Balanced ER20 collet nut?

Looking at getting some additional collet nuts for my HDM VFD. From what I understand, to ensure that they run well and maintain reliability of spindle bearings on higher RPMs (~18-24k) they need to be balanced. Are the nuts balanced for a specific RPM (ie: 24k) or range (ie: 18-24k)? Should I be looking for separate nuts for different RPMs or does the highest RPM rating for a nut ensure it would run optimally at any RPM at or below the stated rating?

Also, I noticed the balancing drill marks on the nut that came with it and assume it’s good to go at 24k?

And are there any specific nuts that anyone can recommend for 24k RPM in particular?

I’ve been going back and forth on what I want to use for collet / collet nuts.

I think I’m going to use Techniks collets and collet nuts. I need both and thinking staying with one brand may avoid issues. Low runout collet and 24k balanced nut.

Others that I have found the would probably be fine are.

pwncnc has collet nuts balanced to 18k
Avid cnc has 25k collet nuts. (Picture references 25k)

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Beware the “balanced” collets on AliExpress, in my experience about 1 in 10 of those are sufficiently balanced to use on a 24k spindle.

This is an area where buying local, whilst more expensive per unit, seems to result in lower overall cost and significantly reduced time.


I came across these guys years ago when stepping up my game on a SO3.

For my HDM, the only nut and collets I use.



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.

This gets confusing as not everyone uses the same standards. Some manufacturers/sellers will just use “balanced for “X” RPM” and some will use ISO 1940-1 “balanced to G"X” at/for “X” RPM". The first one you are taking the manufacturers word for it being good to that RPM. For the second version is listed the residual unbalance at that RPM. This makes the ISO version an empirical measurement that can be applied to other RPMs. e.g. G2.5 at 20KRPM is ~G6.3 at 70KRPM. There’s some more discussion on this here if you’re interested: Source for good quality ER11 collets . Starts about collets but gets into nuts further in.

The above makes it hard to compare some nut balances and without a lot more info it’s hard to know what you “need”. The short version is the lower the “G” value at the same RPM, or the higher the RPM at the same “G” value, the better balanced the nut. If it just says "balanced for “X” RPM, you are just taking the manufacturers word for it. So weight that as you will.

Also, thanks for the shout out Griff, I appreciate it.

Hope that’s useful. Let me know if there’s something I can help with.


Thank you John for the “G2.5” explanation.

I use these: Balanced ER20 Collet Nut | Avid CNC
They are G2.5 at 25k RPM

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Another thumbs up for Precise Bits collets and collet nuts. I had a set of 1/8", 3/16" and 1/4" collets and nuts for my Dewalt router before I switched to a spindle.


I use the same Avid ER20 nuts on my 2.2kw HDM and they are well made and WAYY better than the cheap China nuts available.

No problem.

Thanks, I appreciate it.

We have a decent amount of customers that have Avid machines and we haven’t heard of any issues with their collet nuts. Not going to endorse anything but those should be good. Others would be Techniks (SYIC), Maritool, Pioneer, or Rego-Fix (inventors of the ER collet system).

Collet wise turns into another thing depending on the runout needed but I’ll leave that alone unless someone wants me to go into it again.

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Wait a minute! You guys have machines that can accommodate the ER20 collets? The best my machine can handle is the ER11 collets. I would love to have a spindle that used a bigger collet, even possibly up to the 1/2 shank tools. Then I could buy across the board for both my regular rotor and spindle for my machine. Running these smaller shank bits can be a scare at times when worrying about breakage.

I have used some super tiny drill bits in metal machining and just accidentally dropping the bit on the ground would damage it enough to where it couldn’t be used. It was nerve racking work to most people that ran the job. I loved the challenge of using such a small drill.

I have also found that many of these China made 1/4 shank bits have poor core strength, and they tend to flexibility issues and also bending issues at the shank. This is another reason I don’t always like running the smaller shank bits when I realized that I bought some made in China. Waste of money if you ask me, but budgets still are an issue. Guess, purchasing a good quality bit at a higher price that will last longer and give one more of a peace of mind running would be worth it.

The cool kids w/ ER20 are owners of either Shapeoko HDMs, or who have fitted out 3rd party spindles which use that collet system.

I will note that both the ER-11 and Makita-style collets in Carbide Create Routers and VFDs and use up to 8mm collets, and that 8mm tooling is a marked improvement in rigidity over 1/4" (which itself was a sea change over the 1/8" tooling which we started w/ in the rotary tool which I had in my Shapeko 1) which I believe is worth exploring for folks who want to optimize material removal rates or surface finish.

8mm tooling is becoming popular for the Shaper Origin, and apparently Datron uses it a lot, and their high speed spindles seem to map to tooling which is suited to our machines.

We sell one such tool, the #603E McFly which is I believe worth the effort to use over the 1/4" version, and I had good luck w/ an 8mm tool w/ radius which I use for surfacing/facing off larger projects when I remember to dig it out.

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I don’t mind using the ER-11 collets and actually have bought some of the other sizes of ER-11 collets for holding tools between the 1/4 shanks to 1/8 shanks. I even have the smaller collets for everything down to a 1/32 size shank. I figured that when I want to do some of the finer detailed carvings and/or drilling holes pretty small, then I have the collets for such endeavors. I like having versatility with my machine and nothing more frustrating then to have a tool you want to add to the machine and can’t find a collet to hold it.

So, you are also saying that the ER-11 collets go bigger then the 1/4 shank tools? I’ll look into it, but there isn’t any reason to be purchasing a bunch of extra tools and collets until work picks up and orders are coming in more frequent. I know I must spend money to make money, but if no money is coming back in, then it is a waste to spend money.

My Shapeoko 5 Pro is an extension of my wood shop. That is why I bought it. I wanted to be able to add flourishes and enlayed detail that would be harder to do precisely by hand. The machine also makes for good added details to trims, doors, and carved projects that can add value and detail. But adding these details sometimes with smaller tools because of size limitations can prove to be quite challenging.