Collet size and bit shaft diameter

[mtvannan (Mani Vannan)]

Hi all,
I am a newbie on the CNC journey.
I have a shapeoko 5 pro with a 80mm spindle & ER20 collets.

Do I need exact collet sizes to match different shaft diameter of bits?
example: I have a few 8mm, 10mm and 12mm shaft end mills. DO I need to match the collet sizes exactly or is there a range -

1. can 6mm go into a 1/4" collete
2. Can 12 mm fit 1/2 inch
3. Can 10mm fit into the 1/2" collete -
   I saw a post that said that the ER20 collets have a range of shaft diameter they can take. True?

Thank you.
Mani

[wmoy (Winston)]

The safe rule of thumb is that an ER collet can compress 0.5mm. Some manufacturers say you can do more (~1mm), I stick with half a mm to be safe.

1/4" is 6.35mm. So a 6mm endmill can fit in a 1/4" collet.

A 12mm endmill in a 1/2" collet (12.7mm) is OK, but not ideal.

a 10mm in a 1/2" collet is a hard no.

[mtvannan (Mani Vannan)]

Thank you.

What brand/manufacturer do you recommend for ER20 8, 10, 12 collets, for Shapeoko 5 Pro (80mm Spindle)?
Mani

[WillAdams (William Adams (Carbide 3D))]

When I was looking for collets I wound up buying from Maritool, mostly because they have a straight-forward website which seemed to explain things well (except for not being explicit that one would want to at least consider getting a separate nut for each collet so as to not need to swap a single back and forth). (I would also recommend getting their nifty wrench — a further organization hack I considered, but bailed on due to budget was different types of nuts for metric/Imperial)

Another notable source is:

Collets, Nuts and Toolholders

which company rep @TDA has been very helpful here and made some excellent and informative posts.

[QCDvacuum (Jeff Cable)]

This may be useful… https://www.youtube.com/watch?v=8x8O24xu-y0

[TDA (John Torrez)]

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.

@mtvannan

Do I need exact collet sizes to match different shaft diameter of bits?

Yes and no. Assuming that the collets are made to the correct spec, ER8 / ER11 can compress 0.5mm smaller than nominal and from ER16 up can compress to 1mm smaller than nominal. By spec you should NEVER go larger. Again, this depends on a good bore, taper grind, correct kerf size, and counter bore in the collets. Even within this range, any runout, clamping force, or slip resistance is only spec’ed for nominal bore size.

@mtvannan

What brand/manufacturer do you recommend for ER20 8, 10, 12 collets

I’m somewhat less bias here as at least currently we don’t really offer metric collets. It depends on what you are doing with them. One of the important specs for collets is runout (how much it shift the tool off the center axis of the spindle). If you are dealing with small cutters, chiploads, or cutting metal this can matter a lot more. The manufacturers that I know of that spec that actual collet YOU get and not just an average or AQL are us (PreciseBits), Rego-Fix (inventors or ER collets and the R in ER), Pioneer, Haimer, and Technik’s UP grade. There are different grades from most of those using differing measurement setups/standards.

If you want some more info here’s some other threads I’ve posted to related to collets and collet nuts that might be useful.

Precision collet upgrade worthwhile?

I was just browsing Collets, Nuts and Toolholders (as one does on a lazy morning) and it got me thinking: Given that the majority of my work is with sub-1mm endmills, would a higher precision collet be a worthwhile upgrade? I use as low as 0.3mm endmills ~frequently. I’m at the point where any further “upgrades” to my Nomad 3 would have to be actual modifications. So I’m looking to get whatever little gains i can without any “real” modification. To be clear, I’m not experiencing any issues th…

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 pas…

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 o…

Source for good quality ER11 collets

I normally don’t have the time anymore to hang around the forums but this thread came up in our domain notifications and there’s just too many things I want to say to not post. Quick preface: I work for Think & Tinker (PreciseBits) so I’m biased about everything. I try to keep the information I post brand agnostic and as general use as I can (other than when addressing specifically things about us). But keep that in mind for the below. Thanks for the link and mentioning us. Wouldn’t have seen…

And the one that goes off the rails about torque.

ER20 collet nut tightening torque / tooling?

Hi, So far I have been tightening my collet nuts “monkey tight, not gorilla tight”, and it has worked out nicely. Now that I use ER collets with super low runout, I am wondering if I should be a bit more accurate than this, and have some specific tooling to make sure I apply a controlled and repeatable torque on the collet nut. I read somewhere that the recommanded tightening torque for ER20 collets is 59 ft/lbs. What’s a cheap option/tool to do this ? (bear with me, I’m not a machinist or ev…

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

[QCDvacuum (Jeff Cable)]

A heads up for a great machine tool service (UK based)

I bought several items from a UK based supplier of machine tools. I was struck by how helpful this professional service was. All of my pre-sales questions were answered fully. The prices were very keen for high quality Swiss goods. I decided to purchase REGO-FIX because they were the original developers of the ER collet system in 1972. I bought a complete set of ER20 ultra precision collets with a stated Total Indicated Runout of 5 micron (2 x 10,000"). I also bought a castellated collet clampi…

[Sdraeger (Steve draeger)]

John don’t apologize someone in the biz is invaluable. We respect your opinion

[rogerwiegand]

Collets are cheap. It seems a false economy to not use one that’s at least nominally the right fit.

Changing collets OTOH is a pain. For my regular routers I long ago decided to buy only half inch shaft bits whenever I could so I almost never have to change the collet. (plus having had the experience of bending the shaft on a quarter inch shaft router bit in mid cut I’m not anxious to repeat the adventure) Haven’t yet figured out whether this is really an option for CNC bits.

[WillAdams (William Adams (Carbide 3D))]

An ER collet system will have the nut draw out the collet since it’s attached — the only inconvenience in changing is that one needs to be put away and the other gotten.

[rogerwiegand]

For some reason my collet nut doesn’t thread smoothly onto my spindle. It always takes a half dozen attempts to get it not to try to cross thread. Not having to unscrew it all the way eliminates that issue.
Yes, finding the other collet can also be an issue

[TDA (John Torrez)]

@Sdraeger

John don’t apologize someone in the biz is invaluable. We respect your opinion

It more that I want to be upfront about it and let people make their own decisions with as much information as possible.

Thank you though, I truly do appreciate it.

@rogerwiegand

Collets are cheap. It seems a false economy to not use one that’s at least nominally the right fit.

I agree in general. But, cheap is relative and dependent on what type you are going after. micRun from Rego are over $80, UPP from Pioneer are all over $110. Although to your point, I don’t think anyone would be running those worried about non-nominal.

@rogerwiegand

Changing collets OTOH is a pain. For my regular routers I long ago decided to buy only half inch shaft bits whenever I could so I almost never have to change the collet. (plus having had the experience of bending the shaft on a quarter inch shaft router bit in mid cut I’m not anxious to repeat the adventure) Haven’t yet figured out whether this is really an option for CNC bits.

Some routers have absolutely horrible lead in threads. Might be what you are dealing with there.

More of an issue to run 1/2" tooling on a CNC without a BEEFY CNC. Otherwise you are dumping money on tooling you can’t really make use of (cubic material removed per flute/rev issue). Getting 1/2" shank, smaller diameter tooling is also pretty expensive as most use solid carbide. That’s a lot for the blank and the diamond wheels/machine time to grind it down to a smaller diameter.

@rogerwiegand

For some reason my collet nut doesn’t thread smoothly onto my spindle. It always takes a half dozen attempts to get it not to try to cross thread. Not having to unscrew it all the way eliminates that issue.

If you are having this issue on a spindle too I’d check the threads on the nut and spindle. They are usually pretty good. Might have a bad nut or need to touch up the spindle threads.

It’s best practice to at least pull out the collet and blow everything out at a minimum. Router or spindle. Debris and lacquer can cause runout that will put more stress on the machine and tooling while giving you a worse finish. It can effect it a lot more than most think it would.