Buying a lathe is a big decision. A machine shop owner should consider the type of work they plan to do and future plans.
What to Look For
The lathe is one of the more complex machinery available to home workshop owners, or industrial production shops. It is also one of the most expensive tools to purchase. This is due to the level of engineering that goes into this machine, which can create metal shapes with incredible precision and accuracy. It is no wonder that this tool is so sought after for making everything from aircraft parts to automobiles.
When shopping for a new lathe, there are a few essential factors that should be kept in mind. The first thing to consider is what you will be using the machine for. The size of the work that you will be doing is important as well. It may not be the final decision-maker, but it will help narrow down your options as you shop.
Other things to look at include the swing measurement and bed measurements. Swing is the maximum diameter of a workpiece that can be turned, and bed is the overall length of the lathe that you will be working with. Also be sure to check out the chuck, as this is what will hold your workpieces. Most lathes will have a chuck that can secure workpieces up to about 66 inches in diameter. Some chucks will even have a through-hole, which can allow longer barstock to extend into the back of the lathe.
You will also want to see if the lathe has a quick change gearbox. This makes it much easier to swap out the gears depending on what you are doing, and will save you a lot of time and frustration. The quality of the gears is another important factor; a good set will have little to no backlash and will run smoothly.
A final factor to consider is the power of the motor. The more torque a lathe can provide, the better it will be for things like screw and thread cutting. Many smaller lathes will use a brushed DC motor, but larger machines will likely have an AC induction or brushless DC motor. These are more efficient than a traditional brushed motor and provide more consistent power, especially at lower speeds where the most torque is needed.
Power
Most modern lathes are powered by a geared headstock. This is attached to a carriage for longitudinal movement and a cross slide for axial motion. The geared headstock drives a series of changeable gears, and this in turn provides plenty of power to the rotating spindle.
Depending on the type of work being done, you’ll need different types of accessories. For example, if you’re turning long shafts, you’ll need a steady rest. This bolts to the bed of the lathe and supports the shaft while you’re working on it. You’ll also need a live center and a dead center to hold the workpiece in place. For the tailstock, you’ll want a three-jaw or four-jaw chuck. You can also add a faceplate to work on larger pieces that cannot be held in the tailstock.
Another feature you’ll want in a lathe is speed control. This allows you to run the tool at the correct cutting speed for any diameter you’re working on. This can be manually done by changing belts on stepped pulleys or electronically with a rheostat similar to a light dimmer.
Stability
Before purchasing a new lathe, machinists need to decide what type of work they will be doing with the tool. Lathes are divided into a few categories, including engine lathes and turret lathes for metalwork and woodworking lathes for other projects. When deciding what kind of lathe to purchase, shop owners must also consider the size and geometry of the parts they plan on producing. For example, if a project requires a long, slender shaft, it’s best to buy a lathe that can accommodate this length or consider an addition of a tailstock to the machine.
The basic two-axis lathe consists of the headstock with spindle, chuck for holding the part, carriage and cross-slide, and tool turret. If a project requires the part to be turned on an axis other than the headstock, then a mandrel can be used to hold it. A mandrel is a tapered axle that can be forced into the hole in the workpiece. This can be used for supporting the piece between centers or in a faceplate.
To ensure that a machined workpiece is accurate, the tool bits must be made from the correct material and ground to the proper angles. For example, a roughing tool should have a smaller radius than a finishing tool. In addition, the overall shape of a tool bit can affect the quality and performance of the cutting action.
Shops must always keep a good supply of spare parts and accessories on hand to make the most of their lathes. These include three- and four-jaw chucks, faceplates, live center, and various Morse taper adapters for the tailstock. They should also consider adding a collet chuck and a steady rest to their arsenal of lathe equipment. Lastly, it’s important to have enough power capacity for the lathe machine. If possible, a 220-volt, three-phase electrical system should be used. If not, a phase converter can be purchased to increase power capability.
Safety
A lathe is probably the most important machine tool in any shop. In fact, anything that involves moving or round parts probably has a part made by a lathe somewhere in its construction. This makes it a vital tool for the engineer to have, and one that requires careful consideration when buying.
First of all, the size of the workshop is a major factor in what type and size lathe to buy. There is little point in buying a large, expensive lathe that will only be used for small jobs. On the other hand, a smaller, cheaper machine might be left unattended and unused for long periods of time. In this case, the value of the machine may drop significantly in comparison to its original purchase price.
The next thing to consider is the headstock spindle and chuck. The spindle should be a good fit for the chuck and should not have any looseness. The condition of the chuck should also be considered, as this will affect how true the chuck will spin. In addition, the threads and bearing surfaces on both the spindle and chuck should be well-lubricated.
Finally, a steady rest should be included with the lathe to support shaft work and other longish pieces while turning. This should bolt to the bed and provide a solid mount for between centers work. It should be drilled through with a Morse taper for both live center and tailstock work.
There is no substitute for hands-on experience with a machine, so if you can find a used lathe at a garage sale or at an auction, try it out and see if it meets your needs. It is always better to do this than to be disappointed when you buy a machine that has a number of features that aren’t useful to you. In this way, you can avoid a costly mistake and get the best value for your money.
If you’re interested in purchasing a lathe machine, browse our extensive inventory of used vertical lathe machines and used horizontal lathes. Contact us at Tramar Industries and we’ll help you find the right machine for the job.