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cnc milling machine with control panel

Buying a Used Milling Machine? Here are 10 Things You Should Know

Bridgeport M, CNC Conversion Kit, CNC Machining / By / June 2, 2022
Contents hide
1. What is the Machine’s Table Size?
2. Should you consider a CNC Conversion Kit?
3. Does the Used Milling Machine Have Power Feed on the Longitudinal (X-axis)?
4. Is it Equipped with an Acu-Rite Digital Readout (2-Axis DRO)?
5. Do You Need a Mill That is Also a Drilling Machine?
6. Does the machine tool run on single-phase or 3-phase power?
7. Does the Used Milling Machine Have the Spindle Speeds You Require?
8. Does the milling machine have a warranty?
9. What are the Longitudinal, Saddle, and Knee Travel Limits?
10. Do You Want to do CNC Milling, or is a Traditional Manual Machine All You Need?
Bonus: How will you receive your CNC machine?

Are you thinking about buying a used milling machine? Many business owners, home machinists, and hobbyists prefer a used milling machine because a new one is out of their price range. Fortunately, a carefully chosen used machine tool will get the job done efficiently and save you lots of money.

However, buying a used CNC milling machine or manual Bridgeport-type vertical knee mill is a significant investment. Before making the purchase, there are some essential factors to consider, and let’s look at ten of those factors individually and in more detail. But first, let’s determine which type of milling machine you need.

You Will Likely Search Among Six Types of Used Milling Machines

Depending on the type of milling you will be doing, you will probably choose from the following:

  • Vertical milling machine: Vertical milling machines are used for machining flat surfaces, grooves, and slots. The table moves up and down and feeds in the X-axis and Y-axis (left-to-right and in-and-out).
  • Horizontal milling machine: The spindles are horizontal, and the machines are sturdier with a horizontal milling machine. The horizontal spindle requires different types of tooling compared to the vertical milling machine.
  • Bed type mills: The bed mill differs from the vertical knee mill in that the bed mill’s table is fixed on the Z-axis, while the knee mill’s table moves up and down on the Z-axis.
  • Turret milling machines: Bridgeport-type milling machines or vertical knee mills are pretty versatile and can perform various operations.
  • Universal milling machine: The universal milling machine can perform various operations, especially if you add a rotary table or dividing head. Operators can pivot the table 45 degrees from both sides for even greater versatility.
  • CNC milling machine: CNC milling is a process using a cutting tool on a rotating spindle to remove material from a workpiece mounted on a working surface or in a vise. A multiple-axis CNC can create complex shapes without moving the workpiece to another machine tool for secondary operations.

Should You Buy a Brand Name Such as Bridgeport or Cincinnati?

Brand names influence many purchasing decisions, but how much do they matter? You might recognize words like Acer E-Mill 3VKH, Bridgeport Series I and Series II, the Cincinnati Horizontal Milling Machine, or one of the Seiki brands of CNC machine tools.

You’ll also run into brands you don’t recognize: Acra, Trak, Lagun, and Kearney & Trecker, for example. You might prefer a used milling machine manufactured in the U.S. over one made in Taiwan, for instance. In theory, any manufacturer might design and manufacture quality machines, so you should be careful not to eliminate a machine using the wrong criteria.

Although a used milling machine brand that withstood the test of time has the best chance of being a respected brand, don’t pick your next used milling machine solely on its brand name. There are many more factors to consider including the machine’s features, its warranty, and overall condition. Let’s look at the various factors that typically indicate if the machine tool will fit your requirements, give you value, and then choose. Here we go:

1. What is the Machine’s Table Size?

Maybe a used desktop milling machine is all you need for your operations, but size matters if you intend to machine large metal parts as part of fabrication or repair work. Your working surface must accommodate the largest workpiece you anticipate, so make sure you choose a heavy-duty machine with the appropriate table size.

2. Should you consider a CNC Conversion Kit?

Whether used or new, purchasing any CNC machine is a big investment. However, almost anyone with a compatible milling machine who wants to give their machine features found in CNC machines can use a CNC conversion kit.

A conversion kit can help reduce costs even further, extend the lifespan of your mill, increase production, and provide additional safety. For specific information, please make sure to contact us before purchasing a conversion kit.

3. Does the Used Milling Machine Have Power Feed on the Longitudinal (X-axis)?

It would be a bonus if each axis had a power feed, but it is essential to have it on the X-axis if you plan to do slotting or surface milling. You don’t want to be cranking a handle for hours when you can have a power feed doing the cranking.

4. Is it Equipped with an Acu-Rite Digital Readout (2-Axis DRO)?

You can add a digital readout to the X-axis and Y-axis later, but it would be better if the used mill already had a DRO. A DRO provides a display telling you the distance you moved the table. And even though they aren’t necessary, DROs are far superior to the time-consuming process of reading the dials on the machine.

5. Do You Need a Mill That is Also a Drilling Machine?

If you need a used milling machine that serves as a drilling machine, sometimes called a mill drill, you have narrowed down your choices. It is your best option if the turret milling machine, a.k.a. the Bridgeport-type vertical knee mill, covers all your other requirements. These versatile machines can perform various operations when you clamp the workpiece directly to the table using the t-slots or by fastening a vise to the working surface and holding smaller pieces for milling or drilling.

6. Does the machine tool run on single-phase or 3-phase power?

You probably don’t have 3-phase power at your home, so if you’re buying the used milling machine for your home shop, you’ll be limited to machines that can run on standard household power. However, if you have industrial space with 3-phase power available, you can search for an industrial-grade machine. Or, if you find a 3-phase machine for your home shop, you can replace that spindle motor with a single-phase unit or buy a phase converter.

7. Does the Used Milling Machine Have the Spindle Speeds You Require?

If you are machining materials like aluminum, soft metals, wood, or composites, make sure that you choose a machine with variable speeds with higher spindle speeds optimal for that type of work. A high-speed head could make the difference between buying or moving on to the next mill.

8. Does the milling machine have a warranty?

Buying a used milling machine is an investment. Lightly used machines may have a nice discount, but what about a warranty?

Not all manufacturers will include one, but buying a machine under warranty or obtaining a warranty is a great way to protect yourself in the event the machine has unknown issues.

9. What are the Longitudinal, Saddle, and Knee Travel Limits?

Investigate the travel limits of the longitudinal (X-axis), saddle (Y-axis), and knee travel (Z-axis) to ensure the machine tool can cover the dimensions of a typical workpiece. Otherwise, you’ll spend too much time unclamping and moving the material to reach the entire work surface. If you’re looking at a Bridgeport-type vertical milling machine, remember you’ll have a moveable ram and a turret that swivels to cover even more of the workpiece.

10. Do You Want to do CNC Milling, or is a Traditional Manual Machine All You Need?

If you want or need a CNC vertical or horizontal milling machine with CNC control, now is the time to decide. A quality used Bridgeport Series I vertical knee mill might have everything you need if you’re mainly doing repair or jobbing shop work. On the other hand, if you’re hoping to get into production work or complex parts, the CNC milling machine is the way to go, or you should give it serious consideration.

Bonus: How will you receive your CNC machine?

If you’re buying online from a trusted CNC machine company, chances are they’ll arrange to ship. But some CNC machines are quite large. And even if the machine is picked up in your local area or state, you may need to hire a heavy equipment shipping company to bring the machine home.

You Could Buy a High-Quality New CNC Milling Machine for Not Much More Than a Used Milling Machine?

The professionals at CNC Masters believe you should be able to have a CNC milling machine or lathe without destroying your budget. After you have determined the features you want in a used milling machine, check out our lineup of new machine tools you could add to your shop. All of these machines will provide you with all power and versatility you’ll need to take your business to the next level.

All CNC Masters machines are made in the USA and backed by our one-year limited warranty, so it’s a brand you can trust. We provide excellent and reliable customer support from knowledgeable technicians ready to serve you and answer all your questions. You will always be talking to someone who completely understands our product line.

Contact CNC Masters today and watch your profits soar!

Have Questions? Need a Quote?

Looking for more information about our CNC machines and services? Contact us today.

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MX Software – Easy to Use, Easy to Learn – Included with your machine purchase
The MX software is designed to work seamlessly with your CNC Masters machine. It is made to work with Windows PC – desktop, laptop, or an all in one – on standard USB. Use it on Windows 8 or 10 64-bit operating systems.
No internal conversion printer/serial port to USB software or additional conversion hardware is used with the MX.

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2. Clutter Free Interface
The MX is engineered for the CNC MASTERS machine so you do not have to fiddle with a detailed complicated configuration that can be overwhelming. Just load in the MX and start machining!2. Clutter Free Interface
The MX is engineered for the CNC MASTERS machine so you do not have to fiddle with a detailed complicated configuration that can be overwhelming. Just load in the MX and start machining!

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3. Features Tour and Tutorials Included
The Features Tour will give you a quick run-down on all the features the MX can do for you. The Tutorials are easy to follow even for the first time CNC machinist.
Feel free to download the MX on any of your computers. We recommend downloading the MX along with your CAD and CAM software there at the comfort of your office computer to generate your tool path programs. You don’t need to be hooked up to the machine either to test your program in simulation mode.

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4. Navigate and Edit Your Program through the MX interface with Ease
With a few clicks of the mouse or using touch screen technology, you can easily navigate through the MX interface importing saved programs into the Editor from the File drop down menu. Using standard windows features to edit your program you can then lock the Editor Screen to avoid accidental editing, and if you need to insert a line in the middle of a program, just click on [ReNum] to re-number your tool path list.
You can create a program or import CAM generated G-code tool paths into the Editor
The X Y and Z W arrow jog buttons are displayed from the point of view of the cutter to avoid confusion when the table and saddle are moving. You can also adjust your spindle speed and coolant control while jogging each axis.

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5. Feed Hold – Pause in the Middle of your Program
Feed Hold lets you pause in the middle of a program. From there you can step through your program one line at time while opting to shut the spindle off and then resume your program.
You can also write PAUSE in the middle of your program and jog each axis independently while your program is in pause mode.

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6. Hot Keys
Hot Keys is an alternative method to easily control your machine using your hard or touch screen keyboard. One can press P to pause a program, press S to turn Spindle On, G to run a program, Space Bar to Stop, J to record your individual movements one line at a time to create a program in teach mode.

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7. Pick Menu – for conversational mode programming
Write FANUC style G-codes directly into the Editor or select commands off the [Pick] menu and write your tool path program in conversational mode such as what is written in the Editor box. You can even mix between conversation commands and G-codes in the same program.

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8. Pick Menu List of Options
Use commands such as MOVE, SPINDLE ON/OFF, COOLANT ON/OFF, PAUSE, DELAY, GO HOME…. to write your tool path programs in conversational mode.

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9. Draw the Tool Path to verify it before pressing Go
Hit Draw to view your tool path program drawing, check out its run time, or even simulate the tool path in 3D mode. This can be helpful to quickly verify your program before running it. You can also slow down or speed up the drawing or simulation process.
You can also hit Go within the Draw Window itself to verify the cutter’s position on the machine. The current tool path will be highlighted and simultaneously draw out the next path so you can verify what the cutter will be doing next on the program.

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10. Run each tool path independently to study its movement
1. Run the machine on Trace mode. You can run each tool path independently, one line at a time to study the tool path movement on the machine to verify the position of the application and if any fixture/vise is in the way of the cutter’s path.

2. You can also verify your program by clicking on the Trace and Draw buttons together. This will allow you to view each tool path independently one line at a time in the Draw Window.

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11. Counters display in Inches or Millimeters – Continuous Feed
1. When running a program, the counters will display a “real-time” readout while the machine is in CNC operation without counting ahead of the movement.
2. The current tool path is highlighted while the machine is in operation without causing slight interruptions/pauses as the software feeds the tool path to the machine. The MX internally interprets a program ten lines ahead to allow for “continuous machining” avoiding slight interruptions as the machine waits for its next tool path command.
3. “Run Time” tells you how long it takes to run your tool path program.

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12. Use the “Go From Line” command to start in the middle of your program
If you ever need to begin your program from somewhere in the middle of it, use [Go From Line] which you can find under Tools. The Help guide will walk you through how to position the cutter without losing its position on the machine.

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13. Exact Motion Distance without over-stepping on an axis while jogging
Use “Relative ON” to enter a specific coordinate to jog any of your axes to an exact location without having to write a program. It’s like using “power feed” but easier. You can jog an exact distance on any of the axes without needing to keep the key pressed down and mistakenly over-step the movement releasing your finger too slowly off the jog button.
Let’s say you need to drill a hole exactly 0.525” using the Z. So you enter 0.525 in the Z box. Next, adjust the JOG FEED RATE slider for the desired feed rate. Then “click once” on the +Z or -Z button to activate the travel. In this case you click once the -Z button first to drill the hole exactly 0.525”. Then click once on the +Z button to drive the axis back up 0.525”.

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14. Teach Mode – Jog Input
You can create a tool path program by storing each point-to-point movement by simply jogging an axis one at a time. Click on either of the Jog Input buttons to store each movement on the Editor Screen. You can then add Spindle ON, feed commands, and press GO to run the new program as needed. This is a great feature to help you learn to create a program by the movements you make on the machine without necessarily writing out an entire program first.

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15. Override on the fly to adjust the Jog Feed to Rapid or the Spindle Speed during the middle of a program
1. Jog Feed and Rapid with Override: You can adjust feeds using the slider from slow minimum 0.1″ per minute to a rapid of 100″ per minute of travel. You can even micro-step your jog as low as 0.01”/min. The [-][+] buttons allow you to fine tune feeds in 5% increments while the program is in motion.
2. Spindle Speed with Override: You can adjust speeds using the slider from a slow minimum RPM to the max RPM according to the machine setup. The [-][+] buttons allow you to fine tune feeds in 5% increments while the program is in motion.

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16. Adjust Counters using Pre-Set if you cannot begin the program from 0.00
In a situation where you cannot begin your cutter at it’s 0.00 location, you can “Pre-Set” directly into the counters by typing in your beginning coordinate. You can press Go from here to run your program. You can also “zero all” or “zero” your counters independently. With one click of the [Return to 0.0] button, all axes will travel back to its respective 0.0 on the machine.

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17. Set and Save your 0.00 position for future runs
Set and save your 0.00 position on the machine. These coordinates will be recorded as the first line of the program in the Editor Screen. Should you desire to return to this program at a later date, you only have to click on the Set Zero Return button. This will command the machine to automatically jog each axis to its saved “set” 0.00 position according to the recorded coordinates at the first line of the program.

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18. Create a “Home” position to clear your application and run multiple times
Let’s say you need to machine one application times 100 pieces. This usually requires a jig to retain that physical 0.00 position. But in this case, you want the program to end with a clearance of the axes to easily switch out the next piece of stock and start again. With Save Home, you have the ability to save this offset (home) position while still retaining your Set Zero position where the machine will mill your part out. Pressing [Save Home] will record this new position under the Set Zero line in your program.
Pressing [Go Home] will jog your axes back to your “saved home” position where you originally pressed the Save Home command. You can also input GO_HOME from the Pick Menu as its own tool path in your program. At the completion of your program the axes will end at your Home position. Replace your part, then press [Return to 0.0] button to allow the axes to return to its zero position, and press Go to start your next run.

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19. Disable the axis motors to manually hand crank each axis into place
Easily de-energize the axis motors by clicking [Disable Motors] to crank each axis by hand, and then press [Reset Control] to re-energize the axis motors.

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20. Change up to 30 tools with compensation, and store your tool offsets for other programs
The MX supports…

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21. Use the optional ATC rack up to 8 tools for milling, drilling, and rigid tapping applications
The CNC Masters Automatic Tool Changer Rack and Tools (US Patent 9,827,640B2) can be added to any CNC Masters Milling Machine built with the rigid tapping encoder option. The tutorial will guide you through the set-up procedure using the ATC tools.

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22. Use the optional Rigid Tapping Wizard without the need for tapping head attachments
When you order your CNC Masters machine, have it built with the optional rigid tapping encoder. You can take any drill cycle program and replace the top line with a tapping code created by the wizard to tap your series of holes up to 1/2” in diameter.

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23. Use the optional Digital Probe to scan the profile and/or pockets of your fun/hobby type designs to write your tool path program and machine out a duplicate of your original design To “surface” scan an object, you can program the probe along the X or Y plane. The stylus will travel over the part starting on the left side front corner of the object and work its way to the end of the part on the right side. Depending on how the stylus moves, it will record linear and interpolated movements along the X, Y, and Z planes directly on the MX Editor.
To “pocket” scan an object containing a closed pocket such as circles or squares, the scan will start from the top front, work its way inside of the pocket, and scan the entire perimeter of the pocket.
Under the Setup of the MX software you will find the Probe Tab which will allow you to calibrate and program your probe. Your “Probe Step”, “Feed”, and “Data Filter” can also be changed on the fly while the probe is in the middle of scanning your object.

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24. Use work offsets G54-G59 for nesting applications
The work offsets offer you a way to program up to six different machining locations. It’s like having multiple 0.0 locations for different parts. This is very useful especially when using sub-routines/nesting applications.

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25. Create a Rectangular Pocket / Slot with our selection of Wizards to help you build a tool path program
The Cycle Wizards for the mill or lathe makes it easy to create a simple tool path without needing to use a CAD and CAM software.
On this Wizard, the Rectangular Pocket / Slots, can be used to form a deep rectangular pocket into your material or machine a slot duplicating as many passes needed to its total depth.

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26. Create a Circular Pocket Wizard
Input the total diameter, the step down, and total depth and the code will be generated.

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27. Do Thread Milling using a single point cutter Wizard

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28. Cut a gear out using the Cut Gear Wizard with the optional Fourth Axis

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29. Create a Peck Drilling Program in Circular or Rectangular Patterns
Using the Circular or Rectangular Drilling Wizards, you can program the machine to drill an un-limited series of holes along the X and Y planes. Program it to drill straight through to your total depth, use a high-speed pecking cycle, or deep hole pecking cycle. You can program the cut-in depth and return point for a controlled peck drill application to maximize chip clearance.

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30. The MX interface can easily be interchanged from Mill Mode to Lathe Mode
Use this interface for your CNC Masters Lathe. It contains all the same user-friendly features and functions that comes in Mill Mode. Simply go to the Setup page and change the interface.

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31. Use Tool Change Compensation or the optional Auto Tool Changer Turret if your application requires more than one tool in a single program
You can offset the length and angle of each tool and record it under Tools in your Setup. The program will automatically pause the lathe’s movement and spindle allowing you to change out your tool, or allowing the optional ATC Turret to quickly turn to its next tool and continue machining.
On the MX interface, you also have four Tool Position buttons. Select your desired T position, and the auto tool post will quickly turn and lock itself to that position.

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32. Use the Lathe Wizard Threading Cycle to help you program your lathe’s internal or external threads in inches or metric

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33. Use the Lathe Wizard Turning / Boring Cycle to help you program simple turning and boring cycles without having to go through a CAM or writing a long program with multiple passes

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34. Use the Lathe Wizard Peck Drilling Cycle to help you program your drill applications or for face grooving

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35. Facing / Grooving / Part Off Cycle Wizards – with Constant Surface Speed
These cycles can be used with Constant Surface Speed allowing the spindle speed to increase automatically as the diameter of the part decreases giving your application a consistent workpiece finish. With CSS built into the wizard, there is no need to break down the cycle into multiple paths and multiple spindle speed changes.

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36. This is our list of supported G and M codes which can be found under Tools > G Code/ M Code List in the MX
If you plan to use a third-party CAM software to generate your tool path program, use a generic FANUC post processor and edit it to match our list of codes. As an option, we also sell Visual mill/turn CAM software which comes with a guaranteed post processor for our machines to easily generate your tool path programs based on your CAD drawings.

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37. Our pledge to you…

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