Jacob’s rubber flex collets

[AjohnwParticipant @ajohnw51620]

I may have the opportunity to buy a set that takes from 1/16 to 1 1/4" and wondered if anyone had any opinions about them. There seems to be a lot more of them about in the usa.

The Burnerd chucks usually come in what I feel is too large a size for my Boxford. I have also wondered about large ER but a key operated chuck is more attractive and the collapsible range of the rubber flex is better. I could see myself buying loads of ER40's and only ever using a few. Jacob's also reduce the grip length on the 3 smaller sizes. A plus over Burnerd. As I see it anyway.

John

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[AjohnwParticipant @ajohnw51620]

[Nick_GParticipant @nick_g]

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I have no knowledge of the Jacobs rubber chucks other than knowing they are highly regarded by their owners. (spares maybe by now getting an issue) I do though have both a Burnerd multi size collet chuck and an ER32 from ARC one for my Boxford.

The Burnerd one is outstandingly brilliant and super accurate. But the ER32 one comes into it's own for gripping shorter parts which the Burnerd one is not so good at since each jaw is independent and floating withing it's cage.

I when ever possible will use the Burnerd, but as model engineers very often need to machine short parts the ER32 still gets quite a bit of use.

If I did not have both and only had one as a model maker the ER32 would probably be a better option.

As a side :- The ER32 from ARC is nicely made, accurate and good value. But care needs to be taken when mounting on a backplate (as all chucks do) – Just don't buy cheap collets and throw that away.

Regards, Nick

[John ReeseParticipant @johnreese12848]

I have a rubberflex chuck for my South Bend 10K. The collets each have about a 1/8" grip range if I remember correctly. Maximum size for chuck I have is 1 3/8". Jacobs discontinued the rubberflex lathe chucks some time ago. Collets are still available. Like any other collet chuck that mounts to the spindle nose it is not likeyl to run as true as a collet IN THE SPINDLE. They stick out quite far from the face of the spindle so any error setting up the backplate will be magnifeid. Because of the stickout it somewhat limits the depth of cut to avoid chatter. I mentioned that ncollets are available. They will either used or new old stock. In some old collets the rubber has hardened enough that it will not open full size or it requires a great deal of force to close the collet on smaller work. Rubberflex chucks were made in two styles. One had a handwheel resembling that on a Hardinge-Sjogren chuck. The other used a T wrench resembling a Jacobs chuck wrench. I have the latter. Be careful of the wheel type. The wheel acts asa rotating slide hammer. With it you can grip hard enough to shrink thin walled tubing. I had that happen to me when I worked in the shop associated with the college physics department. After facing off the required length and releasing the collet I found the microscope objective would no longer screw into the tube. I had to learn quickly how to single point an internal thread AND to pick up the existing thread. That was back in 1956.

I also have the 6K collets that came with the lathe and a collet chuck for ER 32 collets. I also made a draw tube adapter and bought a 3C collet closer. That way I can use 3C's for the odd sizes I can not get in 6K. I know that Hardinge still makes 6K collets but the price is $168 each. At thatn price I consider them "not available"

[AjohnwParticipant @ajohnw51620]

I've bought it. It makes good sense for me. I have ER16 and ER25 but currently only use these on the miller. I don't use collets that often on the lathe and prefer to make in one setting but have had to set larger sizes up in the 4 jaw a few times. I also have the boxford collets.

I've been wondering about larger sizes for the lathe on and off for some time. ER32 would give me an extra 4 mms, mixed feeling about that. ER40 larger but what a lot of collets. I had wondered about more than one collet holder and odd sizes in ER40 plus as needed going up from ER25. Don't have to worry about what sizes now. It came with a full set up to 1 1/4. I think that the larger size that is sometimes mentioned needs a different closer in the holder.

It is the T bar type and I just tried closing the 1 1/4 to 1 1/8. No problem really but I can see how it would be very easy to over tighten as the rubber deformation does take some effort. Not all that much but as it didn't stiffen as the collet closed the rubber looks to be ok. I suspect I'll find something like just grips work plus a 1/4 or less turn is fine.

I'm well aware of the need for a back plate that fits rather well. It's for the Boxford which is currently off line. That came with a dummy spindle nose but it wasn't really made to the required accuracy so I will need to make another. My aim is to always to obtain a extremely light interference fit on the spindle register and a close fit on the thread as well. That's not too difficult to do with chasers. That means size on size to maybe a 1/10 or so clearance for the register on the spindle. I suspect Jacob's suggest a very slight taper on the spigot to go into the chuck register for a force fit.

Now some one will tell me they have had one and that they are terrible.

John

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[Michael GilliganParticipant @michaelgilligan61133]

John,

You may find this useful, even though it's for the 'handwheel' version.

MichaelG.

[John ReeseParticipant @johnreese12848]

John,

I have this style chuck, except that mine bolts to a backplate.

The full range of collets, including 1 3/8" all work with the same nosepiece.

[John ReeseParticipant @johnreese12848]

John, My chuck body had about a 7* internal taper. I turned a slightly shallower taper on my backplate. I machined the taper until the flange of the chuck was within .010" or so from the backplate. I tightened the cap screws until the flange was tight against the backplate. That resulted in a strong interference fit between the pilot on the backplate and the recess in the chuck. If your chuck has a similar tapered recess you could follow my procedure. If you have a straight recess then all you need is a lead chamfer on the pilot. Be sure to leave a recess adjacent to the pilot. It will provide clearance in case a bit of metal is shaved off the pilot during assembly.

One last thing: be sure you store your collets on plugs that match the maximum rated size.

John

[AjohnwParticipant @ajohnw51620]

I just measured the largest collet. It is 1 3/8" and actually around 0.025 over. I've seen mention of versions that wont take that size somewhere.

Thanks Michael.

John

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[John Stevenson 1Participant @johnstevenson1]

I have two of the hand wheel variety with full set of collets for each.

TBH I never use them as for what reason I can't put my finger on I just don't like them ?

Years ago I standardised on ER's and haven't really changed my opinion of them.

[AjohnwParticipant @ajohnw51620]

I have considered a full set of ER40 right up to the point of actually buying but the lack of an answer from the seller prevented me from going further. Not a happy choice – far too many collets cluttering the place up and mostly not used especially in respect to all sizes.

I can see myself having both an ER16 and an ER25 collet chuck on one lathe at some point and probably not bothering with the ER16 and just keep that for milling but like most things I tend to wait until I actually have a need or something well priced turns up. eg The Jacob's chuck.

What would be nice is a lathe with a big bore spindle and a full set of proper lathe collets but having seen the likes of what DSG, Lang and CVA offered in that line no chance and an extra ordinary number of collets at a very high price – if they were available.

I do have a full set of Pultra collets, glad it came with some where to keep them and that they are small.

John

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