Holding short lengths

Andrew, how short a part do you think you could hold accurately with the B42's

3-jaw chuck & soft jaws ?

A JCB is handy at time but also has no relevance on a thread called holding short lengths.

It'll hold short lengths for side work John
Feeling a bit Grumpy this morning are we...

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

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

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

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?

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

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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.

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.

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

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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

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

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.

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

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

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

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**LINK**

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