# Machine has a gap on the back side after third setup attempt

**URL:** <https://forum.onefinitycnc.com/t/machine-has-a-gap-on-the-back-side-after-third-setup-attempt/21525>\
**Category:** Uncategorized\
**Created:** [July 21, 2023, 7:13am UTC](https://forum.onefinitycnc.com/t/machine-has-a-gap-on-the-back-side-after-third-setup-attempt/21525 "2023-07-21T07:13:23Z")\
**Posts on this page:** 1\
**Showing post:** 8

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**Author:** ![349iq2345](https://avatars.discourse-cdn.com/v4/letter/3/bb73d2/32.png) [@349iq2345](https://forum.onefinitycnc.com/u/349iq2345)\
**Post date:** [July 21, 2023, 3:03pm UTC](https://forum.onefinitycnc.com/t/machine-has-a-gap-on-the-back-side-after-third-setup-attempt/21525/8 "2023-07-21T15:03:12Z")

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Hey Kevin,

1. If your machine after homing shows a gap between the linear bearing (the big chrome-plated cylinder that sticks out the Y carriage) and the black **front** foot block on one Y side, but not on the other, l would first check if the distance with which the linear bearing sticks out of the Y carriage towards front _is the same on both sides_ (same on left Y carriage as on right Y carriage).  
[![f704eb_79f93b74ee464b4b8e00184c30a45845~mv2](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/a/1/a12d63b4a157e3f3dd35879b948aeae4a2259f07.jpeg)](https://www.onefinitycnc.com/product-page/35mm-linear-bearing)  
_Image 1: One of two linear bearings used in a Y carriage._

They are held with grub screws and it is not impossible that they are not equal.

→ If you finally measure the “gap”, don’t measure this gap, i.e. measure **not** from linear bearing to black front foot block, but from (black) Y carriage block to black front foot block. (by the way, one of the purposes of Bill @Machinist’s homing stops is that on stall homing, it bumps against carriage block and not against linear bearing)

1. Did you already check your machine for **rectangularity** , like → [described here](https://forum.onefinitycnc.com/t/what-do-i-do-first/18349/6)? If you didn’t yet, **please do it now**. If then still there is a different distance between (black) Y carriage block and (black) front foot block on one Y side than on the other, you can do this:

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