Proper Collet Use - Whoops

So I want to start off saying my Nomad is great, and I’ve been using it as much as I can since I got it, and thoroughly enjoy it.

(I felt the need to add a positive note to what some might consider a negatively themed thread)

That being said I have noticed something, and would like to get to the bottom of it, if possible.

I’ve been machining a few parts and after consuming a number of hours of CNC related content on YouTube, the C3D forum, etc., its my understanding that doing a roughing pass leaving somewhere in the neighborhood of .5mm stock to leave and then doing a finish pass should get me me close to the desired final dimension of my part, and closer than ±.2mm

In practice I think (not sure though) my 1/8" collet has some sort of runout, because my pockets in my fixtures are oversized, and the OD of parts I’ve made that should fit in them are undersized, by a pretty consistent margin of .2mm. I actually have stopped using my 1/8" probe that came with the machine as the runout is super obvious with the naked eye to be at least a few mm. I’m not sure if that can be caused by tightening the collet nut too much (I never tighten it without an endmill in place, and usually just leave whatever I last used in the machine, to exchange after homing/initializing)

Also, this isn’t specific to one 1/8" endmill in particular, as I machined the first project with the 102 flat 1/8" that came with the machine, and the second project with some SpeTool 1/8" cutters i picked up off amazon recently.

The last piece of evidence that leads me to the 1/8" collet is that when spinning the spindle with an 1/8" tool in place, ive seen the tool wobble back and forth (indicating runout, the tools are tight in the collet at this point), but not when I put a 1/4" tool in the spindle.

So, now that I’ve spouted off, here is my evidence of some sort of runout or inaccuracy. All of these parts were brought to final dimension with 1/8" tools, so maybe a good starter test would be to cut some squares of material with 1/8" and 1/4" tooling and see if they do the same thing.

for example, my first project, a maker coin made out of 6061 aluminum.

fusion model width: 62.354mm
actual width (measured with amazon calipers) ~62.15mm

my second project, a bearing & fixture to hold that part and others

bearing - fusion model diameter: 131mm
actual diameter: ~130.88

pocket in fixture to hold bearing - fusion model diameter: 131mm
actual diameter: ~131.2mm

Not sure if this should be a separate thread or not, and in theory since I’m using the same collet nut between both collets any inaccuracy should follow it, but my collet nut seems to not be concentric, unless I am ignorant of something

I did my best to get over the collet nut, and not at an angle, so hopefully the fact that the inner hole is offset/not concentric to the other one is clear. Both of my collet nuts are like this, the one that came with my Nomad, and the one that came with my 1/4" collet.

I await any suggestions from…anyone really. Im planning on buying a digital indicator (I have zero interest in trying to interpret an old school needle based one) and seeing if the spindle itself has runout, but any other suggestions would be appreciated. :slight_smile:

Please let us know about these difficulties at and we’ll do our best to work w/ you on this.

Usual preface, I’m with PreciseBits so while I try to only post general information take everything I say with the understanding that I have a bias.

That’s a eccentric extractor ring. It’s made to fit into the slot in the collet so that the the collet is extracted when you unscrew the nut.

Related to your runout if you are not “snapping” the collet into the nut before use the collet will sit in or on the extractor ring which can have very bad effects on the collet and runout. Are you snapping in the collet to the nut?


That’s how a collet nut should look. The off-center hole is how it catches the groove in the collet and makes sure it gets pulled out when you loosen the nut.


i would say no. i typically put the collet into the nut loosely, and then slide the collet into the spindle and make sure the nut threads engage correctly.

my newbness is showing :man_facepalming:

That might be part of the reason for your runout.

Before you do anything else take the collet and look at the end with the short taper on it to check for damage. If there is none than take the collet and push it into the nut (you may find it easier to tilt the collet at an angle while pressing down and rotating it). It should snap into the nut and seat in the ground angle. Then when it’s assembled screw it into the spindle.

i definitely have not snapped the collet into the nut.

ill check my collet and after i take my foolish hat off.

a picture of my collets. not sure if that ring would be considered damage.

Yeah, I wouldn’t use those. That groove ground into the taper will smear into the nut. That will then offset and transfer/damage any other collet that’s used in those nuts.

The main idea with these types of collets is that you are centering them between two precision ground tapers (nut and spindle). When instead they get trapped in the extractor ring that will almost always skew them giving you runout. So that’s probably at least part of the issue you are having with runout.

@WillAdams looks like it was an ID10T error on my part. :person_facepalming:

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weeeeell s**t. off to buy some new collets i guess.

I wouldn’t call it being an idiot or stupid. It’s not intuitive. We sell a lot of collets and this is by far the most common error.

There may or may not be a very popular youtuber known for his tool reviews that machined out his “incorrectly made” collet due to a ring that was keeping the collet from inserting.


the kind words are appreciated :slight_smile: live and learn i guess, and hopefully since its here for all to see someone else might see this thread and not make this mistake.

since im going to have to get new collets, should i pick up new collet nuts as well?

From your pictures your collet nuts look fine. What you will usually see when they need to be replaced is grooves or smeared material in the taper. I would clean them pretty good though to make sure you don’t have any pieces of metal waiting to fall into the taper. That second one is looking pretty dirty and anything between the tapers (nut or spindle) can offset the collet and add TIR.

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the second one is one I just pulled off the my Nomad to grab a picture. I always blow them out before putting them in the machine with an endmill.

Blowing them out is the minimum. Make sure you regularly check the tapers and collets for debris, lacquer, etc. You can use something like a very thin penetrating oil to clean with. Wipe away the excess to leave behind a monolayer of oil. That will also help with overall life of the collets, nuts, and spindle.

One last thing. You’ll probably want to reevaluate your feeds and speeds. One of the bigger issues with runout is that it effects your chipload with multi-flute tools. In the worse case, you can end up running your entire chipload on a single flute. In the not worse case your chipload goes up and down per flute as it rotates. Both lead to less than ideal surface finish.


@TDA good to know, ill definitely have to find an oil to use to care for the collets.

I think in regards to feeds speeds i should be all set, ive been running the f & s @wmoy used in his material monday videos. i wrote them all down in an excel doc that so i can keep track of them for use.

(and i added them into my 1/8" tool in F360 too as presets since thats what i use most)

This should help.

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