice is between a brand new CNC machine and CNC conversion. And while it’s a good idea to buy a fully-fledged CNC machine for a new workshop, if you already own a milling machine, CNC conversion should be your go-to solution. 

Why exactly should you buy a mill CNC conversion kit?

You might be wondering why a mill CNC conversion kit fares better than a brand-new machine for your existing mill. And the answer to this lies in the cost of a CNC mill and that of milling machine CNC conversion


While a new 3-axis milling machine can cost you between $60,000 and $100,000, you can have your existing mill converted to CNC for as less as $5000. 


Not to forget, a conversion kit extends the same CNC features to your mill as a brand new CNC machine. 


So, as a machine shop owner, you can have the best of CNC features on a shoestring budget. 


Awesome, right? 

Things to consider before you opt for milling machine CNC conversion

mill cnc conversion kit

As you can see, CNC conversion is a lucrative project to go for as an owner of a manual mill. 


However, DIY CNC conversion isn’t as simple as it sounds since you’ll need to work with complex mechanical and electrical components. 


Before you begin with your DIY CNC mill with a conversion kit, you should remember that the entire process can take anywhere between a week and a month. Meaning, CNC conversion is time-consuming, and you can’t expect to turn your milling machine within days. 


Also, DIY CNC conversion is something that you can’t do alone, and we suggest you have another person to help you out. 


Why you may ask? 


You see, during the conversion process, you might be required to disassemble the mill or parts of it. And as you know, milling machine components can be too heavy for you to handle by yourself. 


Further, even if you’re a seasoned milling machine operator, you should have knowledge about the various parts of a milling machine. 


While a mill CNC conversion kit may include a user guide, a knowledge of machine parts will come in handy while disassembling or re-assembling its various components. 


That said, with the right conversion kit for your mill and a well-charted plan, you can achieve your CNC goals hassle-free. 

Which is the best mill CNC conversion kit for DIY? 

A DIY CNC conversion is a preferred choice among mill machinists, more so among hobbyists and beginners. And that is despite the fact that CNC conversions are complex projects requiring a lot of time and technical expertise. 


Nevertheless, with the right mill CNC conversion kit, the whole process will not just become simple but also swift. 


For instance, a Harbor Freight mill CNC conversion kit is apt for DIY CNC conversions since they’re the least bulky, easy to work with, and compatible with almost every mini mill. 


So no matter what kind of mill machine your workshop has, you can go for Harbor Freight milling machine CNC conversion. 


Want more? 


A Harbor Freight CNC conversion kit is the most cost-effective way to makeover your old milling machine. That’s because these conversion kits are readily available on the market for well under $2000. 


CNC machining can’t get more affordable than this, can it? 

What tools do you need for DIY CNC conversion? 

mill cnc conversion kit

Now that you know about CNC conversion kits and the ones ideal for DIY projects, you might wonder if you need some additional components too.


You see, in order to turn your existing mill into a CNC milling machine, you do need to buy some additional machining tools. That’s because the tools on your older mill may not be capable of advanced milling, and that will make your CNC mill inefficient. 


If you’re thinking about what these components are, let’s have a look at them. 

#1. Mechanical components to support CNC milling

When you’re converting your manual mill to CNC, you should replace the existing mechanical components like lead screws with a duo of ball screws and double nuts. 


You may wonder why you need to do so. 


The very reason why we recommend you replace these mechanical components is that lead screws on a mill machine have backlash and are not compatible with CNC operations. 


On the contrary, ball screws have very little to no backlash at all and are a go-to choice for the drive of a CNC milling machine. 


And while you may have to buy ball screws and double nuts separately, paying for them over and above the conversion kit, that isn’t always the case. That’s because there are many manufacturers who provide these components in their mill CNC conversion kit package. 


For instance, if you buy a Grizzly G0704 benchtop mill conversion kit, you’ll get 16mm ball screws and double nuts on the X and Y axis, among others, included in the package. 


Sounds amazing, doesn’t it? 

#2. Electrical components for your CNC milling machine 

While buying a mill CNC conversion kit, there are some electrical components that you’ll need to purchase, too, since they’re required to control CNC machining. 


To begin with, you should buy a good quality controller, along with some limit switches, stepper drivers, and mechanical probes to effectively control the X, Y, and Z movements of your machine. 


Next up comes the spindle control, and if you’re looking to control the RPM manually using buttons, we recommend you buy a VFD. 


Lastly, you’ll need a computer placed at the opposite end of the controller to run the CNC software and give instructions to your milling machine. And once you’ve bought the computer, there are many CNC software readily available to install and run, from Mach3 to GRBL to LinuxCNC. 

How to convert your mill with a CNC conversion kit? 

mill cnc conversion kit

The conversion process of mills differs for different milling machines and conversion kits. But, generally speaking, here’s what the whole process includes: 

#1. Mechanical retrofitting of your mill 

Mechanical retrofitting is the first step in CNC conversion, and herein you’ll be required to disassemble the entire mill before you deploy the conversion kit. And it isn’t as simple as merely replacing the components since disassembly and reassembly processes involve dealing with bulky and complex machine parts. 


At first, you should remove each axis of your mill and replace lead screws in each of the axes with ball screws. 


Since the Z axis of your machine, in particular, can weigh a thousand pounds, you simply can’t remove it manually. So we recommend an engine hoist to easily pick up and safely move the axes. 


Also, your mill might well be screwed to the floor with nuts and bolts, which you’ll have to remove. 


When each axis is removed, you can individually add the CNC components to them. 


The next step in mill CNC conversion is attaching stepper motors to your machine’s axis. During this process, you should ensure that the stepper motor is capable of handling the heavy weight of the Z axis. 


After you’ve attached the stepper motors to the X, Y, and Z axis, you’ll need to put them back in their place. 

There’s more to mechanical retrofitting

Before you can start using the milling machine, you need to properly square the Z axis and make sure that it is precisely perpendicular to the work table. This process is also called tramming of the mill and is done using a tramming indicator. 


If you find that the mill isn’t properly trimmed, then you can use the metal sheets under the machine’s base to shim the column and adjust its leaning. 


Once you’ve completed tramming of the column, you need to do the same for the spindle, too, and make sure it’s not tilting.


Having completed tramming on both column and spindle, your milling machine will now be ready to use. 

#2. Electronics installation to make your mill CNC capable

After mechanical retrofitting comes setting up electronic components, which is necessary to enable CNC milling on your machine. 


And here’s a catch you should be aware of. 


You need to install the stepper motors on each axis before you begin installing electrical parts on your machine. 


To start with, you’ll need a control system to be fixed for the stepper motors. You see, the control system is the most critical component of your machine since it makes the mill computer-controlled instead of hand-operated. 


Apart from the control system, there are a host of other electrical components you should purchase for the mill. And that includes an unregulated DC power supply, three limit switches, and two probes. Also, we recommend you buy three stepper motor drivers to run your mill’s stepper motors. 


Next comes the controller of your benchtop CNC mill, something you should carefully choose as the controller needs to be compatible with CNC software. 


However, if the CNC control packages are compatible with Mach3, LinuxCNC, or GRBL, you can certainly go for it. That’s because these are the most common CNC software and many popular mill conversion kit brands include them in their kit package. 

Spindle retrofit to effectively use a mill CNC conversion kit

For an effective CNC conversion of your mill, you’ll need to retrofit the spindle system. 


So, if your mill runs on a spindle motor system that is gear driven, you’ll have to convert it to a belt drive system. And for that matter, a belt drive mill CNC conversion kit will be ideal for converting your milling machine. 


Further, you should get a VFD motor controller apt for the spindle motor to control the spindle of your machine. You’ll usually find manual buttons on VFDs, which you can use to increase or decrease the spindle’s RPM. 

Wrapping it up

A DIY mill CNC conversion is indeed the best project you can undertake for your machine shop, all you need is the right conversion kit. 


And while CNC conversions may sound complicated, if you’re acquainted with milling machines, you can also convert them to CNC without any trouble. 


In fact, the mill CNC conversion kit manufacturers even provide a user manual with a detailed step-by-step process, which you can use to convert the machine. 


If you’re looking for one such mill conversion kit, you can check out our products. We have the best CNC conversion kits on the market from world-renowned manufacturers. And we can ship your ideal conversion kit right to your machine shop, that too, at the most competitive price. 


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