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Pull-Back v/s Dead Length Collet Chucks

Ox

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Joined
Aug 27, 2002
Location
Northwest Ohio
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Backing up 20 yrs, when we first got our Hardinge Twin Turn 65 (twin turret 8x lathe) it actually only came with one collet chuck on it. The machine was stripped... But the sub had a Hardinge B65 dead length collet chuck on it, and that's what was s'posed to have come with. So I bought a new B65 chuck for the main spindle, and a pr of S22 Master Collets. S22 is the biggest that the B65 will support, and I already had many S22 pads around anyhow...

But I found myself battling bars pushing back. The B65 is a style that has a cap on it - just like a Brown and Sharp, Greenlee multi-spindle, or a Swiss lathe. And I don't really have much issue with push back in the Swiss (If I set it tight) and I don't recall ever having any push-back issues with the Greenlee or the B&S.

I can't say fer sure about the Brownie (but I think it does) but I doo know that the Greenlee had the spindle caps drilled out for fines to fling out, and thus, even on long runs, I don't recall having any issues with fine build-up in those. But the B65 caps are NOT drilled out, and they would build up with fines, and sometimes even not-so-fines - between the sliding sleeve and the inside of the cap, thus the actuator ends up losing some of it's thrust on fines. But in all fairness - on the lathe we doo lots of live work that makes chips when the spindle is not turning, so that could result in more buildup / faster? (benefit of doubt)

Sure, I could have drilled the caps out on the B65's, but even when all cleaned out, they still had issues...

Finally - after stewing about this over and over aggin, I finally called Hardinge and ordered a S26 Master Collet and chuck to fit that lathe. They tried to talk me out of it, but I'd had all the advise I could stand, and so they sent me one - with the correct draw-tube adapter.

My push-back problems went away - never to be seen aggin...

Then, as soon as I had two nickles aggin - I ordered another one for the sub.


FFWD to 2023, and we picked up a pair of 8x Nakamura's.
They both came in with 3 jaw chucks on them, but there was 3 ATS collet chucks that came with them. (3? :confused: )
These chucks are all Dead Length as well, but they are S26 masters (or at least the ones for the larger machine are S26's anyhow) and these units doo NOT use a cap on them, so the fines build-up will be a non-issue, so ... we're gunna give'm a shot and hope for the best...

I have been having push-back issues with these on some jobs as well, and the worst job that I have so far - that I haven't been able to program a work-around for is this little 1/2" job where I am drilling a Letter A hole for a 1/4-28 form tap.

Anytime that I have been drilling at or above 50% of the bar diameter is when I git the most trouble. And in this case the pad has such little surface area, that it is not a serrated pad, only making it worse...

I have already taken the stop nut off the pressure regulator for the draw-bar actuator, and I have that bottomed out well into the red zone, and I'm still having issues with this 1/2" part, as well as the one last week.

So, I went on over to the Hardinge - which is currently on sick-leave, and I robbed the chuck off of the sub-spindle. I made up an [draw tube] adapter to fit this machine, and off we go. I just gained another 1.5" of daylight with the change of just the one chuck! (not that the "300" needs more, but ...)

I am sure that my push-back problems are solved, but I will wait a while to make sure all is well, and then maybe I will back off the pressure reg all the way down to the red line.

The thing with Dead Lengths is that you are pushing on the sliding sleeve to tighten it up. With the B65 - you are actually pushing back on the actuator tube, lessening the grip on the bar. In the case of these ATS chucks, the collets are actually fastened solid to the spindle, and should not really have the same effect, but the results seem to be the same.

With a pull-back chuck, the more thrust that you put into it, the more it tightens the grip on the bar - to a point anyhow - depending on the friction coefficient of the collet to the bar grip....

As you can see, these chucks have not been on the machine in quite some time! But now that they have been running almost non-stop for the last 3 months, they don't look that bad now.

DSCN3341.JPG

Here is the one from the sub as of today - looks more better...

DSCN3576.JPG


And here is the new(sed) chuck.

DSCN3577.JPG


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I am Ox and I approve this here post!
 
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We personally haven't had any issues running our royal QG65 dead length on the main spindle side. But this is useful to know in case one day it gives us issues!
 
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Glad to see the two Nakamura's working out well, Ox. First pieces of Japanese iron, eh?

Maybe a report sometime on the machines themselves....comparing to your Hardinge?

And yes, I've always ran pull-back style chucks---can't beat the grip. A little bit of a pain when running bar pullers, as you have to program for a bit of the pullback when clamping.

How do the short bar feeders handle the pullback??

ON EDIT: Seems like push-style collet chucks go against the design of the lathe spindle itself? Lathe spindles have bearing setups primarily designed for axial thrust loading into the spindle from the chuck side, not away from it.

The hydraulic actuator and chuck are trying to push each other apart when clamping a push-style chuck, and they say that's where the loading is occurring.

But...they actuator has to anchor off the rear of the spindle shaft, and thus is trying to push the spindle shaft forward also?

So, push-to-clamp chucks could possible effect your spindle's rigidity and preload??

ToolCat
 
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Actually, we don't have the second one up yet.
It's almost running ... we can see it from here, but we're just not quite there yet...
We seem to have a major air leak somewhere...
Just need to put more time into it...

Actually, yeah, this likely is the first pcs of Jap iron...
My Hardinge mills are Taiwan, but to date, I think that is the only non-USA/European iron that I have ever had?
(intentionally)

Barfeeder would not act any diff than your puller.


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I am Ox and I approve this here post!
 
We seem to have a major air leak somewhere...

Mazak's of yesteryear blow air inside the turret box to cool the hydraulic index motors. And they use air in the ball-nuts: for cooling and to pressurize against contaminants. Annnd, they use air when the "tool eyes" are down in position to use.

I disable all these air functions. With throttled hyd index motors (flow-control valve), reduced rapids, removed rear covers for chip vac-ing, no air needed on the Cat-zaks.

(And I can't stand the whistle of air blowing up in my face when trying to concentrate while using the tool eyes!)

ToolCat
 
Well, the 300 really doesn't use any air at all.

And I asked Wimpy, and maybe others (?) if their 150's use air, and so far the answer is "no".

I did have an air purge in both turrets on the 150 (the 300 doesn't have purged turrets) and I was hoping that once I got plugs made for all holes, that would stop it, but the air volume seemed WAY more than a low pressure purge would likely cause, but I got plugs all made up finally, and that seemed to move the needle on the gauge a slight bit, but it is still dumping air somewhere else.

If it is normal for this machine to gobble air, it is likely to get modified - like yours...
I'm not gunna dedicate a 10hp compressor to just this machine.


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I am Ox and I approve this here post!
 
But...they actuator has to anchor off the rear of the spindle shaft, and thus is trying to push the spindle shaft forward also?

If I understand your question, since the actuator is bolted directly to the spindle, it can't push it forward. Same as you can't push your car forward when you are sitting in the back seat.

The actuator will theoretically elongate the spindle, but so little it can be ignored.
 
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Yeah, I didn't see your edit 'till he quoted it, but - yeah, that should all be internal to the spindle shaft.
You just didn't git much sleep last night.


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I am Ox and I approve this here post!
 
Thanks for the details.
So far so good with the QG-80.
One part about the "Dead Length" that is still a movement problem is the amount of drag the draw tube has on the material as the chuck closes.
I will say this. The Quick Grip collet system makes me giggle every time I change one.
I don't giggle when I buy a QG-80 collet though.. Dang spendy..
 
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Thanks for the details.
So far so good with the QG-80.
One part about the "Dead Length" that is still a movement problem is the amount of drag the draw tube has on the material as the chuck closes.
I will say this. The Quick Grip collet system makes me giggle every time I change one.
I don't giggle when I buy a QG-80 collet though.. Dang spendy..


I have S20 masters for the 65 series.
So far, my 65's start at 2" and go up from there is all.

I would think that you could get S26 master collets for the 80's?
They are likely 1/2 price of the 80's. (no rubber)

You still git the "flat" grip that is championed by the rubber bound collets.


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Think Snow Eh!
Ox
 
Thanks for the details.
So far so good with the QG-80.
One part about the "Dead Length" that is still a movement problem is the amount of drag the draw tube has on the material as the chuck closes.
I will say this. The Quick Grip collet system makes me giggle every time I change one.
I don't giggle when I buy a QG-80 collet though.. Dang spendy..
The S-26 Master also has the rubber. We paid $821 for one last spring for our new Lynx. I hate the work stop design.
 
I use a Riken AD-65 in the Mori, and it does quite well. Dead length and even heavy cuts don't push the material back.
The only real issue is the collets are around $800 each.
 
The S-26 Master also has the rubber. We paid $821 for one last spring for our new Lynx. I hate the work stop design.

Right, the master has the rubber, but you don't pay that fee with every size if you go with the S pads.


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I am Ox and I approve this here post!
 
Right, the master has the rubber, but you don't pay that fee with every size if you go with the S pads.


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I am Ox and I approve this here post!
Luckily they even offer it as an option. We probably have 300+ sets of pads across S-20 thru S-30, I couldn't imagine buying the quick change collets to replace all of them.
 
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I have S20 masters for the 65 series.
So far, my 65's start at 2" and go up from there is all.

I would think that you could get S26 master collets for the 80's?
They are likely 1/2 price of the 80's. (no rubber)

You still git the "flat" grip that is championed by the rubber bound collets.


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Think Snow Eh!
Ox
S26 and S30 are options for the 80s. Although the QG master is a jolly grand and needs another wrench to install it at another $700.. This set-up, while nice, reminds me or road racing motorcycles... Lol $$
 
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