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.

Buy Ball Screw

How to Select Ball Screw Types

List: This may sound trivial but ,I used the double metholdof installing one of the head studs. I was wondering is there is a right way to use the double nuts.

Hebei Bentley Technology contains other products and information you need, so please check it out.

One: screw the first nut until it reaches the end of the threaded area and then screw the second nut until it stops against the first nut.

OR

Two: screw the first nut 2/3 of the way down the threaded area and then screw the second nut hand tight against the first. Then, using two wrenches, tighten the two nuts against one another: one wrench turning clockwise and the other, counterclockwise

I am using stainless steel nuts

The Devil is in the details.
emphasized text
Lou

Was Double Nut Method, Now Head Stud Installation.

OK, so I will use the Double Nut method with the nuts in the center of the threads.

So let’s move to the next step. As I related previously, I drained the coolant out of the block and blew the block thread out with compressed air. Despite that, when I lower a stick down into what I think is the threaded area of the block and withdraw it, there is about 1” of viscous yellow material on the stick. I assume this was too viscous to have drained out via gravity, or maybe it’s actually inside the threaded area that forms a small cup for the stud bottom.

I can think of one or two ways to deal with this. I could knock out the freeze plugs and wipe the threaded area clean, or stick something down the block holes (A giant Q-Tip) to absorb the moisture. I could also use a hack saw to make a vertical cut in the head stud threads so any moisture could squeeze out of the female threaded area (someone already suggested this). Or use compressed air at a low pressure move the moisture out of the female threads. .

Any opinions?

Thanks

For more information, please visit Double Head Screw Nut.

Lou

**
It’s important not only to get moisture out, Lou - you have to ensure that there is no solid residue left either…

Mangling the studs with a hacksaw will not eliminate solid residue - and removing the freeze plugs, while efficacious, seems a bit overkill at this stage. Compressed air, and some bottom scraping should be enough…

However, the real proof of the pudding is that the relevant studs protrude equally when inserted - fairly easily checked. And it’s unlikely that none of the studs are seated…

As for double nutting; there is no point in tightening the studs beyond seating. As you torque up the head nuts, everything moves in the clockwise direction…

Frank
xj6 85 Sov Europe (UK/NZ)
**

I do the second. The only reason is that if you make it tight against the end of the threading, and it slips just a bit as it often does as you are snugging the two together or tightening the stud in place, then when you remove the outer nut, the first one on can be bound against the end of the threading which then requires you to grasp the stud with pliers or something so you can get that nut off without loosening the stud again.

List:

I think the majority felt that putting the two nuts together in the middle of the thread was somewhat preferable to running them down to the bottom of the thread.

Done that way, one can grasp each nut with a wrench and tighten against one another and loosen, for removal, when done, without affecting the final location of the stud.

I think you could also use the same process for nuts driven to the end of the thread.

Lou

Want more information on Heavy Duty Flat Washer? Feel free to contact us.