A level surface is a prerequisite for any kind of machining. You’ll need to know how to level a lathe before using one, no matter what type. CNC, manual, horizontal and vertical lathes all require leveling if you hope to achieve an accurate cut. If you skip leveling, you may end up with a taper that affects the precision of your part. From downtime to reworks, a misaligned lathe makes it inefficient, if not virtually impossible, to create high-tolerance parts.
The leveling process is a little time-consuming but not too complicated, and it’s a vital part of setting yourself up for success. Let’s break down the process of leveling a lathe, so you can ensure precision-cut parts and maintain high productivity.
The Importance of a Properly Leveled Lathe
Before we go into how to level a CNC lathe or a manual lathe, it’s important to understand what it accomplishes and why you’re doing it. Regardless of what kind of lathe you’re using, leveling removes “twist” from the equipment, ensuring that all axes are perpendicular to each other. The lathe’s weight or the force of the bolts keeping it down can cause the bed to shift, both during use and inactivity. These movements cause the headstock and tailstock to shift out of alignment, creating tiny twists in the structure. Since a lathe incorporates three axes — X, Y and Z — they all need to work in concert with each other. Misalignment changes the relationship between them, so one axis is more affected than the others.
Keep in mind that “level” doesn’t necessarily mean the lathe is aligned with the ground. A lathe only needs its three axes to be in agreement to be level. After all, lathes can even be used on ships, where the floor constantly shifts over the waves. Leveling a lathe is about putting these axes perpendicular to each other and ensuring they aren’t twisted.
If your CNC or manual lathe isn’t level, the most obvious effect is an inaccurately cut part. You’ll likely see significant tapering, turning cylinders into cones. These effects can range from subtle to obvious. While some minuscule changes might be acceptable, many applications demand incredibly precise machining, so almost no amount of deviation is appropriate. Allowable variations will depend on the tolerance of your application. Some will call for more precise leveling than others, but even basic leveling is necessary for all projects, particularly large-scale operations.
Skipping leveling can result in costly reworks and downtime, as you must spend time and money remaking every part. Your efficiency will likely decrease to accommodate these requirements and additional needs for cleaning up chips or coolant spills. If an error isn’t caught until far later in production, the costs can be even more pressing and may affect your reputation and compliance with regulatory requirements. Leveling is also crucial for maximizing your investment in the machinery since operating a misaligned lathe can damage the equipment over time and add strain.
In short, leveling is crucial for maintaining optimum performance and machining accurate parts. You will need to level your lathe after installation and again several weeks later, after the floor and the equipment “settle” into place. These small movements can be enough to affect the machine’s position.
When to Re-Level Your Lathe
It can be tempting to think you’re done after those first few levels, but you’ll need to be comfortable with frequent re-leveling. You’ll want to re-level your lathe whenever:
- It is moved to a new location.
- The floor shifts or settles, such as after new construction or with seasonal changes in humidity and heat.
- You struggle to reach particular specs and suspect problems.
Like any material, both the floor and the components of the lathe itself can shift and settle over time. Even if you haven’t touched a lathe in a while, you’ll still need to account for these natural changes. Be ready to re-level frequently so these adjustments don’t affect your machining. Set a regular schedule for leveling your equipment, and be flexible with the need to level if you suspect anything has been thrown off.
How to Level a Metal Lathe
Before you can level a CNC lathe, you’ll need the right tools, including a high-quality precision level. Machinist’s levels are extremely sensitive and can be self-calibrated. At least three sides of these levels will have precise ground surfaces. They’ll have a V-shaped bottom to avoid mating with the machine’s surface, which would cause errors.
Whether you use a machinist’s level or a standard level, get two of them. Multiple levels mean you can place one parallel to the ways and one perpendicular to them for simultaneous measurements.
Other tools you’ll need to level a lathe include:
- A ratchet.
- A wrench.
- A tape measure.
These will be necessary to adjust the leveling screws, so check your machine or its documentation to identify the size of ratchet and wrench you need. With these tools gathered, you can start to rough level before moving on to precision leveling.
1. Rough Level Your Machine
Before precision leveling, you’ll need to conduct some rough leveling to ensure proper coolant flow. Start by placing the lathe at an appropriate height. The coolant pans and conveyors need to fit under the lathe, but you still want to keep the machine as low as possible. Keeping the level screws low helps to improve stability and prevents coolant from splashing onto the floor through the conveyors and coolant tanks. If you collect coolant in drip trays, this is especially important. Another benefit of rough leveling is that it helps ensure proper chip flow.
Adjust your outer level screws to create some space between the floor and the bottom of the base. After setting the height, raise the leveling screws of your machine. The screws and brackets should not touch the ground until you’ve finished leveling.
Put your tailstock or second spindle to the home position, and you can start the precise leveling process.
2. Calibrate Your Precision Levels
Of course, your levels need to be accurate if you want them to work. This is a crucial step that ensures your tools are dependable.
Calibrate your levels before each use:
- Start by placing your level on a known flat surface. This might be a machine that’s already leveled or another surface confirmed to be relatively flat. A granite surface plate works, too, since the plate creates a plane and a plane has at least one level axis. Let the level sit in position for about five minutes so the surface and the level can settle to room temperature. The heat from your hands and other sources can affect the measurements, and you may need to wait for the bubble to stabilize.
- Rotate the level until you find a flat axis. Place a heavy, straight edge against the level with a 1-2-3 block or an angle plate. Then, flip the level 180 degrees, place it against the reference edge and recheck the level.
- Adjust the calibration screw until the bubble is halfway between your two readings. You may need to go back and forth a few times, but try to keep your hands off the level as much as possible to keep it from heating up.
- Once your level reads zero in either direction, you can consider your level calibrated and self-proven.
3. Find the Right Tolerance for Your Application
Depending on your work, you may not need to pursue especially tight tolerances. Finding the appropriate tolerance for your application will help you make sure your leveling is precise enough. If a minimal increase or decrease in the part’s dimensions would cause it to be unusable, you’re working with a tight tolerance band. Tolerance is affected by many factors, like the material, the machine and the final use of the part. Consider the different types of tolerances that might be in play:
- Bilateral tolerance: This measures how far above and below your part can go past the basic size. Variance amounts can be equal or unequal, with the upper variance using a plus symbol and the lower variance using a minus.
- Unilateral tolerance: Unilateral tolerance refers to the variation above or below the basic size but does not allow for variation in both directions. Only one side can deviate. It also uses plus and minus symbols.
- Limit tolerance: This tolerance simply refers to upper and lower limits without any symbols. Any values in between those limits are acceptable.
Research your application and your machine’s characteristics to identify how tight your tolerance needs to be. If it’s particularly tight, you’ll need to ensure your level is precisely centered and has no variation so you can accurately level your machine to meet these tight tolerances.
4. Align All Axes to the Center of the Stroke
Once you know what you’re working toward, move all of the axes to the center of their strokes. This movement balances the weight across the jack screws. Then, place two levels onto the machine surface. One should be parallel to the ways, and the other should be perpendicular to them. You can mount a level to the turret with several methods, such as screwing it on or placing it on a strong magnet. This setup allows you to monitor the movement as the turret crosses an axis.
With the levels in place, start adjusting the jack bolts with the screws on the machine’s sides to achieve a level surface. You’ll either raise or lower these parts to level the machine at various axes and stages of movement. With your axes at the center of the stroke, you can adjust the leveling screws to center the bubble in the level.
5. Move Axes to a Positive Stroke, Then Minus End Stroke
Leveling at the center of the stroke only confirms the level at that stage of machine movement. To check the level at other points, move the axes to a positive stroke and check your levels. If necessary, adjust the jack bolts, ensuring they are in the same position as when the axes were centered.
Then, move the axes to the minus end stroke and adjust the jack bolts as needed.
6. Return to Center to Check for Twist
Level the other axes common to the head to remove any twist. Move all axes to the center of their strokes again and check the column for twist by looking for any deviation in the bubble of the level. You can do this with a square mounted on the table. Another option is to place a level on a flat surface on the column and move the axes as before. If you don’t have a master or flat leveling surface, you can shim the level by placing some clay underneath it. Push it down to move the bubble to the middle.
Once your level is positioned, move the axes bath and forth, looking for movement on the level that indicates twist. Then, you can make adjustments as needed while avoiding the screws near the table that you already adjusted. If the bubble stays in place throughout the machine’s movement, consider it leveled.
7. Check Your Accuracy
Finally, you can confirm your work by placing a square on the table. Touch down all of your supports below the magazine, pallet changer and electrical cabinets. Be careful not to overtighten. When the screws won’t move in any further by hand, use your ratchet wrench to tighten them only by about 10 degrees — just enough to add some tension. Too much tightening here can throw off your leveling. Then, tighten the locking nuts as you hold your leveling screws in place.
Recheck your levels to make sure they haven’t changed by moving the axes one more time and ensuring the bubble stays in the center.
Get the Right Lathe With KAAST Machine Tools
Of course, knowing how to level a manual lathe or a CNC lathe is just one part of the equation. The machine you choose can help you meet tight specifications, improve efficiency and support the unique demands of your organization. Here at KAAST Machine Tools, we focus on reliability and ease of use through a large selection of CNC and manual lathes, such as our CNC Teach Lathes. This model allows users to operate the lathe without prior CNC programming or G-Code backgrounds. A high-quality build and several advanced features can help you minimize leveling requirements and other service tasks.
Our knowledgeable team is here to help every step of the way. We’ll help you find the right piece of equipment for your application, install it and train operators for successful use. Long after it’s installed, we’ll also provide after-sales service to keep your equipment running as long as possible. To learn more about our lathes or any of these services, reach out today for a quote!