Stevensons original collet blocks & Arc Euro 6″ grinder

[JasonBModerator @jasonb]

Yes a torque wrench with suitable fitting for the collet is used, though I doubt many home hobby users bother with one

Mr happy from Hass shows than about 15.30 into this video, some other useful info there too

[Douglas JohnstonParticipant @douglasjohnston98463]

The dense foam sheet used for insulation makes a very good alternative to wood for holding collets. I made one up for R8 collets out of 50mm thick sheet and it is as good as new after 10 years. I used a large diameter end mill to cut out the holes for the collets and fitted it into a large plastic food box. When not in use the plastic lid of the box keeps the contents clean and dry. I have never been happy using wood next to steel parts due to the corrosion risk.

Doug

[Brian GParticipant @briang]

The torque required by ER collets is easy to underestimate – I'm pretty certain I never do them tight enough. Looking at Rego-Fix's chart for ER25, it is between 24Nm for 3mm up to 104Nm for 10mm+. Assuming that I am holding the C-spanner 4" from the collet nut, that means applying a force between that needed to pick up a half-hundredweight sack of potatoes and lifting myself off of the floor. Worse than that, as I don't have a spindle lock I would have to apply the same force in the opposite direction on the chuck!

Brian G

Edit:  Does anybody remember Dynamic Tension?  Why does it take me forever to make an engine when in just seven days I can make you a man.

Edited By Brian G on 18/12/2019 13:05:51

[not done it yetParticipant @notdoneityet]

Posted by Brian G on 18/12/2019 13:04:01:

The torque required by ER collets is easy to underestimate – I'm pretty certain I never do them tight enough. Looking at Rego-Fix's chart for ER25, it is between 24Nm for 3mm up to 104Nm for 10mm+. Assuming that I am holding the C-spanner 4" from the collet nut, that means applying a force between that needed to pick up a half-hundredweight sack of potatoes and lifting myself off of the floor. Worse than that, as I don't have a spindle lock I would have to apply the same force in the opposite direction on the chuck!

Brian G

Longer spanners is the answer. My smallest torque wrench reads in inch pounds force and my largest is about a metre and a half long with a 1” square drive – neither particularly appropriate for this operation!

[Martin ThomsonParticipant @martinthomson36607]

Posted by Brian G on 18/12/2019 13:04:01:

The torque required by ER collets is easy to underestimate – I'm pretty certain I never do them tight enough. Looking at Rego-Fix's chart for ER25, it is between 24Nm for 3mm up to 104Nm for 10mm+. Assuming that I am holding the C-spanner 4" from the collet nut, that means applying a force between that needed to pick up a half-hundredweight sack of potatoes and lifting myself off of the floor. Worse than that, as I don't have a spindle lock I would have to apply the same force in the opposite direction on the chuck!

That's a horrid mix of units…

A C-spanner is almost completely useless for doing up ER collets. You want one like the forged ones Arc (and others) sell – well worth £8. A bearing nut also helps and allows you to reduce the torque by 10-15%.

It is also much easier if you have the collect chuck out of the machine and held securely at about waist height. I hold mine in my bench vice but I do plan to build a proper tightening fixture eventually (I've have the material for it for nearly two years).

I found it nearly impossible to properly tighten in the machine, mostly because it is a small mill with limited space. I do regularly tighten up the er32 collet chuck on the lathe but that's got a lot more space around the chuck.

104Nm is not that hard to do with a proper spanner – about the same as wheel nuts.

In proper commercial workshops torque wrenches are mandatory for this sort of thing. Although I'm told collets are getting less popular these days, all the cool kids are moving to shrink-fit tooling. I got a demo of the shiny new shrink-fit setup at a workshop I visit regularly and it is an impressively simple idea. Sadly not something available at hobbyist level yet.

[Chris VParticipant @chrisv]

How interesting. So turns out my 10" ex WD spanner I bought specially for the ER20 collets is not too big after all.

Cheers

Chris.

[Brian GParticipant @briang]

Posted by Martin Thomson on 18/12/2019 14:28:12:

That's a horrid mix of units…

A C-spanner is almost completely useless for doing up ER collets. You want one like the forged ones Arc (and others) sell – well worth £8. A bearing nut also helps and allows you to reduce the torque by 10-15%….

I normally use one of the "industrial" type spanners, but the arithmetic was much easier with the shorter spanner, so I cheated To be honest, I got into the habit of adjusting variables and mixing units to get simple approximations when carrying out rough-cut production plans and costings. A simplified estimate is a good way of finding out if you have misplaced a decimal (or even divided instead of multiplied) in the proper calculations.

Brian G

[BC ProfParticipant @bcprof]

I called it guesstimation when the 6th form Physics students were doing calculations .

[Ron LadenParticipant @ronladen17547]

A C spanner is almost completely useless for doing up ER collets

I am new to ER collets but C spanners is what I am using and I cant see a problem, to be honest I would have thought there are numerous people using them but maybe not..? To the loading I adjust the collet nut, I have no idea I just go with what I feel is something like correct for the size of tool/work in the collet. I now have a bearing nut which does appear to need less loading than the plain nut.

So it sounds as if I am doing it all wrong but its what I have been doing with no issues to date.

[JasonBModerator @jasonb]

I've been using a C spanner for about 12 years and it works for me. best not mention that on the odd occasion that I use an ER on the lathe quite often tighten the nut by gripping with my hand

As I said in a thread a week or so ago a lot will depend on the individual, a more senior member will not have the same grip and strength of a younger one, I'm sure many here may also struggle to undo wheel nuts.

[Mike PooleParticipant @mikepoole82104]

I always use leg power for wheel nuts but even a youthful me would have struggled to tighten my mill or lathe ER chuck with leg power. I think in industry ER chucks will be set off the machine in a jig and torque tightened. A good spindle lock that can take the tightening torque would be useful but remember that depending where it is installed then the tightening torque may go through the keys and splines of the spindle which they may not like very much.

Mike

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by Brian G on 18/12/2019 13:04:01:

The torque required by ER collets is easy to underestimate – I'm pretty certain I never do them tight enough. Looking at Rego-Fix's chart for ER25, it is between 24Nm for 3mm up to 104Nm for 10mm+. Assuming that I am holding the C-spanner 4" from the collet nut, that means applying a force between that needed to pick up a half-hundredweight sack of potatoes and lifting myself off of the floor. Worse than that, as I don't have a spindle lock I would have to apply the same force in the opposite direction on the chuck!

Brian G

Edit: Does anybody remember Dynamic Tension? Why does it take me forever to make an engine when in just seven days I can make you a man.

Edited By Brian G on 18/12/2019 13:05:51

Hi Brian, If you used two spanners in opposite directions, the total applied force will be the same, given the torque required, i.e. would you not have half of the total torque in each hand? Equal and opposite reaction and all that.

Regards Nick.

[not done it yetParticipant @notdoneityet]

Noo! The full torque will be applied to both hands. One is trying to prevent it turning while the other is trying to tighten it in the opposite direction. Just arm strength, not foot against car wheel analogy.

 

Zero work done, of course, after it stops tightening.

Edited By not done it yet on 19/12/2019 12:28:16

[Brian GParticipant @briang]

If the spindle was locked and the lathe bolted down, the equal and opposite torque would be applied to the floor by the stand. In my case, as the collet chuck is on a mini lathe that isn't bolted down, applying the full force to only one part would result in work being done and a lathe falling onto my foot…

Tightening the chuck on my son's X2.7 is a "fun" exercise though, as it doesn't have any spanner flats and I am relying on the grip of the MT3. If I tighten the drawbar enough to tighten the collet chuck, I have to forget any hope of self-ejecting the chuck – fortunately a tap on the end of the drawbar works wonders.

The sensible move might be to mill flats onto the collet chuck, but that will have to wait until I have a second milling chuck!

Brian G

[Nicholas FarrParticipant @nicholasfarr14254]

Posted by not done it yet on 19/12/2019 12:27:04:

Noo! The full torque will be applied to both hands. One is trying to prevent it turning while the other is trying to tighten it in the opposite direction. Just arm strength, not foot against car wheel analogy.

Zero work done, of course, after it stops tightening.

Edited By not done it yet on 19/12/2019 12:28:16

Hi NDIY, I stand corrected then, I wasn't actually sure, few more grey cells drifting in, or dying off. However, I have always found it less of an effort to use two spanners when tightening a bolt, even if the bolt dose not turn, maybe you just get a better leverage.

Regards Nick.

P.S. I've undone and done up thousands of bolts, with and without a torque wrench, in my day jobs that I've had.

[John HinkleyParticipant @johnhinkley26699]

I've been following this thread with interest. I was completely ignorant of the need to torque ER collet chucks to a specific value. I've always used a C-spanner as supplied with the chuck and a large adjustable on the chuck flats to hold everything fast while applying the tightening force. I have square and hexagonal Stevenson blocks from Arc which are supplied with bearing nuts. I've never had a cutter or workpiece come loose in any of my (many) ER chucks from ER11 to ER32. Can you over-think it and end up with a problem of which you weren't aware?

John

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