ER40 Collet run out.

[Tom GullanParticipant @tomgullan59234]

I am fairly new to Model engineering and am looking for some help with run out on my recently purchased ER40 Collet Chuck.

I have checked the spindle run out on my Myford Super 7 at face of the spindle and at the circumference of the shaft. I have zero run out at the circumference and approximately 0.0003" at the face. I have levelled my lathe as per the handbook using a test bar, I recorded a difference of 0.0002" larger on the right side of the test bar.

I bought a backing plate, mounted it onto my lathe and faced it off. I then turned a register to fit the Collet Chuck then transferred the holes from the Chuck to the backing plate then bored clearance holes. After clamping then together, I used a piece of 12mm Silver Steel in a Collet and checked for run out… I can't remember what the reading was but it was quite a way off.

I then decided to turn the register down by 0.020", bolt he two pieces together, insert a DTI into the collet cup and take a reading. I the tapped lightly on one side of the chuck in order to eliminate the run out (a bit like altering a Griptrue chuck). I then traversed across the length of the cup and registered zero run out.

I then inserted the 12mm Silver Steel once again and checked for run out. At the collet face I registered 0.0003" and at 5" from the collet face I registered 0.007". I also carried out the same test using a 16mm parallel test bar with more or less the same result.

The collet set was purchased from RDG Tools. After contacting then they kindly sent me a ball bearing clamping nut free of charge to see if that would resolve my problem… unfortunately it has not.

I would appreciate any suggestions as to how I can solve this frustrating problem.

Regards, Tom

[Tom GullanParticipant @tomgullan59234]

[Mark RandParticipant @markrand96270]

Have you made sure to hook the extractor groove of the collet into the protruding section of the extractor ring in the nut?

That's the most common cause of alignment problems with ER collets.

[Nigel McBurney 1Participant @nigelmcburney1]

I think the mounting face of the collet chuck is not square to the axis of the collet. As you have a test bar,which I assume has a morse taper and a long parallel portion, fit the test bar into the lathe spindle taper,then part the chuck from its backplate fit a collet to the chuck that will grip on the test bar,no need to pull the collet up dead tight. set a dial indicator to measure runout of the back FACE of the chuck,if it runs true it will at least prove that the axis of the collet is true to the mounting face, I have assumed that you have examined the taper in the chuck where the collet fits and there are no burrs or damage to the taper or the collet,does the runout fault occur with all the collets?,the collet that you first used may be faulty,Should the mounting face prove to be at fault,either return the chuck or mount a piece of steel bar preferably greater than the size of the largest collet available,turn the bar to suit the collet,also the bar will be running true,mount the chuck on the bar via the collet a lightly skim the back face, this action may solve the problem but also invalidate the guarantee.

[Neil WyattModerator @neilwyatt]

Your tests appear to show the collet chuck itself is perfectly concentric, if you are not detecting runout at either end of the tapered hole.

That means that either:

• You have a inaccurate or damaged collet
• A poor nut
• Improperly fitted collet
• Dirt
• Test bar itself not true.
• Insuffcient tightening

[James AlfordParticipant @jamesalford67616]

Posted by Neil Wyatt on 28/03/2017 22:47:55:

• Insuffcient tightening

I had similar inaccuracies when I made my collet chuck back-plate: Insufficient tightening was the main reason for my measured errors: I tightened the collet closer more fully and the errors all but vanished.

James.

[Martin ConnellyParticipant @martinconnelly55370]

According to a blog in CNCCOOKBOOK the torque value for correctly tightening ER40 collet nuts is 140 ft lbs. The blog is quoting Tecknik USA.

**LINK**

Martin C

[MalcBParticipant @malcb52554]

Posted by Neil Wyatt on 28/03/2017 22:47:55:

Your tests appear to show the collet chuck itself is perfectly concentric, if you are not detecting runout at either end of the tapered hole.

That means that either:

• You have a inaccurate or damaged collet
• A poor nut
• Improperly fitted collet
• Dirt
• Test bar itself not true.
• Insuffcient tightening

If you cannot improve things with the above, then you need to further prove out the ER chuck.

Then need to make a tapered mandrel, same taper as the collet location, drilled and tapped to enable clamping back. Initially set compound over by clocking the internal taper of the ER chuck.

Carry out fine tweaking if needed to get a perfect bed using Engineers blue. Clamp back and clock face and recess for true. Any errors are then further magnified at the outer recess diameter and adjacent face.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Connelly on 29/03/2017 08:40:54:

… the torque value for correctly tightening ER40 collet nuts is 140 ft lbs. …

.

Which is "quite difficult" to apply using a spanner in each hand

… with the chuck mounted on a Myford S7

MichaelG.

[Chris Evans 6Participant @chrisevans6]

When using ER collets on a CNC mill at work we had a bench mounted tightening fixture to ensure they could be pulled up tight. Also do not assume 12mm silver steel is going to be round and straight, it very rarely is.

[Neil LickfoldParticipant @neillickfold44316]

With ER40, and any ER for that matter, the thread for the nut must be concentric to the taper bore. I would check that the very inside of the 8 deg taper is concentric to the front of the 8 deg taper. If they are both correct, ie better than 0.01mm in both cases, then check the thread. Set your lathe for screw cuting, set to 1.5 pitch, turn by hand and when the carriage is engaged and feeding at the the same rate as the thread of the collet chuck. Put the dti into the thrade and see if it is concentric to 0.01mm. If both of these tests show to be within 0.01mm, then check with some bearing blue on the 8deg taper and a collet. just lightly hand fitt to check that the tapers are coincident. If all these are good, then most likely it will be in the collets themselves. A simple check is to place the collet in by hand,without the nut, and with a finger indicator, carefully check for the run out of the collet itself. The front of the collet should be less than 0.01mm DTI reading. Then put the collet nut on and test again. This will check if the nut in influencing the concentricity of the collet.

Neil

[Neil LickfoldParticipant @neillickfold44316]

Too late to edit, but for any collet that I want to be running good, I have been buying the high precision collets from Regofix. In saying that, I just tested a cheap set of collets that is going to be used to hold parts for milling hexe's etc, so does not need to be all that concentric, just has to hold the part. To my surprise , the 4mm,6mm, and 8mm were better than 0.01mm at the collet face and at 30mm out from the collet face. This is a cheapo ER20 set. For my cnc wood router I use only regifix and it is ER20 also . I tried the Regofix nuts and the regular nuts on the 6mm collet. Of all the nuts we have, the regofix and 3 of the no brand were very good. 3 of the no brand made the collet not run true at the 30mm mark and next to the collet face was showing nearly 0.02 run out and .06mm run out at the 30mm . This is the worst of the no brand ER20 nuts.I have now identified those nuts and will use them on the milling fixture for Non important things. While at it, I checked with an indicator on a known bad collet for concentricity. As I suspected, it did not run concentric at the front to the back of the collet. It has a reading difference in the front to the back of about 0.03mm. I used a red marker for the front high side and a blue for the rear high side. They are almost opposite, which makes sense and explains why the test piece with that known bad collet is no good. What I will do is set up and regrind the id concentric and see if I can save it. It will become then a special sized collet effectively. I will put that onto the oneday list.

Hope this info may help some people out there. I have read about the high torque required to hold stuff with the ER40 collets, and for what I do with them, have not found a need to tighten any more than what I can on the spanner lengths that are supplied by Regofix or the other spanner suppliers for the various ER sized systems. Granted ,most of the stock I hold is turned finished bar in most cases, or is Carbide cutters.

Neil

[Tom GullanParticipant @tomgullan59234]

Gentlemen,

Thank you for your comments and advice.

[KWILParticipant @kwil]

Micheal,

Why do you need a spanner in each hand? The S7 has a spindle lock. Undoing the collet may be more difficult!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by KWIL on 30/03/2017 19:07:19:

Micheal,

Why do you need a spanner in each hand? The S7 has a spindle lock. Undoing the collet may be more difficult!

.

Because of the stated requirement for 140 foot pounds of torque !!!

I certainly wouldn't risk applying that to my spindle lock … and would be somewhat concerned about twisting the lathe bed, or tearing it from its mounting.

Feel free to try it on yours.

MichaelG.

[Neil LickfoldParticipant @neillickfold44316]

A pair of spanners can allow a zero torque on the spindle and machine tool. Although they have the huge toque value for the ER40, I have only used about 30ftlbs and it is fine for every thing I have been doing. The smaller ER 20 I use less than that. Never had a cutter come out from ER40 or the other smaller ones. I also don't go trying to take the max possible cuts etc either , when holding a cutter or a work piece.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Lickfold on 30/03/2017 19:44:19:

A pair of spanners can allow a zero torque on the spindle and machine tool. …

.

Thanks for the endorsement, Neil [assuming I can take your comment as such]

My initial comment was, of course, made in response to the mention of the specified torque.

MichaelG.

[Tom GullanParticipant @tomgullan59234]

Gentlemen,

Thank you for all you advise and comments.

I still have not been able to resolve my run out problem. Dose anyone know of any Model Engineers in the Aberdeen/Aberdeenshire area who would be willing to have a look at my lathe?

Regards

Tom

[MWParticipant @mw27036]

If it makes you feel any better i have the same problem with a morse taper collet chuck from rdg again. The front of my spindle taper registers zero runout on the bore too. I get around .15 runout. From the collet chuck withva bar held in. Whereas my 3 jaw does the same with 0.02-0.05. I was going to use a flange mounted er chuck with a backplate to see if this would correct it. But seeing this makes me feel uncertain. It would work. Maybe skimming the chuck taper insitu would help?

[Tom GullanParticipant @tomgullan59234]

It has been suggested to me be a local engineer that the spindle may not be running true to the bed of the lathe and that I should consider shimming up the casing that mounts the gearbox/spindle. Has anyone any thoughts?

[JasonBModerator @jasonb]

Before you think about moving the headstock get a MT2 test bar and pop that in the spindle. If you get better results than you were getting from the collet then the fault is not with the spindle.

What was the "test bar" you mention using to set up the lathe in your opening post?

[Nick_GParticipant @nick_g]

.

My advice would be to send both the chuck and collets back. – I initially purchased not knowing any better quite a bit from that company. – Everything (except for a vertex milling vice) has had to be replaced or needs to be.

Then purchase a chuck and collets from somewhere that does quality control to a reasonable standard themselves and does not rely upon the end user (the customer) to do it for them.

I have an ER collet chuck for my lathe purchased from ARC and it is a excellent bit of kit by any standards. Especially for the money.

Nick

[Neil WyattModerator @neilwyatt]

Don't assume a cheap test bar is accurate…

Best check is always a DTI inside the taper.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Neil Wyatt on 04/04/2017 21:20:36:

Don't assume a cheap test bar is accurate…

.

Cheap test bars are available from 'Oxymoron Enterprises'

[ best known for their Chocolate FireGuard ]

MichaelG.

[MWParticipant @mw27036]

Posted by Nick_G on 04/04/2017 20:58:17:

.

My advice would be to send both the chuck and collets back. – I initially purchased not knowing any better quite a bit from that company. – Everything (except for a vertex milling vice) has had to be replaced or needs to be.

Then purchase a chuck and collets from somewhere that does quality control to a reasonable standard themselves and does not rely upon the end user (the customer) to do it for them.

I have an ER collet chuck for my lathe purchased from ARC and it is a excellent bit of kit by any standards. Especially for the money.

Nick

it may be too late for that. I don't think they'd refund it.

Michael W

[Author]

Posts