Anti-backlash nuts, how much force can they take?

I’m curious on how the anti backlash nuts work on the nomad. The y axis in particular feels like it is spring loaded inside the nut. I can push it with light force about .02" (something like 5ish pounds of pressure) but it springs back. I rough like a madman and I’ve been noticing the z axis seems to be pulling downward. I’ve confirmed its not the work shifting or losing steps. Its not effecting the finished parts, my curiosity is just getting the better of me. The only style of antibacklash I’m familiar with is old bridgeport mills where there are 2 nuts that you can adjust the distance between essentially sandwiching the lead screw.

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You have me wondering now as well! I did find a thread for the older Nomad 883 - not sure it is the same for the newer 883 pro, some clever folks will probably pop out and correct me if that is the case!

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they only take so much and then they will either give or wear down (prematurely)
i would guess the stock item should compliment the stock motor torque.

they’re made of delrin/brass/bronze for a lead screw typically. usually a softer material than the screw so that they are the weak link (prone to wear) and allow for ease of replacement. as opposed to the whole lead screw.

perhaps yours is getting worn… perhaps you can try a spring with a slightly higher spring rate (or toss a washer to add to compression if the range will allow)

:man_shrugging:

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Well, internally, yes, they are spring loaded - it amount to a spring between two nuts, forcing them apart. At a force above that of the internal spring they “collapse” and all your backlash is back. For low forces, like in the nomad, it’s not that much of a problem - it simply can’t cut with high enough forces (without more power, 5lb of force is a lot!).

It’s the same basic idea as the big ones you see on a big machine (like a bridgeport) but they’re non-adjustable…“self adjusting” to wear. The plastic they are made of seems to hold up well, but the that self adjustment mechanism via the spring limits the forces they can be used with. That said, they’re really, really cheap to replace.

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As noted, the maximum service force is, in practice, limited by the compressive preload on the spring: when the service force exceeds the preload, you get backlash. If you want pics of the device, google will pull up thousands.

The principal reasons NOT to increase the spring preload are friction and wear. Higher preload produces greater friction at the screw, which is not inconsiderable with a conventional leadscrew-and-nut, even when well lubricated. The increased friction then steals force that could be used to do work, or requires a higher torque motor/more power. The motor and leadscrew will be subject to greater wear, as well.

It is a compromise at design time, and I wouldn’t try to increase the preload, as it seems that the designers made good, balanced, compromises.

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Lots of good info, thank you all for the input. The spring loaded style is new to me. I’ll be keeping an eye out for wear on them as I’m roughing brass and aluminum for hours on end lol