Lathe Leadscrew Backlash Lock Upgrade

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Product Description

Because backlash is a more critical problem in CNC, the normally recommended .003″ to .005″ of backlash on the leadscrew might not be acceptable in some instances. This modification to the leadscrew and the addition of a locking lever allows adjustable control over the leadscrew backlash, making it possible to reduce it to as little as .001″.

The new upgrade is easily installed, requiring no new holes. The saddle nut securing screw is removed and a longer one going through a hole in the locking plate replaces it. A pin on the end of the locking arm goes into a hole in the locking lever which is installed on the leadscrew. Once the lever is positioned to the desired location removing as much backlash as is preferred, it is locked in place with a socket head cap screw.

If you are replacing a worn out saddle nut on an older lathe, this new system will upgrade the function of your machine at the same time. It can be used on both manual and CNC machines. Even if your saddle nut is not worn out, you might want to consider adding this feature to make it possible to lock the saddle on the leadscrew and to control backlash even in manual operations.


The locking lever and securing arm allows the leadscrew to be secured in the locked or unlocked position or any position in between to control backlash. Included is the new lock plate which attaches to the saddle using a longer bolt that goes through the saddle and into the saddle nut. The lever arm is locked in position using a socket head cap screw.

The improper use of machine tools and their accessories can result in serious injury. Before using this tool, thoroughly read the instructions and make sure you understand its proper and safe use.


Always wear safety glasses when operating machine tools.

Download PDF 4417Z Instructions

Instructions PDF Download

40173 Z-Axis Backlash Adjusting Lever
40170 CNC Column Saddle Nut (P/N 41170 metric)
40510 10-32 X 3/8″ SHC Screw
40660 #10 Washer 3/16
40740 10-32 X 7/8″ SHC Screw
44171 Lathe 2-Axis Backlash Body
44172 CNC Saddle Locking Lever-no indent (P/N 44173 metric)

We offer two types of 3D object files: .igs and .stp.

  1. To view .igs files you need an IGS viewer. CLICK HERE to download a FREE IGS viewer.
  2. To view .stp files you need an STP viewer. CLICK HERE to use Autodesk’s FREE A360* online file viewer. STP is a file extension for a 3-D graphic file used by CAD software. STP stands for STandard for the Exchange of Product model data. STP files are used to store 3D image data in an ASCII format, following the standards defined in ISO 10303-21: Clear Text Encoding of the Exchange Structure.
  3. Each 3D file format has been compressed into a .zip file to save file space. Click on the .zip file link below to download it to your computer.
  4. Extract the .zip file to the drive location of your choice.
  5. Open the .igs file using the IGS Viewer, or open the .stp file using the A360 Autodesk online viewer.

*NOTE: There are also other free STP viewers that can be downloaded directly to your computer.

CLICK HERE to download the 3D IGS files
CLICK HERE to download the 3D STP files


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Domestic orders are shipped Monday – Friday. Expedited orders must be placed by 9 am PST to ship the same day.

Orders shipping ground have a processing time of 7 working days for domestic orders and 14 working days for international orders. Click here for more information on our shipping and order policies.


Most merchandise can be returned within 30 day of the purchase date. A refund will be issued to the original form of payment at the original selling price. View our complete return policy and/or start your return online here.