Acceptable run-out on Axminster SX1 milling machine?

Hi all 😀

Somewhat a milling newbie here, just getting an Axminster SX1 mill set up in my tiny home workshop. It came with a 3-jaw drill chuck, and I also got a ‘precision’ ER20 collet holder and two collets from Axminster at the same time.

I’ve been a bit disappointed to find that there’s quite a bit of run out on the edges of the collet holder and even more on the milling cutter - please see the attached image.

Is this normal, or should I return the collets and holder to Axminster for a refund?

I’ve tried cleaning the MT2 taper on the collet holder (and the taper inside the spindle too) but it didn’t make any difference …

Thanks for your help!

David 🙂

The first thing I ask anyone new to milling is have you correctly snapped the collet into the nut before inserting the tool and then screwing the nut on with sufficient force as shown here.

The two readings off the outside of the spindle and collet holder are not really representative of what is going on as they are not critical, better to tale a measurement of the inside of the collet holders taper.

As Jason mentioned, the outside surfaces aren't registering anything. The collet holder registers against the spindle taper. And the collet registers against the holder's internal taper. You'll need a DTI to check both of those, which should show where the problem lies.

Hi Jason, Mike,

Thanks so much for your quick replies, it’s really appreciated 🙂

Yes that was the first mistake I made — not inserting the collet into the nut first…! So it has been inserted correctly 👍🏻

The run out on the internal taper of the spindle is the “<0.01mm” text in green with the arrow pointing to the dotted blue line, so that’s fine.

I’ve just measured it and the run out on the internal taper of the collet holder is about 0.25mm.

I’m thinking of just getting some of these collets instead, to remove the extra source of error by having the collet held by another holder:

**LINK**

I wished I’d gone with these first as I imagine they’ll be much more accurate / less prone to errors?

Thanks again for your help 🙂

David

Your link shows finger collets that are only to be used for cutters/drills of their nominal size.

ER collets will accept cutters/drills/workpieces of the nominal maximum size down to the lower size indicated on the collet. However concentricity may only be to specification at the maximum nominal size indicated. On no account should a larger cutter be inserted.

Do check that there is no swarf in the slots of the collets (a common fault with cheap offerings).

Hi ‘not done it yet’ 🙂

Yes that’s fine by me — I’d rather buy a few more collets of exact sizes and have better accuracy than use something inferior. The collets themselves are broadly the same price (and you then don’t need the additional holder either), so aside from being able to use one ER collet for a range of sizes within a range of 1mm, I don’t really see the advantages of ER collets, given it seems to introduce concentricity errors 🤔

I’ve checked the slots of the collet and they’re clean, but given the taper inside the collet holder is already out by 0.25mm (which is enough to be able to see the collet holder wobbling by eye!), I’m not sure I’ll ever be satisfied with the accuracy of the ER collet system.

I trusted the advice of Axminster when buying the collet holder as I just asked what do I need to hold the milling cutters in the mill and that’s what they recommended … they didn’t even mention finger collets … probably because it’s not something they stock!

I will be returning the ER collet holder and collets as defective and getting myself some finger collets I think … does that sound like a good move? 🙂

Thanks so much!

David

I'd be looking at a different collet holder 0.25mm is more than one would hope for by at least a magnitude of 10.

Finger collets can also make it a bit hard to see what you are doing with small cutters as well as getting in the way of clamps etc. I have some but seldom use them only getting them out for special occasions such as when head room becomes limited

You should be able to get something like this with an ER setup, this is my ER32 in an X3 mill with ARC collet

Edited By JasonB on 20/02/2022 20:18:17

Thanks for your quick reply Jason 🙂

Yes I didn’t think it was normal, particularly as the holder I bought had ‘precision’ in its name!

https://www.axminstertools.com/axminster-er20-precision-collet-holder-2mt-910250

Thats a good point about the disadvantage of finger collets being they make it harder to see what you’re working on, I hadn’t considered that …

Maybe I should first ask Axminster for a replacement to see if it’s any better?

Maybe I’m being a bit pedantic given that I’m so new to all this, but I’d rather make sure I’ve got a good setup from the outset and then any problems I encounter will purely be down to user error! 😄

Thanks again,

David

That's a bit harsh.

The ER collet system was developed by Regoflex in 1972 for professional use. Standard collets should have a runout of better than 0.01mm, precision ones better than 0.005mm and better than 0.002mm if you have deep pockets. i use ER11 and ER20 collets on my CNC mill, and ER20 collets on my Bridgeport, for small cutters and sizes I don't use very often. Can't remember exactly what the runout is but small, around 0.015mm on the cutter shank. I use cutters down to 0.5mm on the CNC mill and any significant runout would fudge the cutter.

It's possible the holder/collets that were bought are not up to scratch. I bought my holders from Tormach (they made my CNC mill) and the collets came from professional tool shops.

I've never used finger collets on any of my mills for holding cutters.

Without a numerical specification the word 'precision' in an advert is simply marketing sitting bulls and can be ignored.

Andrew

Certainly 0.25mm runout on the inside taper of a ER chuck is shockingly bad and you should get a no-questions refund. You might consider whether a replacement from the same stockist will be any better. There are other suppliers of this sort of tooling, Arc Eurotrade who advertise here have always been excellent for me.

Finger collets have another benefit for small mills, which is that they give you an extra 40mm or so daylight under the quill. They can also be hard to remove if they get stuck in the taper, and they need to be very tight to grip well which perhaps makes them more likely to stick.

Edited By Frances IoM on 20/02/2022 21:17:41

I've bought three ER20 collet chucks: one from eBay, two from shop-apt.co.uk.

Runout on all of them was markedly worse than the runout on my ER25 and ER32 collet chucks bought from Arc and apt respectively.

I'm half tempted to believe ER20 collet chucks cannot, for some obscure reason, be easily made to run true when other sizes can.

Have you checked the run-out in the spindle?

Wow thanks for all your kind replies everyone 🙂

Andrew - yes maybe that was maybe a bit harsh, sorry! 😂 And a sample size of 1 isn’t very representative either …

Frances - Yes I found to my cost (literally!) how much more expensive Axminster can be! I ended up getting a precision vice from Chronos and it was about 25% cheaper, and some ground steel parallels from Chronos which were 50% cheaper! … Such a rip off for exactly the same products from the same manufacturer! I bought some other bits from Axminster when I got the mill as I thought it made sense to get everything from one supplier … but I really should have shopped around a bit!

Sorry, what did you mean did I tighten the head? I gently tightened the drawbar on the top of the spindle if that’s what you mean?

not done it yet - yes this was one of the measurements on my drawing and it was extremely straight, I barely saw any change on my DTI’s display which has a resolution of 0.01mm.

I’ve ordered two finger collets from Arc Eurotrade now and have submitted a support request to Axminster for a refund for the collet holder and the two collets I bought from them too (no use to me without a holder!) … will let you know how I get on.

Thanks again for everyone’s support, I’m surprised / grateful how active this forum is! 😀

David

You said you gently snugged up the drawbar, which is all that should be done to it. What you have not mentioned is how much effort you put into tightening the collet nut onto the collet holder. These need a lot of torque to seat them. It will not change the internal runout of the holder though.

A further check that should be done is to mark the collet holder high point with a pen then remove it, replace it in a different position (eg 180° about) and repeat the exercise to see if the high point stays at the same place on the holder or is now in a different place. There is a possibility that the spindle taper is only correct at one point or that there is internal damage or debris stuck in it.

Martin C

I don't think you're being pedantic, and I would ask Axminster to replace the holder. The ER system is very versatile, and worth persevering with to get a set-up you have confidence in.

This sort of thing does happen, as I found with an ER11 collet holder. (Both the original and the replacement were direct from China, though, not via one of the UK agents.)

David,

No it was not. You checked the outside of the spindle, not the internal taper. It has been known that manufacturing has not been to specification.

NDIY look at the top right of the photo 0.01mm pointing to the taper shown with dotted line as hidden

Edited By JasonB on 21/02/2022 17:04:22

Martin – Ah, I tried various degrees of tightness of the collet nut itself, but yes as you mentioned it doesn't change the fact the taper in the collet holder is already way out.

I could definitely do that check of marking the high point, just out of curiosity more than anything else. I did try removing the holder and pushing it back into the spindle taper a few times and it didn't seem to make any difference, but I didn't use any markings to do it very scientifically 🤪

Frances – Ah yes I always engage the lock on the head gib before doing any drilling / milling, although that won't have made any difference in my run out tests I would have thought?

Andy – Interesting, and yes that was the sort of result I was getting ... except it was digits changing drastically rather than a needle waving back and forth 😄

NDIY – As per Jason's post! 😄