HH and ER32 collet holders (MEW195)

[chris stephensParticipant @chrisstephens63393]

Hi Guys and in particular HH,

Having just read the article on ER collets, I too had the problem of them not closing to their minimum. I found the solution to be quite simple and, more importantly, free from cost.

I seem to recall that i first noticed the problem when i tried to hold 6.1mm in a 7mm collet. Despite heaving with great force it would not close tightly, and as you would expect it would not fit in a 6mm collet either so i was stuck. Reasoning that it was the collet holder that was at fault because when I tested the same size material and nut in the mill collet holder(Vertex) I could hold it perfectly well.

So as to the fix, i machined off the first 0.5mm thread from front of the collet holder and tried the closing ability. It was improved but I then took off another 0.5 and it closed just fine. It would not grip 6mm as it should have done, so I then took of a final 0.25mm and it gripped that size too. In case some of you are worrying about this practice, no I should not have needed to do it, yes i could have sent it back to xxxxxx but where's the fun in that? I did make sure that it was the thread that was too long (for the possibly oversized tapered bore) and that the nut would not bottom out to the main body.

I have not named the supplier because it would be unfair to criticise as I gave them no opportunity to correct the problem, but I suspect that my backplate version is not the only style that has problems. The screw-on style as fitted to a friend's Myford also has certain difficulties!

If any of you guys think this all sounds like ER's are not worth having, you could not be more wrong. With my back plate style I was able to get it running true, within the tolerances of the collets, to my satisfaction even being a perfectionist. Admittedly it took time to get right both axially true and wobble free but it is really gratifying to know that a "back street mechanic" (to use the great Dibnah's expression) can do things better than a giant Chinese factory!

chriStephens

[chris stephensParticipant @chrisstephens63393]

A possible solution to ER’s not closing enough.

[modeng2000Participant @modeng2000]

This is very interesting Chris, thanks for bringing this to the forum.

It never occurred to me to check if the nut was bottoming and so was not able to close the collet.

John

[Another JohnSParticipant @anotherjohns]

Chris, John –

I had this on my home-made ER40 holder, getting that distance right seemed to be a bit of a trial and error situation!

Hope you enjoy the ER collets; I think they are great.

Another JohnS.

[AndyfParticipant @andyf]

I once worked out with trig that to get an ER collet to collapse by 1mm, it should have about 4mm of the 8 degree taper projecting out of the chuck when it's inserted gently (i.e. before compression begins). Obviously, the projection can only be measured with the closing nut off.

This applies to ERs with a 1mm "leeway" in all sizes from ER11 to ER40. Those which are only supposed to collapse by 0.5mm will only need 2mm projection.

Andy

[chris stephensParticipant @chrisstephens63393]

Hi John(ME2000)

It was so obvious, little wonder I didn't think of it earlier!

chriStephens

PS I think this is a good example of the worth of 'net forums over letter pages, instant answers.

[Sub MandrelParticipant @submandrel]

I have found no problems holding 1/4" cutters in my 7-6mm collet with my chuck featured in ME about 8-10 years ago, although I had previously made a 1/4" collet as I didn't have the right metric one. I use the metric one in preference as despite great care my home made ones don't seem to self-release as well as metric ones.

My chuck is rather 'industrial' (i.e. huge) but I have found it invaluable.

Neil

[Harold Hall 1Participant @haroldhall1]

Thanks Chris for your comments, following my article in MEW, detailing your findings when closing ER collets. I have to admit now that I should have been concerned about the commercial fixture I was using on my milling machine, as the problem with this was much greater than when using my shop made collet chuck being used on the lathe. I should have asked, why.

Even so, without testing the device, I cannot be sure that a fault with it is the reason and will endeavour to carry out some tests in the next few days. If found faulty, then I will write to David C with a letter to be published in the magazine updating the article.

This will not though effect the main thrust of the article, that is that the increasing torque required as the collet is closed down can make it difficult to be sure that the workpiece is adequately secured.

When using a three jaw, or drilling, chuck the chuck closes easily until it contacts the workpiece where it then quite rapidly changes from easy going to locked solid, virtually. What I call a brick wall effect.

With an ER collet the progressive nature of the operation makes it difficult to determine when a full grip has been achieved. This only of course when closing one down towards its minimum size. I have occasionally thought I had arrived at a good grip only to find that the collet had not even reached the workpiece diameter. It really is a question of getting used to a totally different closing action compared to other chuck forms.

The article was of course to highlight the existence of ball bearing closing nuts and even in the last hour I have received an email from a reader who quickly placed an order and now finds that he can close his 3mm collet down to 2mm relatively easily, something that was very difficult with the solid nut he had been using.

Harold

[Chris TriceParticipant @christrice43267]

I had a related problem when truing the tapered bore of my old Myford Super 7. I gave it just the lightest regrind of the taper to remove some scoring which worked out perfectly in just about every subsequent use except using Myford’s own collets. The screw on cap ran out of travel before I even reached the nominal gripping point and I ended up having to take off roughly 3mm from the front end of the threaded spindle. Obvious in hindsight with the finer angle of a Morse taper but I fell into the trap for not engaging the brain.

[chris stephensParticipant @chrisstephens63393]

Hi Harrold,

I hope you didn't think my post was in anyway critical of your article or your findings. It is just that I always try to engineer my way out of problems rather than buy solutions. As they say, ask fifty engineers about a problem and you are likely to get sixty answers.

I am tempted to get one of those dandy little closing nuts, following your conclusions, because of tightening problems even on the better made holder. Oh wel,l at least Christmas is not too far off.

chriStephens

[Harold Hall 1Participant @haroldhall1]

Please be assured Chris S that I did not see your comments as criticism, only a worthwhile comment from your own experiences. Very worthwhile if I find it to be the reason I had a problem with my milling machine fixture. As I said above I will carry out some tests with it in the next few days.

Initially, when I first purchased the closing nut, I thought it would just provide an item for the trade pages but grew when I started to use it when making the clock.

Harold

[AndyfParticipant @andyf]

I'd like to second your recommendation about ball bearing closing nuts, Harold; after learning about them a couple of years ago, I bought one and it is much easier to use than the solid variety.

In your article, you also mentioned imperial ER collets, and I intend to get some to assist with imperial shanked tooling on my vertical miller. While the nut is being tightened, a metric shank will self-hold in a metric collet, but an imperial shank will fall out unless held up with a third hand while the slack is taken up.

Andy

[Chris TriceParticipant @christrice43267]

Are they available for ER25 size?

[NJHParticipant @njh]

Hi Chris

Yes – look on ebay. I read Harold's article and, with a need to hold a lot of small bits. recognised the problem. I have an ER25 chuck which screws directly to my Myford nose . The ball bearing nut does make life much easier.

Norman

[Ian PParticipant @ianp]

My very recent Ballnut experience (and further ramblings)

After reading Harold's article I ordered a ER25 ballnut. (I was very pleasantly surprised when the postman brought it as I had only clicked the 'Buy it Now' button mid afternoon the previous day!)

I bought it on a whim, not because I was having any problems but just because it seemed the best way to tighten collets. I inserted a 16mm collet, put it on the mill and although I did not cut any metal was pleased with the thought that I hade made an improvement.

Today I needed to use a 6mm cutter and STRUGGLED to get the 16mm one out! Further investigation showed the offset/obloid? hole was poorly deburred. Not wanting to return it I looked to see how to fix it myself. I decided not to dismantle the ballrace part (although I was tempted because it felt rough) but I masked off the gap between the rotating parts and used a mounted diamond burr to clean up the edge of the hole.

I can now install and remove collets although nowhere near as easily as my ball-less nut that has a 'D' shaped hole. I found a big variation between different makes of collets as regards insertability. I have 'run in' the ballrace by rotating it in the lathe but although it feels a little smoother I am not convinced the ballraced cone remains stationary when the nut is tightened so I still need do some more investigating.

Maybe this paragraph should have its own thread but I wonder whether using a ballnut improves the concentricity of collets? The ER type closes when the two cones get closer together, the spindle cone is the primary location but with a conventional nut any eccentricity between the nut thread and cone will tend to tilt or at least apply uneven force to the front of the collet. The ball type nut must have some lateral play so the nut cone then has slight self aligning properties so the collet only centralises on the spindle taper.

Ian

[NJHParticipant @njh]

Hi Ian

Your post prompted me to go out and try inserting and removing collets from my ballnut. The proceedure in the past, with the standard nut, was to incline the collet and rotate it whilst pushing gently and it would pull itself in. The remove rotate and pull gently. This doesn't work with the ballnut of course as the bearing rotates. I find however that it is only necessary to hold the nut with the visable part of the taper uppermost, hold the collet at an angle and fit the slot over the raised part at the bottom of the nut. Simply press from the back then and it will snap into place. To remove simply press it out from the front.

Having tried this a few times I find it easier than the old "rotate" method.

N

[HasBeanParticipant @hasbean]

Maybe just me but I have found an ever so small burr on the edges of some of the slits of my collets which I have had to stone off in order to improve concentricity.

Must add that these collets have come from several different sources.

Paul

[Sub MandrelParticipant @submandrel]

I've just ordered one of these ER25 ball bearing nuts from Gloster Tool Supplies. About £13.50 with VAT and delivery which is cheaper than ebay and another supplier which was about £32 less vat & deliver!

I will see what it's like for quality when I get it. There's enough meat on my home made holder to replace the existing thread with M32, but I might just make a second chuck from scratch.

Update: Arc do a blank end arbor with a big 1 1/2" diameter by 1 1/4" long end – I can make a new on that's more compact than my old one (which screws onto a thread cut on a much smaller blank). the old one will be good for material in the lathe (as it will have a much deeper hole) the new one will be best for milling cutters.

Neil

Edited By Stub Mandrel on 12/03/2013 11:59:07

[NJHParticipant @njh]

Hi Neil

That's where I got mine (Gloster Tool Supplies.) and it's fine.

Cheers

Norman

[Sub MandrelParticipant @submandrel]

That's good to know. I should say the 'other' supplier wasn't one of the normal ME suppliers, but a 'procurement platform' which appears to deal only in multiples of three. Vive la difference!

Neil

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