Inventables Community Forum

X-Carve Pro Collet Nut (ER16-A)

To my disappointment, my XCP only came with one collet nut, seems silly to keep swapping my collets back and forth, so naturally I went online to the shop here and cannot seem to find the ER16-A collet nut for the XCP.

So then I went over to and found it! However when I received the ER16-A collet nut, I quickly realized it’s twice the diameter and does not fit on the XCP.
So do not order the 28mm one from ToolsToday.

Anyone have this same thought, but find the solution? Would love to order a second one in order to streamline bit size changes.

Please advise!



Just remove the hyphen from the search terms

And for a “precision balanced” one:

@SethCNC Do you know these are the correct diameter? Have you ordered and used these yourself?

@SethCNC yeah, i bought the first one off Amazon, and surprise surprise it’s twice the size as well. Now I have six nuts to return and hopefully get my money back on.


Twice the diameter? Got a pic?

These are ER16-A collet nuts, are you sure your spindle uses ER16 collets?

The red is a 1/4" ER11 collet
The red and all of the nuts here are ER16

If the ER16 you’ve purchased are double the size you need, then it seems like you need ER11 not ER16.

I have 3 cncs, two are ER11 and the larger spindle one is ER16
The link yo the multipack is what I purchased for the er16 one and they fit perfectly.

I just scanned through the assembly of the pro and this photo appears

Now let’s compare that to my er11 and er16 1/8" collets (ignore the blackened on the er16 one accidents happen)

Processing: 20211120_201034.jpg…
Processing: 20211120_201030.jpg…
Processing: 20211120_201024.jpg…

In summary, the pro uses er11 collets, you need an er11 collet nut. Not an er16

Er11 are sold right here on inventables website, or on Amazon if you want to save some $

@SethCNC I appreciate you trying to help.

But i’m holding the nut that i use on my X-Carve Pro in my hand and it’s labeled ER16-A.
I only own one CNC, and it’s the one I’m referring to though.

The other two I purchased, are also labeled ER16-A. However, the XCP one is 15/16" in diameter and the other two are 1.25" in diameter. I measured them with a digital caliper.


Hmmm… could the hyphen spec a different sized one how? Your original one is labeled ER16A , just like mine, but all those larger ones have a hyphen in between :man_shrugging:

At this point I’m kinda at a loss for words on why the - ones are larger…

@ForEverSkateStuff Use those digital calipers on your spindle threads. My guess is they’re about 19mm?
The threads are different in your collets. I’ve seen er16 collet nuts with M19 1.0 threads (looks like the XCP) in addition to the standard M22 1.5 threads.
You have to check the thread specification, and you have to trust the sellers published information (tools today - probably, Amazon - maybe).

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Curious to hear what other’s find with the ER11 collets. It would be nice to have the 1/8" collet already set in a nut. I’ve pinched my fingers a few times changing it out. I actually started replacing most of my fine bits and v-carve bits with 1/4" versions for this reason.

My biggest wish/miss for the XCP is to allow 1/2" shank router bits. I’m sure the spindle couldn’t handle some of the larger 1/2" shank bits, but would have been nice to have the option for the ones it could handle.

I asked Inventables and they replied the spindle is M22 x 1.5.

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