Selecting Your First Used Milling Machine
Looking for a milling machine? CNCMachines.net carries used milling machines. Our machines are ready work. Milling machines come in wide range of sizes and prices for various applications. This guide can help you to select the best milling machine for your application and budget.
When you want to start making things out of metal to even moderately tight tolerances, a milling machine might be your most practical option. But for the hobbyist without machining experience it can be confusing. What kind of milling machine should you get? What is the difference between vertical and horizontal milling machines? Do I need CNC when I’m getting started? How much space am I going to need to get started? For the beginner in machining, a basic milling machine is a great place to start and we’ll help answer your questions.
What kind of milling machine should you buy?
To begin with, CNC mills are considerably more complex than standard milling machines. If you plan on eventually producing a lot of parts for commercial sale and you’re willing to learn about programming, please see Find the Perfect Used CNC Mill for guidance. If you know you’re not ready for computer numeric controlled (CNC) milling, then continue on.
Milling machines are divided into two major categories, horizontal milling machines and vertical milling machines. This has to do with the orientation of the machine’s spindle. If the spindle is vertical (up and down), then the machine is a vertical milling machine. Vertical machines have the table mounted perpendicular to the spindle’s zero-tilt position. As the name implies, horizontal milling machines have spindles holding tools horizontally. Both kinds of machines can be used for the same tasks, but some jobs will be a lot easier on one than the other.
Horizontal Milling Machines
Horizontal milling machines have incredible rigidity because their strength is the overarm. It constrains the rotating arbor on two sides. Machinists can make very heavy cuts that would introduce more side load than vertical milling machines can handle. It’s common to stack multiple cutters on the arbor in order to cut, for example, a flat table with slots in one pass. It’s well-suited for surfacing jobs, cutting grooves and slots and similar tasks where the part is flat on one axis. Horizontal milling machines are often used for bigger parts that need lots of power but less versatility.
Vertical Milling Machines
If you need versatility and want to cut on all sides of a part, then you’ll need a vertical milling machine. Vertical milling machines are much more common than horizontal because they work for so many applications. Most of the time new machinists start with vertical milling and only move to a horizontal milling machines if a particular application makes sense.
There are many brands of vertical milling machines available since milling machines have been around for a long time. There aren’t many trade secrets for non-CNC milling machines anymore. Manufacturers of cheaper milling machines may cut corners with poor quality material and under-powered motors that can lead to imprecise machining with loose tolerances. Proven machines by name brands like Bridgeport (now Hardinge) probably carry the least risk. You usually want to buy the heaviest milling machine that you can practically fit. The specifications on the vertical milling machines will also give you the travel distance on the X, Y and Z-axis which is an indication of the size parts that you can make on a particular machine. Smaller desktop machines are extremely limited – they won’t mill anything harder than aluminum and will be imprecise.
Digital Readout (DRO) Modules for Used Milling Machines
A DRO module can be added to each axis of a milling machine and may come with your used machine. If a machine doesn’t have one, you may be able to purchase a kit separately. The DRO gives you a display that tells you how far you’ve moved the table which makes every operation easier. While a DRO isn’t totally necessary, since all mills have dials for measuring movement, these are often cumbersome and time-consuming to read. Used milling machines may also have slop in the screws that causes backlash. This is easy to compensate for with a DRO but not as much with the dials.
Power Feeds for Used Milling Machines
Power feed can also be added to each axis. This allows you to toggle a motor that can move the table for you instead of you having to crank the handle. If you’re doing much milling, then this will make your job much easier. It also helps give you a better surface finish on the cut since the speed stays consistent throughout the cut. Ask if the machine comes with power feeds or if you will need to add them later.
Spindle Horsepower on Used Milling Machines
Machinists pay a lot of attention to horsepower because it drives so much of a machines capability. You don’t want the cutter stalling as it’s going through material. Milling different kinds of material requires different power. Most mills have some way to gear down a motor to gain torque, but this is at the expensive of speed. You need high torque and low-speed to mill steel and low torque with high-speed for aluminum. Even though you can compensate some for low horsepower, you should probably avoid anything less than 1 hp. Keep in mind that high-horsepower milling machines will need 3-phase electric. Most homes are not equipped with 3-phase power, so you will either need major upgrades or have an industrial workspace already equipped with 3-phase power. If 3-phase power is not a good option for you, but you find a great inexpensive used milling machine that requires it, you may want to consider replacing the spindle motor with a single-phase unit or buying a phase converter.
Inspecting a Used CNC Milling Machine
Inspecting a used CNC mill is similar to inspecting a used car. Make sure everything is working, there isn’t excessive wear and that it’s been taken care of. Ask for any maintenance records and records of parts or motors replaced. It’s ok if it’s dirty, but the spindle should spin smoothly and have no play. (If you can measure the runout, this is a good idea.) Grab the table and jiggle it to make sure it can’t move around and wiggle. Look at the screws and see if they are clean. The smooth metal that the table slides on (the ways) should be clean, lubricated and without any gouges. If the machine feels solid and doesn’t have obvious signs of abuse like cracked castings, then chances are good that it has many years of service left. Age doesn’t need to be a primary consideration for used milling machines since they are far less complex than CNC milling machines.
If you are in the market for a used milling machine, we are a leading expert in used milling machines for sale and can provide you with options. We would love to help you find the perfect used milling machine for your shop. Contact one of our used milling machine experts today for more details: 844.262.6789.