Stopping the Z Axis Drop with heavy spindles

The Elite series included a more “aggressive” thread pitch in the ball screw assembly, which when coupled with a heavier spindle in lieu of the Makita milling motor, has resulted in the Z axis dropping uncommanded when power is lost to the Z axis. This drop can happen when the Emergency Stop is pressed, or when power to the system is interrupted.

I have designed and tested over 4 weeks of use, and several versions of mounts, spring values, and design improvements to offer the solution called the Zee Keeper.

The Zee Keeper is available at The kit attaches to the 80mm motor clamp bolts with the top attaching to the “Suck It” dust boot attach slides on the left side of all Z16 or Z20 assemblies. It comes with all fasteners and hardware provided and can be installed in about 30 minutes. It only requires a 4mm hex wrench and a 6mm combination wrench (5/16").


Thats a good solution. One other option would be to install a digital brake, this one is for 3D printers but might do the job: Z Motor Brake -


Hey Jim,

you could post the direct link so forum visitors don’t need to search the store:


We’ve introduced a new add on, the z-20 motor brake. This is a plug and play solution that requires no extra hardware, wiring, or external drivers. When power is removed from the machine, the motor locks in place holding your spindle and z-slider in their current location. We’ve tested this up to 150lbs. of holding force. This break is an Official Onefinity product, therefore, it is officially supported and will not void your warranty.

See more here:


Should I move to an Elite upgrade I’ll be sure to keep this offering in mind while placing my order.

On the other hand though, Jim’s design specifically states it accommodates non-elite machines with heavy spindles too. Since my 1F is early vintage and out of warranty, it offers me a solution to axis drop.

You gotta love this forum where member prove necessity truly is the mother of invention!


Is Onefinity working on a Z brake solution for non elite Onefinity machines?

You may want to try the zee keeper, which is linked in the third post. I haven’t tried it, but it’s a decent idea.

I have the Onefinity breaking stepper motor, and I’m not really a fan. It’ll stop the spindle/bit from going through the spoilboard, but it’s not perfect. My spindle visibly drops on power loss, every time I hit the e-stop button, before the break engages. You wouldn’t have this issue with a spring that is effectively reducing the weight of the spindle.

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@Pleased2fly Hey Jim, installing the Zee Keeper doesn’t require modifying the Z slider in any way, does it?