# Z axis rigidity

**URL:** <https://forum.onefinitycnc.com/t/z-axis-rigidity/10732>\
**Category:** Original/PRO Series (Buildbotics) (Gen 1)\
**Created:** [January 28, 2022, 5:16pm UTC](https://forum.onefinitycnc.com/t/z-axis-rigidity/10732 "2022-01-28T17:16:58Z")\
**Posts on this page:** 1\
**Showing post:** 5

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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:** [January 28, 2022, 6:48pm UTC](https://forum.onefinitycnc.com/t/z-axis-rigidity/10732/5 "2022-01-28T18:48:37Z")

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Hey Jesse,

> [@TonyStark39](#):
>
> The increased surface area/holding/clamping ability would be so nice to have.

which spindle do you intend to use?

My spindle manufacturer writes in the manual that the 80 mm spindle requires the clamping force be spread over 8000 mm² of surface. With 80 mm diameter = 40 mm radius this would give

```auto
$ bc -l
pi=4*a(1)
8000/(2*pi*40)
31.83098861837906715400

```

31.8 mm minimal height of spindle mount. Since [Onefinity 80 mm mount](https://www.onefinitycnc.com/product-page/80mm-spindle-mount) is [2″ (51 mm) high](https://forum.onefinitycnc.com/t/any-hobbyist-grade-solutions-for-adding-automatic-tool-changes-to-onefinity/8476/10) this is enough (for this spindle).

Of course, the leverage force exerted on the Z rails and their linear bushings will be greatly reduced if distributed over a greater length, such as by stacking the two mounts on top of each other

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