# All items created are .015" too small

**URL:** <https://forum.onefinitycnc.com/t/all-items-created-are-015-too-small/18330>\
**Category:** Uncategorized\
**Created:** [January 23, 2023, 3:06pm UTC](https://forum.onefinitycnc.com/t/all-items-created-are-015-too-small/18330 "2023-01-23T15:06:29Z")\
**Posts on this page:** 1\
**Showing post:** 47

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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:** [April 20, 2023, 6:47pm UTC](https://forum.onefinitycnc.com/t/all-items-created-are-015-too-small/18330/47 "2023-04-20T18:47:00Z")

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Hey Bill,

I would think of two possible causes: **Deflection under load** and possibly also backlash. Did you measure **ball screw backlash**?

When you calibrate, you use the machine _with no load_. Under load, the Onefinity CNC machine has the Z slider as its weak spot (see [here](https://forum.onefinitycnc.com/t/half-inch-bit-limitations/19031/3), [here](https://forum.onefinitycnc.com/t/machinist-in-x-50/8159/7), and [here](https://forum.onefinitycnc.com/t/waste-board-location/19854/2)). That’s why I would think of **deflection under load** first.

What does you machine show regarding deflection when you make [this test](https://youtu.be/vB_FvkllLPc?t=658)? I assume you don’t get the diameter of a red blood cell as deflection like Marco Reps gets on his DIY machine ☹ However to perform this test, to get a meaningful result, you would better attach the [force gauge](https://en.wikipedia.org/wiki/Force_gauge) to the end of the milling bit, as it’s there where the deflection finally does it bad influence 🙂

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