Holding short lengths

[AjohnwParticipant @ajohnw51620]

Posted by Gary Wooding on 25/09/2016 11:03:08:

I use ER32 in my mill and lathe and both chucks have an internal taper that fits precisely the external taper of the collet. I don't see how the "rear" of the collet can close more than the "front" to cause bell-mouthing. Can somebody explain please?

I already explained why the wont do that in another thread. Long, no notice taken so I just sit here laughing saying up yours. I should have added a bit more though.

There is a good reason normal spring collets usually have a grip length of around twice the dia. They will grip less but a problem occurs at some point. Say it was 10% of the dia. That is no where near enough to guarantee that the clamped part is lined up in the collet it could be at an angle. People who feel 1 dia is all that is needed should go talk to the makers, People who think that normal spring collets should be split 4 ways should do the same.

ER collets follow a lightly different grip length rule. Some spring one may too. It's circa 1 1/2 diameters. Going on that comments I have seen about 2/3 of it used should be ok. Below that there will be more risk of not aligning correctly. The ancient venerable 1 dia rule used for many relatively low precision things even guides in an odd way.

All rubbish so why is it so easy to mount bar in a 3 jaw chuck and not have it running as true as the jaws do ? If badly out it will probably work loose as soon a decent cut is put on but there are degrees where it wont do that.

It's all common sense really.

John

–

Edited By Ajohnw on 25/09/2016 12:33:06

[Raymond AndersonParticipant @raymondanderson34407]

Hi Nick H, I have soft jaws, but I really would prefer a collet system. Even if it comes down to making a shed load of me own blanks I would happily do that. Am still at the mulling over / checking out the options stage. Either way I'm changing, although I'm still keeping me ER'S They won't be getting ditched In fact I will probably end up using them as much as the new system [ whatever that turns out to be ]

cheers

[Gary WoodingParticipant @garywooding25363]

Posted by Ajohnw on 25/09/2016 12:32:12:

I already explained why the wont do that in another thread. Long, no notice taken so I just sit here laughing saying up yours. I should have added a bit more though.

Can you supply a link please. I still don't understand. Does hardened steel compress to any noticeable extend when used as the springy jaws of a collet?

[Speedy Builder5Participant @speedybuilder5]

What is the used trying to make? Double sided coins ?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Gary Wooding on 25/09/2016 13:05:53:

Posted by Ajohnw on 25/09/2016 12:32:12:

I already explained why the wont do that in another thread. Long, no notice taken so I just sit here laughing saying up yours. I should have added a bit more though.

Can you supply a link please. I still don't understand. Does hardened steel compress to any noticeable extend when used as the springy jaws of a collet?

.

Gary,

Mark's pictures on this page **LINK** will do more than thousands of words, to explain what's going on.

http://www.model-engineer.co.uk/forums/postings.asp?th=120333&p=9

MichaelG.

[Raymond AndersonParticipant @raymondanderson34407]

Hello Speedy Builder, Now there's a thought… make a double sided coin ,comes the toss of a coin.. Heads or tails? Jesus, I could never lose If only I wasn't so honest.

cheers.

[MWParticipant @mw27036]

I don't know why, but the rubberflex jacobs system just seems so revolutionary, i honestly can't see why this never caught on with it's combination of materials. It's like the very first "composite collet".

Just not marketed outside the US?

Michael W

 

Edited By Michael Walters on 25/09/2016 16:29:22

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Walters on 25/09/2016 16:22:30:

I don't know why, but the rubberflex jacobs system just seems so revolutionary …

.

Here's the manual **LINK**

http://www.tools-n-gizmos.com/info/Jacobs_Rubber_Collet_Chuck.pdf

MichaelG.

[MWParticipant @mw27036]

Posted by Michael Gilligan on 25/09/2016 16:56:08:

Posted by Michael Walters on 25/09/2016 16:22:30:

I don't know why, but the rubberflex jacobs system just seems so revolutionary …

.

Here's the manual **LINK**

http://www.tools-n-gizmos.com/info/Jacobs_Rubber_Collet_Chuck.pdf

MichaelG.

Thanks Michael, Will make for interesting reading, i wonder how the the rubber is treated to ensure a good life, i'd imagine you'd need to take great care when using them.

Michael W

[MWParticipant @mw27036]

When you see even the chuck created for the collets, it's a marvelous looking thing.

Jacobs, which pretty much set the standard blueprint for the drill chuck used on alot of machines. Created this to accomodate the need for collet users, they could've done a worse job i say! But it never caught on…?

Michael W

[John Stevenson 1Participant @johnstevenson1]

They are horrible to use.

Sounds like sour grapes but it's not, I have two complete chuck assemblies here with collets.

To use, you have pull the inner ring out, the one with the angled teeth on then spin the big ring hard until it stops and then repeat this hammering action until the chuck becomes loose, swap the part, then repeat in a reverse order hammering the ring round by hand until it's tight then piss about pushing the locking ring in whilst rotating the outer ring until it locks in.

So what should be open, swap part, close is translated into pulling and spinning highly polished pieces of metal, usually with slippy hands if you are using coolant, many times over.

Sorry after 5 parts you loose the will to live and even a 4 jaw looks tempting.

Why they attract the price they do I'll never know. I got both my sets for different guys who also hated them and were glad to see the back of them.

I only mentioned these initially to put forward the rubber bung idea to be used on ER's but I have a sneaking suspicion that nothing will come of it because Raymond's mind is already made up no matter what's posted.

[Nick HulmeParticipant @nickhulme30114]

There's space in my ER collet drawers for stepped brass bungs for the back end, I use a small polyurethane insert in a hole on the OD for retention. My bungs see regular re-use and you only have to make a given size once so I don't see 2 minutes of time invested to make them as lost.

– Nick

P.S. I know it's sacrilege of the highest order but I thought I'd also mention here that I've successfully used ER40 collets on tapered work, some with 2 feet hanging out the back of the head and concentricity was good

[Raymond AndersonParticipant @raymondanderson34407]

Hi John, You are correct about me mind being made up. Only thing is to what system? Did you ever get a chance to look at the 2 pics of the B 60 ? I am going to get a price for a set of the 16's up to 42.50 Ø and a price for the B 60's They go up in 0.5mm steps to 60.50 Ø but I will stop at 45 Ø. although I need to be sure that I can use the B60's manually. They will no doubt cost an arm and a leg ,but I don't want to have to sell a kidney aswell.

What are you're thoughts on me making bigger versions of me test ones ?

cheers

[John Stevenson 1Participant @johnstevenson1]

Yes I did look and when I went into work today I took some pictures of the manual B whatever they are size.

 

I also took some pics of how I hold short lengths and thin sections in soft jaws, a method that has been used for 200 odd years so I question why you have to reinvent the wheel but as you say your mind is made up and so I'll just be spending time that could be used far more productive to me.

 

So I will wish you the best of luck and perhaps one day revisit her to find out just how many angels you got onto the pin head.

Edited By John Stevenson on 25/09/2016 19:16:44

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nick Hulme on 25/09/2016 18:44:34:

… some with 2 feet hanging out the back …

.

**LINK**

[Mark CParticipant @markc]

Reading all the buff about the various types, I have one of my machines more or less permanently fitted with a Crawford hydraulic chuck and a set of "C" type multisize collets. They are really good and very easy to use. Tighten the chuck key locks it up solid in a big way and then undo and spin the nose closing nut off to change size. Takes no time at all and works every time. Run out is very good (have never measured it but re-fitting a job will be visually close when you start turning again – perhaps within a thou or so) but I rarely put short lengths in it. I always try to ensure there will be enough material to reach the back of the collet.

I don't have any to try but I think it will take the Jacobs Rubberflex collets? I have a Jacobs manual chuck but I never use it as I never got round to mounting it on a backing plate (my machine takes L00 fittings and the back plates are very expensive to buy)

It is also useful in that it is a "dead length" system which is very handy on a lathe at times.

Mark

[AjohnwParticipant @ajohnw51620]

Posted by Gary Wooding on 25/09/2016 13:05:53:

Posted by Ajohnw on 25/09/2016 12:32:12:

I already explained why the wont do that in another thread. Long, no notice taken so I just sit here laughing saying up yours. I should have added a bit more though.

Can you supply a link please. I still don't understand. Does hardened steel compress to any noticeable extend when used as the springy jaws of a collet?

That's what I pointed out. You don't want to read who knows how many pages there are on the ER collet thread – so just believe me.

John

–

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Ajohnw on 25/09/2016 19:28:28:

Posted by Gary Wooding on 25/09/2016 13:05:53:

Posted by Ajohnw on 25/09/2016 12:32:12:

I already explained why the wont do that in another thread. Long, no notice taken so I just sit here laughing saying up yours. I should have added a bit more though.

Can you supply a link please. I still don't understand. Does hardened steel compress to any noticeable extend when used as the springy jaws of a collet?

That's what I pointed out. You don't want to read who knows how many pages there are on the ER collet thread – so just believe me.

John

–

.

The hardened steel doesn't need to compress noticeably … The ER collet is split at both ends; it's the shape that can 'compress noticeably', not the material.

MichaelG.

[Raymond AndersonParticipant @raymondanderson34407]

JS, John, there is no need for sarcasm. I appreciate you're efforts in this as I do Jason's, Nick's, and the others.

I stated that I wanted collets only question was what system. I have cut soft jaws before and yes they are extremely accurate and very versatile. But in this case I want collets. Had I known that you were very helpfully going to take pics of the soft jaws, I would have told you not to bother.

So I repeat, Thanks to you and all others who posted on this. Its going to be Collets of some type, nothing else.

cheers.

[SteveIParticipant @stevei]

Raymond,

I note you mention a possible solution based on 16C collets. Is this solution for your DSG 17T, and does the 17T not have a bigger spindle bore (D1-8) than the range for 16c? Would you not be better off with 20C or 25C? Perhaps i have missed something and it is for another lathe…. It would also be interesting to learn what chuck or closer solution you plan to use with the chosen collets.

5C collets have a very limited working range. In my (limited) experience I think some of the responses are misleading and that the actual range is much more limited. Outside of this you risk poor runout and damaging the collet. Normal range is just a thou or so oversize and approx 4-6 thou undersize before they are being used outside specification. So a 64ths set (which is a lot of money for the hobbyist) does not provide a continuous clamping range solution, nor would a 128ths set but only just. Hardinge make them in 1 thou increments in imperial and 0.1mm for metric for a reason. In my (limited) experience the top brand collets have a slightly larger undersize range than the no name. Even so that is just a few thou and for such an expensive item why risk damaging it?

I've tried a google but I have not yet found the working range of 16C. I expect it is a little more generous but it would be educational to learn if it was more than 0.016" under size.

Steve

[SteveIParticipant @stevei]

it seems "riten" offer a undersize range of 0.010". So perhaps my info above is a little conservative.

http://www.riten.com/wp-content/uploads/2014/12/collet-chuck-catalog-2007.pdf

I haven't spotted the Schaublin spec yet.

Having said that for the hobbyist if you are looking at name brand, new collets, then perhaps the funds for a large set is achievable.

[Raymond AndersonParticipant @raymondanderson34407]

Hello SteveI thanks for you're post.. yes, I am going to use them on the DSG. As these are only for my hobby uses I only want ones up to around 40/45 mm The B60's go quite a bit above that and the 16 C's stop at around 42.50 [I think ].

I understand exactly where you are coming from as regards "damaging " them, got some prices in today and even though I get a very good discount they are still extremely spendy But if they do what I want then fine.

I did look at the Riten ones and very nice gear. The ones I got prices for are by Crawford. I am still at the checking stage just now, and you will appreciate that I have to get this "right " first time or sell a kidney to go along with me remaining arm and leg.

Would you have any views on another option ie, Me making bigger ones than my test ones that I posted pics of .

They work very well, and are repeatable to within the 0.01mm which is good enough for my uses. Only be a case of keeping the same angle of taper and just beefing up the body size and upping the drawbar thread from M8 to M12. 

cheers.

Ps, They are only for holding short length parts.

Edited By Raymond Anderson on 26/09/2016 14:59:46

[SteveIParticipant @stevei]

Raymond,

How short is short?

For a D1-8 spindle out of the C collets you would be wanting 25C to maximise future flexibility, but you'll not have the very small sizes available and you'll need a chuck. However if you only need short parts and 40 something mm bore then the 5C system will do the job. The Number "5" spindles that were native for a 5C collet also have a fixing arrangement for step collet closers, chucks etc with either a spindle screw thread or 4 deg taper and bayonet mount system.

With a step collet (a collet that does not have the rated size right through the whole collet) will do all you need. You'll need the step collet and the correct closer which mounts on the outside of the spindle. Then with 2",3" and emergency step collets your all set. Either regular or extra depth depending on how short, short is and make each you can't buy manually. With this system I get less than 0.01mm repeatability so no problem on 2nd operations.

Hardinge used to make a speed chuck "sjogren" for 5C collets with either plain (not step collet support), 5C-X (4 deg taper nose) or 5C-T (threaded nose). I have a 5C-X with a D1-6 back plate. "ATS work holding" make them these days and they also do a D1-8 sized version. (I am not sure if Hardinge ever made a D1-8.) They won't be cheap though but Hardinge have more than a reasonable reputation regarding work holding.

Having said that, to my mind this is a variation of the soft jaw solution you have already rejected. However in case it was something you were not familiar with I thought it might be of interest. Plus it will be cheaper than a larger collet based system and more flexible.

Steve

[John Stevenson 1Participant @johnstevenson1]

Just had a quick reckon up and my soft jaw setup which only uses one set of chuck jaws and for an outlay of £20 ? for the rest can hold 324 different sizes. If I open or close the jaws by 2mm either way then it's up to 1,000's of sizes.

Nothing new, because industry has been holding short lengths of bar for nearly 300 years so why do we have to reinvent the wheel unless you have shares in the OCD Collet Co, Ltd.

[Raymond AndersonParticipant @raymondanderson34407]

Steve, many thanks for the info, I didn’t think the 5c went as far as 40mm That sounds promising, could you tell me who makes the system you mention ie, step collets, closers ect would it be ATS. The shortest grip length would be around 5/6 mm. Any short length part over about 40/45 dia I use either a split bushing or the soft jaws. so the collets are only for up to 40/45
Are you familar with the dsg 17t?
Many thanks.
Cheers.

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