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A lead screw is a long, threaded rod. The carriage on your lathe is the same size as the nut, so when the rod turns, the carriage slides along. The nut and screw fit snugly together, almost like twisting a jar lid. When you stop the motor, the carriage usually stays put because the parts “grab” each other.
A ball screw looks the same on the outside, but inside it has many small steel balls rolling along curved tracks. Rolling reduces friction, so the carriage moves faster and with less effort. The nut can move backwards because it can turn freely. This would not be possible unless the control system holds it, or a brake is fitted.
Friction and Power
Lead screw: Sliding metal against metal can reduce a motor’s power by 40-70%, which is because heat is lost.
Ball screw: Rolling balls only waste a very small amount of energy (5–10%). The motor can be smaller or the speed higher.
Speed in Daily Use
Lead screw: You’ll be happy with slow to moderate feeds, which are great for manual cuts or hobby work.
Ball screw: It can handle quick movements on CNC lathes, with some machines running at 5 metres per minute or more.
Holding Position When Power Stops
Lead screw: Built-in “grip” keeps the tool from slipping and helps you work more easily on vertical machines.
Ball screw: It needs to be able to brake or it might backfire.
Accuracy and Wear
Lead screw: It will start out with play of between 0.05 and 0.10 millimetres, but this will increase as it wears. It’s good for general turning.
Ball screw: The factory setting reduces the backlash to almost zero and keeps it low for years. It is perfect for when you need to make very precise measurements and get a very smooth finish.
Cost Up Front and Over Time
Lead screw: The price is low, and spare nuts are cheap. More power and more frequent adjustments mean higher running costs.
Ball screw: Three times more expensive to buy, but it saves energy, cuts cycle time, and stays accurate longer.
| Your situation | Better choice | Why |
| Weekend tinkering or school shop | Lead screw | Low cost, easy to maintain, accuracy is “good enough.” |
| Job shop CNC turning | Ball screw | Faster feeds and repeatable accuracy pay back the extra cost. |
| Heavy vertical turning | Lead screw | Self locking stops the carriage from sliding when power fails. |
| Medical or aerospace parts | Ball screw | Holds ±0.005 mm without constant adjustments. |
Just make sure you don’t get any chips on the screw. Use a brush or vacuum after each time you use it.
Lubricate on schedule. Use light oil for a lead screw and grease or oil mist for a ball screw.
Check for any new noises or tight spots. They will warn you before any serious damage starts.
Protect the surface with covers if you cut materials that are likely to cause abrasion. Grit shortens the life of any screw.
A lead screw is a great pickup truck for a lathe because it is cheap, strong and automatically locks itself. A ball screw is the quick, efficient sports car. It is fast and precise, but more demanding and more expensive. Choose the right screw type for your job, give it a quick clean and oil it regularly, and you’ll get perfect results every time.
Tags: Screw
