# Z Axis Calibration Issue

**URL:** <https://forum.sienci.com/t/z-axis-calibration-issue/27209>\
**Category:** ❓ Question\
**Created:** [October 4, 2026, 5:34pm UTC](https://forum.sienci.com/t/z-axis-calibration-issue/27209 "2026-10-04T17:34:06Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![SD\_Fitts](https://forum.sienci.com/letter_avatar_proxy/v4/letter/s/bb73d2/32.png) [@SD\_Fitts](https://forum.sienci.com/u/SD_Fitts)\
**Post date:** [October 4, 2026, 5:34pm UTC](https://forum.sienci.com/t/z-axis-calibration-issue/27209/1 "2026-10-04T17:34:06Z")

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My Z axis calibration is off by a quarter inch or more. If I set the thickness of .75 inches, z axis only carves down .5 inches even though z has been zeroed out. Z axis is lead screw driven. Other axes are correct.

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**Author:** ![Chucky\_ott](https://forum.sienci.com/user_avatar/forum.sienci.com/chucky_ott/32/8692_2.png) [@Chucky\_ott](https://forum.sienci.com/u/Chucky_ott)\
**Post date:** [October 4, 2026, 6:07pm UTC](https://forum.sienci.com/t/z-axis-calibration-issue/27209/2 "2026-10-04T18:07:43Z")

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@SD_Fitts Which machine? Which controller ?

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**Author:** ![SD\_Fitts](https://forum.sienci.com/letter_avatar_proxy/v4/letter/s/bb73d2/32.png) [@SD\_Fitts](https://forum.sienci.com/u/SD_Fitts)\
**Post date:** [October 4, 2026, 11:11pm UTC](https://forum.sienci.com/t/z-axis-calibration-issue/27209/3 "2026-10-04T23:11:34Z")

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I am using a Vevor 4040 S1 CNC and my CAD side is Vectric V-Carve Desktop and G-Sender for the CAM. For a .75 inch board, I have to use .91 inches to go through with a profile cut.

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**Author:** ![Chucky\_ott](https://forum.sienci.com/user_avatar/forum.sienci.com/chucky_ott/32/8692_2.png) [@Chucky\_ott](https://forum.sienci.com/u/Chucky_ott)\
**Post date:** [October 4, 2026, 11:25pm UTC](https://forum.sienci.com/t/z-axis-calibration-issue/27209/4 "2026-10-04T23:25:50Z")

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@SD_Fitts Probably first thing I would check is the distance the spindle travels when you manually jog. In other words, move the spindle to its highest point, note down the Z coordinate. Manually jog down by a known distance (using a ruler, dial gauge, or other method). Note the new z coordinate and see if it corresponds to the actual movement.

There is a calibration function in gSender.