Double Nut vs Single Nut Ball Screws

Choosing the Best Backlash Elimination Method for Your Machine

Ball screws are the unsung heroes in machines that need pinpoint accuracy, like CNC routers or robot arms. The big challenge? Making sure there’s no wiggle room (called “backlash”) when the screw changes direction. That’s where double nuts come in—they’re like a dynamic duo that clamps down on gaps way better than a single nut ever could. Let’s break down how these systems work and where they shine.Spacer-Type Double Nuts: The Set-and-Forget SolutionImagine two nuts stacked on a screw with a tiny spacer wedged between them. This spacer isn’t just a filler—it’s carefully sized to squish the nuts against each other, creating a tight fit that kills backlash. Factories often preset these spacers, so you can bolt them straight into your machine without tweaking. They’re tough, simple, and perfect for heavy-duty jobs like CNC machines that run nonstop. Just remember: if you ever replace the screw or nuts, you’ll need a new spacer too.Thread-Adjusted Nuts: The DIY FixSome double nuts let you play mechanic. One nut has threads on the outside, so you can twist it with a wrench to squeeze the pair together, then lock it in place with a second nut. It’s handy for quick fixes—like tuning up a 3D printer mid-project—but there’s a catch. If you crank it too hard or too loose, the adjustment might drift over time. Think of it as a “good enough” fix for smaller, less demanding machines.Tooth Differential Nuts: Precision for PerfectionistsThis method feels like solving a tiny puzzle. Both nuts have gear-like teeth on their edges, but one has exactly one more tooth than the other. By rotating them just one notch relative to each other, you create a microscopic shift that erases backlash. It’s ultra-precise (think semiconductor factories or laser cutters) but pricey and tricky to assemble. Not your everyday solution, but unbeatable when you need perfection.Spring-Loaded Nuts: The Self-Healing SystemHere’s where springs do the heavy lifting. A compressed spring sits between the nuts, constantly pushing them apart to keep tension on the screw. Even as parts wear down or temperatures change, the spring adapts to maintain that “no gap” promise. You’ll see these in cars or planes—places where vibrations or heat could throw off ordinary systems. It’s like having a built-in safety net against wear and tear.Tips for Keeping Double Nuts HappyNo matter which type you pick, a little TLC goes a long way. Don’t crank the preload too tight—aim for 2–10% of the screw’s max load rating. Keep things greased up to reduce friction, and double-check that everything’s aligned straight. For critical jobs, test backlash occasionally with a dial gauge. And remember: double nuts aren’t just about brute force—they spread stress evenly, last longer, and handle way more scenarios than single nuts.Why Bother with Double Nuts?Single nuts try to fight backlash by squeezing oversized ball bearings into the screw, but it’s a Band-Aid fix. Double nuts attack the problem head-on with adjustable, rock-solid setups. They’re the go-to for anything where “close enough” isn’t an option—like carving a titanium airplane part or positioning a surgical robot. By choosing the right style and sticking to maintenance basics, you’ll keep your machines running smooth and accurate for years.Zenda Linear Motion is a premier manufacturer specializing in ball screws and linear guides. We take pride in offering a wide range of ball screws designed to meet the diverse needs of our customers. Our products are available at competitive and economical prices, ensuring that you receive exceptional value.

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How to Select Ball Screw Types

A double head bolt, as the name suggests, has threads on both ends and a bare rod in the center, either thick or thin. It is also called double head screw or double head stud. It is generally used on large main equipment, such as mining machinery, bridges, automobiles, reducer frames and so on.

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In what cases are double-headed bolts used?

1. When the thickness of the connecting body is large and the length of the bolt is long, double-headed bolts are used.

2. Double-head bolts are used to connect thick plates and places where it is inconvenient to use hexagonal bolts, such as concrete roof frames, roof beams hanging monorail beams suspension parts, etc.

3. In large-scale main equipment, some connectors need to be frequently disassembled, the external thread is easily damaged, then the application of double-headed bolts will be more convenient to disassemble and replace.

Double head bolts are manufactured in accordance with GB897-GB901 standards, the material used: Q235, 45#, 40Cr, 35CrMoA, Q345D, specifications: M3mm-M100mm, length can be customized according to user needs.

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High-strength double-head bolts made of 35#, 45#, 35CrMoA, 25Cr2MoV, 304, 316, 304L, 316L, 2H, 2HM, B7, B7M, B16, B8, 8, B8M, 8M, are widely used in the fields of electric power, chemical industry, petroleum refining, valves, railroads, bridges, steel constructions, automobile and motorcycle parts and so on.

How to install double-headed bolts?

1. Use lubricating oil when installing the double-headed bolts to prevent the bolts from being jammed during screwing in, and they can also be disassembled for repeated installation.

In order to ensure the fastening end of the double-headed bolts and the tightness of the equipment body threads, and not in the process of loading and unloading nuts, double-headed bolts appear any loosening phenomenon, so the fastening end of the double-headed bolts should be used over the wave, to give the back of the diameter of the center has a certain amount of surplus, you can choose to use the form of the shoulder structure or the back of the threads of a few turns of the shallower depth of the tightening method, when the double-headed bolts are installed into the body of the soft material threads, the surplus can be slightly When the double-headed bolts are installed into the soft material threaded body, the interference can be slightly larger.

2. Double head bolts axis line must be perpendicular to the surface of the body, in the bottom hole and tapping must pay attention to this point, the installation of the best angle ruler to check, when the axis line and the surface of the body of a small amount of tilt, you can use a tap to correct the screw holes, tilt larger than the corrections can not be made with brute force to bolt damage.

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