# Air cooled spindle?

**URL:** <https://forum.onefinitycnc.com/t/air-cooled-spindle/5951>\
**Category:** Original/PRO Series (Buildbotics) (Gen 1)\
**Created:** [June 6, 2021, 1:07pm UTC](https://forum.onefinitycnc.com/t/air-cooled-spindle/5951 "2021-06-06T13:07:09Z")\
**Posts on this page:** 1\
**Showing post:** 65

<div class="post-metadata">

**Author:** ![349iq2345](https://avatars.discourse-cdn.com/v4/letter/3/bb73d2/32.png) [@349iq2345](https://forum.onefinitycnc.com/u/349iq2345)\
**Post date:** [February 3, 2024, 5:59pm UTC](https://forum.onefinitycnc.com/t/air-cooled-spindle/5951/65 "2024-02-03T17:59:17Z")

</div>

Hey Greg,

1. If it is a collet for 6 mm, you cannot use it for a 6.35 mm (=1/4") bit shank. You can ruin your collet this way. [See here for explanation](https://youtu.be/WKikm6cQKh0?t=384).

> [@ER11 collets for China spindles](https://forum.onefinitycnc.com/t/er11-collets-for-china-spindles/13208/12):
>
> - [**Is the collet size a plus x or a minus x number?** – Haas Automation](https://youtu.be/WKikm6cQKh0?t=384)

1. Many beginners mount the ER collet nut by first inserting the bit and the collet, and then they put the collet nut over it and try to screw it down, like they are used to from their router. **That is definetely wrong!** You got to know [this](https://youtu.be/WKikm6cQKh0?t=778) about how ER collets and their collet nuts work.

> [@Upgrading stepper motor for 80mm Spindle](https://forum.onefinitycnc.com/t/upgrading-stepper-motor-for-80mm-spindle/6717/63):
>
> ER collets are not mounted the way a trim router collet is mounted. Most people put the collet into the axle of the spindle and then they put the collet nut over it. **That is definetely wrong!** An ER collet has a groove that goes all the way around near the top of the collet. The corresponding **collet nut** of an ER collet has an excentric extractor ring or offset lip inside. It is absolutely mandatory to fully engage (clip in) the collet inside the nut **before** you tighten it onto the holder, as shown at [this moment of the video “ER Collets | 5 Things to Know for Beginners”](https://www.youtube.com/watch?v=R0tJorTM0BE&t=153s). See also this picture from my spindle manual:
> 
> ![Mechatron__Installing_Collet_into_Nut](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/6/1/61594bd2483e75da373dc60176160f9ec009bc77.png)
> 
> – Source: Mechatron HFS Spindle User’s Manual
> 
> [![ER_collet__Excentric_Extractor_Ring_-Offset_Lip-_SS_Workshop](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/2X/a/ac7f0864fd297dd32b88c7c2c94cff54c6033045.jpeg)  
> ER Collets | 5 Things to Know for Beginners - Youtube ](https://www.youtube.com/watch?v=R0tJorTM0BE&t=153s)
> 
> [![ER_collet_Excentric_Extractor_Ring_-Offset_Lip-_Haas_Automation](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/f/6/f6c2544e0ea9ad9586d32abb4c0a70c396b01b6f.png)  
> ER Collet Essentials. Do You Know? – Haas Automation Tip of the Day - Youtube](https://youtu.be/WKikm6cQKh0?t=778)

---

_[View the full topic](https://forum.onefinitycnc.com/t/air-cooled-spindle/5951)._